Patent ID: 8597197

Claim:
A system comprising: an implantable heart sound sensor circuit configured to produce an electrical heart sound signal representative of a heart sound of a subject; a second sensor circuit that includes a respiration sensor configured to produce a respiration signal representative of respiration of the subject; a processor circuit coupled to the heart sound sensor circuit and the second sensor circuit, wherein the processor circuit includes: a detection circuit configured to detect a phase of a respiration cycle using the respiration signal; a heart sound feature circuit configured to identify a heart sound feature in the electrical heart sound signal according to sensitivity of the identified feature to a change in the respiratory cycle, determine a metric for the identified heart sound feature, and select the identified heart sound signal feature for trending according to the determined metric; and a trending circuit configured to trend a difference between the identified heart sound feature during the detected phase of the respiration cycle and outside the detected phase of the respiration cycle, and wherein the processor circuit is configured to generate an indication of a change in a physiologic condition of the patient according to the trend and provide the indication to a user or process.