Striking electrical and mechanical alternans associated with cardiac tamponade.

Document Type



Internal Medicine (East Africa)


A 39-year-old woman with several weeks’ history of malaise and shortness of breath was referred because of acute deterioration. Examination revealed a regular tachycardia of 110 bpm, evidence of pulsus alternans and a blood pressure of 120/74, but was otherwise unremarkable. A routine admission 12-lead ECG (figure 1) demonstrated low voltage QRS alternans. As a result of this finding, an urgent transthoracic echocardiogram (TTE) was arranged.

TTE (figure 2, video files) confirmed a large, circumferential pericardial effusion with signs of tamponade. Soon after, the patients condition declined and blood pressure dropped to 95/65 with pulsus paradoxus >10 mm Hg detected manually. Pericardiocentesis under echo-guidance was performed promptly and 900 ml of serosanguineous fluid was removed with immediate resolution in symptoms and an improvement in blood pressure to 139/ 87. Repeat ECG (figure 3) after drainage revealed resolution of electrical alternans.

Pericardial effusion should be considered likely when electrical alternans is seen in the presence of pulsus alternans, particularly when there is no evidence of explanatory arrhythmia on ECG. When present in this context, QRS alternans typically signifies a large, haemodynamically significant, effusion and urgent imaging to confirm the diagnosis and to guide treatment is important. In effusionrelated QRS alternans, the heart swings once every second beat (2:1 swinging). This pendular cardiac motion is visible on echocardiography. True 2:1 QRS alternans occurs within a limited range of heart rates defined mathematically by the relative durations of diastole and systole.


This work was published before the author joined Aga Khan University.

Publication (Name of Journal)

BMJ Case Reports