Quantitative analysis of the signal-averaged QRS in patients with arrhythmogenic right ventricular dysplasia.

Temporal signal averaging of the surface QRS (V1 + V3 + V5) was performed in 16 patients with arrhythmogenic right ventricular dysplasia and in 16 normal subjects. The differences between ARVD patients and normals were large for the filtered QRS duration (FQRSd) (146.2 +/- 18.9 ms vs. 91.8 +/- 4.1 ms, P less than 0.000001), the late potential duration (LPd) (83.5 +/- 23.3 ms vs. 23.6 +/- 4.6 ms, P less than 0.00001), the LPd/FQRSd ratio (53.9 +/- 10.1% vs. 25.8 +/- 5.1%, P less than 0.00001), the filtered QRS amplitude (234.0 +/- 61.1 microV vs. 429 +/- 94.2 microV, P less than 0.001), and the root mean square voltage of the signals in the terminal 40 and 50 ms of the FQRS (RMS40 and RMS50) (18.4 +/- 10.0 microV vs. 118.4 +/- 49.8 microV, P less than 0.0005 and 27.9 +/- 19.2 microV vs. 217.0 +/- 66.3 microV, P less than 0.000002). RMS50 less than 40 microV discriminated best between ARVD and normals (81% sensitivity and 100% specificity). The right-sided predominance of the abnormalities in ARVD was demonstrated by the significantly longer FQRSd and LPd, and the higher ratio LPd/FQRSd in right than in left precordial leads. The arrhythmia susceptibility did not seem to influence the presence of or properties of LP in the ARVD group. Patients with multiple QRS morphologies during ventricular tachycardia (VT) had, compared with patients with only one type of VT, longer LPd (108.3 +/- 46.4 ms vs. 64.2 +/- 31.7 ms, P less than 0.02) and lower RMS40 voltage (9.4 +/- 9.9 microV vs. 25.4 +/- 21.6 microV, P less than 0.05). The relative heart volume was positively correlated with delayed activity, but an enlarged heart was not a pre-requisite for the presence of LP. The method thus identifies changes which are specific to ARVD. The findings indicate that certain electrical or morphological conditions are required for the occurrence of arrhythmias.