Late-Term Myocardial Infarction After Surgical Ligation of a Giant Coronary Artery Fistula

Large coronary artery fistulae have been associated with complications such as congestive heart failure, myocardial ischemia, endocarditis, rupture and arrhythmias.1 To reduce the risk of complications, large coronary artery fistulae are often treated with surgical ligation or percutaneous device closure. Because this is an uncommon malformation, there is little information on outcomes after interventions, and there may be under-reporting of late-term complications. We report a case of recurrent myocardial infarction occurring after successful surgical closure of a giant coronary artery fistula. Case Report. The patient was serendipitously discovered to have a large coronary artery fistula at age 37. While working in a hospital, he volunteered to be imaged for a demonstration of echocardiographic equipment, during which a large vascular structure was identified. Subsequent cardiac catheterization (Figure 1) revealed a giant coronary artery fistula arising from the circumflex coronary artery and emptying into the coronary sinus. The circumflex artery was dilated and tortuous, with dilatation also in the left main coronary artery. A smaller fistula arising from the distal right coronary artery also emptied into the coronary sinus. Left ventricular size and function were normal. It was decided to treat this expectantly. Seven years later, the patient returned to medical attention because of atrial fibrillation. An echocardiogram now revealed an increase in left ventricular size. Catheterization and magnetic resonance imaging continued to demonstrate the fistulae, without evidence of obstructive coronary artery disease, and confirmed the increase in left ventricular size. He was referred for surgical correction. The circumflex coronary artery was ligated immediately after a second obtuse marginal branch, and the right coronary artery was ligated just after the origin of the posterolateral branch. A modified Maze procedure was also done. Post-operative atrial fibrillation was treated with procainamide, digoxin, beta-blockers, warfarin and dipyridamole. He has had no further episodes of atrial fibrillation. Warfarin was continued for 6 months, after which he was switched to aspirin and dipyridamole. An exercise study was normal 6 months after surgery and the patient continued to play competitive ice-hockey. One and a half years after surgery, the patient developed an episode of chest discomfort accompanied by lateral ST-segment depressions. Coronary angiography revealed a proximally occluded circumflex coronary artery (Figure 2A). Intracoronary fibrinolytics were administered and balloon angioplasty was performed on the circumflex coronary artery with reinstitution of patency, but persistent proximal narrowing. Also noted was thrombus, which had migrated back slightly to the level of the left main coronary artery (Figure 2B). A stent was inserted at the level of the persistent narrowing. After further balloon inflations, contrast staining and filling defects appeared outside of what was originally felt to be the arterial lumen (Figure 2C). This likely represented flow into the large, thrombus-laden circumflex, and now into the interstices of the laminated thrombus. Cardiac catheterization the next day disclosed a patent vessel, but persistent filling defects consistent with thrombus. He was given intravenous abciximab. Further improvement was seen the following day (Figure 2D). Clopidogrel was administered for 30 days, as well as aspirin and warfarin. The patient remained asymptomatic for 6 months, when he returned with recurrent chest pain and coronary angiography revealed recurrent occlusion of the proximal circumflex coronary artery. Intracoronary fibrinolytics were administered via an infusion catheter, together with intravenous abciximab. Flow remained suboptimal after balloon angioplasty, so an additional stent was placed with a good angiographic result and normal flow. Discharge medications were as before, but warfarin was increased to achieve an international normalized ratio (INR) of approximately 3 instead of 2.5 Coronary angiography 6 months later revealed in-stent restenosis of approximately 75%, which was successfully dilated with balloon angioplasty. Left ventricular function remained normal, with a reduction in left ventricular size. Six months later, the patient had recurrent chest pain and coronary angiography again revealed an occluded obtuse marginal branch of the circumflex with thrombus close to the left main coronary artery. Coronary artery bypass graft surgery was performed to the first and second obtuse marginal coronary arteries, with ligation of the proximal circumflex coronary artery. Twelve months later, he remains free of symptoms. Discussion. Since individuals with coronary artery fistulae may develop symptoms or complications, such as cardiomegaly, congestive heart failure, myocardial ischemia, endocarditis or rupture,1,2 prophylactic closure of the coronary fistula has been recommended when anatomically feasible.1,3,4 Early post-operative mortality is reported to be 0–4%, with a 3.6% rate of early post-operative myocardial infarction due to