What is the role of Saphenous Vein Grafts (SVGs) in Coronary Artery Bypass Grafting (CABG)?

Role of Saphenous Vein Grafts in CABG

Saphenous vein grafts (SVGs) serve as the most commonly used supplemental conduits in CABG when arterial grafts are insufficient or unavailable, but they are inferior to arterial conduits and should be used selectively given their poor long-term patency rates. 1

Primary Conduit Strategy

• The left internal mammary artery (LIMA) to the left anterior descending artery (LAD) is the gold standard with >90% patency at 10-15 years, compared to only 25-50% for SVGs at the same timepoint 2, 3
• The radial artery is now the preferred second conduit over SVGs for the second most important non-LAD vessel (Class I, Level B-R recommendation) 2, 4
• Bilateral internal mammary artery (BIMA) grafting should be strongly considered in patients ≤60 years with few comorbidities (Class 2a recommendation) 1, 2

When SVGs Are Appropriate

SVGs should be used when:

• Arterial conduits are unavailable, unsuitable, or insufficient to achieve complete revascularization 1
• Multiple grafts are needed beyond available arterial options 1
• The patient has limited life expectancy where long-term patency is less critical 1

SVG Patency Rates and Failure Patterns

The fundamental problem with SVGs is progressive failure over time:

• 10-25% occlude within the first year after CABG 1
• Additional 1-2% occlude annually during years 1-5 1
• 4-5% occlude annually during years 6-10 1
• At 10 years, only 50-60% remain patent, and only half of these are free of atherosclerosis 1, 3
• By 10 years, 40-50% of SVGs have failed in most series 5

Mechanisms of SVG Failure

SVG failure occurs through distinct pathophysiological stages:

Early Failure (0-30 days)

• Endothelial damage during harvesting and exposure to arterial pressure leads to platelet aggregation and acute thrombosis 1
• Technical complications at anastomotic sites 1

Intermediate Failure (1 month to 1 year)

• Intimal hyperplasia develops from platelet adherence and smooth muscle cell migration 1
• Perianastomotic stenoses are common during this period 1

Late Failure (>1 year)

• Accelerated atherosclerosis unique to SVGs, with friable plaques occurring in 44% of SVGs versus 0% in native arteries 1
• Complex lesions with thrombi occur in 37% of SVGs versus 12% in native vessels 1
• Obstructive lesions develop in 53% within 5 years, 76% at 5-10 years, and 92% beyond 10 years 1

Optimizing SVG Performance

Harvesting Technique

• No-touch harvesting technique (preserving surrounding tissue, vasa vasorum, and nerves) improves patency rates comparable to arterial grafts and is a Class IIa recommendation 6, 7
• Avoid endoscopic harvesting as it has been associated with vein graft failure and adverse outcomes 2

Target Vessel Selection

• SVG patency to the LAD (69%) is superior to right coronary artery (56%) or circumflex (58%) 3
• Recipient vessel diameter >2.0 mm predicts better patency (88% versus 55% in vessels ≤2.0 mm) 3
• SVGs should target vessels with adequate size and distal runoff 1

Perioperative Management

• Perioperative aspirin and dipyridamole administration improves early (1 month) and 1-year SVG patency 1
• Use buffered storage solutions during graft preparation 7
• Intraoperative graft flow measurement to ensure technical adequacy 7

Long-term Medical Therapy

• Aspirin therapy is essential for maintaining SVG patency 3, 7
• High-intensity statin therapy reduces lipid accumulation in SVG intima 7
• Dual antiplatelet therapy is recommended for off-pump CABG and recent acute coronary syndrome 7

Clinical Implications for Post-CABG Patients

• Up to 20% of UA/NSTEMI patients have prior CABG, and conversely 20% of post-CABG patients develop UA/NSTEMI within 7.5 years 1
• Maintain a low threshold for angiography in post-CABG patients presenting with ischemia given multiple potential anatomic culprits 1
• For early ischemia (<30 days post-CABG), urgent angiography is indicated as this typically reflects acute graft thrombosis requiring PCI 1
• For multiple SVG stenoses, repeat CABG is reasonable, especially with significant stenosis of a graft supplying the LAD 1
• For focal SVG stenosis, PCI is reasonable but carries higher risk of embolization from friable atherosclerotic material 1

Critical Pitfalls to Avoid

• Do not use SVGs as first-line conduits when arterial grafts are available and suitable 2, 4
• Do not bypass vessels with inadequate stenosis severity as this promotes graft failure through competitive flow 1
• Do not neglect aggressive risk factor modification post-operatively, as SVG atherosclerosis is accelerated compared to native vessels 7
• Do not assume SVG patency based on symptom status alone - intermediate (30-60%) SVG stenoses often progress rapidly and require surveillance 7