Medical Definition of alternans
: alternation in the pattern of activity (such as that produced by the heartbeat) <Her electrocardiogram showed small spikes that alternated in shape—a classic sign of cardiac tamponade called electrical alternans.—Tony Dajer, Discover, March 2002> <The noninvasive detection of an increased risk of ventricular fibrillation may be made possible by the identification of T-wave alternans, a beat-to-beat fluctuation in the area under the T wave that is associated with an increased risk of lethal arrhythmia.—James E. Muller and Richard L. Verrier, The New England Journal of Medicine, 15 Feb. 1996>—see pulsus alternans
Seen and Heard
What made you want to look up alternans? Please tell us where you read or heard it (including the quote, if possible).