Patent ID: 8140156

Claim:
A method comprising: determining that a cardiac rhythm of a heart of a patient is treatable by delivery of an antitachyarrhythmia therapy from a medical device to the patient based on an analysis of electrical activity of the heart of the patient; receiving a heart sound signal from a heart sound sensor, the heart sound signal representing sounds generated by the heart and bloodflow of the patient; detecting a plurality of heart sounds within the heart sound signal; classifying each of the detected heart sounds as one of a first classification or a second classification based on one or more features of the detected heart sounds; selectively delivering or withholding the antitachyarrhythmia therapy based on the classifications of the detected heart sounds; and generating an envelope signal of the heart sound signal, wherein detecting a plurality of heart sounds within the heart sound signal comprises detecting a plurality of heart sounds within the envelope signal, wherein generating the envelope signal comprises: bandpass filtering the heart sound signal; rectifying the filtered signal; smoothing the rectified signal; and applying a box-car filter to the smoothed signal to generate the envelope signal.