Abstract: A multiprogrammable, telemetric, implantable defibrillator contains a high energy shock system to revert VT/VF's to normal sinus rhythm and a multi-programmable VVI bradycardia support system. When the apparatus is in an automatic shock sequence, there are two points of reconfirmation: at the programmed minimum time to shock and after the full charge has been reached, or at thirty seconds, whichever comes first. Reconfirmation involves testing the tachycardia detection output (TDO). If the TDO is high, reconfirmation occurs. If the TDO is low, reconfirmation will not occur and the device will subsequently dump the discharge. Two reconfirmations must occur before a shock is delivered to the patient. If the TDO is low at either reconfirmation, the charge will be dumped.

Abstract: A vein suture collar for anchoring an electrode lead to a vein in which the lead is inserted includes a sleeve member having three longitudinally spaced circumferential suture grooves in the exterior surface and a raised web area formed on the interior sleeve surface radially inward of each groove. The three raised web areas are angularly spaced about the sleeves axis and a longitudinal slit through the sleeve thickness can be provided. The slit collar can be separated at the slit and used to enclose the portion of the vein having the inserted electrode.

Abstract: A pacemaker which is provided with an improved automatic regulation circuit which is capable of distinguishing between a fusion beat and loss of capture. The failure to sense an evoked potential following a stimulus may be due to either. The cause is determined by generating a high-energy back-up pulse shortly after the stimulus. Failure to capture by the back-up pulse is an indication that there was just a fusion beat; the sensing of an evoked potential is an indication that the stimulus failed to capture.

Abstract: A pacemaker which is provided with an improved automatic regulation circuit which is capable of distinguishing between a fusion beat and loss of capture. The failure to sense an evoked potential following a stimulus may be due to either. The cause is determined by generating a high-energy back-up pulse shortly after the stimulus. Failure to capture by the back-up pulse is an indication that there was just a fusion beat; the sensing of an evoked potential is an indication that the stimulus failed to capture.

Abstract: A pacemaker which is provided with an improved automatic regulation circuit which is capable of distinguishing between a fashion beat and loss of capture. The failure to sense an evoked potential following a stimulus may be due to either. The cause is determined by generating a high-energy back-up pulse shortly after the stimulus. Failure to capture by the back-up pulse is an indication that there was just a fusion beat; the sensing of an evoked potential is an indication that the stimulus failed to capture.

Abstract: A pacemaker which is provided with an improved automatic regulation circuit which is capable of distinguishing between a fusion beat and loss of capture. The failure to sense an evoked potential following a stimulus may be due to either. The cause is determined by generating a high-energy back-up pulse shortly after the stimulus. Failure to capture by the back-up pulse is an indication that there was just a fusion beat; the sensing of an evoked potential is an indication that the stimulus failed to capture.

Abstract: A pacemaker which is provided with an improved automatic regulation circuit which is capable of distinguishing between a fusion beat and loss of capture. The failure to sense an evoked potential following a stimulus may be due to either. The cause is determined by generating a high-energy back-up pulse shortly after the stimulus. Failure to capture by the back-up pulse is an indication that there was just a fusion beat; the sensing of an evoked potential is an indication that the stimulus failed to capture.

Abstract: A method and apparatus for differentiating between arrhythmia and noise in an antiarrhythmia device. A noise detection criteria is applied to a detected signal so as to detect noise simultaneously at two different sensitivity levels. When noise is not detected on the high gain channel the low gain channel is used for detecting arrhythmias. Arrhythmia therapy is then delivered.

Abstract: An apparatus and method for tachyarrhythmia reversion uses multiple sensitivities programmed for automatic operation. A first (medium) sensitivity is used normally for the detection of sinus rhythm and ventricular tachycardia. A second (higher) sensitivity is designed for differentiating ventricular fibrillation from asystole. A third (lower) sensitivity can also be programmed into the device to differentiate between R-waves and high amplitude current of injury T-waves which may occur post shock. Following the delivery of antitachycardia therapy in the form of either antitachycardia pacing therapy or cardioversion shock therapy, there is a pause, or post therapy pacing delay for a period of time prior to the commencement of bradycardia support pacing. The magnitude of the delay period is substantially greater than the normal bradycardia support pacing standby interval.

Abstract: A patch-type defibrillator electrode for direct contact with the heart has a thin, flat, flexible generally circular mesh or foil conductive member with a pattern of slits for enabling continuous contact with the three dimensional, time-varying heart surface topography. The slit pattern includes two pairs of non-intersecting semicircular slits oriented along mutually perpendicular axes, and interior portions of the conductive member are flexibly movable in a direction normal to the plane member and are flexibly tiltable about the axes to provide the conforming contact. The slits may also be radial slits which do not meet at the center so the leaves of conductive members are independently mobile with respect to every other leaf. A Dacron envelope having a thrombus formation inhibiting agent surrounds the conductive member including the peripheral edges to reduce the risk of tissue burning from current supplied to the center of the conductive member by an electrode lead.

