Dispersion of ventricular repolarization in the long QT syndrome

To identify markers of dispersion of the ventricular repolarization in the idiopathic long QT syndrome, body surface potential maps were analyzed in 40 such patients (mean age ± standard deviation 21 ± 11 years) and in 30 healthy control subjects (mean age 24 ± 7 years). In each subject, 117 chest leads were recorded and maps of the integral values of the QRST interval were calculated. A multipolar distribution of the values, a marker of gross electrical inequalities of repolarization, was found only in 4 patients. To detect minor regional disparities of ventricular recovery, all the ST-T waveforms were analyzed in each subject. The ST-T waves were represented by a discrete series of potential values. The "similarity index" was computed by applying a principal component analysis, which represents (in percent) to what extent 1 fundamental pattern of ST-T reproduces all the recorded waveforms. The mean value of the similarity index was significantly lower in patients with long QT syndrome than in control subjects (49 ± 10 vs 77 ± 8%, p <0.0001). A value