[The influence of myocardial ischemia on the electrocardiogram under stress]

Abstract

Ventricular late potentials (LP) seem to reflect mixed, anatomic and electrophysiologic substrate for ventricular reentrant tachyarrhythmias. Ischemic events can perform areas of delay and dispersion of conduction and refractoriness in patients with ischaemic heart disease (CAD), especially after myocardial infarction (MI). These electrophysiological disturbances can induce the reentry phenomenon. LP are present in 18-53% patients with CAD, but in selected groups of patients after MI with ventricular tachycardia or/and cardiac arrest in the past, LP are registered in 63-92% objects. The influence of acute ischemia provoked by the effort and pharmacological stress testing isn't significant in groups with CAD without MI. Occurrence of LP increase in a small grade only in post-MI patients but differences of time domain parameters of signal-averaged ECG (SAECG) are not statistically significant. There are no correlations between LP incidence during ischemia and left ventricle wall motion disturbances, ejection fraction, localisation of MI, date of MI and number of occluded coronary vessels in the greater part of investigations, but the results are divergent and the matter has to be studied. Time domain SAECG is one of admitted methods of risk stratification of incidence of sustained ventricular tachycardia in patients with CAD, but the parameters of frequency domain SAECG still are not standardized, so its clinical usefulness isn't clear.