A cardiac rhythm management system selects an atrioventricular (A-V) delay based on a time-interval between an atrial depolarization and mitral valve closure (MVC). For several different A-V delays, the system measures time intervals between atrial depolarizations (i.e., sensed or paced P-waves) and accelerometer-detected MVCs. Based on this information, the system selects a particular A-V delay for improving cardiac output during subsequent delivery of cardiac rhythm management therapy.