Currently in the United States, 17.5% of all percutaneous coronary interventions (PCIs) are performed in patients with prior coronary artery bypass graft surgery (CABG) (1
): 11% are performed in native coronary arteries, 6.1% in saphenous vein grafts (SVGs), 0.4% in arterial grafts, and 0.04% in both arterial grafts and SVGs (1
). SVGs have high failure rates: 40% to 50% are occluded 10 years after CABG (2
). With longer time from CABG, proportionately more interventions are required in SVGs, which is consistent with the accelerated atherosclerotic process of these grafts.
Intervention in bypass grafts is challenging because of (a) difficulties in graft localization and engagement; (b) high rates of periprocedural myocardial infarction caused by distal embolization in SVGs; and (c) high restenosis rates. Prior CABG patients undergoing PCI of a native coronary artery have better outcomes compared with those undergoing bypass graft PCI; hence PCI of a native coronary artery is preferred over graft PCI if technically feasible.
Percutaneous revascularization is generally preferred over surgical revascularization in patients with prior CABG, given the higher risk of repeat CABG compared with first CABG and comparable postprocedural outcomes (3
). Factors favoring repeat CABG include vessels unsuitable for PCI, multiple diseased bypass grafts, availability of the internal mammary artery for grafting chronically occluded coronary arteries, and good distal targets for bypass graft placement (4
). In contrast, factors favoring PCI over CABG include limited areas of ischemia causing symptoms, suitable PCI targets, a patent graft to the left anterior descending artery, poor CABG targets, and comorbid conditions (4
BYPASS GRAFT ANATOMY
Knowledge of bypass graft anatomy is critical for optimizing interventions among prior CABG patients: when the anatomy in advance of catheterization is not known, more contrast, fluoroscopy time, and catheters are needed to identify all patent grafts (5
). Graft markers are helpful for engaging bypass grafts, but are not used in most patients. When the CABG anatomy is unknown, or it is known but the grafts cannot be engaged, and/or perfusion of all myocardial territories cannot be ascertained, ascending aortography can assist with graft localization.
If graft intervention is needed, obtaining adequate guide catheter support is critical. This can be accomplished by using largersize guide catheters (7 F or 8 F), supportive guide catheter shapes (such as Amplatz), or by deep graft intubation, for example, by using a guide catheter extension, such as the Guideliner (6
A significant difference between native vessel and SVG PCI is that glycoprotein (GP) IIb/IIIa inhibitors are not beneficial (7
) and may be harmful (8
). Hence, GP IIb/IIIa inhibitors should not be used in SVG interventions, with the possible exception of heavily thrombotic lesions, yet they are still frequently used (in 40% of SVG PCI in the United States in the National Cardiovascular Data Registry— NCDR) (9
). The 2011 American College of Cardiology/American Heart Association (ACC/AHA) PCI guidelines state that “platelet GP IIb/IIIa inhibitors are not beneficial as adjunctive therapy during SVG PCI” (Class III, level of evidence: B) (4
Intragraft vasodilators, such as adenosine (10
), nitroprusside (11
), nicardipine (12
), and verapamil (13
), might also be useful in preventing no-reflow and periprocedural myocardial infarction during SVG interventions, and are often used because of low cost and risk, although not proven to be effective in randomized controlled trials.
CHOICE OF STENTS IN SVGS
Several studies have compared various PCI techniques in SVGs (Table 26-1
). The SAphenous VEin De novo (SAVED) trial compared bare-metal stent (BMS) implantation with balloon angioplasty. Although the study missed its primary angiographic endpoint (6-month binary angiographic restenosis), it demonstrated improved procedural success and lower incidence of the composite endpoint of death, myocardial infarction, and target vessel revascularization at 6 months (Table 26-1
). Similar results were observed in the Venestent trial (15
), and stent implantation became the standard of care for the percutaneous treatment of SVG lesions.
Covered stents were subsequently developed and tested in SVGs in an attempt to reduce the rates of distal embolization and periprocedural myocardial infarction. However, none of four randomized trials showed a decrease in the incidence of periprocedural myocardial infarction (16
), and covered stents also had higher risk for subsequent myocardial infarction and thrombotic occlusion (19
). As a result, covered stents are currently used in SVGs only for the treatment of perforations. Newer micromesh-coated stents are currently being developed in an effort to prevent distal embolization, but have undergone limited clinical evaluation (25
Whether drug-eluting stents (DES) provide better outcomes in SVGs remains controversial. Three published prospective, randomized controlled trials have compared DES with BMSs in SVG lesions (Table 26-1
The Reduction of Restenosis In Saphenous vein grafts with Cypher sirolimus-eluting stent trial (RRISC) compared a sirolimuseluting stent (Cypher, Cordis, Warren, NJ) with a BMS of similar design in 75 patients (20
) and reported less angiographic restenosis and target lesion revascularization at 6 months. However, at a median follow-up of 32 months, mortality was higher in the sirolimus-eluting stent (SES) group (29% vs. 0%, p = 0.001), and there was no reduction with DES in the incidence of target vessel revascularization (21
). The RRISC study raised concerns about the long-term safety of DES in SVGs; however, these results have not been replicated in subsequent studies, and it is highly unusual for
patients undergoing SVG PCI with BMSs to have 0% mortality for nearly 3 years (mortality during the first-year post SVG PCI is approximately 5% in most series).
TABLE 26-1 Large Published Trials of Stenting for SVG lesions