Abstract: A demand pacemaker which regulates its pacing rate based upon sensed oxygen saturation percentage. The pacemaker employs a two wavelength reflectance oximeter as a sensor. The sensor includes an oscillator which sequentially activates red and infrared diodes. The duty cycle of the oscillator is regulated by the relative amounts of red and infrared light reflected by the blood. The construction of the sensor allows the sensor to operate with only two conductors, optimizing it for incorporation in a standard, bipolar pacing lead.

Abstract: Apparatus and method for sensing the probable onset of ventricular fibrillation or other harmful tachyarrythmias and delivering electrical cardioverting stimulation pulses in response thereto. The sensing of the onset of the harmful tachyarrhythmia is accomplished using two different types of sensors. The first sensing technique utilizes an intracardiac ECG observed within three dimensional space. Directional changes of the current vector within the intracardiac ECG are used to predict the onset of harmful ventricular tachyarrhythmias. The second sensing technique employs a chemically sensitive semiconductor device which measures the level of ionic potassium found within the intracardiac blood. Rapid changes in ionic potassium level are used to predict the onset of detrimental ventricular tachyarrhythmias. An implantable device uses both types of sensors in a programmable fashion to deliver cardioverting electrical stimulation pulses based upon the predicted onset of ventricular fibrillation.

Abstract: Improved methods of ionophoretic drug delivery are described. By the intentional selection of drug(s) with specific characteristics, of ionotophoresis device, components or both permits the efficiency of drug delivery is increased.

Abstract: Improved iontophoresis drug delivery apparatus or device wherein one or more electrochemically active components are employed or "sacrificed" so as to minimize the hydrolysis of water during drug delivery. Efficiency of drug delivery is increased and pH changes in the device or adjacent the patient's skin are minimized.

Abstract: A method and apparatus for providing muscle stimulation in the field of Function Electrical Stimulation, particularly electrical stimulation to a muscle employed as a myocardial substitute. The Latissimus Dorsi muscular flap is divided into two parts to cover the surfaces of the heart and inserted into a thoracic cavity by means of a segmental resection of the second rib. After or before positioning the muscle in this fashion, first and second stimulating electrodes are threaded into the muscle at desired locations to effect contraction of the muscle around the heart upon application of electrical stimulating pulses between the two electrodes. Stimulating pulses having suitable parameters chosen to effect the desired functional contraction of the muscle are generated in synchrony with natural or stimulated heart contractions.

Abstract: An enclosure for electronics, particularly adapted for implantation in the human body. The enclosure is provided with at least one transparent wall allowing it to be used in applications requiring light emission or light detection such as reflectance oximeters. The mechanical elements of the enclosure are particularly adapted to facilitate the use of welding to provide a hermetic seal for the enclosure.

Abstract: Ventricular fibrillation and other tachyarrhythmias are controlled by delivery of two sequential impulses to two pairs of electrodes placed partially within or adjacent to the heart. One electrode pair is provided by an endocardial lead which includes a distal electrode adapted to reside in the apex of the right ventricle and a proximal electrode designed to lie in the superior vena cava. The second electrode pair comprises the distal electrode within the right ventricle and a further electrode lodged in or adjacent to the coronary sinus. The metal case of the implantable pulse generator which supplies pulses to the electrode pairs may be substituted for the coronary sinus electrode if the pulse generator is implanted above and to the left of the heart in the left pectoral region of the patient's body. Alternatively, a subcutaneous plate electrode may be substituted for the can, obviating the need for implanting the generator in the left pectoral region.

Abstract: A multiple wavelength light source and a method of constructing a multiple wavelength light source. The light source includes a plurality of light emitting diodes mounted to a substrate, located closely adjacent to one another. A single optical fiber is mounted to the substrate, appropriately positioned to provide a desired ratio of wavelengths at a desired amplitude.

Abstract: An iontophoresis device including a control module and a disposable electrode module. The control module includes a flexible printed circuit board carrying the battery and other electrical components. The control module is so configured that by trimming it along one of several labeled lines, various current levels may be selected. Trimming the control module provides a simple method for varying the dosage of the drug delivered by the iontophoresis device and simultaneously provides an easily readable visual indicator of the dosage level.

Abstract: A visual (as opposed to mechanical or electronic) method for detecting the state of dehydration (or hydration) of a biomedical hydrogel is disclosed. The method contemplates incorporating a pH sensitive indicator into the hydrogel as it is prepared and applying the hydrogel to the skin-contacting surface of a biomedical device such as an electrode. Shortly before the biomedical device is to be used, the color of the hydrogel on the device is visually compared with its freshly-prepared color to determine the approximate state of dehydration of the gel.

