VfA cardiac therapy uses an implantable medical device or system. The implantable medical device includes a tissue-piercing electrode implanted in the left ventricular myocardium of the patient's heart from the right atrium through the right atrial endocardium and central fibrous body. The device may include a right atrial electrode, a right atrial motion detector, or both. The device may be implanted completely within the patient's heart or may use one or more leads to implant electrodes in the patient's heart. A separate medical device may be used to provide some functionality for cardiac therapy. The implantable medical device or separate medical device may be used to measure physiological response information, such as cardiac electrical heterogeneity information. The physiological response information may be used to calibrate and deliver adaptive pacing therapy.
