Methods and implantable medical devices (IMDs) are provided for monitoring a cardiac function of a heart. A heart sound sensor is configured to sense heart sound signals of the subject. The IMD includes a memory to store program instructions. The IMD includes a processor that, when executing the program instructions, is configured to identify S2 signal segment from the heart sound signals, analyze the S2 signal segment to identify a pulmonary valve signal (P2 signal) and an aortic valve signal (A2 signal) within an S2 signal segment of the heart sound signals. The processor is configured to determine a time interval between the A2 and P2 signals, characterize the S2 signal segment to exhibit a first type of S2 split based on the time interval, and identify a cardiac condition based on a comparison of the first type of S2 split and a cardiac condition matrix.
