Saphenous Vein Graft Aneurysm - An Unusual Cause of Mediastinal Mass

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Abstract

We report the case of a 78-year-old man who was incidentally found to have a large, ovoid mass on a chest X-ray. Nineteen years before, he had undergone a coronary artery bypass graft (CABG). A chest computed tomography (CT) scan revealed a 6.8 x 6.7 cm aneurysm of the saphenous vein bypass graft anastomosed to the distal right coronary artery with contrast filling only the proximal end of the graft. The inferior wall of the left ventricle was akinetic on echocardiography, suggesting prior myocardial infarction of this vascular bed. Because of the patient’s comorbidities, occlusion of the graft, and prior inferior infarction, clinical observation was elected.

Citation
American Heart Hospital Journal 2011;9(1):52-4
DOI
https://doi.org/10.15420/ahhj.2011.9.1.52

Saphenous vein graft (SVG) aneurysms are a rare complication of coronary artery bypass grafting (CABG), typically occurring 10 to 20 years after surgery. In most cases, they present as an incidental finding on chest X-ray, and thus should be considered in the differential diagnosis of a chest mass in a patient with previous CABG. Although patients may be asymptomatic, these aneurysms can lead to myocardial ischemia or potentially rupture. Therefore, clinical recognition of this entity is an integral component of the management of CABG patients.

Case Presentation

A 78-year-old man presented with a large, asymptomatic ovoid mass on a posterior-anterior chest X-ray (see Figure 1). He had been admitted for management of a transient ischemic attack owing to carotid artery disease. Nineteen years before admission, the patient had undergone CABG with placement of a SVG to the distal right coronary artery. Past medical history also included ischemic cardiomyopathy (left ventricular ejection fraction, 25 %), hypertension, implantable cardiac defibrillator placement, and two transient ischemic attacks. The patient had stable New York Heart Association class II symptoms and no chest pain.

To evaluate the mass further, a CT chest with contrast was performed. This demonstrated a 6.8 x 6.7 cm occluded aneurysm within the body of the bypass graft to the right coronary artery (see Figure 2). Echocardiography demonstrated the inferior wall to be akinetic, consistent with a clinical history of prior inferior myocardial infarction (see Figure 3). Because resection of the aneurysm and revascularization of the inferior wall would be of minimal benefit, conservative management with clinical observation was elected.

Discussion

Saphenous vein graft aneurysms are defined as a permanent localized dilatation of >3 cm in diameter. Mild dilatation of saphenous grafts occur in up to 14 % of patients after CABG, but true aneurysms are believed to be rare.1 The lifetime incidence has been reported to be 0.07 %, but the true rate is unknown because patients are frequently asymptomatic.2 Among those who are found to have an SVG aneurysm, the average time from surgery is about 15 years.2

The pathophysiology of vein graft aneurysms is related to graft atherosclerosis, leading to structural weakness and subsequent dilation. Notably, pathologic studies have found that dilation begins near venous valves, where the muscle fibers of the vascular media have a longitudinal instead of circular orientation.3 In contrast, pseudoaneurysms more often occur near sites of surgical anastomosis. Surgical technical issues as well as infections are possibly involved in the formation of pseudoaneurysms.4,5

The most common presentation of SVG aneurysms is an incidental finding on chest X-ray, which occurs in about 50 % of these patients. Symptoms of myocardial ischemia are also common, occurring in about 40 %.1,6 Myocardial ischemia may occur, owing to distal embolization, thrombosis, fistula drainage with coronary steal, or mass effect on the native vessel.7 Approximately 5 % of patients present with heart failure. Other uncommon presentations include fistulas into the right atrium, right ventricle, pulmonary artery, or bronchi.8–12

Once the diagnosis is suspected, computer tomography with intravenous contrast is the test of choice. The goal of imaging is to determine the size of the aneurysm, its mass effects, and patency of the SVG. Two dimensional and Doppler echocardiography is helpful to determine cardiac function.13 Selective angiography of the vein graft frequently is required to examine through both the aneurysm and into the distal vascular bed.

Rupture of SVG aneurysms is the most feared complication, presenting as sudden death, hemothorax, hemopericardium, or massive hemoptysis. Because the natural history of SVG aneurysms is largely unknown, consensus on appropriate management is lacking. Large aneurysms with persistent flow are generally considered to have a higher risk of complications.

When considering surgical resection, other important factors are patient comorbidity and the need for revascularization of the distal arterial bed. In general, owing to potential life-threatening complications, surgery should be considered in all appropriate candidates. In selected patients, percutaneous therapy, consisting of vascular coils, occlusive devices (e.g. Amplater Septal Occluder), and covered stents have been used successfully.14–17

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