Intermittent High-Grade Atrioventricular Block as a Presenting Sign of Left Ventricular Noncompaction

Unexplained high-grade atrioventricular block in a young adult should prompt advanced structural evaluation-including cardiac magnetic resonance-to exclude left ventricular noncompaction and other cardiomyopathies. Preserved ejection fraction and absent late gadolinium enhancement can coexist with clinically relevant conduction disease in left ventricular noncompaction. Implantable loop recorder-guided surveillance enables individualized timing of device therapy and complements genetic evaluation and cascade family screening.