Abstract: A package of defibrillator electrodes having a date indication element and a circuit for determining a date of manufacture of medical electrodes within the package is provided. Specifically, by the circuit and package design of the present invention, the presence of a fresh package of electrodes can be detected. A circuit detectable package of medical electrodes is provided including first and second electrodes within the package. An electrical interconnection means is provided between the first and second electrodes for electrically completing a circuit connecting the lead wire of the first electrode to the lead wire of the second electrode, and includes a date identification element which when subjected to an applied voltage by way of the lead wires generates a measurable affect representative of the manufacturing period of the defibrillator electrodes. The date identification element may comprise a passive element, a value of which represents a date and can be measured.

Abstract: The device senses Natural Heart Acceleration (NHA), isolating at least one segment (t) thereof corresponding to an isovolumetric phase, such as isovolumetric contraction (P1, P2) and/or isovolumetric relaxation (P3, P4). Preferentially, the action of isolation of the aforesaid segment is made starting from the electrocardiogram (ECG) signal. Among other things, the device may be used to carry out pacing functions (pacemaker, defibrillator, pacer cardioverter defibrillator) and/or to pick up, possibly by telemetry, data on the myocardial function and/or also to control a system of drug administration.

Abstract: A device for detecting a state of imminent cardiac arrhythmia, relative to a normal state for a heart, in response to activity in nerve signals conveying information from the autonomic nerve system to the heart, contains a sensor body for sensing neural activity, a comparator with a threshold value forming a condition for the presence of an arrhythmia, the comparator emitting an arrhythmia-indicating output signal depending on whether neural activity meets the condition, and the sensor body being placeable in an extracardiac position for at least one of the sympathetic and vagus nerves. The sensor body directly senses activity in the nerve at that location in direct contact with the nerve. An implanted blood pressure sensing cuff also can be provided which generates signals indicative of blood pressure which can be evaluated in combination with the nerve signals for identifying the state of imminent cardiac arrhythmia.

Abstract: An automatic atrial defibrillator which includes a mechanism for sensing the occurrence of atrial fibrillation in a patient's heart and in response thereto delivers an atrial defibrillation pulse. The device also has the ability to determine whether the patient is likely to be asleep. Defibrillation pulses which are at energy levels which would normally be painful to the patient are delivered only in response to occurrences of atrial fibrillation while the patient is determined to likely be asleep. Defibrillation pulses at lower, non-painful levels may be delivered while the patient is not determined to be asleep.

Abstract: The device senses Natural Heart Acceleration (NHA), isolating at least one segment (t) thereof corresponding to an isovolumetric phase, such as isovolumetric contraction (P1, P2) and/or isovolumetric relaxation (P3, P4). Preferentially, the action of isolation of the aforesaid segment is made starting from the electrocardiogram (ECG) signal. Among other things, the device may be used to carry out pacing functions (pacemaker, defibrillator, pacer cardioverter defibrillator) and/or to pick up, possibly by telemetry, data on the myocardial function and/or also to control a system of drug administration.

Abstract: An electrotherapy method and apparatus for delivering a multiphasic waveform from an energy source to a patient. The preferred embodiment of the method comprises the steps of charging the energy source to an initial level; discharging the energy source across the electrodes to deliver electrical energy to the patient in a multiphasic waveform; monitoring a patient-dependent electrical parameter during the discharging step; shaping the waveform of the delivered electrical energy based on a value of the monitored electrical parameter, wherein the relative duration of the phases of the multiphasic waveform is dependent on the value of the monitored electrical parameter.

Abstract: This invention provides an external defibrillator and defibrillation method that automatically compensates for patient-to-patient impedance differences in the delivery of electrotherapeutic pulses for defibrillation and cardioversion. In a preferred embodiment, the defibrillator has an energy source that may be discharged through electrodes on the patient to provide a biphasic voltage or current pulse. In one aspect of the invention, the first and second phase duration and initial first phase amplitude are predetermined values. In a second aspect of the invention, the duration of the first phase of the pulse may be extended if the amplitude of the first phase of the pulse fails to fall to a threshold value by the end of the predetermined first phase duration, as might occur with a high impedance patient.

