Techniques are provided for discriminating episodes of cardiac ischemia indicated based on shifts in ST segment elevation from false detections due to atrial fibrillation (AF) or other confounding factors such as premature ventricular contractions (PVCs.) In an example for use with a single-chamber device, in response to a possible ischemic event, the single-chamber device assesses ventricular stability based an examination of ventricular intracardiac electrogram (IEGM) signals. If the ventricular IEGM is unstable due to paroxysmal AF or frequent PVCs, the ischemic event is rejected as a false detection. Otherwise, the device responds to the event by, for example, generating warning signals, recording diagnostic data or controlling device therapy. The stability discrimination techniques are particularly advantageous for use within single-chamber devices that lack automatic mode switching but are also beneficial within at least some dual-chamber devices or multi-chamber systems.
