Which ECG findings are characteristic of pericardial effusion?

Updated: Nov 28, 2018
  • Author: William J Strimel, DO, FACP; Chief Editor: Terrence X O'Brien, MD, MS, FACC  more...
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Electrical alternans, which is the beat-to-beat variation in the direction and amplitude of the QRS complex, is the electrical signature of “swinging” of the heart in the pericardial fluid. In extreme cases, it can involve the P as well as the T waves. It is specific, but not sensitive, for tamponade and can also be seen in large pericardial effusions. [26]

Low-voltage QRS complexes, classically defined as total amplitude of the QRS complex less than 0.5 mv in the limb leads and less than 1 mv in the precordial leads, can also be seen in large effusions and tamponade. One study using limb lead criteria showed that it is more specific for tamponade rather than an effusion. [27]

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