Abstract: A cardiac blood flow sensor includes a light source and a photodetector within a housing. The light source projects a beam through a fiber optic line having a first end optically connected to the housing and a distal tip positioned within the patient's heart. Light intermittently reflected off the moving blood cells is transmitted back through the optic line to the detector, which generates a varying signal proportional to the reflected light, and thus proportional to the blood flow rate within the heart. The flow sensor may be contained in a common housing with a defibrillator that is implanted in a patient. The sensor may remain inactive until a potentially unhealthy heart beat rate is detected, upon which the light source is activated. The defibrillator may be activated only if the flow sensor has detected a blood flow rate below a predetermined level.

Abstract: An implantable automatic cardioverter/defibrillator device for a cardiac patient is automatically responsive to sensing of electrical cardiac activity of the heart of a patient in which the device is implanted for detection and treatment of fibrillation. A prescribed electrical shock waveform regimen is generated as electrical defibrillation therapy for application to the heart in response to detection of fibrillation of the heart. A timing function circuit responds to the detection by timing the delivery of the generated prescribed electrical waveform regimen to be applied at a point in time at which the fibrillation ECG has substantially its highest amplitude and lowest frequency, as a point of high susceptibility to reversion to sinus rhythm upon application of a shock, and with low defibfillation threshold, to enhance the probability of successful defibrillation, and to synchronize the shock delivery to this sensed intracardiac event.

Abstract: An atrial defibrillator coordinates atrial cardioversion with ischemia detection. The defibrillator includes a plurality of sense amplifiers for sensing electrical activity of a heart. An ischemia detector is responsive to the sensed electrical activity of the heart for detecting ischemia of the heart. An atrial fibrillation detector is responsive to the sensed electrical activity of the heart for determining if the atria are in need of cardioversion, and a cardiovertor applies cardioverting electrical energy to the atria of the heart if the atria of the heart are in need of cardioversion and if the ischemia detector fails to detect ischemia of the heart.

Abstract: Arrhythmia is prevented by detecting a high risk of arrhythmia and then stimulating afferent nerves to prevent the arrhythmia. By monitoring the sympathetic and parasympathetic nerve activity of a patient the risk of arrhythmia may be assessed. An apparatus for monitoring of parasympathetic and sympathetic nerve activity and stimulating the afferent nerves may be implanted in a patient. Furthermore, the apparatus and method for the prevention of arrhythmia may be combined with apparatus for the treatment of arrhythmia through electric shock to facilitate treatment and prevent reoccurrence of arrhythmia.

Abstract: A defibrillator, such as an atrial defibrillator, applies cardioverting electrical energy to the atria of a heart when the atria are in need of cardioversion. The atrial defibrillator includes an atrial sense channel for sensing atrial activity and ventricular sense channels for sensing ventricular activity to generate heart activity data, a memory for storing the heart activity data, and a cardiovertor which applies cardioverting electrical energy to the atria if the heart activity satisfies a predetermined criteria. A storage control causes at least a portion of the heart activity data to be retained in the memory if the heart activity data fails to satisfy the predetermined criteria.

Abstract: A pacemaker system for a heart having an external muscle is used to control pacing of the heart during normal or even arrhythmic modes. In these modes, the muscle is stimulated synchronously with the heart to augment the heart's cardiac functions. When the heart undergoes ventricular fibrillation, the muscle is provided with a signal to cause the muscle to contract and expel blood from the heart chambers. Defibrillation shock is then applied to the heart to halt the fibrillation. The system is rendered more effective, safer and uses less power because the defibrillating energy is efficiently transferred to the heart muscles and not to the blood contained in its chambers. The system includes a microprocessor, muscle stimulating circuitry, defibrillation circuitry and an interface for exchanging signals between the microprocessor and the remaining components.

