AORTIC OCCLUDER WITH ASSOCIATED FILTER AND METHODS OF USE DURING CARDIAC SURGERY
A balloon arterial cannula and methods for filtering blood. The devices generally include a mesh for filtering blood flowing within a blood vessel, particularly within an artery such as the aorta, a structure adapted to open and close the mesh within the blood vessel, a means to actuate the structure, and a balloon occluder which typically includes a flexible material enclosing a chamber. The methods generally include the steps of introducing a mesh into a blood vessel to capture embolic material, adjusting the mesh, if necessary, during the course of filtration, inflating the balloon occluder to occlude the vessel upstream of the mesh, and thereafter deflating the balloon occluder and removing the mesh and the captured foreign matter from the blood vessel. Additionally, visualization techniques are used to ensure effective filtration.
This application is a continuation of Barbut et al., U.S. application Ser. No. 08/854,806, filed May 12, 1997, which is a continuation-in-part of U.S. application Ser. No. 08/645,762, filed May 14, 1996, now abandoned, the contents of which are incorporated herein by reference.FIELD OF THE INVENTION
The present invention relates generally to blood filter devices having an associated balloon occluder for temporary placement in a blood vessel, and more particularly to a cannula device, having an associated blood filter and balloon occluder, for placement in a blood vessel to carry blood to an artery from a bypass-oxygenator system and to capture embolic material in the vessel. The invention also relates to catheters having a balloon occluder and associated filter to capture embolic material. More particularly, the invention relates to a blood filter device to be placed in the aorta during cardiac surgery, the device further having a balloon occluder which, when deployed, reduces or eliminates the need for aortic cross-clamping. The present invention also relates to methods for temporarily filtering blood to capture and remove embolic material, and to methods for protecting a patient from embolization which may be caused by the balloon occluder having dislodged atheromatous material from the arteryBACKGROUND OF THE INVENTION
Currently, the most common method of temporarily occluding the ascending aorta during open heart surgery utilizes a mechanical cross clamp. Once the chest cavity has been opened, access to the heart and to the adjacent vessels is provided. The ascending aorta is partially dissected from the surrounding tissue and exposed. Arterial and venous cannulas are inserted and sutured into place. The cannulas are connected to the cardiopulmonary bypass machine, and bypass blood oxygenation is established.
At this point, the heart must be arrested and isolated from the rest of the circulatory system. A mechanical cross clamp is positioned between cardioplegia cannula and the aortic cannula and actuated. The aorta is completely collapsed at the clamp site, thus stopping flow of blood between the coronary arteries and the innominate artery the oxygenated bypass blood is shunted around the heart. Once the vessel occlusion has been completed, cardioplegia solution is introduced through the cardioplegia cannula to arrest the heart. The surgeon may now proceed with the desired operation.
Other less common means of occluding the aorta include percutaneous balloon catheter occlusion, direct aortic balloon catheter (Foley) occlusion, aortic balloon occluder cannula, and an inflating diaphragm occluder (Hill—occlusion trocar). The percutaneous balloon catheter is inserted typically from the femoral artery feed through the descending aorta, across the aortic arch into position in the ascending aorta. Once in the ascending aorta, the balloon occluder is inflated and flow stopped.
As a simple replacement for the mechanical cross clamp, a Foley catheter may be placed through an additional incision site near the standard cross clamp site. Once inserted, the Foley catheter balloon is inflated and flow is stopped. Similarly, an aortic balloon occluder cannula is placed directly into the aorta. This occluder cannula replaces the standard aortic cannula by delivering the CPB blood back to the arterial circulatory system The occluder balloon is located on the cannula proximal to CPB blood exit port on the cannula. It may also replace the need for a cardioplegia cannula with an additional infusion port proximal to the occluder balloon. The occlusion trocar is described to offer similar features as the aortic balloon occluder cannula and would be used in place of the standard aortic cannula. However, it relies on an inflatable diaphragm to occlude the vessel.
The use of a balloon to occlude an artery has been disclosed by Gabbay, U.S. Pat. No. 5,330,451 (this and all other references cited herein are expressly incorporated by reference as if fully set forth in their entirety herein). The Gabbay device included a perfusion cannula having a proximal balloon occluder and a distal intra-aortic balloon to divert blood to the carotid arteries. The Gabbay perfusion cannula is disclosed for use during open heart surgery in order to prevent complications associated therewith.
Moreover, Peters, U.S. Pat. No. 5,433,700, discusses a method for inducing cardioplegic arrest using an arterial balloon catheter to occlude the ascending aorta. The Peters method includes the steps of maintaining systemic circulation using peripheral cardiopulmonary bypass, venting the left side of the heart, and introducing a cardioplegic agent into the coronary circulation. This procedure is said to prepare the heart for a variety of surgical procedures. Disclosures of similar endovascular occlusion catheters can be found in Machold et al., U.S. Pat. No. 5,458,574, Stevens, International Application No. PCT/US93/12323, and Stevens et al., International Application No. PCT/US94/12986.
There are a number of known devices designed to filter blood. The vast majority of these devices are designed for permanent placement in veins, in order to trap emboli destined for the lungs. For example, Kimmell, Jr., U.S. Pat. No. 3,952,747, discloses the so-called Kimray-Greenfield filter. This is a permanent filter typically placed in the vena cava comprising a plurality of convergent legs in a generally conical array, which are joined at their convergent ends to an apical hub. Each leg has a bent hook at its end to impale the internal walls of the vena cava.
Cottenceau et al., U.S. Pat. No. 5,375,612, discloses a blood filter intended for implantation in a blood vessel, typically in the vena cava. This device comprises a zigzagged thread wound on itself and a central strainer section to retain blood clots. This strainer section comprises a meshed net and may be made from a biologically absorbable material. This device is also provided with attachment means which penetrate into the wall of the vessel.
Gunther et al., U.S. Pat. No. 5,329,942, discloses a method for filtering blood in the venous system wherein a filter is positioned within a blood vessel beyond the distal end of a catheter by a positioning means guided through the catheter. The positioning means is locked to the catheter, and the catheter is anchored to the patient. The filter takes the form of a basket and is comprised of a plurality of thin resilient wires. This filter can be repositioned within the vessel to avoid endothelialization within the vessel wall.
Similarly, Lefebvre, french Patent No. 2,567,405, discloses a blood filter for implantation by an endovenous route into the vena cava. The filter is present in the form of a cone, and the filtering means may consist of a flexible metallic grid, or a flexible synthetic or plastic grid, or a weave of synthetic filaments, or a non-degradable or possibly biodegradable textile cloth. In order to hold the filter within the vein, this device includes flexible rods which are sharpened so that they may easily penetrate into the inner wall of the vena cava.
There are various problems associated with permanent filters. For example, when a filter remains in contact with the inner wall of the vena cava for a substantial period of time, endothelialization takes place and the filter will subsequently become attached to the vena cava. This endothelialization may cause further occlusion of the vessel, thereby contributing to the problem the filter was intended to solve. Except for the Gunther device, these prior art filters do not address this problem.
A temporary venous filter device is disclosed in Bajaj, U.S. Pat. No. 5,053,008. This device treats emboli in the pulmonary artery which, despite its name, is in fact a vein. The Bajaj device is an intracardiac catheter for temporary placement in the pulmonary trunk of a patient predisposed to pulmonary embolism because of hip surgery, stroke or cerebral hemorrhage, major trauma, major abdominal or pelvic surgery, neurosurgery, neoplasm, sepsis, cardiorespiratory failure or immobilization.
The Bajaj device includes an umbrella made from meshwork which traps venous emboli before they reach the lungs. This device can also lyse emboli with a thrombolytic agent such as tissue plasminogen activator (TPA), destroy emboli with high velocity ultrasound energy, and remove emboli by vacuum suction through the lumen of the catheter. This very complex device is designed for venous filtration and is difficult to justify when good alternative treatments exist.
