FIG 50.21 Sequelae after treatment of coronary artery fistula (CAF) Moderate-sized distal left anterior descending (LAD) fistula draining into the left ventricle, showing moderately dilated conduit LAD (A) After coil occlusion, a follow-up angiogram 6 months later demonstrated optimal remodeling with decrease in conduit LAD caliber to normal (B, white arrows) Moderate to large distal left circumflex fistula to the right ventricle, with the third obtuse marginal branch noted proximal to the drainage site (C, white arrow) After coil occlusion at the drainage point, there was clot formation in the dilated left circumflex artery occluding the third obtuse marginal branch (D, thick white arrow) 12 hours after closure, causing acute myocardial infarction The third obtuse marginal branch is not visible due to occlusion (small white arrow) Large distal right coronary artery fistula draining to the right ventricle (E) After surgical occlusion at the drainage point, a follow-up angiogram 2 years later demonstrated asymptomatic thrombosis of the entire right coronary artery, with evidence of revascularization with threadlike vessels (F, white arrows) Large distal dilated tortuous right coronary artery fistula showing persistent coronary dilation (white arrows) at baseline (G) At follow-up angiogram 10 years later, persistent coronary dilation secondary to partial spontaneous closure of the fistula with a small amount of residual flow (H, white arrows) Follow-up coronary anatomic and functional evaluation by Gowda and colleagues after CAF closure demonstrated posttreatment sequelae to include (see Fig 50.21): (1) remodeling of the fistula and/or conduit coronary artery segment with uniform decrease in coronary artery size toward normal (favorable remodeling) or areas of discrete intimal stenosis (unfavorable remodeling), (2) persistent coronary dilation in patients with residual flow, (3) asymptomatic or symptomatic thrombosis (myocardial infarction) of the proximal conduit coronary artery occluding normal adjacent coronary branches, and (4) the thrombosed vessel showed threadlike revascularization, as well as collateral vessel formation from adjacent branches Based on their institutional experience and extensive review of literature, they identified 25 patients with reported coronary artery events following CAF closure From the available data for review, 14 of 16 patients with coronary events had large size and distal CAF Although older patients were at higher risk, even younger patients with large distal CAF demonstrated symptomatic and asymptomatic coronary thrombosis Partial closure of large distal CAF in symptomatic patients (Fig 50.22) has been recently advocated by a few clinicians (author's experience and personal communications) to mitigate the risk of postclosure acute or chronic coronary event/coronary thrombosis causing myocardial infarction Partial closure can eliminate the hemodynamic burden, while allowing persistent residual flow and thus preventing the risk of stasis and thrombosis in large distal CAFs FIG 50.22 Partial closure of coronary artery fistula (CAF) Moderatesized distal left anterior descending (LAD) fistula with restriction at the drainage site (A, arrow) and large right coronary artery distal fistula with restriction and minimal contrast flow at the drainage site (B, arrow) demonstrate natural spontaneous partial closure A large distal right coronary fistula (C) was partially closed using a coil showing minimal residual flow (D, arrow) Therefore, based on knowledge of the postclosure sequelae and risk factors for coronary events, a modified contemporary approach to the management of CAF is illustrated in Fig 50.23.112 In summary, medical observation and no intervention are required (transcatheter or SC) for small-size proximal and distal