Pericardial effusion with electrical alternans

ECG: This tracing shows a sinus tachycardia and an electrical alternans of the QRS-complexes (alternans between 2 QRS of different morphology and amplitude); low QRS voltage in limb leads and precordial leads; A cardiac ultrasound revealed a substantial pericardial effusion (2 cm circumference) with a swinging heart pattern explaining the electrical alternans pattern; pericardial puncture by the sub-xyphoidal route allowing to evacuate 750 ml;

ECG 2:

ECG 2: Tracing recorded after the puncture; resolution of the electrical alternans patternComments: This patient presented an episode of cardiac tamponade due to abundant pericardial effusion requiring an emergency pericardial puncture. The electrocardiogram preceding the puncture showed the presence of an electrical alternans which was reflected by the alternans between 2 QRS-complexes of slightly different morphology and amplitude. This particular pattern does not result from successive modifications in atrial and ventricular myocardial activation but of pendular movements of the floating cardiac mass within a pericardial effusion (swinging heart). While the association between electrical alternans and sinus tachycardia is relatively specific to the poorly-supported diagnosis of abundant pericardial effusion, it does not allow a definitive diagnosis. Indeed, an alternans can also be observed during deep inspiration, severe left ventricular decompensation, accessory pathway orthodromic tachycardia, bidirectional ventricular tachycardia, a variable aberration during a supraventricular tachycardia or compressive pneumothorax (significant movements of the rib cage).

Take-home message: The association between sinus tachycardia and electrical alternans of QRS, P-wave and/or T-wave patterns should point to a diagnosis of abundant pericardial effusion.