There are very few intravascular devices designed for arterial use. A filter that functions not only in veins, but also in arteries must address additional concerns because of the hemodynamic differences between arteries and veins. Arteries are much more flexible and elastic than veins and, in the arteries, blood flow is pulsatile with large pressure variations between systolic and diastolic flow. These pressure variations cause the artery walls to expand and contract. Blood flow rates in the arteries vary from about 1 to about 5 L/min.
Ginsburg, U.S. Pat. No. 4,873,978, discloses an arterial device. This device includes a catheter that has a strainer device at its distal end. This device is normally used in conjunction with non-surgical angioplastic treatment. This device is inserted into the vessel downstream from the treatment site and, after the treatment, the strainer is collapsed around the captured emboli, and the strainer and emboli are removed from the body. The Ginsburg device could not withstand flow rates of 5 L/min. It is designed for only small arteries and therefore could not capture emboli destined for all parts of the body. For example, it would not catch emboli going to the brain.
Ing. Walter Hengst GmbH & Co, German Patent DE 34 17 738, discloses another filter which may be used in the arteries of persons with a risk of embolism. This filter has an inherent tension which converts the filter from the collapsed to the unfolded state, or it can be unfolded by means of a folding linkage system. This folding linkage system comprises a plurality of folding arms spaced in parallel rows along the longitudinal axis of the conical filter (roughly similar to branches on a tree). The folding arms may be provided with small barbs at their projecting ends intended to penetrate the wall of the blood vessel to improve the hold of the filter within the vessel.
Moreover, da Silva, Brazil Patent Application No. PI9301980A, discusses an arterial filter for use during certain heart operations where the left chamber of the heart is opened. The filter in this case is used to collect air bubbles in addition to formed particles such as platelet fibrin clots not removed on cleaning the surgical site.
Each of the existing methods of blocking aortic blood flow carries with it some undesired aspects. The mechanical cross clamp offers simplicity and reliably consistent operation. However, the physical clamping action on the vessel has been linked to may adverse body responses. Barbut et al. noted the majority of embolic events (release) is associated with the actuation and release of the cross clamp during coronary bypass graph surgery. The clamping action may be responsible for breaking up and freeing atherosclerotic buildup on the vessel walls. In addition, the potential for vascular damage, like aortic dissections, may also incur during the clamp application.
The percutaneous balloon catheter occluder has a distinct drawback in that it must be placed with visionary assistance. Fluoroscopy is typically used to position the device in the aorta. This added equipment is not always readily available in the surgical suite. In addition, the catheter placement up to the aorta may also create additional vascular trauma and emboli generation.
The use of a Foley catheter to occlude the aorta requires an additional incision site to place the device. This extra cut is an additional insult site and requires sutures to close. Generation of emboli and the potential of aortic dissection directly associated with just the incision may potentially outweigh the benefits of using the balloon occlusion technique.
The aortic balloon occluder cannula addresses many of the deficiencies of the previous devices. Placement is easy to visualize and no extra cuts are required. With the cardioplegia port included, this design offers a complete package while potentially reducing the number of incision sites and removing the need for the potentially traumatic cross clamp. However, this “all-in-one” design possesses several deficiencies. First, there is one inherent drawback with using a balloon to occlude a vessel. Balloons are always susceptible to failure (e.g., popping, leaking). In addition, the cannula has a limited placement region. It must be inserted sufficiently proximal to the innominate artery to allow room for occlusion balloon to seat within the vessel and not occlude or block the innominate artery. This cannula design has at least two critical functions (three with the cardioplegia port). A balloon failure means either replacing the cannula (stopping the CPB and cardioplegia), or immediately placing the cross clamp and inserting a cardioplegia cannula. Life support, occlusion, and cardioplegia depend on one device. This situation is less than optimal. The risks associated to a failure are multiplied when one device is used for more than one critical operation.
A need exists for an arterial cannula having both a balloon occluder, which reduces or eliminates the need for aortic cross-clamping, a major contributor to atheromatous embolization, and an associated filter which captures any embolic material dislodged during balloon occlusion. Existing devices are inadequate for this purpose.SUMMARY OF THE INVENTION
The present invention relates to arterial medical devices, and particularly cannulas and catheters having an occlusion balloon and optionally a blood filter device, and to methods of using the devices during cardiac surgery. The devices of the present invention may be adapted to filter embolic material from the blood. Embolic material or foreign matter is any constituent of blood, including gaseous material and particulate matter, which may cause complications in the body if allowed to travel freely in the bloodstream. This matter includes but is not limited to atheromatous fragments, fat, platelets, fibrin, clots, or gaseous material.
In one embodiment, the device includes a blood cannula having a balloon occluder at a distal region of the blood cannula. In another embodiment, the device includes an intravascular catheter having a balloon occluder at a distal region of the catheter. The balloon occluder may consist of a flexible material surrounding a chamber which is expandable between a deflated, contracted condition and an inflated, enlarged condition. The balloon occluder may be circumferentially disposed about a distal region of the catheter or blood cannula, or may be attached to the catheter or blood cannula at a specific radial position about the distal region of the catheter or blood cannula. The balloon occluder, when in the contracted condition, is closely associated with the distal region of the catheter or blood cannula, while the balloon occluder expands upon inflation to occupy an area which may occlude blood flowing within an artery.
In another embodiment, the blood cannula or catheter will further include filtration means disposed about the distal region of the catheter or blood cannula. Several designs for blood filtration cannulas are disclosed in Barbut et al., U.S. application Ser. No. 08/553,137, filed Nov. 7, 1995, Barbut et al., U.S. application Ser. No. 08/580,223, filed Dec. 28, 1995, Barbut et al., U.S. application Ser. No. 08/584,759, filed Jan. 9, 1996, and Barbut et al., U.S. application Ser. No. 08/640,015, filed on Apr. 30, 1996, and Barbut et al., U.S. Application Serial No. [attorney docket no. 224/194], filed Apr. 16, 1997, and the contents of each of these prior applications are incorporated herein by reference in their entirety. Thus, in one embodiment, the balloon aortic cannula as disclosed herein will include a filtration means having an expandable member, such as an inflation seal, disposed about the distal end of the blood cannula, which is expandable between a deflated, contracted condition and an inflated, enlarged condition. The filtration means will further include a mesh having an edge attached to the expansion means. The mesh may optionally include a second edge which is closely associated with the outer surface of the blood cannula, or the mesh may be continuous and unbroken at its distal region. The filtration means will generally be disposed about the distal end of the blood cannula and the balloon occluder at a region proximal of the mesh, so that the balloon occluder expands upon inflation to substantially occlude an artery upstream of the mesh. For those embodiments using an intravascular catheter, the balloon occluder is typically upstream of the filtration means, or with reference to the catheter, distal the filtration means.
In another embodiment, a cannula with filtration means further includes a blood flow diffuser. The blood flow diffuser may be located inside or outside of the blood cannula. In both the intra-cannula and extra-cannula diffuser embodiments, the flow diffuser can be located either proximal or distal to the filtration means. The diffuser may be similarly used for intravascular catheter embodiments of the device.
In another embodiment, a cannula with attached filtration means includes a sleeve which, when unrolled, captures the filtration means thereby closely securing the filter components against the cannula wall during insertion and retraction. The sleeve may be similarly used for intravascular catheter embodiments of the device. In another embodiment, a cannula is made of an elastomeric material which collapses along part of the cannula length so as to absorb the filtration means during cannula insertion and retraction.