Abstract: The device senses Natural Heart Acceleration (NHA), isolating at least one segment (t) thereof corresponding to an isovolumetric phase, such as isovolumetric contraction (P1, P2) and/or isovolumetric relaxation (P3, P4). Preferentially, the action of isolation of the aforesaid segment is made starting from the electrocardiogram (ECG) signal. Among other things, the device may be used to carry out pacing functions (pacemaker, defibrillator, pacer cardioverter defibrillator) and/or to pick up, possibly by telemetry, data on the myocardial function and/or also to control a system of drug administration.

Abstract: An atrial defibrillator implantable beneath the skin of a patient includes an intervention sequencer for performing an intervention sequence. The intervention sequencer includes an atrial fibrillation detector for determining if atrial fibrillation is present in a patient's heart and a cardiovertor for applying cardioverting electrical energy to the atria of the patient's heart if the atrial fibrillation detector determines that atrial fibrillation is present. A sequence initiating stage includes a receiver for receiving a sequence command generated from external to the patient. The sequence initiating stage causes the intervention sequencer to perform the intervention sequence upon receipt of a sequence command.

Abstract: A processing system and method are provided for deriving an improved hemodynamic indicator from cardiac wall acceleration signals. The cardiac wall acceleration signals are provided by a cardiac wall motion sensor that responds to cardiac mechanical activity. The cardiac wall acceleration signals are integrated over time to derive cardiac wall velocity signals, which are further integrated over time to derive cardiac wall displacement signals. The cardiac wall displacement signals correlate to known hemodynamic indicators, and are shown to be strongly suggestive of hemodynamic performance. An implantable cardiac stimulating device which uses cardiac wall displacement signals to detect and discriminate cardiac arrhythmias is also provided.

Abstract: A medical interventional device adapted to be implanted in the body of a patient provides a plurality of cardiac therapeutic functions including bradycardia pacing, rate adaptive pacing, antitachycardia pacing, cardioversion and defibrillation on demand. An accelerometer in or associated with the device senses accelerational and gravitational effects indicative of at least one of position, posture and physical activity of the patient, and generates an electrical signal representative of the position, posture and physical activity of the patient of which the sensed effect is representative. The accelerometer acts as a transducer to convert mechanical movement to an electrical output representative of such movement. Another sensor detects a physiologic parameter of the patient indicative of cardiac activity of the patient, and generates another electrical signal representative of the cardiac activity.

Abstract: A medical interventional device is adapted to be implanted in a patient's body to provide a number of different controllable therapeutic functions including cardiac pacing, antitachycardia pacing, cardioversion and defibrillation. A sensor generates an electrical signal representing sensed variations of a physiologic parameter of the patient indicative of the substantially instantaneous hemodynamic condition of the patient. The physiologic parameter sensed may be any of blood pressure, blood oxygen content, minute ventilation, central venous temperature, pulse rate, blood flow, physical activity, or other parameter for that purpose. A computer calculates the mean and standard deviation of the generated signal over a predetermined time interval, and especially the quotient of the standard deviation and the mean from which to determine a sudden hemodynamic change such as a precipitous drop in cardiac output.

Abstract: Heart function is monitored by monitoring the momentum or velocity of the heart masses, preferably by means of a sensor implanted in the heart mass.

Abstract: A defibrillator pulse generator for pectoral implant utilizing the metal case as an electrode and operative to supply unique patterns of monophasic, biphasic, or pairs of electrical pulses to the connected electrodes.

