PCI in Saphenous Vein Grafts
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Background
Coronary artery revascularization with saphenous veins (saphenous vein grafts or SVGs) has become a modern surgical standard for the treatment of coronary artery disease. This technique can be employed when a native coronary artery is blocked, thus causing a reduction or obstruction in blood flow. Cardiac surgeons use the sutured graft to connect the aorta to the coronary artery beyond the area of obstruction, so that blood flow may resume.
Despite their ability to restore blood flow, SVGs commonly encounter stenosis problems. The incidence of SVG stenosis is 15-30% one year after surgery, and it increases to 50% 10 years after surgery. Several factors contribute to stenosis of saphenous vein grafts, including intimal hyperplasia, plaque formation, and graft remodeling. Additionally, arterialization of the graft accelerates atherosclerosis. Furthermore, atheroma found in SVGs are more friable (easily break into small pieces) and more prone to thrombus than plaques found in native vessels. Another reason why SVGs are more susceptible to thrombotic occlusion is that they lack side branches.
Although intervention on a chronic total occlusion of a SVG may seem like an effective treatment strategy, it is best avoided.
Goals of Treatment
Primarily, the goal should be to detect and treat a SVG stenosis early in the development of ischemia while the SVG is still patent. As long as the SVG is not completely occluded, intervention can be performed.
Two additional overall goals of treating SVG stenosis include the resolution of symptomatic ischemia and the prevention/treatment of distal embolization.
Treatment Options
There are many different choices to consider when deciding the most appropriate treatment for SVG stenosis, including PTCA, PCI with bare metal or drug-eluting stents, PCI with covered stents, embolic protection devices, debulking/thrombus removal, and surgical revascularization.
Percutaneous Transluminal Coronary Angioplasty (PTCA)
PTCA has high initial revascularization success rates in the treatment of SVG stenosis. However, it is also associated with high rates of periprocedural complications, including acute vessel closure secondary to dissection and in-situ thrombosis. Additional complications include distal embolization and no reflow, which can lead to periprocedural infarction.
In modern interventional cardiology, PTCA is not often used as the sole means of treatment for SVG stenosis. Instead, stenting has become the cornerstone of treatment, while the use of PTCA has been limited to pre-dilation and post-dilation.
PCI with Bare Metal Stents (BMS) or Drug-eluting Stents (DES)
Most current vein graft treatment strategies utilize PCI with stents (BMS or DES), since stenting is a superior treatment when compared to PTCA alone. As demonstrated in the Saphenous Vein De Novo (SAVED) Trial, the use of stents is associated with higher revascularization success rates, decreased restenosis rates, and improved clinical outcomes when compared to PTCA. [1] Generally, DES are preferred over BMS, since DES are associated with reduced rates of restenosis and target vessel revascularization.
Despite their higher success rates, stents are not immune to restenosis. Predictors for restenosis include long stent length, multiple stents, overlapping stents, smaller vessel size, diabetes mellitus, and stenosis at the coronary or aortic anastomosis.
PCI with Covered Stents
Theoretically, stents covered with a polymer membrane would have higher success rates than standard BMS and DES. One would expect covered stents to effectively trap friable atheroma and isolate the graft lumen from the diseased wall, thereby reducing incidence of restenosis, distal embolization, and no reflow in comparison to traditional stents. However, the RECOVERS[2] (The Randomized Evaluation of polytetrafluoroethylene COVERed stent in Saphenous vein grafts) and STING[3](STents IN Grafts) trials did not show any advantage in using covered stents when compared to bare metal stents for SVG lesions.
Embolic Protection Devices
During PCI of SVGs, atheroembolic debris can be liberated. This debris contains vasoactive substances that can contribute to no reflow, which can in turn considerable increase the risk of major adverse clinical events (MACE)[4]. Fortunately, embolic protection devices help capture this debris and improve outcomes in PCI for SVG stenosis. Therefore, they should be utilized in the intervention of most SVG lesions.
Currently, the FDA has approved five embolic protection devices in the United States. Specifically, these devices include one distal occlusion device, three filters, and one proximal occlusion device.
The FDA-approved distal occlusion device is called the PercuSurge Guardwire, which entails inflating a balloon distal to the stenosis to occlude flow, thereby trapping the debris and vasoactive substances and preventing them from flowing downstream.
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- ↑ Savage MP, Douglas JS, Fischman DL; et al. (1997). "Stent placement compared with balloon angioplasty for obstructed coronary bypass grafts. Saphenous Vein De Novo Trial Investigators". N. Engl. J. Med. 337 (11): 740–7. PMID 9287229. Unknown parameter
|month=ignored (help) - ↑ Stankovic G, Colombo A, Presbitero P; et al. (2003). "Randomized evaluation of polytetrafluoroethylene-covered stent in saphenous vein grafts: the Randomized Evaluation of polytetrafluoroethylene COVERed stent in Saphenous vein grafts (RECOVERS) Trial". Circulation. 108 (1): 37–42. doi:10.1161/01.CIR.0000079106.71097.1C. PMID 12821546. Unknown parameter
|month=ignored (help) - ↑ Schächinger V, Hamm CW, Münzel T; et al. (2003). "A randomized trial of polytetrafluoroethylene-membrane-covered stents compared with conventional stents in aortocoronary saphenous vein grafts". J. Am. Coll. Cardiol. 42 (8): 1360–9. PMID 14563575. Unknown parameter
|month=ignored (help) - ↑ Salloum J, Tharpe C, Vaughan D, Zhao DX (2005). "Release and elimination of soluble vasoactive factors during percutaneous coronary intervention of saphenous vein grafts: analysis using the PercuSurge GuardWire distal protection device". J Invasive Cardiol. 17 (11): 575–9. PMID 16264199. Unknown parameter
|month=ignored (help)