A rare presentation of infective endocarditis: Phase 4 block of the left bundle branch as key for the diagnosis. A case report.

Definitive diagnosis of infective endocarditis (IE) is mainly based on microbiological and imaging criteria. In a minority of cases, particularly when perivalvular area is involved, cardiac conduction disorders (CCD) may appear, which implies worse prognosis. In this scenario, different degrees of auriculoventricular block can occur, but development of bundle branch block is rare. Herein, we present a case of IE with negative initial imaging tests, where the occurrence of phase 4 bundle branch block after a sequence of type I second degree AV block was crucial to establish a definitive diagnosis and an optimal therapeutic approach.