An example medical system includes a plurality of electrodes configured to sense a cardiac electrogram of a patient; and processing circuitry configured to: perform feature extraction of the sensed cardiac electrogram to extract a plurality of features from the sensed cardiac electrogram; convert one or more of the plurality of extracted features to a respective feature image; apply a machine learning model, trained using cardiac electrogram data for a plurality of patients, to an image of the sensed cardiac electrogram and at least the respective feature image to determine whether one or more particular heartbeats in the sensed cardiac electrogram indicate a premature ventricular contraction (PVC) beat; and in response to the determination that the one or more particular heartbeats indicates a PVC beat, output a classification that the one or more particular heartbeats is a PVC beat.