Saphenous Vein Graft-to-Left Atrium Fistula Treated with
Percutaneous Transcatheter Embolization with Coils

Coronary artery fistulae (CAF) are direct precapillary communications which bypass the myocardial capillary network and connect a coronary artery to another vessel or cardiac chamber (cameral).¹ CAF are reported in 0.1–0.7% of patients undergoing coronary angiography and account for 13% of congenital coronary artery anomalies.^1,2 Acquired CAF occur as complications of myocardial infarction, traumatic accidents, invasive cardiac procedures or cardiac surgery.¹ Acquired CAF were present in 30% of 96 fistulae reported between 1985 and 1995.¹ Fistulae between arterial or venous bypass grafts and cardiac or noncardiac structures occur rarely after bypass grafting. To the best of our knowledge, we present the first case of fistula formation between a left circumflex (LCX) vein graft and the left atrium that was treated with percutaneous transcatheter embolization (PTE) with coiling. The first coil was lost in the left atrium, but was successfully retrieved and the fistula was closed with 7 coils. We review the literature of acquired CAF and discuss the treatment options.

Case Report. A 56 year-old white female with hypertension, hypercholesterolemia and cerebrovascular disease presented in 1996 with worsening class IV NYHA congestive heart failure (CHF) symptoms. She had a history of rheumatic fever with severe aortic stenosis and moderate aortic regurgitation. She underwent a Manougian aortic root enlargement, aortic valve replacement with a 19 mm Carpentier Edwards pericardial prosthesis, transaortic septal myomectomy and patch enlargement of supravalvular aortic stenosis. In September 2000 she presented with recurrent CHF and unstable angina symptoms. Coronary angiography revealed severe left anterior descending (LAD) and mild-to-moderate dominant LCX coronary artery disease. She subsequently underwent an off-pump left internal mammary artery (LIMA)-to-LAD bypass. She presented again in July 2001 with unstable angina. Coronary angiography showed severe disease involving trifurcation of the distal left main and the ostia of the LAD and LCX with a patent left LIMA-to-LAD. The patient was subsequently referred to our institution and underwent a second coronary artery bypass grafting with a saphenous vein graft to the LCX.

The chest was opened through a left thoracotomy in the fourth interspace. The anatomical situation was quite difficult because of dense scar tissue and small vessels. Extensive time was spent dissecting the lateral aspect of the left ventricle looking for a suitably-sized marginal branch. Thus, the initially planned off-pump procedure was switched to cardiopulmonary bypass. Eventually, a marginal artery was identified deep within the atrioventricular groove at the base of the left atrial appendage. The saphenous vein graft was anastomosed end-to-side to the circumflex artery and the surgery was completed successfully. The patient presented again in November 2001 with unstable angina and class 3 NYHA CHF symptoms. On physical examination, she had clear lungs, elevated jugular venous pressure at 10–12 cm of water, regular rate and rhythm, a systolic ejection murmur at the base of the heart, soft S3 gallop and trace pedal edema. Adenosine myocardial perfusion imaging revealed LCX ischemia with normal left ventricular function. An echocardiogram showed a normally functioning prosthetic aortic valve, normal left and right ventricular sizes and functions, moderately dilated left atrium and minimal mitral and tricuspid regurgitations. Coronary angiography showed a communication between the vein graft presumably anastomosed to the LCX and the left atrium in the vicinity of the pulmonary vein (Figure 1). The vein graft was supplying the left atrium rather than the LCX territory. The vein graft was engaged with a 6 Fr guiding catheter and had a mean pressure of 20 mmHg. An attempt to deliver a coil (Tornado^® Embolization Microcoil, MWCE- 18S-8/4, Cook Inc., Bloomington, Indiana) to the distal segment of the vein graft was initially unsuccessful with migration of the coil into the left atrium. The coil was successfully retrieved with a 4 mm endovascular microsnare (Microvena Corp., White Bear Lake, Minnesota). Following this, a total of 7 coils (Tornado Embolization Microcoil, MWCE-18S-10/14,8/5 and 18/4) were deployed, with successful occlusion of the vein graft fistula to the left atrium (Figure 2) and improvement of pressure that became equivalent to the aortic pressure. The patient tolerated the procedure well without complications. She presented 1 month later for a staged percutaneous transluminal coronary angioplasty and rotational atherectomy to the LM and LCX arteries, which she underwent successfully. Coronary angiography performed 12 months later for recurrence of chest pain showed 40–50% stenosis of LCX, a patent LIMA-to-LAD and no fistula between the vein graft and left atrium.

