I spy with my MRI: Cause of complete heart block in a young patient revealed

A 21-year-old female patient presented with unexplained weight gain and dyspnoea on exertion. The ECG showed third-degree atrioventricular (AV) block with a junctional escape rhythm of 45 bpm (Fig. 1). Echocardiography showed no cardiac abnormalities. However, subsequent CMR using late gadolinium enhancement (LGE) revealed a single region (32 × 15mm) of intramyocardial, high-intense, homogeneous contrast enhancement with a well-defined border in the basal inferoseptal myocardium (Fig. 2). Additional sequences ruled out the presence of fat. The septal localisation, homogeneous high-intense contrast enhancement with smooth borders, in the absence of fat, pericardial effusion or systemic disease such as sarcoidosis, all attest to an intramyocardial fibroma as the most likely diagnosis. The fibroma is thought to impede the conductive system, in this case leading to third-degree AV block. Cardiac fibromas are benign congenital tumours