Cystic Tumor of the Atrioventricular Node Causing Rapid-Onset and Reversible Complete Heart Block

Cystic tumors of the atrioventricular node are rare primary cardiac neoplasms, frequently reported as a postmortem diagnosis during autopsy. Despite their small size, they can present with complete heart block or sudden cardiac death. Herein, we present a case of rapidly progressing high-grade atrioventricular block that improved after surgery. (Level of Difficulty: Intermediate.)