ST alternans induced by propafenone. Use-dependence of heart rate phenomenon demonstrated in clinical practice.

ST alternans reflects changes in action potential duration with increased electrical heterogeneity proportional to the alternation intensity. Although the mechanisms of ST and T alternans are still largely unknown, four mechanisms have been proposed: a) calcium overload, b) effect of chemicals from sustained ischemia, c) stimulation of the 5-HTreceptor and d) inhomogeneous blockade of sodium channels. Propafenone is a class IC sodium channel blocker, frequently used in the pharmacological cardioversion of atrial fibrillation, and has a use-dependence of heart rate phenomenon that can induce a Brugada pattern and electrical alternans. In this article, a clinical case demonstrating these two phenomena is presented. [ABSTRACT FROM AUTHOR]