In an alternate embodiment, a blood cannula includes a conduit to provide a solution, such as cardioplegia solution, to the heart side of an aortic balloon occluder while providing oxygenated blood into the arterial circulation of the systemic side of the occluder.
The methods of the present invention include protecting a patient from embolization during cardiac surgery by using a balloon aortic cannula as described above or other intravascular or intra-arterial procedure resulting in distal embolization. The distal end of the arterial cannula is inserted into a patient's aorta while the filtration and expansion means is in the contracted condition. The expansion means, including associated mesh, is inflated to expand and thereby achieve contact with the inner wall of the artery, preferably the aorta. Once the filtration means are in place and deployed, the balloon occluder is activated by inflating to occlude the artery, preferably the aorta, in a region upstream of the mesh. In other embodiments, the balloon occluder may be inflated before the expansion means is inflated. During balloon occlusion, certain embolic material may be dislodged from the artery, and thereafter captured by the deployed filtration system. The cannula is used to supply blood to the aorta from a bypass-oxygenator machine. A surgical procedure may then be performed on the heart, aorta, or vasculature upstream of the deployed filtration system. During this procedure, further embolic material may be dislodged and enter the circulation, and thereafter be captured by the deployed filtration mesh. After the surgery is performed, the balloon occluder is deflated, and further embolic material may be dislodged and captured by the filtration system. The expansion means of the filtration system is then contracted by deflating to resume a small shape, and the arterial cannula with captured embolic material is removed from the aorta.
In a preferred method, balloon occlusion occurs, and blood is filtered during cardiac surgery, in particular during cardiac bypass surgery, to protect a patient from embolization. In this method, the mesh is positioned in the aorta where it filters blood before it reaches the carotid arteries, brachiocephlalic trunk, and left subclavian artery.
The present invention was developed, in part, in view of a recognition of the occurrence of embolization during cardiac surgery. Emboli are frequently detected in cardiac surgery patients and have been found to account for neurologic, cardiac and other systemic complications. Specifically, embolization appears to contribute significantly to problems such as strokes, lengthy hospital stays and, in some cases, death. Of the patients undergoing cardiac surgery, 5-10% experience strokes and 30% become cognitively impaired. In addition, it has been recognized that embolization is often the result of procedures performed on blood vessels such as incising, clamping, and cannulation, wherein mechanical or other force is applied to the vessel. See, for example, Barbut et al., “Cerebral Emboli Detected During Bypass Surgery Are Associated With Clamp Removal,” Stroke 25(12):2398-2402 (1994), which is incorporated herein by reference in its entirety. These procedures are commonly performed in many different types of surgery including cardiac surgery, coronary artery surgery including coronary artery bypass graft surgery, aneurysm repair surgery, angioplasty, atherectomy, and endarterectomy, including carotid endarterectomy. It has also been recognized that reintroducing blood into blood vessels with a cannula or catheter during these procedures can dislodge plaque and other emboli-creating materials as a result of blood impinging upon the vessel wall at high velocities. See, for example, Cosgrove et. al., Low Velocity Aortic Cannula, U.S. Pat. 5,354,288.
Finally, it has been found that the occurrence of embolization is more likely in certain types of patients. For example, embolization occurs more frequently in elderly patients and in those patients who have atheromatosis. In fact, atheromatous embolization, which is related to severity of aortic atheromatosis, is the single most important contributing factor to perioperative neurologic morbidity in patients undergoing cardiac surgery.
Embolic material, which has been detected at 2.88 mm in diameter, will generally range from 0.02 mm (20 μm) to 5 mm, and consists predominantly of atheromatous fragments dislodged from the aortic wall and air bubbles introduced during dissection, but also includes platelet aggregates which form during cardiac surgery. See Barbut et al., “Determination of Embolic Size and Volume of Embolization During Coronary Artery Bypass Surgery Using Transesophageal Echocardiography,” J. Cardiothoracic Anesthesia (1996). These emboli enter either the cerebral circulation or systemic arterial system. Those entering the cerebral circulation obstruct small arteries and lead to macroscopic or microscopic cerebral infarction, with ensuing neurocognitive dysfunction. Systemic emboli similarly cause infarction, leading to cardiac, renal, mesenteric, and other ischemic complications. See Barbut et al., “Aortic Atheromatosis And Risks of Cerebral Embolization,” Journal of Cardiothoracic and Vascular Anesthesia 10(1):244-30 (1996), which is incorporated herein by reference in its entirety.
Emboli entering the cerebral circulation during coronary artery bypass surgery have been detected with transcranial Doppler ultrasonography (TCD). TCD is a standard visualization technique used for monitoring emboli in the cerebral circulation. To detect emboli using TCD, the middle cerebral artery of a bypass patient is continuously monitored from aortic cannulation to bypass discontinuation using a 2 MHZ pulsed-wave TCD probe (Medasonics-CDS) placed on the patient's temple at a depth of 4.5 to 6.0 cm. The number of emboli is determined by counting the number of embolic signals, which are high-amplitude, unidirectional, transient signals, lasting less than 0.1 second in duration and associated with a characteristic chirping sound.
TCD is useful in analyzing the relationship between embolization and procedures performed on blood vessels. For example, the timing of embolic signals detected by TCD have been recorded along with the timing of procedures performed during open or closed cardiac surgical procedures. One of these procedures is cross-clamping of the aorta to temporarily block the flow of blood back into the heart. It has been found that flurries of emboli are frequently detected after aortic clamping and clamp release. During the placement and removal for the clamps, atheromatous material along the aortic wall apparently becomes detached and finds its way to the brain and other parts of the body. Similarly, flurries of emboli are also detected during aortic cannulation and inception and termination of bypass.
Transesophageal echocardiography (TEE), another standard visualization technique known in the art, is significant in the detection of conditions which may predispose a patient to embolization. TEE is an invasive technique, which has been used, with either biplanar and multiplanar probes, to visualize segments of the aorta, to ascertain the presence of atheroma. This technique permits physicians to visualize the aortic wall in great detail and to quantify atheromatous aortic plaque according to thickness, degree of intraluminal protrusion and presence or absence of mobile components, as well as visualize emboli within the vascular lumen. See, for example, Barbut et al., “Comparison of Transcranial Doppler and Transesophageal Echocardiography to Monitor Emboli During Coronary Bypass Surgery,” Stroke 27(1):87-90 (1996) and Yao, Barbut et al., “Detection of Aortic Emboli By Transesophageal Echocardiography During Coronary Artery Bypass Surgery,” Journal of Cardiothoracic Anesthesia 10(3):314-317 (May 1996), and Anesthesiology 83(3A):A126 (1995), which are incorporated herein by reference in their entirety. Through TEE, one may also determine which segments of a vessel wall contain the most plaque. For example, in patients with aortic atheromatous disease, mobile plaque has been found to be the least common in the ascending aorta, much more common in the distal arch and most frequent in the descending segment. Furthermore, TEE-detected aortic plaque is unequivocally associated with stroke. Plaque of all thickness is associated with stroke but the association is strongest for plaques over 4 mm in thickness. See Amarenco et al., “Atherosclerotic disease of the aortic arch and the risk of ischemic stroke,” New England Journal of Medicine 331:1474-1479 (1994).
Another visualization technique, intravascular ultrasound, is also useful in evaluating the condition of a patient's blood vessel. Unlike the other techniques mentioned, intravascular ultrasound visualizes the blood vessel from its inside. Thus, for example, it may be useful for visualizing the ascending aorta overcoming deficiencies of the other techniques. In one aspect of the invention, it is contemplated that intravascular ultrasound is useful in conjunction with devices disclosed herein. In this way, the device and visualizing means may be introduced into the vessel by means of a single catheter.
