UMEM Educational Pearls

Category: Cardiology

Title: pericardial effusions and electrocardiography

Keywords: pericardial effusion, tamponade (PubMed Search)

Posted: 6/13/2010 by Amal Mattu, MD (Updated: 1/18/2022)
Click here to contact Amal Mattu, MD

Pericardial tamponade is a physiological diagnosis, not an ECG diagnosis. At best, the ECG can suggest the presence of large pericardial effusions--look for the combination of low voltage, tachycardia, and electrical alternans.

Be aware, however, that electrical alternans is only present in < 1/3 of patients with large pericardial effusions. Although it is "classic" and always seems to show up on board exams, in the textbooks, and in lectures, electrical alternans in not a consistent finding in patients with large effusions or tamponade.