Signal Averaging in Patients withCoronary Artery Disease:

Late Potentials in CAD. In patients who have survived acute myocardial infarction, thepresence of ventricular late potentials using the high resolution signal-averaged KCG indicatesareas of slow conduction and delayed activation that may potentially serve as a substrate lormalignant ventricular arrhythmias. Although detection of late potentials is technique specific, signal-averaged analysis in the time or frequency domain may he a useful index for riskstratification with regard to ventricular tachycardia or sudden cardiac death. The sensitivityand specificity of late potentials for this purpose may he enhanced by comhination with othervariables, such as left ventricular ejection fraction and presence of complex ventricular ectopy, Therefore, the presence of ventricular late potentials in postmyocardial infarction patients, particularly in those patients with impaired left ventricular function, identifies those patienlswho are at high risk of malignant ventricular tachyarrhythmias, However., (he strategies forprevention of serious arrhythmia complications during follow-up need to be established, Thenegative predictive value of late potentials is very high. Thus, the absence of late potentialsindicates a low propensity to sustained ventricular tachycardia or sudden death, even in thepresence of complex ventricular ectopy. Interventions may therefore not be necessary orshould even he avoided, The incidence of late potentials in patients with spontaneous orinduced ventricular fibrillation is lower and, if present, less pronounced than in those with sustained monomorphic ventricular tachycardia. This presumably is due to a lower degree of conduction delay, which serves as a substrate for reentry. Therefore, the ability of the signal-aver-aged ECG to predict a propensity to ventricular fibrillation is limited, Despite these limitations, the signal-averaged ECG may be used as a risk predictor in evaluation of patients aftermyocardial infarction. Unfortunately, at least as far as time domain analysis is concerned, itcannot be used as an efficacy predictor for response to pbarniacologic interventions, Furtherstudies will determine whether other modes of signal-averaged analysis can predict theresponse to drugs.