Discussion
Coronary artery fistula is a condition with direct communication between the coronary artery and the large vessels or the atria/ventricle by abnormal blood vessels without passing through the capillary beds. CAFs are found in 0.18% of patients who have undergone coronary angiography1. In previous research, most CAFs have been found to originate from the RCA or LCA.9,10,11Five cases at our hospital showed RCA origin, and a further five originated from both the RCA and LCA. The right heart system is known to be the most common perfusion site for CAFs.9,10,11,12. In our cohort, 10 (77%) cases drained into the PA, two (15%) into the CS, and one (8%) into the PA & CS. All cases drained into the right heart system.
CAFs are indicated for surgery when associated with symptoms, such as coronary steal phenomenon due to fistula, myocardial ischemia caused by increased shunt blood flow, heart failure, arrhythmia, cardiac dilatation, and infective endocarditis.2,4Furthermore, due to reports of ruptured aneurysms,3cases that develop an aneurysm, though asymptomatic, are also considered for treatment. Surgical indication for asymptomatic cases without an aneurysm, however, is controversial. Some literature recommends surgery for coronary arteriovenous fistulas during diagnosis to prevent future coronary artery disease and infective endocarditis.4,5,6 However, surgery does not lead to long-term changes in some cases, and follow-up observation has been recommended.13 Seven cases (54%) at our hospital were indicated for surgery owing to CAFs (dyspnea on exertion or aneurysm formation). However, six cases (46%) were indicated for surgery owing to comorbid cardiac disease. The concurrent intervention of CAFs during surgery of comorbid cardiac disease is considered useful in preventing future complications related to CAFs.
For CAF surgery, abnormal blood vessels are treated with procedures including ligation of the abnormal blood vessel from the epicardial side, direct closure of the fistula, and indirect closure of the fistula from the epicardium.7,12 Surgical methods also vary depending on the use of other techniques, including the cardiopulmonary bypass and the coronary artery bypass graft surgery.7,14 In principle, the resection of an aneurysm is necessary due to its reported rupture risks.3 At our hospital, cardiopulmonary bypass was used in all cases.
Perioperative death has been previously reported in some CAF cases, with myocardial ischemia and arrhythmia presenting as critical perioperative complications.7,8,9 Said et al. reported that perioperative myocardial ischemia was an important perioperative complication.7 Risk factors in early and late postoperative periods include large fistula formation, coronary artery dilation, and aneurysm formation. Myocardial ischemia in the early postoperative period is caused by the occlusion of critical branches during the treatment of a fistula. Conversely, myocardial ischemia in the late postoperative period is caused by thrombus formation in coronary arteries. To prevent myocardial ischemia in the early postoperative period, Cheung et al. performed the temporary clamping of a fistula before its ligation during surgery and monitored changes in hemodynamics and ischemia.14 The wall motion after ligation was assessed by transesophageal echocardiography. Revascularization, such as coronary artery bypass graft surgery, is considered when myocardial ischemia is indicated by clinical findings. An approach to treating myocardial ischemia in the late postoperative period is the use of warfarin to prevent thrombus formation.14
Although no perioperative deaths were observed at our hospital, one case (8%) showed poor contrast RCA#2-4 on postoperative coronary CT. In this case, myocardial scintigraphy showed small ischemia in the region supplied by the RCA, while postoperative myocardial scintigraphy showed no significant change compared to the preoperative state. Revascularization was not performed because asynergy was not observed either pre- or peri-operatively. This case was asymptomatic and showed no postoperative asynergy; therefore, we followed up with oral administration of aspirin and warfarin.