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Initial depolarizing potentials in wolff‐parkinson‐white syndrome using signal‐averaged electrocardiograms: Correlation with reciprocating tachycardia

Initial depolarizing potentials were examined in patients with Wolff‐Parkinson‐White (WPW) syndrome using signal‐averaging techniques. In all, 25 WPW patients and 21 agematched healthy children were studied. Ten of the patients were symptomatic and 15 were asymptomatic. Symptomatic patients with supraventricular tachycardias had longer durations of lowamplitude signals (LAS) < 40 μ V in the initial portion of the QRS complex (initial LAS, 49 ± 7 ms vs. 37 ± 9 ms, p < 0.01) and lower root‐mean‐square (RMS) voltage in the initial 40 ms of the QRS complex (initial RMS, 12 ± 4 μ V vs. 23 ± 8 μ V, p < 0.01) compared with asymptomatic patients. When a symptomatic patient was defined as having an initial LAS of > 46 ms or an initial RMS of < 15 μ V, the sensitivity and specificity for predicting documented supraventricular tachycardia were 100 and 67%, respectively. These SA‐ECG findings may reflect instability of conduction in symptomatic patients through an accessory pathway and may identify those at high risk for supraventricular tachycardia.