Case:

A 55YO man with history of hypertension and lung cancer presents after an episode of syncope. Patient states he has been feeling a bit lightheaded intermittently over the past week and reports some diarrhea.

His initial ECG is shown:

Computer Interpretation: Sinus tachycardia, Low voltage

Physician Interpretation: Tachycardia, Sinus Rhythm, Normal Axis, Normal Intervals, Isoelectric in AVL, and wandering baseline in lead II, ?different QRS morphology and amplitude in lead V3

Differential: Pericardial Effusion, Tamponade, Obesity, COPD, Infiltrative or Connective Tissue disorders, Dilated Cardiomyopathy

Why this ECG: This is an important and subtle finding on ECG that may get overlooked often. The low voltage ECG has a wide differential but what is crucial for the EM provider is to consider pericardial effusion and, if severe, tamponade physiology. The definition of low voltage is QRS height in the limb leads less than 5mm or less than 10mm in precordial leads. Pathophysiology of low voltage on ECG can be due to (1) low energy (infiltrative diseases, hypothyroidism, dilated cardiomyopathy) or (2) barrier effect (fat, air, or effusion). Considering the patient’s history of syncope and a reported history of malignancy, a pericardial effusion and cardiac tamponade should be first on our differential. If we also pay close attention to leads II and V2 we can see a wandering baseline, of which our differential should include patient respirations, movement, tremors or muscle fasciculations and importantly pericardial effusion. Lastly, if we pay careful attention to lead V3 you can see a subtle finding of electrical alternans with different QRS amplitudes varying by beat giving us further clues to our suspected diagnosis.

Can cardiac tamponade be diagnosed by physical exam? You may recall Beck’s triad for tamponade which includes the constellation of hypotension, jugular venous distention, and muffled heart sounds. Though important for board exams, a retrospective study found that the sensitivity of Beck’s triad was 0% and the sensitivity for one finding to diagnose tamponade was 50% (1). So don’t rely on Beck’s triad as a screening tool for the diagnosis of tamponade.

What did we do next?: Bedside Echocardiography (POCUS) revealed [...] :

Physician Interpretation of Echo: Large pericardial effusion, Right ventricular diastolic collapse and right atrial systolic collapse, concern for cardiac tamponade

Upon reviewing the POCUS, Cardiology was consulted and the patient was taken to the cardiac catheterization lab for an emergent pericardial window.

Repeat ECG after the window:

The Heart of the Matter:

Be wary of low voltage ECGs, especially if new compared to previous ECGs
Use bedside echocardiography to diagnose Cardiac Tamponade in the ED

Written by Joshua Kim, DO

Chief Resident, Cook County Health

Twitter: @joshekim

Edited by Tarlan Hedayati, MD

Chair of Education, Department of Emergency Medicine, Cook County Health

Twitter: @HedayatiMD

For more reading:

Life in the Fast lane: https://litfl.com/low-qrs-voltage-ecg-library/

Cardiac Tamponade from ECG weekly: https://ecgweekly.com/2019/09/amal-mattus-ecg-case-of-the-week-september-2-2019/

Cardiac Tamponde from Dr. Smith’s ECG Blog: https://hqmeded-ecg.blogspot.com/2020/07/a-young-woman-in-her-early-20s-with.html

References:

Stolz L, Valenzuela J, Situ-LaCasse E, et al. Clinical and historical features of emergency department patients with pericardial effusions. World J Emerg Med. 2017;8(1):29-33. doi:10.5847/wjem.j.1920-8642.2017.01.005

the County Consult