electrical alternans

alternans /al·ter·nans/ (awl-ter´nanz) [L.]

1. alternating; see pulsus alternans.

2. alternation.

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electrical alternans  alternating variations in the amplitude of specific electrocardiographic waves over successive cardiac cycles.

mechanical alternans  alternation of the heart, particularly in contrast to electrical alternans.

pul´sus alternans  see under pulsus.

total alternans  pulsus alternans in which alternating beats are so weak as to be undetected, causing apparent halving of the pulse rate.

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electrical alternans

Cardiology Marked swings in the QRS complex amplitude, which occur every 2 to 3 beats, caused by 'circus movement' in the myocardium Etiology Cardiac tamponade, pericardial effusion, pneumopericardium, cardiac muscle dysfunction, and paroxysmal SVT; EA may presage sudden cardiac death, and may precede V Fib in Pts undergoing coronary angioplasty or those with Prinzmetal's angina, congenital prolonged QT syndrome, acute MI, catecholamine excess, electrolyte derangements; EA affecting the ST segment and T wave is common in Pts at risk for ventricular arrhythmias–VAs and may be a noninvasive marker of susceptibility to VAs