Coronary artery bypass surgery other non-atherosclerotic saphenous vein graft diseases


 * Associate Editors-in-Chief:, Mohammed A. Sbeih, M.D.[mailto:msbeih@perfuse.org]

Saphenous vein graft aneurysms
This disease process is also known as SVGA, aortocoronary saphenous vein graft aneurysms, saphenous vein graft aneurysm disease and saphenous vein graft aneurysmal dilatation and is defined as a local dilation of the vessel more than 1.5 X the adjacent reference segment. The aneurysms can be up to 14 cm in diameter.

Classification

 * True aneurysms: All 3 layers of the vessel wall are involved
 * Pseudoaneurysms: There is disruption of 1 or more layers of the vessel wall.

Epidemiology and demographics
Over the course f a SVGs 7 year lifetime, the risk of aneurysm development is 14%. True aneurysms outnumber false ones by a ratio of 2:1.

Pathophysiology
Causes of saphenous vein graft aneurysms include the following:


 * Atherosclerosis
 * Hypertension
 * Mycotic
 * Postoperative mediastinitis
 * Previous aneurysms
 * Torn sutures

Natural history and complications
SVGAs can rupture which is associated with a high rate of morbidity and even mortality. They can also be a nidus for embolization.

History
If a patient with a history of CABG develops chest pain and has a mediastinal mass, an SVGA should be suspected.

The majority of patients are asymptomatic with a true aneurysm, and most often the SVGA is an incidental finding on an imaging study. If the patient is symptomatic, about half the time it presents as an acute coronary syndrome. Very rarely tamponade from compression of the right atrium or ischemia due to compression of the left internal mammary artery bypass graft has been observed.

In contrast to true aneurysms, patients with false aneurysms are symptomatic in 85% of cases. About two thirds of the time they present with an acute coronary syndrome. If a patient with an SVGA does present with chest pain or hemoptysis, it may be due to the formation of a fistula.

Physical examination
Rarely on physical examination a murmur will be auscultated or cutaneous bleeding will be observed (both due to a fistula).

Imaging
SVGA can be definitively diagnosed on either coronary angiography or CT angiography. On occasion, an SVGA can be observed as either hilar or mediastinal mass on chest x ray.

Management
Pharmacologic management consists of aspirin and lipid-lowering therapy. The benefit if any of coumadin and beta-blockers is not known.

A surgery or a percutaneous intervention is suggested if:
 * A pseudoaneurysm is present
 * The aneurysm is more than 2 cm greater than the adjacent vessel
 * A fistula is present (surgery, coiling, or stenting)
 * If the aneurysm is mycctic (surgery)

Surgery
There are multiple surgical approaches to repairing an aneurysm:
 * Ligate the aneurysm-containing SVG and place a new SVG.
 * Resect the aneurysmal portion of the diseased graft and sew a new SVG segment in in an end-to-end fashion
 * Ligate the old SVG without revascularization
 * Evacuate the hematoma and repair the SVG with a venous patch graft.

Percutaneous intervention
In the past, percutaneous intervention was reserved for patients who were too sick to undergo surgery. However, due to the improved tools that are available, more patients are undergoing percutaneous intervention as described below:
 * Coil embolization: This technique has evolved so that a stent excludes the coil form lying in the lumen of the SVG.
 * Covered stents: The JOSTENT Coronary Stent Graft (Abbott Vascular, Redwood City, Calif) can be used to exclude the aneurysm form the body of the SVG. The device is made up of an ultra-thin layer of polytetrafluoroethylene  (PTFE).
 * Multiple overlapping stents can be used to exclude the aneurysm.

Amyloidosis of saphenous coronary bypass grafts
Amyloid has been associated with accelarated disease in saphenous vein grafts.

Rupture of the saphenous vein coronary artery bypass grafts
Aspergillus species causing a necrotizing vasculitis have been associated with rupture of a saphenous vein grafts.