Phase 2 reentry in man.

Area of Science:

• Cardiology
• Electrophysiology
• Cardiac Arrhythmias

Background:

• Ventricular extrasystoles typically exhibit a fixed coupling interval relative to the preceding QRST complex.
• The precise electrophysiological mechanisms initiating human ventricular extrasystoles remain incompletely understood.

Purpose of the Study:

• To investigate if the QRST complex preceding ventricular extrasystoles differs from other sinus beats.
• To determine if phase 2 reentry, a mechanism shown in animal models, plays a role in human ventricular extrasystoles and tachycardia.

Main Methods:

• Signal-averaged ECG and single-beat analysis of intracardiac electrograms were used in 18 patients.
• Patients included those with ventricular extrasystoles/tachycardia, some with Brugada syndrome or right ventricular outflow tract ectopy.
• Analysis focused on the sinus beat immediately preceding ventricular ectopy.

Main Results:

• Significant ST-elevation and/or T-wave changes were observed in the preceding sinus beat in 6 out of 7 patients (group A).
• Similar changes, including ST-elevation and T-wave alterations, were found in 9 out of 11 patients (group B) near ablation sites.
• J-point elevation was also noted, with significant changes found in 15 out of 18 patients (83%).

Conclusions:

• Observed J-point elevation, ST-elevation, and T-wave changes preceding ventricular extrasystoles align with phase 2 reentry.
• This suggests phase 2 reentry may be the underlying mechanism for ventricular extrasystoles, ventricular tachycardia, and ventricular fibrillation in humans.
• This mechanism was previously demonstrated primarily in animal experiments.