Abstract: A rate-responsive cardiac pacemaker implements a novel scheme which detects incipient vasovagal syncope (or other episodes caused by a vasodepressive or cardioinhibitory disorder) when a) the heart rate drops below a programmable minimum size, and b) the rate after said drop is below a programmable maximum drop ending rate. The pacemaker implements a stability and intervention procedure upon the detection of an episode, in which it ignores transient drops in rate, and paces at a predetermined high rate if the drops are stable. The pacemaker then gradually reduces the pacing rate over a predetermined time to the pre-episodic level. A sleep disable feature disables the vasovagal syncope detection and therapy features during the patient's sleeping hours to reduce or eliminate false positive responses.

Abstract: A heart defibrillator includes a defibrillation circuit for delivering defibrillation pulses. The defibrillation circuit also emits a pre-pulse before the defibrillation pulse. The pre-pulse is not as intense as the defibrillation pulse, but is still intense enough to induce mechanical contraction of muscles in parts of the thorax and possibly the heart.

Abstract: A defibrillator patient connection system is disclosed for automatically identifying to a defibrillator system the type of pads or paddles assembly connected to the system for conveying electrical energy to shock a patient. Each of the available pads or paddles assemblies is identified by a corresponding analog voltage level provided to the base unit through a corresponding cable assembly. The identification voltage is sensed by an A/D converter in the defibrillator base unit. The identification voltage is provided to the base unit on a charge-done signal line which otherwise is asserted by the base unit to controllably actuate a charge-done indicator light in an external paddles assembly. The disclosed methods and apparatus thus maintain a simple defibrillator/cable assembly interface and require no additional signal lines for implementing automatic identification.

Abstract: The model that is developed in the present invention is based upon the pioneering neurophysiological models of Lapicque and Weiss. The present model determines mathematically the optimum pulse duration, d.sub.p, for a truncated capacitor-discharge waveform employed for defibrillation. The model comprehends the system time constant, RC, where R is tissue resistance and C is the value of the capacitor being discharged, and also the chronaxie time, d.sub.c, defined by Lapicque, which is a characteristic time associated with the heart. The present model and analysis find the optimum pulse duration to be d.sub.p =(0.58)(RC+d.sub.c). Taking the best estimate of the chronaxie value from the literature to be 2.7 ms, permits one to rewrite the optimum pulse duration as d.sub.p =(0.58)RC+1.6 ms.

Abstract: A device-implemented method detects and treats abnormal (i.e., pathologic) tachycardias experienced by a patient with an implanted automatic defibrillator. The defibrillator has the capability to distinguish pathologic tachycardia from physiologic tachycardia by the application of predetermined distinction criteria programmed into it. Changes in a physiologic parameter of the patient which signify a physiologic basis for increase or decrease of the patient's heart rate are detected, and in response, the distinction criteria are modified to enhance the capability of the defibrillator to make the distinction between pathologic and physiologic tachycardia when this change in circumstances that would otherwise tend to obscure the distinction is factored in. In one method, the parameter under detection is patient activity, and the distinction criteria include a threshold heart rate above which the patient is presumed to be experiencing a pathologic tachycardia.

Abstract: A system and method is provided for implantable cardioverter defibrillators to truncate peak current output during defibrillation countershock therapy to a safe level irrespective of the resistance of the myocardium between the discharge electrodes implanted within the heart.

Abstract: An apparatus for producing signals indicative of power levels of depolarizations of heart tissue, particularly adapted for use in an implantable antiarrhythmia device or an implantable pacemaker. The device distinguishes between the power level of sensed depolarization signals in order to distinguish between different types of depolarization waveforms. In particular, the measured power level of the sensed depolarizations may be employed to distinguish between normally conducted and ectopic beats, for use in controlling the operation of an implantable antiarrhythmia device such as an implantable pacemaker/cardioverter/defibrillator or for use in controlling the operation of a bradycardia pacemaker.

