15. Ventricular Arrhythmias: 15.1 Phase - 2 Reentry in Man

Ventricular extrasystoles are characterized by a fixed coupling interval to the last QRST-complex preceding it. We hypothesized that this QRST-complex differed from QRST-complexes of other sinus beats not followed by ventricular extrasystoles. Further, we investigated whether phase-2 reentry, demonstrated recently in animal experiments to initiate ventricular extrasystoles, ventricular tachycardia and ventricular fibrillation, also could play a role in humans.

We examined 18 patients with ventricular extrasystoles and/or ventricular tachycardia by signal averaging of the ECG (group A) or by single beat analysis of intracardiac electrograms (group B).

Group A consisted of 6 patients without structural heart disease and one patient with the Brugada syndrome. Six of the 7 patients had right ventricular outflow tract ventricular extrasystoles. In 6 of the 7 patients we demonstrated significant ST-elevation and/or T-wave changes in the sinus beat preceding ventricular extrasystoles compared to the second last sinus beat in one or more of the three orthogonal leads X, Y and Z.

Group B consisted of 11 patients undergoing radiofrequency ablation. Eight of the 11 patients had right ventricular outflow tract extrasystoles. In 9 of the 11 patients, single beat analysis of unipolar and bipolar electrograms recorded close to successful ablation sites demonstrated similar changes i.e. ST-elevation (median peak voltage gradient 150 microvolt (range 0-1700) and T-wave changes in the sinus beat prior to ventricular ectopy. In addition J-point elevation was demonstrated in several cases. In total, significant changes were demonstrated in 15 of the 18 patients studied (83%).

The J-point elevation, the ST-elevation and the T-wave changes documented in the last sinus beat prior to ventricular extrasystoles are in agreement with phase-2 reentry suggesting that this may be the responsible mechanism for ventricular extrasystoles and/or ventricular tachycardia/fibrillation The phenomenon has hitherto been demonstrated in animal experiments only.