Clinical Pearls & Morning Reports
After coronary-artery bypass grafting (CABG), mild dilatation of a saphenous-vein graft is common, but saphenous-vein–graft aneurysm appears to be rare. The true incidence of saphenous-vein–graft aneurysm is unknown, because routine screening is not performed and the condition can be clinically silent. Read the latest NEJM Case Records of the Massachusetts General Hospital here.
Q: What mechanisms might contribute to the formation of saphenous-vein–graft aneurysms?
A: Mechanisms of the formation of saphenous-vein–graft aneurysm late after CABG include atherosclerotic degeneration, vessel-wall ischemia (i.e., disruption of the vasa vasorum at the time of harvest), and wall stress due to increased luminal pressure that occurs when a venous structure is ligated into the pulsatile arterial system. Saphenous-vein–graft aneurysm may occur at sites of anastomoses and also at sites of venous valves owing to reduced circular smooth muscle.
Q: What are some of the features of saphenous-vein–graft aneurysms?
A: A systematic review of saphenous-vein–graft aneurysm showed that it arises a mean of 13 years after the initial bypass surgery, usually occurs during the sixth decade of life, and is found predominantly in men, which may reflect the higher incidence of atherosclerotic coronary artery disease in men than in women. Aneurysmal saphenous-vein grafts are most commonly targeted to the right coronary artery (in 38% of cases). Aneurysm growth rates vary, but larger aneurysm portends an increased risk of complications; the mean size of the aneurysm at the time of its identification is 6.0 cm.
A: Signs and symptoms of saphenous-vein–graft aneurysm are more likely to occur when the aneurysm is larger, because it compresses adjacent mediastinal structures, such as heart chambers, great vessels, or even the bronchial tree. External compression of the right atrium or right ventricle occurs in nearly 20% of cases. Chest pain or shortness of breath develops in more than half the cases of saphenous-vein–graft aneurysm, but in nearly one third of cases, the aneurysm is discovered incidentally. Myocardial infarction is the presenting symptom in approximately 8% of cases, and heart failure and syncope each occur in approximately 2%.
A: Angiography of the coronary artery and graft may be of limited use if there is an intraluminal thrombus or the aneurysm is thrombosed, because the aneurysm can be missed or its size underestimated. Cardiac computed tomography (CT) is the preferred test, with cardiac magnetic resonance imaging (MRI) as an alternative, to confirm the diagnosis and determine the effect on adjacent heart structures. Mechanical complication, such as compression of mediastinal structures or impending rupture or fistula involving the saphenous-vein–graft aneurysm, is an indication for aneurysmectomy. Repeat revascularization is also indicated when evidence of ischemia is present.