A Case of Swinging Heart

Dr.John R. Kapoor at Stanford University, Stanford, CA has reported a case of swinging heart -Electrical alternans due to the pendular motion of the heart within the enlarged pericardial sac in a large pericardial effusion. The case appears in The New England Journal of Medicine, NEJM.

According to the history, a 39-year-old woman with a 1-year history of Stage IV melanoma presented with progressive shortness of breath, fatigue, and oedema in the legs, which had developed over the course of the previous week. A mediastinal and right supraclavicular mass had been seen without identification of a primary tumour at the time of the melanoma diagnosis. The patient received five cycles of biochemotherapy and then with antibodies against cytotoxic T lymphocyte antigen 4.

After that the superior vena cava syndrome and tracheal compression had developed, which required stenting. Consequently, she had radiation therapy. And her integrated positron-emission tomography and computed tomography continued to show active and spreading disease.

On physical examination, she revealed hypotension, tachycardia, jugular venous distention, pulses paradoxes, and distant heart sounds. Her blood pressure was 82/64 mm Hg, and the heart rate was 110 beats per minute. She was subjected to transthoracic echocardiography which showed a large pericardial effusion with swinging of the heart and collapse of the right atrium (RA) and left atrium (LA) in end diastole (Panel A, arrows) and diastolic collapse of the right ventricle (RV) (Panel B, arrows), which was consistent with pericardial tamponade.

She had pericardiocentesis which yielded 1.6 litres of bloody fluid which was subsequently shown to be a malignant effusion. Such swinging of the heart that is due to a large pericardial effusion is responsible for the beat-to-beat shift in the axis, amplitude, and morphology of the QRS interval (electrical alternans) on electrocardiography.

In the instant case, the condition resulted in a “pseudo” 2: AV block pattern, with an absent QRS interval after every other P wave (Panel A, arrowheads), despite ventricular contraction on echocardiography. Follow-up echocardiography over the next 2 days showed no reaccumulation of effusion. Paclitaxel was administered, but the patient died within 2 months after the initiation of therapy.

In cases of pericardial effusions. term electrical alternans is a misnomer since true electrical alternans is associated with abnormal conduction by Purkinje fibres or ventricular myocardium.

In fact, in all large pericardial effusions, the so-called electrical alternans results from the pendular motion of the heart within the enlarged pericardial sac and this motion changes the anatomical relation of the heart to the recording electrodes. Therefore a mechanical component has also been suggested as a potential cause in this setting.