Right ventricle septal papillary muscle involvement and progressive enlargement in a patient with a rare case of isolated cardiac sarcoidosis

A 52-year-old man presented with paroxysmal palpitations and lightheadedness for 1 month and was referred to our hospital. The electrocardiogram revealed paroxysmal ventricular tachycardia. The cardiac magnetic resonance (CMR) revealed a space-occupying lesion of the right ventricle near the septal papillary muscle region (Panels A–C and Supplementary material online, Video S1). T2-tirm hyperintensity indicated oedema in the lesion (T2 = 60.3 ms, Panels B and D), and diffuse late gadolinium enhancement (LGE) indicated fibrosis (Panel C). Due to the paroxysmal ventricular tachycardia, the patient was referred for catheter ablation. Eight months later, the patient came to our hospital again with worsening palpitations and lightheadedness. Electrocardiogram revealed dual-source ventricular tachycardia. The repeated CMR showed the lesion increased from 2.93 to 4.50 cm (Panels E–G) and native T2 was elevated(64.8 ms, Panel H). Positron emission tomography (PET) revealed enhanced glucose metabolism in the...