Through visualization techniques such as TEE epicardial aortic ultrasonography and intravascular ultrasound, it is possible to identify the patients with plaque and to determine appropriate regions of a patient's vessel on which to perform certain procedures. For example, during cardiac surgery, in particular, coronary artery bypass surgery, positioning a probe to view the aortic arch allows monitoring of all sources of emboli in this procedure, including air introduced during aortic cannulation, air in the bypass equipment, platelet emboli formed by turbulence in the system and atheromatous emboli from the aortic wall. Visualization techniques may be used in conjunction with a blood filter device to filter blood effectively. For example, through use of a visualization technique, a user may adjust the position of a blood filter device, and the degree of actuation of that device as well as assessing the efficacy of the device by determining whether foreign matter has bypassed the device.
It is an object of the present invention to eliminate or reduce the problems that have been recognized as relating to embolization. The present invention is intended to capture and remove emboli in a variety of situations, and to reduce the number of emboli by obviating the need for cross-clamping. For example, in accordance with one aspect of the invention, blood may be filtered in a patient during procedures which affect blood vessels of the patient. The present invention is particularly suited for temporary filtration of blood in an artery of a patient to capture embolic debris. This in turn will eliminate or reduce neurologic, cognitive, and cardiac complications helping to reduce length of hospital stay. In accordance with another aspect of the invention, blood may be filtered temporarily in a patient who has been identified as being at risk for embolization.
As for the devices, one object is to provide simple, safe and reliable devices that are easy to manufacture and use. A further object is to provide devices that may be used in any blood vessel. Yet another object is to provide devices that will improve surgery by lessening complications, decreasing the length of patients' hospital stays and lowering costs associated with the surgery. See Barbut et al., “Intraoperative Embolization Affects Neurologic and Cardiac Outcome and Length of Hospital Stay in Patients Undergoing Coronary Bypass Surgery,” Stroke (1996).
The devices disclosed herein have the following characteristics: can withstand high arterial blood flow rates for an extended time; include a mesh that is porous enough to allow adequate blood flow in a blood vessel while capturing mobile emboli; can be used with or without imaging equipment; remove the captured emboli when the operation has ended; will not dislodge mobile plaque; and can be used in men, women, and children of varying sizes.
As for methods of use, an object is to provide temporary occlusion and filtration in any blood vessel and more particularly in any artery. A further object is to provide a method for temporarily filtering blood in an aorta of a patient before the blood reaches the carotid arteries and the distal aorta. A further object is to provide a method for filtering blood in patients who have been identified as being at risk for embolization. Yet a further object is to provide a method to be carried out in conjunction with a blood filter device and visualization technique that will assist a user in determining appropriate sites of filtration. This visualization technique also may assist the user in adjusting the blood filter device to ensure effective filtration. Yet a further object is to provide a method for filtering blood during surgery only when filtration is necessary. Yet another object is to provide a method for eliminating or minimizing embolization resulting from a procedure on a patient's blood vessel by using a visualization technique to determine an appropriate site to perform the procedure.
Another object is to provide a method for minimizing incidence of thromboatheroembolisms resulting from cannula and catheter procedures by coordinating filtration and blood flow diffusion techniques in a single device. Another object is to provide a method of inserting or retrieving a cannula or catheter with attached filtering means from a vessel while minimizing the device's profile and diameter.
Thus, we disclose herein each of the individual designs listed below which are grouped into three categories.
Reference is next made to a brief description of the drawings, which are intended to illustrate balloon aortic cannula and catheter devices for use herein. The drawings and detailed description which follow are intended to be merely illustrative and are not intended to limit the scope of the invention as set forth in the appended claims.
To filter blood effectively, i.e., to capture embolic material, without unduly disrupting blood flow, the mesh must have the appropriate physical characteristics, including area (AM), thread diameter (Dr), and pore size (SP). In the aorta, the mesh 40 must permit flow rates as high as 3 L/min or more, more preferably 3.5 L/min or more, more preferably 4 L/min or more, more preferably 4.5 L/min or more, more preferably 5 L/min or more preferably 5.5 L/min or more, and most preferably 6 L/min or more at pre-filter pressures (proximal to the mesh) of around 120 mm Hg or less.
In order to capture as many particles as possible, mesh with the appropriate pore size must be chosen. The dimensions of the particles to be captured is an important factor in this choice. In the aorta during cardiac surgery, for example, individual particle diameter has been found to range from 0.27 mm to 2.88 mm, with a mean diameter of 0.85 mm, and individual particle volume has been found to range from 0.01 mm3 to 12.45 mm3, with a mean particle volume of 0.32 mm3. Approximately 27 percent of the particles have been found to measure 0.6 mm or less in diameter. During cardiac bypass surgery in particular, the total aortic embolic load has been found to range from 0.57 cc to 11.2 cc, with a mean of 3.7 cc, and an estimated cerebral embolic load has been found to range from 60 mm3 to 510 mm, with a mean of 276 mm3.
By way of example, when a device as disclosed herein is intended for use in the aorta, the area of the mesh required for the device is calculated in the following manner. First, the number of pores NP in the mesh is calculated as a function of thread diameter, pore size, flow rate, upstream pressure and downstream pressure. This is done using Bernoulli's equation for flow in a tube with an obstruction:
In this equation, P is pressure, ρ is density of the fluid, g is the gravity constant (9.8 m/s2), V is velocity, K represents the loss constants, and f is the friction factor. The numbers 1 and 2 denote conditions upstream and downstream, respectively, of the filter.
The following values are chosen to simulate conditions within the aorta:
P1=120 mm Hg;
P2=80 mm Hg;
Assuming laminar flow out of the mesh filter, f is given as
where Re is the Reynold's number and the Reynold's number is given by the following equation:
where μ is the kinematic viscosity of the fluid and Ah is the area of one hole in the mesh given by SP*SP.
Conservation of the volume dictates the following equation:
where Q is the flow rate of the blood. In addition, V1 is given by:
where Avessel is the cross-sectional area of the vessel. Substitution and manipulation of the above equations yields Np.
Next, the area of the mesh is calculated as a function of the number of pores, thread diameter and pore size using the following equation:
In an embodiment of the device 10 that is to be used in the aorta, mesh with dimensions within the following ranges is desirable: mesh area is 3-10 in2, more preferably 4-9 in2, more preferably 5-8 in 2 more preferably 6-8 in2, most preferably 7-8 in2; mesh thickness is 20-280 μm, more preferably 23-240 μm, more preferably 26-200 μm, more preferably 29-160 μm, more preferably 32-120 μm, more preferably 36-90 μm, more preferably 40-60 μm; thread diameter is 10-145 μm, more preferably 12-125 μm, more preferably 14-105 μm, more preferably 16-85 μm, more preferably 20-40 μm; and pore size is 50-300 μm, more preferably 57-285 μm, more preferably 64-270 μm, more preferably 71-255 μm, more preferably 78-240 μm, more preferably 85-225 μm, more preferably 92-210 μm, more preferably 99-195 μm, more preferably 106-180 μm, more preferably 103-165 μm, more preferably 120-150 μm. In a preferred embodiment of the invention, mesh area is 3-8 in2, mesh thickness is 36-90 μm, thread diameter is 16-85 μm, and pore size is 103-165 μm. In a further preferred embodiment of the invention, mesh area is 3-5 in2, mesh thickness is 40-60 μm, thread diameter is 20-40 μm, and pore size is 120-150 μm.
The calculation set forth above has been made with reference to the aorta. It will be understood, however, that blood flow parameters within any vessel other than the aorta may be inserted into the equations set forth above to calculate the mesh area required for a blood filter device adapted for that vessel.
