Abstract: An implantable cardiac defibrillator includes electrodes coupled to a patient's heart, a sensing system having inputs connected to the electrodes for sensing cardiac electrical signals from the atrial and/or ventricular channels, means for storing a charge, and means for delivering a shock to the heart. The sensing system includes switched capacitor means for amplifying the cardiac electrical signal with non-binary gain changing steps.

Abstract: A cardiac therapy method with duration timer is disclosed, using an implanted cardiac pulse generator. A patient's heartbeat is sensed and the intervals between heartbeats are averaged. The number of temporary storage bins, in the form of RAM locations, are provided, including a sinus bin, a low rate tachycardia bin, a high rate tachycardia bin, and a fibrillation bin. The storage bin corresponding to the cardiac rhythm band of the determined average heartbeat interval is incremented. A maximum count limit is assigned to each storage bin. When the first bin reaches its maximum count limit, a diagnosis of the patient's cardiac rhythm is provided. Upon detection of a tachycardia, a duration timer is started and the tachycardia is treated in accordance with a programmed routine. If sinus is detected during the predetermined time period, then the duration timer is cleared.

Abstract: A cardiac therapy method is disclosed, using an implanted cardiac pulse generator. A patient's heartbeat is sensed and the intervals between heartbeats are averaged. The number of temporary storage bins, in the form of RAM locations, are provided, including a sinus bin, a low rate tachycardia bin, a high rate tachycardia bin, and a fibrillation bin. The storage bin corresponding to the cardiac rhythm band of the determined average heartbeat interval is incremented. A maximum count limit is assigned to each storage bin. When the first bin reaches its maximum count limit, a diagnosis of the patient's cardiac rhythm is provided. Upon detection of a tachycardia, a duration timer is started and the tachycardia is treated in accordance with a programmed routine. If sinus is detected during the predetermined time period, then the duration timer is cleared.

Abstract: An implantable cardiac defibrillator includes electrodes coupled to a patient's heart, sensing circuitry having inputs connected to the electrodes for sensing cardiac electrical signals, charging means for storing a charge, and discharge means for delivering a shock to the heart. The sensing circuitry includes switched capacitor gain/filter means for providing an output signal which is transient-free during a gain change operation and which maintains a constant filter bandwidth for each gain setting.

Abstract: An implantable cardiac defibrillator employing a switched capacitor stage wherein the switches are clocked in a non-50%/50% ratio such that an operational amplifier has greater than 50% of the clock period to acquire the desired voltage and less than 50% of the clock period to hold the acquired voltage, thereby allowing the circuit to run at an overall lower current drain.

Abstract: A method for cardiac defibrillation is described, for use with an implanted defibrillator. A patient's R-waves are sensed to detect the R-R intervals. If an arrhythmia is detected, the charging of a capacitor is commenced. Determination are made whether the arrhythmia is still in progress and whether the capacitor is charged a predetermined amount. If the arrhythmia is not still in progress, the charging is discontinued. If the arrhythmia is still in progress and the capacitors are charged a predetermined amount, another R-R interval is detected and if the R-R interval is shorter than a selected amount, a shock is delivered to the heart.

Abstract: An implantable defibrillation electrode of a shape requiring minimal incision in the body is disclosed. The electrode has a flexible insulated guide and terminates in a preconfigured flexible distal portion with an exposed conductive element. The electrode may be straightened, as for example by insertion of a stylet into the body of the electrode, for ease of insertion into the body.