Abstract: Methods and systems are provided that comprise: sensing cardiac events of a heart; utilizing one or more processors to perform: declaring a ventricular fibrillation (VF) episode based on the cardiac events charging a single charge storage capacitor; delivering a multi-phase VF therapy that includes phase I and phase II therapies, wherein: a) during the phase I therapy, a combination of two or more medium voltage (MV) shocks are delivered entirely from the single charge storage capacitor; and b) during the phase II therapy, a low voltage pulse train is delivered at least partially from the single charge storage capacitor.

Abstract: Methods and systems are provided that comprise: sensing cardiac events of a heart; utilizing one or more processors to perform: declaring a ventricular fibrillation (VF) episode based on the cardiac events charging a single charge storage capacitor; delivering a multi-phase VF therapy that includes phase I and phase II therapies, wherein: a) during the phase I therapy, a combination of two or more medium voltage (MV) shocks are delivered entirely from the single charge storage capacitor; and b) during the phase II therapy, a low voltage pulse train is delivered at least partially from the single charge storage capacitor.

Abstract: An implantable electrical device that includes a control unit and one or more leads. The leads are configured to be implanted in the chambers of the heart of a patient and the control unit is configured to be implanted in the body of the patient. The control unit induces the leads to provide therapeutic electrical stimuli to the heart. The control unit also includes a magnetoresistive sensor that senses the presence of an externally applied magnetic field. The sensor outputs a signal which has a value that is proportionate to the sensed magnitude of the externally applied magnetic field. The control unit initiates a preprogrammed activity, which for example can be either a function or a change in the mode of operation of the device, when it receives a signal from the magnetic field sensor indicating that the magnitude of the sensed magnetic field has a value corresponding to the magnitude of a magnetic field that occurs as a result of positioning a selected external magnet adjacent the control unit.

Abstract: An improved input protection circuit for use in a circuit for processing sensor signals from a piezoelectric patient activity sensor is provided. The input protection circuit includes a field-effect transistor to prevent the voltage at an input terminal of the processing circuit from rising beyond a first predetermined voltage or falling below a second predetermined voltage. The gate and drain terminals of the transistor are connected to a first of two input terminals of the processing circuit and the source and body terminals are connected to the second terminal. When the voltage at the first terminal rises or falls sufficiently, the transistor conducts current, thereby preventing the voltage from rising or falling further.