[QT time and the ventricular refractory period in programmed electrical stimulation of the heart in patients with ventricular and supraventricular tachycardias--effect of sotalol].

The QT-interval in the surface electrocardiogram (usually lead II) and the effective refractory period of the right ventricle (ERP-V) were investigated in 16 patients with documented supraventricular tachycardia (SVT) and in 18 patients with documented ventricular tachycardia (VT) during basic pacing (QT1) and programmed stimulation of the right ventricular apex (QT2) (single-test stimulation at 3 different rates, BCL: 600 ms, 500 ms, 430 ms). The effects of intravenous and oral Sotalol were analysed in the SVT-group. An increase in heart rate was followed by a significant decrease of the QT-intervals and ERP-V in both groups. The QT-intervals and the ERP-V were statistically significantly prolonged by intravenous Sotalol. The VT-group showed a statistically significant longer shortest QT2-interval during programmed stimulation, which can be explained by a greater dispersion of action potentials leading to an inhomogenous ventricular recovery process, which may represent the electrical substrate for the arrhythmia.