Basic mechanisms of reentrant arrhythmias

The mechanisms responsible for active cardiac arrhythmias are generally divided into two major categories: (1) enhanced or abnormal impulse formation and (2) reentry. Reentry can be subdivided into three subcategories: (1) circus movement, (2) reflection, and (3) Phase 2 reentry. Reentry occurs when a propagating impulse fails to die out after normal activation of the heart and persists to re-excite the heart after expiration of the refractory period. Evidence implicating reentry as a mechanism of cardiac arrhythmias stems back to the turn of the century. Amplification of intrinsic electrical heterogeneities provides the substrate responsible for developing Phase 2 and circus movement reentry, which underlie Ventricular tachycardia in the long QT and Brugada syndromes. Curr Opin Cardiol 2001, 16:1-7 (C) 2001 Lippincott Williams & Wilkins, Inc.