To test the mesh under conditions simulating the conditions within the body, fluid flow may be observed from a reservoir through a pipe attached to the bottom of the reservoir with the mesh placed over the mouth of the pipe through which the fluid exits the pipe. A mixture of glycerin and water may be used to simulate blood. Fluid height (h) is the length of the pipe in addition to the depth of the fluid in the reservoir, and it is given by the following equation:
where ρ is given by the density of the glycerin-water mixture, and g is given by the gravity constant (9.8 ms2).
Bernoulli's equation (as set forth above) may be solved in order to determine (Dt/SP)Equiv. V1 is given by the following equation:
where Q is the flow rate which would be measured during testing and A1 is the cross-sectional area of the pipe. V2 is given by the following equation:
where N is the number of pores in the mesh and A2 is the area of one pore. Further, P1=120 mm Hg and P2=0 m Hg and SP is the diagonal length of the pore. Reynold's number (Re) is given by the following equation:
where ρ and μ are, respectively, the density and kinematic viscosity of the glycerin-water mixture.
Once appropriate physical characteristics are determined, suitable mesh can be found among standard meshes known in the art. For example, polyurethane meshes may be used, such as Saati and Tetko meshes. These are available in sheet form and can be easily cut and formed into a desired shape. In a preferred embodiment, the mesh is sonic welded into a cone shape. Other meshes known in the art, which have the desired physical characteristics, are also suitable. Anticoagulants, such as heparin and heparinoids, may be applied to the mesh to reduce the chances of blood clotting on the mesh. Anticoagulants other than heparinoids also may be used, e.g., monoclonal antibodies such as ReoPro (Centocore). The anticoagulant may be painted or sprayed onto the mesh. A chemical dip comprising the anticoagulant also may be used. Other methods known in the art for applying chemicals to mesh may be used.
In an embodiment of the devices suited for placement in the aorta, the expansion means, upon deploymnent, has an outer diameter of approximately 100 Fr., more preferably 105 Fr., more preferably 110 Fr., more preferably 115 Fr., more preferably 120 Fr., and most preferably 125 Fr., or greater, and an inner diameter of approximately 45 Fr. (1 Fr.=0.13 in.) when fully inflated. The dimensions of the expansion means may be adjusted in alternative embodiments adapted for use in vessels other than the aorta. Alternatively, expandable members other than a balloon also may be used with this invention. Other expandable members include the umbrella frame with a plurality of arms as described in U.S. application Ser. Nos. 08/533,137, 08/580,223, 08/584,759, 08/640,015, [attorney docket no. 224/194], and [attorney docket no. 222/133].
All components of this device should be composed of materials suitable for insertion into the body. Additionally, sizes of all components are determined by dimensional parameters of the vessels in which the devices are intended to be used. These parameters are shown by those skilled in the art.
By way of purely illustrative example, the operational characteristics of a filter according to the invention and adapted for use in the aorta are as follows:
Modification of the operational characteristics set forth above for use in vessels other than the aorta are readily ascertainable by those skilled in the art in view of the present disclosure. An advantage of all embodiments disclosed herein is that the blood filter will capture emboli which may result from the incision through which the blood filter is inserted. Another advantage is that both the balloon occluder and the filter means enter the vessel through the same incision created for the blood cannula, and therefore the devices and methods herein economize on incisions made in the blood vessel, often the aorta.
In addition, use of visualization techniques is also contemplated in order to determine which patients require filtration (identify risk factors), where to effectively position a blood filter device to maximize effectiveness, when to adjust the device if adjustment is necessary, when to actuate the device and appropriate regions for performing any procedures required on a patient's blood vessel.
In accordance with one aspect of the invention, a visualization technique, such as TCD, is used to determine when to actuate a blood filter device. For example, during cardiac bypass surgery, flurries of emboli are detected during aortic cannulation, inception, and termination of bypass and cross-clamping of the aorta. Therefore, a mesh may be opened within a vessel downstream of the aorta during these procedures and closed when embolization resulting from these procedures has ceased. Closing the mesh when filtration is not required helps to minimize obstruction of the blood flow.
According to another embodiment, a visualization technique is used to monitor emboli entering cerebral circulation to evaluate the effectiveness of a blood filter device in trapping emboli. Also, a visualization technique is useful to positioning a device within a vessel so that it operates at optimum efficiency. For example, a user may adjust the position of the device if TCD monitoring indicates emboli are freely entering the cerebral circulation. In addition, a user may adjust a mesh of a blood filter device to ensure that substantially all of the blood flowing in the vessel passes through the mesh.
According to yet another embodiment, a visualization technique, such as intravascular ultrasonography, TEE, and epicardial aortic ultrasonography, is used to identify those patients requiring blood filtration according to the present invention. For example, these visualization techniques may be used to identify patients who are likely to experience embolization due to the presence of mobile plaque. These techniques may be used before the patient undergoes any type of procedure which will affect a blood vessel in which mobile plaque is located.
Additionally, visualization techniques may be used to select appropriate sites on a blood vessel to perform certain procedures to eliminate or reduce the occurrence of embolization. For example, during cardiac bypass surgery, the aorta is both clamped and cannulated. According to methods disclosed herein, the step of clamping may be replaced by deployment of a balloon occluder. These procedures frequently dislodge atheromatous material already present on the walls of the aorta. To minimize the amount of atheromatous material dislodged, a user may clamp or cannulate a section of the aorta which contains the least amount of atheromatous material, as identified by TEE, epicardial aortic ultrasonography or other visualization technique such as intravascular ultrasonography.
Procedures other than incising and clamping also tend to dislodge atheromatous material from the walls of vessels. These procedures include, but are not limited to, dilatation, angioplasty, and atherectomy.
Visualization techniques also may be used to select appropriate sites for filtering blood. Once atheromatous material is located within a vessel, a blood filter device may be placed downstream of that location.
Visualization techniques, other than those already mentioned, as are known to those skilled in the art, are also useful in ascertaining the contours of a blood vessel affected by surgical procedure to assess a variety of risk of embolization factors, and to locate appropriate sections of a vessel for performing certain procedures. Any suitable visualization device may be used to evaluate the efficacy of a device, such as those disclosed herein, in trapping emboli.
In one embodiment, a balloon aortic cannula with associated filter is provided as depicted in
Blood supply cannula 10 may have certain features in common with a standard arterial cannula and is generally a substantially cylindrical, semi-rigid, and preferably transparent tube. The blood cannula is slidable within the pressurizing cannula, and the blood cannula will typically include a fitting or molded joint at its proximal end (not shown) which is adapted for coupling to a bypass-oxygenator system, and may have any of the features disclosed in U.S. application Ser. Nos. 08/553,137, 08/580,223, and 08/584,759. Blood cannula 10 is adapted to carry blood to the aorta from the bypass-oxygenator system.
With reference to
Inflation seal 70 may be constructed from elastomeric or non-elastomeric tubular material which encloses a donut-shaped chamber. When deployed, the inflation seal will expand to a diameter which fits tightly against the lumen of aorta 99. The inflation seal will thus be capable of expansion to an outer diameter of at least 1 cm, more preferably at least 1.5 cm, more preferably at least 2 cm, more preferably at least 2.5 cm, more preferably at least 3 cm, more preferably at least 3.5 cm, more preferably at least 4 cm, more preferably at least 4.5 cm, more preferably at least 5 cm, more preferably at least 5.5 cm, more preferably at least 6 cm. These ranges cover suitable diameters for both pediatric use and adult use. The inflation seal is typically a continuous ring of very thin tubing attached on one side to the filter mesh and on the other side to the pressurizing cannula by holding strings.
