LAUSR

A 60-year-old woman with a known right coronary artery (RCA) to coronary sinus (CS) fistula presented with a 2-month history of dyspnea and chest tightness on exertion and persistent atrial tachycardia. Chest X-ray revealed biventricular dilation, which had not been seen 7 years before (Figure 1). The transthoracic echocardiography showed a normal left ventricular ejection fraction with no wall motion abnormalities, enlargement of all four chambers, and left-to-right shunting with a pulmonary-to-systemic flow ratio (Qp/Qs) of 1.3. Transesophageal echocardiography demonstrated a dilated, tortuous RCA, a fistula between the RCA and dilated CS, and stenosis of CS ostium oppressed by the dilated RCA (Figure 2). Computed tomography (CT) angiography confirmed the echocardiographic findings: a significantly dilated and tortuous RCA and CS with a single fistula between the terminal RCA and the aneurysmal CS (Figure 3). Additionally, an epicardial collateral vessel was visualized from the distal left anterior descending artery to the distal RCA. N-ammonia positron emission tomography (PET)/CT during adenosine triphosphate (ATP)-induced coronary hyperemia revealed a reversible perfusion abnormality in the inferior and inferolateral regions of the left ventricle. The coronary flow reserve ratio (CFR) was decreased in the RCA territory (Figure 4A). The patient underwent