Atrial Flutter as an Initial Presentation of Malignant Pericardial Effusion Caused by Lung Cancer.

Pericardial effusion is a common cardiac condition that can be lethal if left untreated. Patients who have pericardial effusion often present with dyspnea, chest discomfort, chest tightness, and cough. Cardiac arrhythmia as an initial presentation of pericardial effusion is not common. While the most common cardiac arrhythmia associated with pericardial effusion is atrial fibrillation, atrial flutter as a presenting symptom of malignant pericardial effusion has been described rarely. Herein, we present the case of an elderly man who had developed atrial flutter due to malignant cardiac effusion, which subsequently led to the diagnosis of lung cancer. Clinicians should broaden the differential diagnosis of patients who present with atrial flutter. Also, point-of-care ultrasound (POCUS) may help determine the etiology of a new-onset atrial flutter.