Adaptively creating a table of optimal, patient-specific atrioventricular (AV) delays for a an implantable medical device (IMD) begins as the IMD detects the patient entering a target heart rates within a defined range of elevated heart rates. On detection, the device begins testing AV delays by pacing the heart at a number of different AV delays. The IMD selects the optimal AV delay based on a comparison of measurements of cardiac output obtained during each delay's test pacing period. The optimal AV delay corresponds to the one which resulted in the highest cardiac output. The device selects this optimal AV delay and stores it in an AV delay table on the device. The process continues as the device detects the patient entering the other target heart rates in order to complete the table.