The inflation seal should be able to maintain an internal pressure in chamber 319, without bursting, of greater than 55 mm Hg, more preferably greater than 60 mm Hg, more preferably greater than 70 mm Hg, more preferably greater than 80 min Hg, more preferably greater than 90 mm Hg, more preferably greater than 100 mm Hg, more preferably greater than 110 mm Hg, more preferably greater than 120 mm Hg, more preferably greater than 130 mm Hg, more preferably greater than 140 mm Hg, more preferably greater than 150 mm Hg. The internal pressure needed will depend on the pressure maintained in the aorta against the mesh. Thus, if the aortic pressure is 55 mm Hg, then the pressure in the inflation seal must be greater than 55 mm Hg to prevent leakage around the seal. Typically, the aortic pressure will be at least 75 mm Hg because this level of pressure is needed to ensure adequate brain perfusion. It will be recognized that such inflation seal pressures are much higher than the maximum level that can be used in the pulmonary venous system because the veins and arteries therein will typically hold no more than about 40-50 mm Hg, or at most 60 mm Hg without rupture.
Chamber 71 is in fluid communication with a first tubular passage 56 and a second tubular passage 57 which permit chamber 71 to be inflated with gas, or preferably a fluid such as saline. Passage 57 is in fluid communication with a third lumen of pressurizing cannula 50 (not shown), while passage 56 is ill fluid communication with a fourth lumen of pressurizing cannula 50 (not shown). Passages 56 and 57 thereby interconnect chamber 71 with the third and fourth lumens, respectively, of pressurizing cannula 50.
In certain embodiments, inflation seal 70 will include a septum (not shown) which blocks the movement of fluid in one direction around chamber 71. If the septum is positioned in close proximity to the fluid entry port, then the injection of fluid will push all gas in chamber 71 around inflation seal 70 and out through passage 56. In one embodiment, the entry port and the exit port are positioned in close proximity, with the septum disposed between the entry and exit port. In this case, injection of fluid will force virtually all gas out of inflation seal 70.
Filter mesh 75 is bonded at its proximal end to inflation seal 70 and at its distal end to blood cannula 10. Mesh 75 can be made of a material which is reinforced or non-reinforced. Mesh 75, when expanded as shown in
Much like the inflation seal, the balloon occluder 65 may be constructed from elastomeric or non-elastomeric material and, with reference to
With reference to
In certain embodiments, the pressurizing cannula 50 will be provided with an additional lumen (not shown) in fluid communication with balloon occluder 65. A system having two lumens in communication with balloon occluder 65 can be used to enter saline into the balloon occluder and purge all gas therefrom to prevent the formation of an air embolism in a patient's circulation should the balloon occluder rupture during use. Thus, if pressurized saline is advanced through lumen 60, the gas present in balloon occluder 65 will be forced out through the additional lumen in communication with the balloon occluder. A septum may be included in the balloon occluder and disposed between entry and exit ports to ensure that all gas is purged on entry of saline.
It will also be understood for this cannula apparatus that blood flow to the patient is maintained by blood passage through blood cannula 10, and not through mesh 75. Thus, the cannula must have an inner diameter which allows blood throughput at a mean flow rate of at least 3.0 L/min., more preferably 3.5 L/min., more preferably 4 L/min., more preferably at least 4.5 L/min., more preferably at least 5 L/min., and more. Of course, flow rate call vary intermittently down to as low as 0.5 L/min. Therefore, the inner diameter of blood supply cannula 10 will typically be at least 9 F (3.0 mm), more preferably 10 F, more preferably 11 F, more preferably 12 F (4 mm), more preferably 13 F, more preferably 14 F, more preferably 15 F (5 mm), and greater. Depending on the inner diameter and thickness of the tubing, the outer diameter of blood cannula 10 is approximately 8 mm. Meanwhile, the pressurizing cannula 50 may have an outer diameter of approximately 10.5 mm. The foregoing ranges are intended only to illustrate typical device parameters and dimensions, and the actual parameters may obviously vary outside the stated ranges and numbers without departing from the basic principles disclosed herein.
In use, the balloon aortic cannula with associated filter is provided, and saline is injected into both the balloon occluder and the inflation seal until saline exits from the exit ports and exit lumens, thereby purging substantially all gas from the inflation seal, the balloon occluder, and dual lumen systems associated with each. Cardiac surgery can then be conducted in accordance with procedures which employ standard cannula insertion, as discussed more fully herein. The mesh 75, inflation seal 70, and balloon occluder 65 are maintained in a deflated, fully contracted condition about the pressurizing cannula and/or blood cannula. The cannula is introduced into the aorta, preferably the ascending aorta, of a patient through an incision, and the incision may be tightened about the cannula by use of a “purse string” suture. Cardiopulmonary bypass occurs through blood cannula 10.
With the cannula in place, the filter is ready for deployment. The filtration means are first exposed by removing a handle or enclosure which may cover the expansion means and mesh. Then, saline or gas is advanced under pressure through lumen 57 to expand the inflation seal. The inflation seal expands to ensure contact with the inside of the aorta at all points along the circumference of the lumen, as depicted in
The balloon occluder 65 is then deployed to occlude the aorta upstream of the filter. Saline or gas is advanced under pressure through lumen 60 to expand the balloon occluder, as shown in
At the end of the cardiac surgery, the balloon occluder is depressurized, and any embolic material dislodged by this step is captured by the filter. The filter is then depressurized and removed from the ascending aorta. The syringe lock is released and saline is withdrawn from the balloon occluder, and then from the inflation seal. This will cause both the balloon occluder and inflation seal to contract to a deflated condition with minimum cross-sectional diameter, as the device was configured before deployment. Notably, embolic material collected in the filter is trapped under the contracted filter. Once the inflation seal, associated filter, and balloon occluder have been deflated, the cannula can be removed from the patient without damaging the aortic incision by using standard procedures.
The devices disclosed herein may optionally include a handle adapted to cover and enclose the inflation seal, mesh, and balloon occluder. Moreover, before deployment, the inflation system for either the balloon occluder, inflation seal, or both, may be carried by either the pressurizing cannula or the blood cannula. In certain embodiments, the blood cannula and pressurizing cannula will be integrally combined into a single unitary component, or the pressurizing cannula is eliminated and the inflation system may be carried either within or on the outside of the blood cannula.
In another embodiment, a balloon aortic cannula is provided as depicted in
Upon inflation, balloon occluder 65 assumes a shape as depicted in FIGS. 5 or 6. With reference to
It will be understood that the balloon occluders as disclosed herein and depicted on balloon aortic cannulas may be used in combination with any of a number of arterial cannulas having associated filtration means as previously disclosed. Thus, the balloon occluders disclosed herein can be used in combination with any of the arterial cannulas disclosed in Barbut et al., U.S. application Ser. No. 08/584,759, filed Jan. 9, 1996, Barbut et al., U.S. application Ser. No. 08/580,223, filed Dec. 28, 1995, Barbut et al., U.S. application Ser. No. 08/553,137, filed Nov. 7, 1995, Barbut et al., U.S. application Ser. No. 08/640,015, filed Apr. 30, 1996, Barbut et al., U.S. Application Serial No. [attorney docket no. 224/194], filed Apr. 16, 1997, and Maahs et al., U.S. Application Serial No. [attorney docket no. 225/108], filed May 8, 1997, and any of the features disclosed in these applications can be used on the balloon aortic cannulas described herein. Accordingly, the entire disclosures of these prior applications are incorporated herein by reference, and it is noted that the devices, methods, and procedures disclosed in these applications can be used in combination with the balloon occluder and balloon aortic cannula disclosed herein.
