[Electrocardiographic alternans]

Abstract

A simple ECG curiosity or a precursor of serious arrhythmia, associated with pericardial effusion or a sign of inotropic alteration, the phenomenon of electrical alternans has intrigued clinicians and research workers in its multiple facets, mechanical and electrical, consequences on PR interval, QRS complex or ventricular repolarisation. As a consequence, the causal mechanisms are very different, but these last few years, a predominant role of calcium flux, especially intracellular, has been demonstrated. Recently, clinical interest in this phenomenon has been revived with the demonstration of micro-alternans of repolarisation, apparently a new marker for the risk of sudden death.