The electrocardiographic diagnosis of acute myocardial infarction in patients with ventricular paced rhythms

The electrocardiographic diagnosis of ischemic heart disease is more difficult in the setting of ventricular-paced rhythms (VPR). ST segment/T wave configurations are changed by the altered intraventricular conduction associated with ventricular pacing. The anticipated, or expected, morphology in patients with VPR is one of QRS complex-ST segment/T wave discordance. An awareness of the anticipated ST segment morphologies of VPR is mandatory for the emergency physician. This knowledge is not dependent on additional diagnostic testing, medical records, or expertise in pacemaker function. Two cases are presented in which an analysis of the electrocardiogram in the setting of VPR assisted the treating physicians in establishing the correct diagnosis of acute myocardial infarction and arranging for urgent revascularization.