Abstract: A leadless implantable cardiac arrhythmia alarm is disclosed which continuously assesses a patient's heart function to discriminate between normal and abnormal heart functioning and, upon detecting an abnormal condition, generates a patient-warning signal. The alarm is capable of sensing impedance measurements of heart, respiratory and patient motion and, from these measurements, generating an alarm signal when the measurements indicate the occurrence of a cardiac arrhythmia. Because it requires no external leads or feedthrough connectors, the hermetically-sealed patient alarm is minimally invasive and results in reduced trauma to a patient.

Abstract: In order to be able to set the distribution of current of the defibrillation current across the heart muscle, a defibrillator/cardioverter has n (n.gtoreq.3) electrodes connected to a pulse generator having n-1 outputs with a total of n output terminals to which the electrodes are connected. A measuring unit generates a measured signal dependent on the geometrical arrangement of the electrodes with reference to the heart. This measured signal is utilized for setting the pulse heights of the defibrillation pulses to be simultaneously generated at the outputs.

Abstract: In a method and apparatus for detecting ventricular fibrillation, a measured impedance signal, dependent on the blood volume in the heart, is evaluated, and ventricular fibrillation is assumed to be present if the level of the measured impedance signal falls below a predetermined threshold. This is based on the perception that as the heart fills with blood, given the presence of ventricular fibrillation, the level of the measured impedance signal will decrease. The apparatus also includes circuitry for treating the detected ventricular fibrillation.

Abstract: A method and apparatus for delivering an adaptive n-phasic waveform to the heart in either a fixed-tilt delivery mode or a fixed-duration delivery mode. A first phase of a first polarity is delivered to the heart. The first phase is set to terminate upon decaying to a preset level. If the first phase does not decay to the preset level within a predetermined maximum period of time, the first phase is terminated and the subsequent phases are delivered in a fixed-duration delivery mode. Because the first phase did not decay fast enough, it is determined that the patient has a relatively high system impedance. Therefore, subsequent phases will be delivered to the patient in a fixed-duration mode to insure the defibrillation is reversed. Otherwise, if the first phase decays to the preset level in less than the maximum predetermined period of time, it is determined that the patient has a relatively low system impedance and subsequent phases should be delivered in a fixed-tilt mode.

Abstract: Circuits for controlling the current flow of an energy pulse as a function of the temperature of a resistive element in the circuit so that the current flow varies over time in accordance with a predetermined waveform. The circuits include at least one negative temperature coefficient thermistor connected between an energy storage device and connectors for delivering energy stored in the storage source to an external load. In one embodiment of the invention the circuit includes a second thermistor for shunting a residual portion of the current delivered by an energy pulse away from the external load. In another embodiment of the circuit, a small inductive device is used for adjusting the shape of the predetermined waveform. In yet another embodiment of the device, a plurality of thermistors arranged in a bridge-like configuration are used to control the current of the energy pulse so that its waveform is biphasic.

Abstract: An implantable medical interventional device responds to detection of cardiac activity of the patient indicative of ventricular tachycardia (VT) or fibrillation (VF) by successively applying to the patient's heart selected ones of different electrical waveforms for treatment to break the VT or VF, respectively, until the monitored cardiac activity indicates that the treatment has been successful. An accelerometer adapted to sense position and movement of the patient along three mutually orthogonal axes acts as an activity status sensor to detect physical activity and inactivity of the patient to complement the detection of the patient's cardiac activity for confirming that a detected VT is a pathologic tachycardia rather than a physiologic tachycardia, and in response to such confirmation the device selects an appropriate electrical waveform for the treatment.

Abstract: A system for treating the malfunctioning heart of a patient includes means which derive at least one electrical signal from the patient's heart and means which derive at least two physiologic signals from or related to the patient's circulatory system. The physiologic signals, or functions thereof, are weighted and algebraically summed in a central processing unit, which may be a programmable microprocessor, having a RAM and a ROM, receives and responds to the at least one electrical signal and to the at least two physiologic signals. Output means, which may include a heart assist pump, pacers, drug delivery devices and cardioverting/-defibrillating apparatuses, controlled by the central processing unit provides corrective measure(s) to the patient. Heart-rate zone signals and the algebraic sum, at any given time effect selection of a particular treatment modality, if needed.

