What are the electrocardiogram (ECG) findings suggestive of pericardial effusion?

From the Guidelines

ECG findings suggestive of pericardial effusion include electrical alternans, low voltage QRS complexes, and sinus tachycardia, as noted in the 2020 European Heart Journal study 1. These findings are critical in the diagnosis of pericardial effusion, as they can indicate the presence of a large effusion. Electrical alternans, characterized by beat-to-beat variation in the amplitude or axis of the P wave, QRS complex, or T wave, is highly specific for large pericardial effusions.

• Low voltage QRS complexes, defined as QRS amplitude less than 5 mm in all limb leads or less than 10 mm in precordial leads, occur because the fluid surrounding the heart dampens electrical signals.
• Sinus tachycardia develops as a compensatory mechanism to maintain cardiac output when ventricular filling is compromised. Other potential findings include PR segment depression, widespread ST segment elevation, and T wave inversions, though these are more indicative of associated pericarditis rather than the effusion itself, as discussed in the 2015 ESC guidelines for the diagnosis and management of pericardial diseases 1. These ECG changes result from the insulating effect of fluid accumulation in the pericardial space, which reduces the electrical signal transmission to the body surface. It's essential to note that these ECG findings are not always present, especially in small to moderate effusions, and echocardiography remains the gold standard for diagnosis of pericardial effusion, as emphasized in the 2015 European Heart Journal study 1.

From the Research

ECG Findings Suggestive of Pericardial Effusion

• Low QRS voltage: defined as a sum of limb lead QRS amplitudes of 30 mm or less 2
• Electrical alternans: although this occurs only in a small percentage of patients with large effusions 2, 3
• P wave changes and T wave inversion: these changes have been described in textbooks, but their association with pericardial effusion is not well established 3
• Increased heart rate: a mean heart rate increase from 98 beats per minute to 106 beats per minute was associated with the development of effusion 3

Novel ECG-Based Tools

• The ARENA score: a novel ECG-based score that demonstrates higher sensitivity and accuracy in detecting pericardial effusion compared to traditional low-voltage ECG criteria 4
• Traditional low-voltage criteria: have limited sensitivity and specificity for diagnosing pericardial effusion 2, 3, 4

Limitations of ECG Findings

• ECG findings are often subtle, insensitive, and nonspecific, making them less useful as indicators of pericardial effusion 3
• No single ECG variable is sensitive for the detection of pericardial effusion 3
• The correlation between QRS voltage and effusion size is weak 2, 3