Coronary Artery to Right Atrium Fistula Associated With First Degree Atrioventricular Block: A Rare Association

A 40 year-old man with no significant past history except for asymptomatic 1 st degree heart block presented for general health screen. Clinical examination revealed a loud continuous murmur with diastolic accentuation in the left precordium, non-collapsing pulse, and no differential pulses in the upper and lower limbs. The ECG showed normal sinus rhythm with PR interval of 220 milliseconds. Transthoracic echocardiogram (Figure 1) showed a dilated right coronary artery that was enlarged, forming multiple saccular aneurysms distally that drain into the roof of right atrium. The right heart was normal in size and function. CT angiogram (Figure 2) later confirmed the presence of a coronary artery fistula from the right coronary artery draining into the right atrium. Right coronary artery is dilated and the distal segment of the RCA is tortuous and aneurismal. Nuclear myocardial perfusion imaging showed no inducible ischemia during exercise stress. He declined cardiac catheterization, and was advised for corrective surgery. This case illustrated a rare saccular aneurysm formation in a right coronary artery to right atrium (coronary-cameral) fistula associated with 1 st degree atrio-ventricular (AV) block. Coronary arterio-venous fistula (CAVF) arises as a persistence of sinusoidal connections between the lumens of the primitive tubular heart in the early embryologic period. It is reported in 0.1%–0.2% of all cases of selective coronary angiography[1]. Most fistulae originate from the right coronary artery (60%) and terminate in the right side of the heart such the right ventricle or atrium, coronary sinus, and pulmonary vasculature. Most often congenital, a CAVF may rarely arise as a consequence of surgical complication, endomyocardial biopsy, invasive procedures[2, 3] or penetrating trauma. It could cause myocardial stealing due to runoff from the coronary vasculature to a low-pressure receiving cavity. Coronary artery that feeds the fistula progressively dilates, leading to