The value of time and frequency domain, and spectral temporal mapping analysis of the signal-averaged electrocardiogram in identification of patients with hypertrophic cardiomyopathy at increased risk of sudden death

Late potentials detected by the signal-averaged ECG (SAECG)identify post-infarction patients at risk from sustained ventriculartachycardia (VT) and sudden death. Hypertrophic cardiomyopathy(HCM) is also associated with increased risk of sudden death.In adults, episodes of non-sustained VT on ambulatory ECG monitoringare a marker of high risk patients. In children and adolescents,however, there is no reliable ECG marker, and clinical featureshave low predictive accuracy. The prognostic value of the SAECGin HCM has not been systematically evaluated. We examined the relation of detailed time domain, frequencydomain, and spectral temporal mapping analysis of the SAECGand clinical and echocardiographic features, and the resultsof 48 h ambulatory ECG monitoring in 121 consecutive patientswith HCM. Non-sustained VT on Holter monitoring was recordedin 27 (23%) patients. An abnormal time domain SAECG was presentin three (11%) patients with VT vs three (3%) without VT (ns).Of the SAECG variables, reduced (below 150 µ V) voltageof the initial 40 ms of the signal-averaged QRS complex wasthe best predictor for non- sustained VT (sensitivity: 95% specificity:74% ;positive predictive accuracy: 64%; negative predictiveaccuracy: 97%). Nine patients (of whom eight were 30 years ofage) experienced catastrophic events: three died suddenly andsix had been resuscitated from out-of-hospital ventricular fibrillation.None of them had an abnormal time domain SAECG. The frequencydomain analysis and spectral temporal mapping of the SAECG didnot improve the identification of patients with VT or patientswith catastrophic events. In conclusion, alterations of the initial portion of the signal-averagedQRS complex identified patients with HCM and non-sustained VT,but the SAECG was not useful in identifying young patients whosuffered cardiac arrest.