Mechanism of electrical alternans in patients with pericardial effusion

ECG Changes Post-pericardiocentesis for Cardiac Tamponade Secondary to Non-small Cell Carcinoma of the Lung

Electrical alternans on electrocardiograph (ECG) is an uncommon but nearly pathognomonic sign of cardiac tamponade. Here, we present a male quadragenarian who came to the emergency department complaining of low back and right upper abdominal pain. Work-up revealed a large pericardial effusion associated with electrical alternans on ECG and clinical findings of cardiac tamponade. Pericardiocentesis drained approximately 1 liter of hemorrhagic fluid with resolution of cardiac tamponade and normalization of the ECG. Further evaluation with right hilar lymph node biopsy confirmed a diagnosis of poorly differentiated non-small cell adenocarcinoma of the lung.

Cardiac Alternans: From Bedside to Bench and Back

Cardiac alternans arises from dynamical instabilities in the electrical and calcium cycling systems of the heart, and often precedes ventricular arrhythmias and sudden cardiac death. In this review, we integrate clinical observations with theory and experiment to paint a holistic portrait of cardiac alternans: the underlying mechanisms, arrhythmic manifestations and electrocardiographic signatures. We first summarize the cellular and tissue mechanisms of alternans that have been demonstrated both theoretically and experimentally, including 3 voltage-driven and 2 calcium-driven alternans mechanisms. Based on experimental and simulation results, we describe their relevance to mechanisms of arrhythmogenesis under different disease conditions, and their link to electrocardiographic characteristics of alternans observed in patients. Our major conclusion is that alternans is not only a predictor, but also a causal mechanism of potentially lethal ventricular and atrial arrhythmias across the full spectrum of arrhythmia mechanisms that culminate in functional reentry, although less important for anatomic reentry and focal arrhythmias.

The importance of an ECG: back to basics

A 48-year-old man presented to accident and emergency with syncope on a background history of 3 weeks of increasing shortness of breath. He collapsed at home prompting admission. He was a smoker with a 30-pack-year history. On examination, he was found to be tachypnoeic and hypoxic, with a raised JVP and quiet heard sounds. He was haemodynamically stable and a chest x-ray showed right upper-lobe collapse. His resting ECG demonstrated electrical alternans prompting urgent referral to the cardiologist for echocardiography. This revealed a large pericardial effusion with evidence of right ventricular diastolic collapse. In view of this, he underwent urgent pericardiocentesis. A subsequent CT scan showed bilateral pleural effusions and multiple lung nodules. Both pericardial and pleural fluid cytology were reported as metastatic non-small cell adenocarcinoma. The pericardial fluid continued to reaccumulate requiring a pericardial window. He was referred to the oncology team for palliative chemotherapy.