Abstract: A method of determining a defibrillation threshold for an implantable cardiac defibrillator, based upon determining the 50% probability of reaching the upper limit of vulnerability. The 50% probability of reaching the upper limit of vulnerability at the mid-upslope of the T-wave is found to closely approximate the 50% probability of successful defibrillation used to set the shock energy level of the defibrillator. A delayed up-down algorithm is used to determine the shock strength associated with 50% probability of reaching the upper limit of vulnerability.

Abstract: A method and apparatus for cardioverter/pacemaking utilizing neurosensing. The invention utilizes the baroreceptor nerves found in the body. A neurosense electrode is placed around the carotid sinus nerve and a sense amplifier with automatic gain control and an integral band pass filter provides a frequency-to-voltage converter with a frequency proportional to the stimulus received from the carotid sinus nerve. The voltage from the frequency-to-voltage converter is sent to the analog-to-digital converter where it is bussed to a microprocessor. The microprocessor then drives a pacing lead and in the presence of a cardiac signal the microprocessor provides a cardioverting signal to the cardioverting lead if ventricular arrhythmia is sensed. The microprocessor also drives a telemetry coil and receives ventricular information from the ventricular sensing lead.

Abstract: An implantable cardiac electrode for use in defibrillation. The electrode comprises a plurality of layers of porous conductive screens and backed by an insulation layer. When implanted on or about the heart surface, body fluids can flow through the screens thus increasing the effective surface area of contact. Each individual layer of mesh can be microscopically textured to create indentations on the layer for further increasing the surface area of each screen, and thus, the surface area of body fluid contact. Also disclosed is an electrode without an insulative backing facing away from the heart.

Abstract: A method of treating hemodynamic disfunction by simultaneously pacing both ventricles of a heart. At least one ECG amplifier is arranged to separately detect contraction of each ventricle and a stimulator is then activated for issuing stimulating pulses to both ventricles in a manner to assure simultaneous contraction of both ventricles, thereby to assure hemodynamic efficiency. A first ventricle is stimulated simultaneously with contraction of a second ventricle when the first fails to properly contract. Further, both ventricles are stimulated after lapse of a predetermined A-V escape interval. One of a pair of electrodes, connected in series, is placed through the superior vena cava into the right ventricle and a second is placed in the coronary sinus about the left ventricle. Each electrode performs both pacing and sensing functions. The pacer is particularly suitable for treating bundle branch blocks or slow conduction in a portion of the ventricles.

Abstract: An implantable cardiac electrode for use in defibrillation and methods of implanting same. The electrode has a metallic mesh electrode surface surrounded by an insulating material. At the proximal end of the electrode there is defined a fin area designed to facilitate placing and securing the electrode proximate the heart. The electrode may be implanted without major surgery in a number of ways, one of which requires a specialized insertion tool which cooperates with a pocket formed in the electrode.

Abstract: An externally controlled implantable electronic device for delivering a cardioverting pulse of energy to an ailing heart. A defibrillator produces a first signal when its storage device is fully charged and ready to be discharged, and a second signal when a predetermined characteristic of an ECG signal is detected. An actuator is provided for determining the presence of both of these signals. If during a predetermined time period, there is a simultaneous occurrence of the first and second signals, then the defibrillator will be activated to deliver the cardioverting shock to the heart. In the absence of either of the two signals, the defibrillator will not deliver a shock.

Abstract: The present invention relates to a method and apparatus for delivering two or more individual low-level pulses to correct certain cardiac arrhythmias such as high-rate ventricular tachycardia and ventricular fibrillation; at least the latter shocks are delivered in synchronism with a repeatable characteristic of the heart's electrical activity. Basically, the apparatus comprises an electrode sensor placed in the right ventricle of the heart or in the coronary sinus to act as a detector for the electrical activity of the heart. Connected to the electrode sensor is an arrhythmia detector chosen to detect such arrhythmias as ventricular tachycardia and ventricular fibrillation. Upon detection of one of these arrhythmias, the detector issues a signal which is interpreted by a programmable logic device to activate an energy storage device for delivering a first low-level shock to the heart through a shock delivering electrode. A slew rate detector is then activated by the logic device.

Abstract: A ski boot for more easily concentrating the weight of a skier over the inside edge of a ski. A ski boot is provided with a sole having toe and heel pieces protruding therefrom, but offset in a direction toward the outside edge of the boot. The protruding portions are engageable by a conventional ski binding so that the weight of the skier is more concentrated over the inside edge (the edge closest to the inside of a skier's foot) of the ski.

