Electrical alternans is associated with Massive Pericardial Effusion

Massive pericardial effusion produces a triad of:

• Low QRS voltage
• Tachycardia
• Electrical alternans

ECG findings with Electrical alternans

Electrical alternans occurs when

• consecutive, normally-conducted QRS complexes alternate in height.
• the heart swings backwards and forwards within a large fluid-filled pericardium.

Management

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

How to diagnose pericardial tamponade on bedside echo, Part 1 and Part 2 (from the Ultrasound Podcast)

References

• Dr Smith’s ECG Blog: Differential diagnosis of low QRS voltage
• Mugmon, M. Electrical alternans vs. pseudoelectrical alternans. J Community Hosp Intern Med Perspect. 2012; 2(1) [PMC 3714094]

LITFL Further Reading

• ECG Library Basics – Waves, Intervals, Segments and Clinical Interpretation
• ECG A to Z by diagnosis – ECG interpretation in clinical context
• ECG Exigency and Cardiovascular Curveball – ECG Clinical Cases
• 100 ECG Quiz – Self-assessment tool for examination practice
• ECG Reference SITES and BOOKS – the best of the rest

Advanced Reading

• Brady WJ, Truwit JD. Critical Decisions in Emergency and Acute Care Electrocardiography
• Surawicz B, Knilans T. Chou’s Electrocardiography in Clinical Practice: Adult and Pediatric
• Wagner GS. Marriott’s Practical Electrocardiography 12e
• Chan TC. ECG in Emergency Medicine and Acute Care
• Rawshani A. Clinical ECG Interpretation
• Mattu A. ECG’s for the Emergency Physician
• Hampton JR. The ECG In Practice, 6e