Abstract: A physiological monitoring system for monitoring the condition of a patient's body tissue. The device includes electrodes for contacting the tissue to be monitored, circuitry for generating electrical signals at at least two frequencies for application to the tissue and circuitry for monitoring the impedance of the tissue, at the frequencies applied. The device includes in addition apparatus for detecting changes in the relationship of the measured impedances at the frequencies applied, and for processing the detected changes in impedance relationship to provide an indication of the condition of the tissue. The monitoring apparatus may be practiced in the context of an implantable stimulator, such as a cardiac pacemaker, in which the pulse frequency is varied as a function of the detected condition of the tissue.

Abstract: Circuits for controlling the current flow of an energy pulse as a function of the temperature of a resistive element in the circuit so that the current flow varies over time in accordance with a predetermined waveform. The circuits include at least one negative temperature coefficient thermistor connected between an energy storage device and connectors for delivering energy stored in the storage source to an external load. In one embodiment of the invention the circuit includes a second thermistor for shunting a residual portion of the current delivered by an energy pulse away from the external load. In another embodiment of the circuit, a small inductive device is used for adjusting the shape of the predetermined waveform. In yet another embodiment of the device, a plurality of thermistors arranged in a bridge-like configuration are used to control the current of the energy pulse so that its waveform is biphasic.

Abstract: Method and apparatus for detecting the open or closed state of a pair of manually-operated switches 116, 118 associated with a pair of defibrillation pulse electrodes, the switches being normally open and being manually closed by an operator, the two switches connected in series with discharge control circuitry 32 for initiating a defibrillation energy pulse. The control circuitry 32 is configured so that when the switches 116, 118 are both closed a defibrillation pulse is initiated. Each of the switches is connected in parallel with a corresponding circuit element 124, 126, each having a characteristic impedance, and being shorted out when the corresponding switch 116, 118 is closed. The invention provides for measuring an indication of the series impedance of the discharge control circuitry 32 to determine the open or closed state of the switches by comparing a measured impedance value indication with an impedance value indication calculated for a given open or closed state of the switches.

Abstract: A system for monitoring a patient and treating the malfunctioning heart of the patient, either in an automatic mode or in a semiautomatic mode, includes means which derive at least one electrical signal resulting from action of the patient's heart and means which derive at least one physiologic signal from or related to the patient's circulatory system. A central processing unit, which may be a programmable microprocessor, with a RAM and a ROM, receives and responds to the at least one electrical signal and to the at least one physiologic signal. Output means, which may include a heart assist pump, pacers, drug delivery devices and cardioverting/-defibrillating apparatuses, controlled by the central processing unit provides corrective measure(s) to the patient. Adjustable or variable baselines, against which a representation of the current, short-term magnitude of the selected physiologic parameter or parameters are provided.

Abstract: A method and apparatus for delivering electrical therapy to the heart are disclosed. The apparatus detects and confirms the arrhythmia. However, during confirmation, if the arrhythmia is present but not too severe, it is allowed to continue in the hope that it will spontaneously revert. The arrhythmia is reconfirmed later and, if it is still present, electrical therapy is delivered to the heart. Thus, for mild arrhythmias, electrical shock therapy is withheld for a specified time period in the hope that the arrhythmia will revert spontaneously. More severe arrhythmias which are not hemodynamically sustaining are immediately electrically shocked in an effort to revert the heart back to normal sinus rhythm.

