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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. The device is capable of recognizing from detected physical activity the occurrence of a sudden vigorous movement associated with a syncope by calculating variances relative to the mean of the detected physical activity, and of responding to such recognition by selecting a defibrillating waveform for immediate application to the patient's heart. A scoring system based on assigned weightings of subparameters of detected cardiac activity and detected physical activity or inactivity is used to determine the likelihood that a physiologic tachycardia, a pathologic tachycardia, or fibrillation is being detected.

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