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A time–domain signal-averaged ECG was performed in 52 patients with arrhythmogenic right ventricular dysplasia (ARVD) proven by angiography, in 45 control subjects with normal hearts, and in 132 patients with various types of ventricular arrhythmias and no evidence of cardiac disease during routine cardiac examination. Based on the results of control subjects, patients with at least 2/3 abnormal parameters (QRS ≥ 113 ms, LAS ≥ 38 ms, RMS 40 ≥ 16 μV) were considered as having late potentials (LP). Prevalence of LP was 75% (39/52) in patients with ARVD, 19% (25/132) in patients with apparently idiopathic ventricular arrhythmias, and 4% (4/45) in controls (P < 0.01). In ARVD, no relationship was found between LP and age, type of ventricular arrhythmia (sustained or not), or extent of the disease on angiography. A significant correlation was found between the values of two parameters (QRS and LAS length) and the delay between the first ventricular arrhythmia and the examination (r = 0.39 and 0.42 respectively, P < 0.01). Further examinations (echo and/or angiography) revealed underlying heart disease in 26/132 patients with apparently normal hearts, including 13 with ARVD. LP were present in 21/26 patients (81%) with diseased heart vs 4/106 (4%) in those with normal hearts after complete examination, giving a sensitivity of 86%, and a specificity of 96% for detecting underlying heart disease. During a follow-up of 3.1 ± 1.2 years after signal-averaged ECG, only one patient died from heart failure. He had the highest LAS value and the lowest total RMS of the studied population, reflecting a dramatic drop in ventricular electrical activity. No patient died suddenly, but ventricular fibrillation was recorded in three patients before the examination: LP were absent in these three cases. Absence of LP cannot rule out the presence of ARVD or the risk of sudden death. Presence of LP in patients with apparently normal hearts is a strong argument in favour of cardiac disease, especially ARVD.
Leclerco et al. (Thu,) studied this question.