Copyright © 1993 by the European Society of Cardiology.
© 1993 The European Society of Cardiology
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
Department of Cardiological Sciences, St George's Hospital Medical School London, U.K.
Received 21 September 1992; revised 27 January 1993; .
Correspondence: William J. McKenna, MD, Department of Cardiological Sciences. St George's Hospital Medical School, Cranmer Terrace, London SWl7 0RE, U.K.
Abstract
Late potentials detected by the signal-averaged ECG (SAECG) identify post-infarction patients at risk from sustained ventricular tachycardia (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 monitoring are a marker of high risk patients. In children and adolescents, however, there is no reliable ECG marker, and clinical features have low predictive accuracy. The prognostic value of the SAECG in HCM has not been systematically evaluated.
We examined the relation of detailed time domain, frequency domain, and spectral temporal mapping analysis of the SAECG and clinical and echocardiographic features, and the results of 48 h ambulatory ECG monitoring in 121 consecutive patients with HCM. Non-sustained VT on Holter monitoring was recorded in 27 (23%) patients. An abnormal time domain SAECG was present in three (11%) patients with VT vs three (3%) without VT (ns). Of the SAECG variables, reduced (below 150 µ V) voltage of the initial 40 ms of the signal-averaged QRS complex was the best predictor for non- sustained VT (sensitivity: 95% specificity: 74% ;positive predictive accuracy: 64%; negative predictive accuracy: 97%). Nine patients (of whom eight were 
30 years of age) experienced catastrophic events: three died suddenly and six had been resuscitated from out-of-hospital ventricular fibrillation. None of them had an abnormal time domain SAECG. The frequency domain analysis and spectral temporal mapping of the SAECG did not improve the identification of patients with VT or patients with catastrophic events.
In conclusion, alterations of the initial portion of the signal-averaged QRS complex identified patients with HCM and non-sustained VT, but the SAECG was not useful in identifying young patients who suffered cardiac arrest.
Key Words: Late potentials • ventricular tachycardia
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