Abstract: A method of controlling cardiac ventricular fibrillation and other tachyarrhythmias. A catheter carrying a first and second electrode is located in the right ventricle such that the first electrode is located in the right ventricle and the second electrode is located in the superior vena cava. A third electrode is located either at the chest wall or at the abdominal cavity. The third electrode can be implanted subcutaneously in the left chest wall. It can also be located in the abdomen immediately beneath the diaphragm. It could also be implanted in the epigastric area overlying the superficial abdominal muscles and underneath the skin and fat. The second and third electrodes are sequentially paired and pulsed with the first electrode to control ventricular fibrillation and other tachyarrhythmias.

Abstract: A simplified gas sensor which includes a pH sensitive transducer having a gate-insulated field effect transistor (FET) structure. The gas sensor is particularly adapted to detect carbon dioxide in fluids.

Abstract: A defibrillator/pacer having separate energy storage circuits for pacing and defibrillating. The pacing energy storage is charged from residual energy from the defibrillator source to permit high energy pacing after defibrillation. In operation, energy is transferred from the defibrillation energy storage source to the pacing energy storage source which is utilized to provide energy for pacing the heart after defibrillation.

Abstract: An implantable drug administration device can be non-invasively programmed to change both the dosage amount and the dosage interval. Verification of received dosage and interval commands is being achieved by means of an audio transducer which is attached to the device case. Application of a magnet or a programmer to the device inhibits drug delivery.

Abstract: A "tissue valve type" heart valve prosthesis is disclosed which has a biocompatible plastic sewing ring adapted to be surgically implanted into the mitral, aortic or tricuspid annulus of the human heart. The sewing ring has internal square threads and a biocompatible fabric mesh or cloth is embedded into the sewing ring so that the cloth can be fully wrapped around the sewing ring covering all of its plastic surfaces except for the internally protruding threads. A biocompatible plastic stent support ring has externally disposed threads to lock with the threads of the sewing ring in approximately one turn, or less. The stent support ring also embeds a biocompatible fabric mesh which can be wrapped around the stent support ring to cover all of its plastic surfaces, except for the protruding threads, and to form a cloth pocket wherein a solid stent is mounted. A porcine trileaflet valve is mounted to the stent.

Abstract: A monitor designed to aid in the instruction of electric arc welding. The device is electrically isolated from the welder arc voltage by an optical coupling device which provides an isolated output signal linearly proportional to either arc voltage or arc current. Audio alarms are triggered when the arc voltage is either too high or too low indicating arc lengths that are too low indicating arc lengths that are too long or too short to provide acceptable weld quality. A self test switch is included to demonstrate the upper and lower voltage alarm operation.

Abstract: A sense amplifier for a cardiac pacemaker which has an amplifier section with two feedback paths. One path contains small valued capacitors and clock activated switches to form a discrete time feedback path. The other path contains unclocked passive components to form a continuous time feedback path. The sense amplifier generates a detect signal in response to a depolarization of cardiac tissue.

Abstract: An improved telemetry transmission system for transmitting electrocardiographic information, indications of the occurrence of the pacing pulse and for transmitting digitially encoded information from an implanted pacemaker, an implanted drug dispensing device, or other implanted device, to a remote receiver. Digital data transmitted by the implanted system may include all programmed parameters as well as power source status and self test indications, or other programmed digital data such as the device serial number and lot number.

Abstract: An atrial-ventricular demand pacemaker having improved atrial pulse artifact rejection includes a blanking circuit (30, 100) connected in the signal path from the ventricular output terminal (17) to the sensing amplifier (21) to blank the signal during an atrial pulse. A holding circuit including a low-pass filter (46, 137) and a switching element (43, 112) stores a prior signal value at the sensing amplifier input during the blanking interval, and delays return to normal operation until after the blanking circuit has returned to normal. Artifact rejection is also improved by limiting atrial pulse output circuit recharge time and by limiting polarization current driven into the ventricular output circuitry by an atrial output pulse.

Abstract: An epicardial pacing lead for the delivery of stimulation energy to and the sensing of electrical signals from the myocardium of a human heart. The lead includes an electrode which penetrates the myocardium and serves to anchor the lead to the heart. The lead contains a drug for delivery through the electrode, to the myocardium. The electrode is provided with a bore for passage of the drug to the stimulation and fixation site.