Abstract: A pacemaker which generates a triphasic stimulus; the first and third phases are positive pulses, and the second is the negative stimulus. After-potentials are so low that reliable sensing of evoked signals are possible. The rapidity of the charge balancing is not affected by the stimulus amplitude because the relative amplitudes of the three phases are maintained independent of the stimulus amplitude.

Abstract: A rate-responsive heart pacer in which rate-control parameter (RCP) values are arranged in a percentile ranking and mapped onto a percentile ranking of a desired rate distribution. By monitoring the RCP values over an extended time interval and developing a corresponding percentile ranking, the pacemaker automatically self-adapts to long-term changes in RCP measurements and insures that the desired rate distribution is obtained.

Abstract: A rate-responsive pacemaker whose rate control parameter is minute volume derived over a bipolar lead. An algorithm based on averaged samples and zero crossings provides enhanced accuracy. Sustained exercise at high pacing rates is possible.

Abstract: Apparatus and method for treating tachyarrhythmias wherein the presence of a patient tachyarrhythmia is detected and a first antitachyarrhythmia therapy (antitachycardia pacing) is given at a first energy level. The haemodynamic condition of the patient is measured and a length of time to therapy switchover is continually derived during the application of the first antitachyarrhythmia therapy. The length of time to switchover is a function of the haemodynamic condition of the patient. When the time following detection of the patient tachyarrhythmia exceeds the length of time to switchover, a second antitachyarrhythmia therapy (a high energy shock) at a second energy level is provided. The average cardiac cycle length may be used as an indicator of the haemodynamic condition.

Abstract: A system is provided for cardiac pacing, in which the output levels of the electrical stimulus pulses are responsive to the detection or non-detection of cardiac pacer evoked potentials. A pulse generator is provided for emitting electrical stimulus pulses at variable output levels. A pulse to pulse interval and an evoked response sensing period are provided. At the beginning of the pulse to pulse interval, an electrical stimulus having a first output level is emitted. If no evoked response is sensed during the sensing period, then an electrical stimulus at a selected maximum output level is emitted and, thereafter, the next electrical stimulus pulse is emitted at a second output level that is greater than the first output level.

Abstract: A pacemaker which is provided with an improved automatic regulation circuit which is capable of distinguishing between a fusion beat and loss of capture. The failure to sense an evoked potential following a stimulus may be due to either. The cause is determined by generating a high-energy back-up pulse shortly after the stimulus. Failure to capture by the back-up pulse is an indication that there was just a fusion beat; the sensing of an evoked potential is an indication that the stimulus failed to capture.

Abstract: An apparatus and method for controlling pulse energy in an arrythmia control device wherein bradycardia pacing pulses are normally delivered at a first energy, and after antitachycardia therapy, bradycardia pulses are delivered at a second energy, the second energy being greater than the first energy. The antitachycardia therapy may be at least one of antitachycardia pacing, cardioversion and defibrillation; and is delivered at a third energy level greater than said second energy level. The second energy level is maintained for a predetermined period of time and then returned to the normal bradycardia pacing energy.

Abstract: A rate-responsive heart pacer in which rate-control parameter (RCP) values are arranged in a percentile ranking and mapped into a percentile ranking of a desired rate distribution. By monitoring the RCP values over an extended time interval and developing a corresponding percentile ranking, the pacemaker automatically self-adapts to long-term changes in RCP measurements and insures that the desired rate distribution is obtained.

Abstract: Polymer hydrogels are adapted for surgical implants by chemical modification of the surface to stimulate the attachment and growth of cells thereto. The modification may be by oxidative acid etching or by copolymerization with methacrylic acid and diethylaminoethyl methacrylate.

Abstract: The apparatus for pacing a heart in accordance with the heart rate needed to produce a required cardiac output while the person is exercising, comprises a pacer adapted to be implanted in a human body and having a pulse generator and control circuitry (e.g. a microprocessor) therein, a pacing lead adapted to be implanted in a heart and having a distal electrode adapted to engage and supply pacing pulses to a right ventricle of a heart, and a pO.sub.2 sensor for sensing pO.sub.2 of the blood in the heart. An algorithm or routine utilizing same are stored in the control circuitry (microprocessor) and are adapted to relate pO.sub.2 and/or .DELTA.pO.sub.2 with the required heart rate or change in heart rate, .DELTA.R, needed to supply a desired cardiac output and to cause the pacer to pace the heart at the required heart rate when the heart is not naturally paced.