Abstract: A pulse generator for use in implantable atrial defibrillator provides cardiovertinq electrical energy to the atria of a heart through at least one lead having a pair of electrodes associated with the atria of the heart. The pulse generator includes a depletable, low voltage, power source such as a battery. A charging circuit coupled to the battery includes a flyback transformer for converting the battery voltage to low duty cycle pulsating high voltage electrical energy to store the high voltage electrical energy in a storage capacitor coupled to the charging circuit. A crosspoint switch selectively couples the storage capacitor to the electrodes for applying a portion of the stored electrical energy to the atria of the heart for cardioverting the atria of the heart.

Abstract: An antiarrhythmia pacemaker and method detect and confirm the occurrence of an abnormal condition of a patient's heart selected from the group comprising tachycardia, fibrillation and precursors thereof, and, in response thereto, deliver an antiarrhythmia therapy to the patient which includes two components, electrical stimulation of the heart and electrical stimulation of a skeletal muscle graft which has been surgically grafted to the heart to augment performance of the heart. The antiarrhythmia pacemaker and method control electrical stimulation of the heart in terms of timing, frequency, amplitude, duration and other operational parameters, to provide such pacing therapies as antitachycardia pacing, cardioversion and defibrillation. A skeletal muscle graft stimulation electrode, which is driven by a skeletal muscle pulse stimulator, stimulates preselected nerve fibers within the skeletal muscle graft.

Abstract: Method and apparatus for discharging a defibrillation discharge circuit 30 across a short circuit load 166 for monitoring defibrillation pulses 180 generated by the circuit to test that the pulses are acceptable. The discharge circuit 30 comprises an electrical capacitor 34 for storing defibrillation pulse energy and an electrical inductor 38 in series with the capacitor for shaping the discharge pulses. In the invention, parameters representative of the shape of the defibrillation pulse are detected as the pulse is discharged and are compared to predetermined values characteristic of the shape of an acceptable pulse. Based on the outcome of this comparison, an output is provided indicating whether the pulse is acceptable.

Abstract: An electrode arrangement for a cardiac defibrillator includes one or more physiological sensors disposed in an electrode carrier for planar application against the exterior of the heart. The sensor contained in the electrode carrier is connected to a housing, containing a defibrillation power source and signal processing circuitry, via a sensor line, and the electrical signals obtained from the sensor are used for controlling operation of the defibrillator.

Abstract: A cardiac electrotherapy system has flow velocity measurement capability for measuring a velocity of blood flow at a region of a tricuspid valve of a heart. A pacing system is provided which outputs a pacing electrical signal to the heart. A control unit which is responsive to a measured flow velocity from the flow velocity measurement unit detects heart irregularities and controls electrical pacing signals to the heart. In detecting heart irregularities, peak flow velocity waveforms are detected and analyzed. The flow velocity measurement employs a Doppler ultrasonic transducer which is mounted on a cardiac pacing lead in spaced relation to a pacing electrode at a distal end of the lead. When the pacing lead is inserted in the heart, the pacing electrode is placed at an apex of the right ventricle and the piezoelectric Doppler transducer is positioned at or near the tricuspid valve. The flow velocity transducer is preferably formed as an annular piezo body having associated electrodes.

Abstract: A method for discrimination between ventricular and supraventricular tachycardia and an apparatus for performing the method. In response to the detection of the occurrence of an tachycardia, stimulus pulses are delivered to one or both of the SA and AV nodal fat pads. The response of the heart rhythm to these stimulus pulses is monitored. Depending upon the change or lack of change in the heart rhythm, a diagnosis is made as to the origin of the tachycardia.

Abstract: A primary central controller switch box for providing a centralized means for alternatively coupling a defibrillator, a plurality of pacers and recorders in conjunction with a quadripolar endocardial catheter, an apex and back body surface electrode, and an arterial or ventricular catheter having a means for selection therebetween. The switch box incorporates a plurality of switches allowing for manual selection of each of said instruments in predetermined combinations to eliminate the possibility of multiple support therapy and further decrease the time it takes to switch between instruments when used in a cardiac catheterization environment, electro physiological environment, cardiac resuscitation ward, ablation study, or the like clinical settings.