From the Guidelines
Electrical alternans is a cardiac rhythm abnormality characterized by beat-to-beat alternation in the amplitude or direction of the QRS complex on an electrocardiogram (ECG), most commonly occurring in patients with pericardial effusion and cardiac tamponade. This condition is identified by the alternating height of the QRS complexes, where one beat appears tall and the next appears small, creating a pattern that repeats throughout the ECG.
- The presence of electrical alternans is a significant finding that should prompt immediate evaluation for cardiac tamponade, particularly when accompanied by other clinical signs like hypotension, jugular venous distention, and muffled heart sounds (Beck's triad) 1.
- The physiological basis for this phenomenon is the mechanical swinging of the heart within fluid-filled pericardium, changing the electrical vector with each heartbeat.
- While most strongly associated with pericardial effusion, electrical alternans can occasionally be seen in severe heart failure, certain tachycardias, or other cardiac conditions, as noted in various studies on cardiac arrhythmias and their management 1.
- It is essential to recognize electrical alternans as it may indicate a life-threatening condition requiring emergency intervention, such as pericardiocentesis to remove the fluid and relieve pressure on the heart.
From the Research
Definition of Electrical Alternans
- Electrical alternans is an electrocardiographic phenomenon characterized by an alternating amplitude or axis of the QRS complexes in any or all leads 2.
Clinical Association
- It is most commonly associated with a large pericardial effusion and impending threat of cardiac tamponade 2.
Clinical Significance
- Electrical alternans can be seen in a variety of other clinical scenarios with varying etiologies and prognoses 2.
- It is considered an electrocardiographic sign, rather than a diagnosis, with a broad differential for potential etiologies 2.
Mechanisms and Research
- The potential mechanisms and clinical significance of electrical alternans are not fully understood and require further research for some causes 2.