In another embodiment, a cannula is provided as depicted in
In anther embodiment, a balloon aortic cannula is provided as depicted in
Blood supply cannula 350 may have certain features in common with a standard cannula, and is generally a substantially cylindrical, semi-rigid, and preferably transparent tube which includes a rib 351 disposed about the circumference at a distal region thereof. The blood cannula is slidable within the pressurizing cannula, and in the proximal region, the blood cannula 350 may be angled to adopt a shape which does not interfere with syringe 307. Moreover, the blood cannula will typically include a fitting or molded joint 352 which is adapted for coupling to a bypass-oxygenator system. Blood cannula 350 is adapted to carry blood to the aorta from the bypass-oxygenator system.
The pressurizing cannula may also include an inserting and retracting handle 380 comprising a substantially cylindrical tube disposed about the intermediate region of pressurizing cannula 300. Handle 380 will generally include a rigid or semi-rigid, preferably transparent tube with molded hand grip to facilitate holding and inserting. With reference to
Handle 380 may also include an enlarged end region 384 which encloses the blood filtration assembly 315 as described in Barbut et al., U.S. application Ser. No. 08/640,015, filed Apr. 30, 1996. This housing enclosure 384 is a particularly preferred component because it prevents inadvertent deployment of the blood filtration assembly and balloon occluder, and it provides a smooth outer surface to the cannula which facilitates entry through an incision in the aorta without tearing the aorta. In the absence of such housing enclosure, the balloon and filter are liable to scrape against the inner wall of a vessel, and thereby damage or rupture the vessel. At its distal end, handle 380 may include inverted cuff 385 which bears against rib 351 of blood cannula 350 to form a seal when the filtration assembly 315 is enclosed by handle 380.
The distal region of pressurizing cannula 300 is shown with blood filtration assembly 315 deployed in the ascending aorta 399 of a human. Handle 380 has been moved proximally to expose filter assembly 315. The distal region of pressurizing cannula 300 includes a plurality of holding strings 316 made from Dacron® or other suitable material. Holding strings 316 connect the distal region of the pressurizing cannula 300 to inflation seal 317 as described above. The inflation seal is attached to filter mesh 318 on its outer side. Filter mesh 318 is bonded at is distal end around the circumference of blood cannula 350 preferably at a cross-sectional position which closely abuts rib 351.
Chamber 319 is in fluid communication with a first tubular passage 320 and a second tubular passage 322 which permit chamber 319 to be inflated with gas, or preferably a fluid such as saline. Passage 320 is in fluid communication with second lumen 312 of pressurizing cannula 300, while passage 322 is in fluid communication with third lumen 314 of pressurizing cannula 300. Passages 320 and 322 thereby interconnect chamber 319 with the second and third lumen 312 and 314, respectively, of pressurizing cannula 300.
In certain embodiments, inflation seal 317 will include a septum 321 which blocks the movement of fluid in one direction around chamber 319. If septum 321 is positioned in close proximity to the fluid entry port, then the injection of fluid will push all gas in chamber 319 around inflation seal 317 and out through passage 322, as described above. In one embodiment, the entry port and the exit port are positioned in close proximity with septum 321 disposed between the entry and exit port. In this case, injection of fluid will force virtually all gas out of inflation seal 317.
With reference to
In yet another embodiment, a balloon aortic cannula is provided as depicted in
Umbrella frame 430 comprises a plurality of arms 432 (some of which are not shown), which may include 3 arms, more preferably 4 arms, more preferably 5 arms, more preferably 6 arms, more preferably 7 arms, more preferably 8 arms, more preferably 9 arms, and most preferably 10 arms. Socket 434 may be connected to insertion tube 420 by welding, epoxy, sonic welding, or adhesive bonding. A further detailed description of the construction of filtration assembly 410 can be found with reference to Barbut et al., U.S. application Ser. No. 08/584,759, filed Jan. 9, 1996, and other references cited herein.
End plate 460 comprises a one-piece injection molded component, made of plastic or metal. Arms 432 are bonded to end plate 460 at arm junctures 461 spaced at equal increments along a circumference of a circle. Activation tube 450 extends from end plate 460 through insertion tube 420 to adjustment device 470 housed in handle 480 as shown in
With reference to
In another embodiment, an arterial balloon catheter is provided as depicted in
In another embodiment, an arterial balloon cannula with associated filter and distal flow diffuser is provided as depicted in
As shown in
In another embodiment, an arterial balloon cannula with filtration means is provided as depicted in
The intra-cannula flow diffusers of
In another embodiment, an arterial balloon cannula is provided as in
In another embodiment, an arterial balloon cannula is provided as in
Although cannulas have been selected for purposes of example, the inventions of
It is to be understood that flow diffusers such as those of
In an alternative embodiment, shown in
As shown in
In contrast, roll-up control lines 902a and 902b are attached to the cannula at points 918 and 920, respectively. Both points 918 and 920 are located on arc 910. When the sleeve is rolled-up, as shown in
When the sleeve is in the unrolled state, the roll-up control lines 902a and 902b run from points 918 and 920 respectively, along the underside of the sleeve 908, around the proximal end of the sleeve, and then distally along the outer side of the sleeve before entering the control lumens 922 and 924 at points 926 and 928 respectively. After entering at points 926 and 928, the roll-up control lines 902a and 902b travel through the control lumens until exiting the control lumens at points (not shown) located at the proximal region of the cannula. When the sleeve is in the unrolled position as shown in
In another embodiment of an arterial balloon cannula, shown in
In another embodiment of an arterial balloon cannula, with associated filter shown in
In this embodiment, the filter 908 is fixed to the outer diameter of the unexpanded elastic cannula by tether lines 954 and 956 such that, when the stylet is introduced, cannula expansion causes the tether lines to go taut, which in turn contours the filter to the cannula. Consequently, as shown in
In another embodiment shown in
In another embodiment shown is
In another embodiment shown in
It is to be understood that the cannula devices of
In another embodiment of an arterial balloon cannula, as shown in
In another embodiment of an arterial balloon cannula, as shown in
In an arterial balloon catheter embodiment, as shown in
In another embodiment, a device for occluding arterial vessels is provided by a cannula having a dam or other impermeable structure as shown in
A balloon occluder on a catheter in accordance with another embodiment is depicted in
A cannula with a self-inflating balloon is shown in
An adhesive coated balloon cannula is shown in
An expandable wire occluder is shown in
A cannula introducer is shown in
An integrated occlusion cape cannula is shown in
The use of a balloon occluder catheter in conjunction with a cardioplegic catheter is depicted in
An aortic occluder with modular design is shown in
Human anatomy including the rib cage with deployed occluder is depicted in
A single-piece occluder is shown in
An alternate design for a single-piece occluder is depicted in
A multiple component port access aortic occluder is depicted in
An aortic balloon cannula is depicted in
In use, the arterial balloon catheter is deployed through the femoral artery while maintaining peripheral cardiopulmonary bypass as described in Peters, U.S. Pat. No. 5,433,700, Machold et al., U.S. Pat. No. 5,458,574, Stevens, International Application No. PCT/US93/12323, and Steven et al., International Application No. PCT/US94/12986. Thus, the catheters of
As a purely illustrative example of one of the methods of filtering blood as disclosed herein, the method will be described in the context of cardiac bypass surgery as described in Manual of Cardiac Surgery, 2d. Ed, by Bradley J. Harlan, Albert Sparr, Frederick Harwin, which is incorporated herein by reference in its entirety.
A preferred method of the present invention may be used to protect a patient from embolization during cardiac surgery, particularly cardiac bypass surgery. This method includes the following steps: introducing a mesh into an aorta of the patient; positioning the mesh to cover substantially all of the cross-sectional area of the aorta so that the mesh may capture embolic matter or foreign matter in the blood; adjusting the mesh to maintain its position covering substantially all of the cross-sectional area of the aorta; and removing the mesh and the captured foreign matter from the aorta. A variant comprises placing a cylindric mesh at the level of the take off of the cerebral vessel to divert emboli otherwise destined for the brain to other parts of the body.