Discussion. Acquired CAF occur as complications of myocardial infarctions, mural thrombosis (dilated cardiomyopathies, left atrial appendage), blunt or penetrating chest trauma, per cutaneous coronary interventions, endomyocardial biopsies, permanent ventricular pacemaker leads or cardiac surgery.^1,3 Fistulae occurring after cardiac surgery can involve the native coronary arteries or the bypass grafts. Coronary arterycameral fistulae have been reported in the setting of atrial injury during right atrial cannulation for cardiopulmonary bypass⁴ or during left atriotomy,⁵ LAD damage during right orleft ventricular outflow myomectomy,⁶ direct trauma to the right ventricular free wall during surgery,³ or after coronary snaring in coronary artery bypass graft surgery.⁷ CAF develops in 5.4–14% of heart transplant recipients due to repeated endomyocardial biopsies or to the implantation surgery, according to the Lowe-Shumway technique.⁸
Iatrogenic aorto-coronary venous and IMA graft fistulae can result from their inadvertent anastomosis into cardiac veins, most commonly into the proximal great cardiac vein in proximity to the LAD, and less commonly into the left marginal and the posterior intraventricular coronary veins.⁹ Aorto-coronary bypass graft fistulae can develop as a complication of saphenous vein graft aneurysms and have been described to communicate with the right atrium,^10–12 right ventricle¹³ and pulmonary artery.¹⁴ The aneurysms cause pressure necrosis on nearby structures leading to fistula formation between the aneurysm and the structure in question.¹³ Left IMA fistulae to the lung parenchyma¹⁵ or the pulmonary vasculature have been described.^16–20 These probably occur as a result of direct contact between the dissected and exposed IMA and the pulmonary vasculature or parenchyma across a disrupted visceral pleura.¹⁵ Simultaneous IMA and venous trauma during placement of the parasternal wires can cause fistulae between the IMA and the internal mammary, thymic or second intercostal veins.^16,21,22 Madu et al²⁰ described 4 cases of LIMA to pulmonary artery fistulae in 595 consecutive cardiac catheterizations of CABG involving the LIMA.
In our case, the patient had 2 previous cardiac surgeries and developed extensive scarring that made the redo bypass surgery technically challenging as described above. Conceivably the vein graft to the left atrium fistula could have occurred from inadvertent anastomosis to the left atrium or due to direct trauma to the left atrial wall during surgery. Fistulae have been described to occur secondary to neovascularization in areas of mural thrombosis or following trauma to a cardiac chamber.³ The granulation tissue formed in response to injury promotes neovascularization which persists after healing and fibrosis of the injured area, leading to fistula formation.³
Patients with coronary fistulae can be asymptomatic in 50–60% of cases, or can present with dyspnea on exertion, chest pain, CHF, continuous murmurs,¹ or can develop mycotic aneurysms, endocarditis, aneurysmal expansion and rupture, hemoptysis or pulmonary hypertension.^23,24 These fistulae can cause coronary steal and result in worsening angina symptoms and myocardial ischemia on stress testing, or can cause left-to-right shunting and result in CHF or right volume overload if significant shunting is present. Most patients have a continuous murmur on physical examination, and some have evidence of right-sided volume overload or left-to-right shunting. In our case, the patient had recurrent angina with myocardial ischemia on adenosine myocardial perfusion imaging along the LCX territory, which was not vascularized by the vein graft that was now supplying the left atrium. Additionally, she had class III NYHA symptoms with preserved left ventricular function, which we thought was related to diastolic dysfunction exacerbated by volume overload on the left chambers from left-to-left shunting. A Qp/Qs was not measured. The fistula was closed, as it was not supplying the LCX territory and was thought to be contributing to her CHF symptoms from left-to-left shunting, and also to prevent the formation of mycotic aneurysms and rupture.
The management of small and asymptomatic CAF (Qp/Qs £ 1.5) is usually conservative, with medical follow up. Some native small CAF can close spontaneously and are usually benign, with a good prognosis. Large (Qp/Qs > 2.0) or symptomatic fistulae can be closed with PTE, or surgically, if the anatomy is not amenable to PTE.¹ PTE is usually performed with coils (microcoils, trefoil or standard steel coils, controlled release coils), detachable balloons, umbrella devices, covered stents, or a combination of detachable balloons and coils.^1,25 The management of aortocoronary vein fistulae includes surgical ligation with or without revascularization of the diseased artery, or PTE with or without angioplasty of the stenosed coronary artery.^15,24,26 The literature on the management of vein graft fistulae is limited because of their rare occurrence. However, the results of PTE of native CAF are encouraging. Qureshi et al²⁵ presented the experience of catheter closure of CAF in 40 patients. The rate of successful total fistulae occlusion was 97%, with 82% occurring immediately. The main complication was a 17% rate of embolization of the occlusion devices ,which were all successfully retrieved. Armsby et al^25,27 presented the outcomes of PTE in 33 patients from a single institution and from 44 patients from the literature. The overall complication rate from both series (78 patients) was 28% and included transient ischemic ST-T changes (12%), transient arrhythmias (6%), unretreived coil embolization (6%), infarction (1%), fistula dissection (1%), distal coronary spasm (1%) and death (1%). The rate of complete occlusion was 82% in this series of 33 patients.

Conclusion
Iatrogenic vein graft fistula to the left atrium is a rare complication of coronary artery bypass graft surgery. It can present as worsening angina and manifest as myocardial ischemia on stress testing. PTE with coiling was successful in closing the fistula without the need for surgical intervention that could have been problematic and risky in our patient who had previously undergone 3 open-heart surgeries.

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