sidebranch closures.3–5 However, certain individuals with fistulae seem to do well when untreated, and some autopsy series have disclosed previously undetected coronary fistulae in individuals with normal life-spans.6–8 The case presented herein demonstrates the potential risks of deferring intervention in giant coronary fistulae. However, after surgical closure of the patient’s fistulae, a complication arose that has only been rarely described in the cardiovascular literature, namely late myocardial infarction. The etiology of the myocardial infarction in this case was ascribed to the development of thrombus within the blind pouch created by the surgical closure of the fistula, with subsequent proximal propagation. The large vascular chamber appeared to promote blood stagnation and thrombus development. The circumflex artery was re-opened into the first obtuse marginal artery by coronary angioplasty; however, the circumflex artery had been ligated after the second obtuse marginal artery. The blind pouch extending between the first and second obtuse marginal arteries lent itself to the thrombosis. This is analogous to the complication of embolization arising from an internal carotid stump, the so-called “stump syndrome”.9–11 There are two previous descriptions in the literature of acute myocardial infarction occurring late after surgical closure of a giant coronary artery fistula.12,13 In both cases, the fistulae were occluded at the termination points into the respective right heart chambers, leaving lengthy blind pouches. In the current example, care was taken to close the fistula proximally, but this vessel occluded because of inadequate flow in the small second obtuse marginal branch, leaving a more extensive blind pouch than intended. The flow through the second obtuse marginal branch was apparently insufficient to prevent closure of that vessel, with the resultant development of a blind pouch between the first obtuse marginal branch and the site of the ligation distal to the second obtuse marginal branch. The true prevalence of this complication in treating coronary artery fistulae is unclear. There may be under-reporting of this complication, since most published reports addressing rare conditions focus on the ability to successfully perform a given procedure, and generally only provide in-hospital or 30-day complication rates. Few series have provided longer-term follow-up,14–17 but of the 3 reported cases, all blind pouch complications were associated with giant coronary artery fistulae. Myocardial infarction due to embolization of thrombus developing within a coronary artery fistula has also been reported in patients with untreated coronary artery fistulae.18–23 This mechanism should be differentiated from myocardial ischemia due to coronary artery steal.1,24,25 To minimize this complication, closure of the fistula should create as little of a blind pouch as possible, employing proximal ligation. When a small distal tributary vessel is present, as in this case, the surgeon must decide between varying strategies. The surgeon may elect to close the feeding vessel distal to the small branch, running the risk of the complication described herein, or perform the closure proximal to the sidebranch, minimizing the potential development of a large blind pouch. Aneurysmorrhaphy of the dilated proximal vessel may also be considered to reduce the size of the remaining vascular chamber.13,26,27 It is of interest that our patient developed thrombotic recurrence despite treatment with warfarin, aspirin and clopidogrel. Currently, some recommend giving warfarin after closure of a coronary fistula,1 which was in fact done for the first 6 months after surgery in this patient. Because of its rarity, it is difficult to know the relative value of surgical and medical strategies to minimize the risk of this particular complication. To close a coronary artery fistula percutaneously, thrombus development is encouraged by the placement of metal coils or other devices, leading to occlusion of the fistula.28–33 These coils are frequently coated with fibrin to encourage thrombus development. The interventionalist must struggle with the appropriate location for placement of the coils. Avoidance of a large blind pouch might be achieved by attempting to place the coils close to a large tributary vessel, without actually occluding that vessel. Such precise localization in the closure of a giant fistula such as this may be more challenging for the interventionalist using the percutaneous approach than surgically, because of the need for multiple coils or devices which extend a certain distance proximally and distally within the vessel. The role of post-procedure anticoagulants is also unclear. Conclusion. A case is presented of recurrent late myocardial infarctions after surgical closure of a giant coronary artery fistula, apparently due to the large amount of thrombus deposition within a surgically-created blind pouch. This is a rare complication, but should be considered to be a possibility in patients presenting with chest pain after closure of a large coronary artery fistula, either by surgical or percutaneous methods.

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