A leadless cardiac pacemaker configured to sense cardiac activity and to deliver pacing therapy to a patient's heart, the LCP comprising: a housing having a proximal end and a distal end; a first electrode secured relative to the housing and exposed to the environment outside of the housing; a second electrode secured relative to the housing and exposed to the environment outside of the housing; a diaphragm that is exposed to the environment outside of the housing, the diaphragm is responsive to an external pressure applied to the diaphragm by the environment outside of the housing; a piezoelectric membrane having a first pressure sensor electrode and a second pressure sensor electrode, the piezoelectric membrane is configured to generate an electrical voltage between the first pressure sensor electrode and the second pressure sensor electrode in response to a pressure change applied to the diaphragm, the electrical voltage representative of a change in external pressure applied to the diaphragm; and circuitry in the housing operatively coupled to the first electrode and the second electrode of the LCP, and also operatively coupled to the first pressure sensor electrode and the second pressure sensor electrode, the circuitry is configured to deliver a pacing therapy to the patient's heart via the first electrode and the second electrode of the LCP, wherein the pacing therapy is dependent, at least in part, on the electrical voltage generated by the piezoelectric membrane and that is representative of the change in external pressure applied to the diaphragm; and wherein the circuitry is configured to identify one or more pressure events associated with the patient's heart based, at least in part, on the electrical voltage generated by the piezoelectric membrane, and time delivery of at least part of the pacing therapy based on one or more of the identified pressure events. a housing having a proximal end and a distal end; a first electrode secured relative to the housing and exposed to the environment outside of the housing; a second electrode secured relative to the housing and exposed to the environment outside of the housing; a diaphragm that is exposed to the environment outside of the housing, the diaphragm is responsive to an external pressure applied to the diaphragm by the environment outside of the housing; a piezoelectric membrane having a first pressure sensor electrode and a second pressure sensor electrode, the piezoelectric membrane is configured to generate an electrical voltage between the first pressure sensor electrode and the second pressure sensor electrode in response to a pressure change applied to the diaphragm, the electrical voltage representative of a change in external pressure applied to the diaphragm; and circuitry in the housing operatively coupled to the first electrode and the second electrode of the LCP, and also operatively coupled to the first pressure sensor electrode and the second pressure sensor electrode, the circuitry is configured to deliver a pacing therapy to the patient's heart via the first electrode and the second electrode of the LCP, wherein the pacing therapy is dependent, at least in part, on the electrical voltage generated by the piezoelectric membrane and that is representative of the change in external pressure applied to the diaphragm; and wherein the circuitry is configured to identify one or more pressure events associated with the patient's heart based, at least in part, on the electrical voltage generated by the piezoelectric membrane, and time delivery of at least part of the pacing therapy based on one or more of the identified pressure events.