This document discusses, among other things, a system comprising an implantable medical device (IMD) including an implantable heart sound sensor circuit configured to produce an electrical heart sound signal representative of a heart sound of a subject and a processor circuit. The processor circuit is coupled to the heart sound sensor circuit and includes a detection circuit, a heart sound feature circuit and a trending circuit. The detection circuit configured to detect a physiologic perturbation and the heart sound feature circuit is configured to identify a heart sound feature in the electrical signal. The processor circuit is configured to trigger the heart sound feature circuit in relation to a detected physiologic perturbation. The trending circuit is configured to trend the heart sound feature in relation to a recurrence of the physiologic perturbation. The processor circuit is configured to declare a change in a physiologic condition of the patient according to the trending.