Echocardiographic Demonstration of Electrical Alternans
A 49-year-old male with a history of small-cell lung cancer and distant metastasis presented with progressive dyspnea on exertion lasting 2 weeks. Physical examination demonstrated a pulse of 118 beats per minute, blood pressure of 104/62 mm Hg, jugular venous pressure of 15 cm water, pulsus paradoxus of 20 mm Hg, clear lungs, and distant heart sounds. The 12-lead ECG revealed sinus tachycardia and electrical alternans (Figure 1). Echocardiography (Figure 2A and 2B and Movie) showed a beat-to-beat swinging motion with a nearly 90° change in position of the heart in large pericardial effusion. This beat-to-beat mechanical swinging motion of heart from position A (QRS A) to position B (QRS B) explains the shift in QRS axis and hence the “electrical alternans” seen on surface ECG. Pericardiocentesis to remove 1000 mL of bloody fluid resulted in prompt clinical improvement and disappearance of the electrical alternans (Figure 3). Subsequently, the patient underwent pericardial “window.”
The Movie is available in the online-only Data Supplement at http://circ.ahajournals.org/cgi/content/full/113/24/e866/DC1.