We present a patient with chest pain and suspicious findings in electrocardiography and myocardial perfusion scintigraphy for myocardial ischemia. Coronary angiography and then echocardiography and magnetic resonance imaging revealed a dilated left anterior descending coronary artery, which has fistulous communication with a large, separate chamber that occupies the infero-apical interventricular septum. This is a challenging congenital anomaly for a clinician in many aspects, which are discussed in the report.