ECG diagnosis of acute myocardial infarction in patients with pacemakers.

Ventricular pacing may mimic or obscure the Q waves of myocardial infarcton. Although ST-T changes may occur for other reasons, their presence should alert the physician to the possibility of acute infarction. QRS complexes may be evaluated for infarction if supraventricular beats without left bundle-branch block occur prematurely, as part of a supraventricular tachycardia or as escape beats after inhibition of the articifial pacemaker.