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.