THE ELECTROCARDIOGRAPHIC DIAGNOSIS OF ACUTE MYOCARDIAL-INFARCTION IN PATIENTS WITH VENTRICULAR PACED RHYTHMS

Use of the ECG for diagnosis of ischemic heart disease is more difficu lt in the setting of ventricular paced rhythms (VPRs). ST-segment/T-wa ve configurations are changed by the altered intraventricular conducti on associated with ventricular pacing. The anticipated, or expected, m orphology in patients with VPRs is one of QRS-complex-ST-segment to T- wave discordance. Several strategies are available to the physician to assist in the correct interpretation of the 12-lead ECG in patients w ith permanent ventricular pacemakers, including: a knowledge of the an ticipated ST-segment-T-wave changes of VPRs and consequently the abili ty to recognize acute, ischemic morphologies; the performance of seria l ECGs or ST-segment trend monitoring demonstrating dynamic changes en countered in acutely ischemic patients; a comparison with previous ECG s; and, if appropriate, an analysis of the native, underlying rhythm. The first strategy, an awareness of the anticipated ST-segment morphol ogies of VPRs, is the most important and not dependent on additional d iagnostic testing, past medical records, or additional expertise in pa cemaker function, Two cases are reported in which an analysis of the E CG in the setting of VPR assisted the treating physicians in establish ing the correct diagnosis of acute myocardial infarction.