ECG Findings in Massive Pericardial Effusion

Massive pericardial effusion produces a characteristic ECG triad of:

Electrical alternans
  • Consecutive, normally-conducted QRS complexes that alternate in height
  • Occurs when the heart swings backwards and forwards within a large fluid-filled pericardium
Electrical alternans: Alternating QRS complex height best seen in lateral precordial leads


Patients with this ECG pattern need to be immediately assessed for clinical and echocardiographic evidence of tamponade.

Example 1
Alternating QRS amplitude and axis
Alternating QRS amplitude and axis. Mugmon 2012

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Emergency Physician in Prehospital and Retrieval Medicine in Sydney, Australia. He has a passion for ECG interpretation and medical education | ECG Library |

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

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