Massive pericardial effusion: A rare and easily missed finding in myocardial perfusion scintigraphy.

A 72-year-old gentleman underwent myocardial perfusion scintigraphy (MPS) for sinus tachycardia of unknown cause. Baseline electrocardiography (ECG) showed sinus tachycardia and electrical alternans. Thallium-201 stress-redistribution MPS was performed with dipyridamole stress. On the raw projection images, a photopenic "halo" was noted surrounding the heart. Reconstructed slices showed small left ventricle with no obvious perfusion defect. Review of single-photon emission computed tomography/computed tomography images showed suspected large pericardial effusion. The patient was admitted and Echocardiography showed significant circumferential pericardial effusion with early tamponade effect. Subsequent bedside pericardiocentesis aspirated 800 ml blood-stained fluid and the cytology yielded metastatic adenocarcinoma with features suggestive of pulmonary primary. Pericardial effusion is a rare finding in MPS. Finding of a "halo" around the heart should raise suspicion on the presence of pericardial effusion and confirmatory investigation such as ECG may be warranted.