During the cardiac surgery, the aorta is either clamped a number of times or occluded with a balloon occluder as disclosed herein. Because balloon occlusion and/or clamping the aorta dislodges atheromatous material from the walls of the aorta, which is released into the bloodstream, the mesh must be positioned within the aorta before clamping or balloon occlusion begins. Atheromatous material also accumulates behind the balloon occluder and/or clamps during the surgery and, because removal of the clamps and/or deflation of the balloon occluder releases this material into the bloodstream, the mesh must be maintained within the blood stream for about four to ten minutes after deflation of the occluder and/or removal of the clamps. Because the aorta is often a source of much of the atheromatous material that is eventually released into the bloodstream, it is preferable to place the mesh in the aorta between the heart and the carotid arteries. This placement ensures that foreign matter will be captured before it can reach the brain.
For illustration purposes, the method for balloon occlusion and filtering blood will be described in connection with the device depicted in
Saline is introduced into the inflation seal 70 through the actuation assembly (not shown) from an extracorporeal reservoir, and the inflation seal gradually assumes an open position in which the balloon 70 is inflated in a donut-shape and the mesh 75 is opened to cover substantially all of the cross-sectional area of the vessel. In the opened position, the mesh is ready to capture foreign matter in the blood flow. By adjusting the amount of saline introduced into the balloon 70, the surgeon may control the amount of inflation and consequently the degree to which the mesh 75 is opened. Saline is then introduced into balloon occluder 65 under pressure through lumen 60, and from an extracorporeal reservoir, and the balloon occluder gradually assumes an open position (see
It will be understood that balloon occlusion is used to block the flow of blood back into the heart. Balloon occlusion may dislodge atheromatous material from the walls of the aorta and releases it into the blood flow. Because balloon occlusion is performed upstream from the filter 75, the atheromatous material will be filtered from the blood by mesh 75. While the aorta is occluded, the surgeon grafts one end of a vein removed from the patient's leg on to the coronary artery. In another embodiment, arterial grafting, such as internal mammary artery grafting, may be employed. After the surgeon checks the blood flow to make sure there is no leakage, the balloon occluder is deflated. Atheromatous material accumulates behind the balloon occluder and, when it is deflated, this material is released into the blood flow, which will be filtered by mesh 75. The flow rate from the bypass machine is kept low to minimize embolization, and the heart is made to beat again.
During surgery, the position of the mesh may require adjustment to maintain its coverage of substantially all of the cross-sectional area of the aorta. To accomplish this, the surgeon occasionally palpates the outside of the aorta gently in order to adjust cannula 10 so that the mesh 75 covers substantially all of the cross-sectional area of the aorta. The surgeon may also adjust the location of cannula 10 within the aorta.
The balloon aortic cannula may also be used in conjunction with TCD visualization techniques. Through this technique, the surgeon may actuate the inflation seal and mesh only when the surgeon expects a flurry of emboli such as during aortic cannulation, inception, and termination of bypass, balloon occlusion, deflation of an occlusive balloon, aortic clamping, and clamp release.
The surgeon then occludes and/or clamps the aorta longitudinally to partially close the aorta, again releasing the atheromatous material to be filtered by the mesh. Holes are punched into the closed off portion of the aorta, and the other end of the vein graft is sewn onto the aorta where the holes have been punched. The balloon occluder is deflated and/or the aortic clamps are removed, again releasing accumulated atheromatous material to be filtered from the blood by the mesh. The surgeon checks the blood flow to make sure there is no leakage. The heart resumes all the pumping, and the bypass machine is turned off, marking the end of the procedure.
The saline is then removed from the balloon occluder and the inflation seal via the actuation assembly, deflating the balloon occluder, inflation seal, and closing the mesh around the captured emboli. Finally, the balloon aortic cannula, along with the captured emboli, are removed from the body. Because the balloon aortic cannula is in place throughout the procedure, any material released during the procedure will be captured by mesh 75.
When the balloon arterial cannula is used in conjunction with other invasive procedures, the dimensions of the device should be adjusted to fit the vessel affected. An appropriate mesh also should be chosen for blood flow in that vessel. In use, the device may be positioned so that it is placed downstream of the portion of the vessel that is affected during the procedure, by occlusion and/or clamping or other step in the procedure. For example, in order to capture emboli material in a leg artery, the cone-shaped filter can be placed such that the cone points toward the foot.
An advantage of the devices and methods of the present invention and the methods for filtering blood described herein is that it is possible to capture foreign matter resulting from the incisions through which the devices are inserted. Another advantage of the devices of the present invention is that the flexibility of the inflatable balloon allows it to conform to possible irregularities in the wall of a vessel.
While particular devices and methods have been described for filtering blood, once this description is known, it will be apparent to those of ordinary skill in the art that other embodiments and alternative steps are also possible without departing from the spirit and scope of the invention. Moreover, it will be apparent that certain features of each embodiment, as well as features disclosed in each reference incorporated herein, can be used in combination with devices illustrated in other embodiments. Accordingly, the above description should be construed as illustrative, and not in a limiting sense, the scope of the invention being defined by the following claims.
1. A balloon cannula comprising:
- a filtration assembly; and
- an cannula with a collapsible section configured to accommodate the filtration assembly.
2. A balloon cannula of claim 1, wherein the cannula includes an elongate member with a tubular wall, said collapsible section including a portion of the tubular wall that is inwardly collapsible toward an axis of the elongate tubular wall member.
3. A balloon cannula of claim 2, wherein the collapsible section is comprised of an elastomeric material.
4. A balloon cannula of claim 3, wherein the collapsible section includes a balloon.
5. A balloon cannula of claim 4, wherein the collapsible section includes a double-walled balloon.
6. A balloon cannula of claim 2, wherein the collapsible section is comprised of a flexible memory material.
7. A balloon cannula of claim 2, wherein the filtration assembly includes a filter and the collapsible section is configured to collapse inwardly a sufficient amount to allow the filter, in a collapsed condition, to have a diameter smaller than an adjacent, non-collapsible portion of the tubular wall.
8. A balloon cannula of claim 7, wherein the filtration assembly includes a filter seal and wherein collapsible section is configured to collapse inwardly a sufficient amount to allow the filtration assembly, in a collapsed condition, to have a diameter smaller than an adjacent, non-collapsible portion of the tubular wall
9. A balloon cannula of claim 8, wherein the collapsible section begins just proximal to the filter seal when the filter is in a collapsed state.
10. A balloon cannula of claim 9, wherein the collapsible section has a length at least equal to the filter and filter seal.
11. A balloon cannula of claim 10, wherein the length of the collapsible section extends to a distal tip of the cannula.
12. A balloon cannula of claim 1, wherein the collapsible section is comprised of a flexible memory material.
13. A balloon cannula of claim 12, wherein the collapsible section is configured to return to a non-collapsed state when the filter assembly is expanded.
14. A balloon cannula of claim 13, wherein the collapsible section is configured to expand when pressurized blood flow occurs in the cannula.
15. A method of preparing a filtration assembly and cannula for insertion into a patient, the method comprising:
- collapsing a section of the cannula; and
- collapsing a filtration assembly against an outer wall of the collapsed section of the cannula.
16. A method of claim 15, further comprising expanding the filtration assembly and expanding the collapsed section of the cannula by flowing blood therethrough.
Filed: Nov 16, 2007
Publication Date: Mar 13, 2008
Inventors: Denise Barbut (New York, NY), Jonathan Root (San Francisco, CA), Giovanni Pastrone (Los Gatos, CA), Tracy Maahs (Redwood City, CA), Ross Tsugita (Mountain View, CA)
Application Number: 11/941,872
International Classification: A61M 25/10 (20060101);