Abstract
BACKGROUND: Right-sided interatrial septal pouches (RSSPs) are an uncommon anatomical variant with unclear clinical significance. CASE SUMMARY: We present a unique case of a patient who was found to have a RSSP thrombus following an initial episode of pulseless electrical activity cardiac arrest, likely due to massive bilateral pulmonary embolism. DISCUSSION: Existing literature on atrial septal pouches predominantly focuses on left-sided presentations and their potential clinical implications. Documented cases of RSSP are limited. TAKE-HOME MESSAGE: RSSPs are uncommon anatomical variants that may serve as embolic sources even in the absence of traditional thrombotic risk factors. This case underscores the diagnostic importance of transesophageal echocardiography which may identify RSSPs missed on routine transthoracic echocardiography or computed tomography.