Palpitations in a 64-year-old man.

A 64-year-old man presented with several weeks of intermittent irregular palpitations. He had no prior history of cardiac disease, hypertension or syncope. A 12-lead ECG revealed sinus rhythm with premature atrial and ventricular contractions and high QRS voltages consistent with LV-hypertrophy. Cardiac MR revealed asymmetrical septal hypertrophy and marked mid-myocardial hyperenhancement of the interventricular septum.