electrical alternans
Pronunciation: al-TER-nans
Beat-to-beat alternation in QRS amplitude or axis on ECG, most commonly indicating pericardial effusion with cardiac tamponade.
Full Definition
Electrical alternans refers to the alternating pattern of QRS voltage, axis, or morphology on consecutive beats, creating a characteristic every-other-beat variation on the ECG. While total electrical alternans (involving P waves, QRS complexes, and T waves) is pathognomonic for large pericardial effusion with tamponade physiology, QRS alternans alone may also occur in massive pulmonary embolism, severe heart failure, or other conditions causing marked ventricular loading changes. Recognition triggers urgent echocardiographic evaluation and consideration of pericardiocentesis.
Usage
Usage note: Specify whether referring to total electrical alternans or QRS alternans only.
In Context
- "The ECG demonstrated electrical alternans with beat-to-beat variation in QRS amplitude." — Emergency department note
- "Electrical alternans raised immediate concern for cardiac tamponade requiring urgent echo." — Cardiology consultation