Abstract: An implantable heart stimulator and related method calls for the determination of a given heart condition from among a plurality of conditions, the selection of at least one mode of operation for treating the determined condition, and the execution of the mode of operation selected, so as to treat the determined condition. In one embodiment of the invention, wherein a plurality of modes of operation for treating the various conditions are provided, the implantable heart stimulator includes processors, each processor being designed to efficiently execute a respective group of modes of operation. A further embodiment of the present invention calls for the implantable heart stimulator to be implemented by at least one programmable microprocessor. A still further embodiment calls for the provision of a data input/output channel, by means of which data can be provided to and retrieved from the implantable heart stimulator.

Abstract: An externally controlled implantable electronic device for delivering a cardioverting pulse of energy to the atrium of an ailing heart. In one embodiment, the device is particularly suited for use when the patient visits the office of his physician, and contemplates the transmission of both information and powering energy through the skin of the patient. In another embodiment, the device can be readily operated at home, by the patient, and without the intervention of the physician. Here, the source of energy is permanently implanted.

Abstract: A device for recording and subsequently reproducing information, such as desired portions of an ECG signal produced by a heart prior to and during the occurrence of a disturbance in cardiac electrical activity. Two basic embodiments of the inventive recorder are contemplated. One embodiment is fully implantable and is encased with sensing and defibrillating electronics. With this embodiment, a low-power, low-capacity, continually updated recorder is continually operative, and a high-capacity stand-by recorder is actuated upon the sensing of fibrillation. An external device is used to retrieve by telemetry, the information stored in the implanted recorder. The second embodiment of the inventive recorder is an external device which has external electrodes for associating with the patient; ECG information is transmitted to the recorder unit by telemetry. Here, because power consumption is not so critical as with the implantable embodiment, a delay-type continually updated memory is continuously operative.

Abstract: Disclosed is a method and an apparatus for monitoring heart activity, for indicating or detecting abnormalities in such activity, and for taking corrective measures to return an arrhythmic heart to normal sinus rhythm. In one embodiment, monitoring and detecting are accomplished by developing a probability density function from ECG signals, or by sampling at least two portions of a probability density function. In another embodiment, a phase lock loop circuit is utilized to indicate fibrillation by the loop's inability to lock onto R--R interval signals. And in still another embodiment, cardiac electrodes are used to sense pulsatile impedance changes, absent in the presence of fibrillation. Also disclosed is a two-stage detector whose second stage is brought out of a stand-by state only after an arrhythmic condition is indicated by the first stage.

Abstract: Disclosed are two embodiments of a circuit for analyzing the ECG signals of a heart and for delivering a cardioverting pulse of energy to the heart if the heart is in an arrhythmic state in need of cardioversion. In the first embodiment, the ECG is filtered by a high pass filter to provide the derivative of the ECG, is reviewed by a window detector to determine the average time that the input ECG spends at high slope, and then the average occurrence of high slope segments is compared with a predetermined reference to determine whether the ECG is normal. Cardioversion is effected if the ECG is abnormal. In the second embodiment, an absolute value circuit and a level comparator is used in place of the window detector. The input ECG is normalized by an automatic gain control where the AGC voltage is derived from the ECG signals after high pass filtration.

Abstract: Disclosed are several embodiments of an electrode system for ventricular defibrillation, and the methods of using and implanting the electrode system. In one embodiment, the electrodes are in a generally base-apex configuration having a split conformal base electrode residing above the base of the ventricles (a transecting plane separating the atria from the ventricles) in the region of the atria and a conformal apex electrode in the form of a rotated conic section residing at the apex of the heart. In another embodiment, defibrillation is accomplished by the apex electrode acting against a catheter electrode situated high in the heart or in the superior vena cava.The electrodes themselves are in the form of planar metallic mesh elements adapted to lie in contact with body tissue on an active surface, insulated on the opposite surface. In another embodiment, the conductive portions of the respective electrodes are developed from metallic plates, exposed on one surface and insulated on the other.

Abstract: An externally controlled implantable electronic device for delivering a cardioverting pulse of energy to the atrium of an ailing heart. In one embodiment, the device is particularly suited for use when the patient visits the office of his physician, and contemplates the transmission of both information and powering energy through the skin of the patient. In another embodiment, the device can be readily operated at home, by the patient, and without the intervention of the physician. Here, the source of energy is permanently implanted.

Abstract: Apparatus and method for either manually or automatically initiating the cardioversion of a malfunctioning heart. The apparatus includes a single intravascular catheter electrode system which allows for a much more compact cardioverting system capable of being completely implanted within the patient. The heart function is continuously monitored, and when the function becomes abnormal, the malfunctioning heart is shocked by a voltage of sufficient amplitude to restore the heart to normalcy. If the heart does not return to its normal functions after a given interval, then it is again shocked. Normal heart activity ensures that the shocking mechanism remains inert.