What should I assess on an angiographic image to evaluate the position and patency of a coronary artery bypass graft?

Angiographic Assessment of Coronary Artery Bypass Graft Position and Patency

When evaluating bypass grafts on angiography, you must systematically assess graft location, patency status, anastomotic sites, flow characteristics, and any evidence of stenosis or thrombosis. 1

Essential Components to Evaluate

Graft Identification and Location

• Document the origin of each graft from the aorta (for saphenous vein grafts and free arterial grafts) or from the subclavian artery (for internal mammary arteries), noting the precise aortic attachment site 1
• Identify the course of the graft through the mediastinum, checking for any kinking, twisting, or compression that could compromise flow 2
• Confirm the distal anastomotic target vessel (LAD, diagonal, obtuse marginal, RCA, posterior descending artery, etc.) and document whether it is proximal, mid, or distal in location 1

Patency Assessment

• Determine if the graft is patent, stenotic, or occluded - this is the most critical assessment 1
• For patent grafts, assess the quality of contrast opacification throughout the entire length from proximal to distal anastomosis 1
• Total occlusion occurs in 10-25% of saphenous vein grafts within the first year, with vein grafts showing higher occlusion rates than arterial grafts 1, 3
• Internal mammary arteries demonstrate >90% patency at 10 years, making them far superior to vein grafts 1

Anastomotic Site Evaluation

• Examine both the proximal (aortic) and distal (coronary) anastomoses for narrowing, stenosis, or technical problems 1, 2
• Anastomotic complications are a major cause of early graft failure and should be carefully scrutinized 1
• Look for dissection at the anastomotic sites, though this may be difficult to detect on standard angiography 2

Stenosis and Atherosclerotic Disease

• Assess for stenoses ≥50% anywhere along the graft body or at anastomotic sites 4
• Saphenous vein grafts develop accelerated atherosclerosis with 50-60% patent at 10 years, and only half of those free of atherosclerotic disease 1
• Document whether disease is focal or diffuse along the graft length 1

Thrombus Detection

• Look for filling defects or haziness suggesting intra-graft thrombus, which occurs in 37% of culprit vein grafts in unstable angina versus only 12% in native vessels 3
• Thrombus is particularly common in vein grafts and may be associated with total occlusion 3

Flow Characteristics and Competitive Flow

• Assess distal runoff into the native coronary artery beyond the anastomosis 1
• Evaluate for competitive flow, particularly in arterial grafts to vessels without critical stenosis 5
• Arterial grafts to vessels with <70% stenosis (left-sided) or <90% stenosis (RCA) are prone to failure from competitive flow 5

Graft-Specific Considerations

Saphenous Vein Grafts

• More prone to early thrombosis and late atherosclerosis than arterial grafts 1
• Higher likelihood of total occlusion (49% in unstable angina) compared to native vessels 3
• Friable atherosclerotic plaques occur in 44% of SVGs versus 0% in native arteries 6

Internal Mammary Artery Grafts

• Typically have excellent long-term patency (>90% at 10-15 years) 1
• Less prone to atherosclerosis due to continuous internal elastic lamina and endothelial factors 1
• May be more difficult to visualize on some imaging modalities 7

Radial and Other Arterial Grafts

• Muscular arteries prone to vasospasm, particularly when grafting vessels without severe stenosis 1, 5
• Should only be used for severely stenotic vessels (≥70% for left-sided, ≥90% for RCA) 5, 8

Additional Structures to Document

Native Coronary Anatomy

• Comment on the dominance of the coronary system (right versus left dominant) by identifying the origin of the posterior descending artery 1
• Document progression of disease in ungrafted native vessels 1
• Assess grafted native vessels both proximal and distal to graft insertion sites 3

Surrounding Cardiac Structures

• Note any aneurysmal or pseudoaneurysmal dilations of coronary arteries or grafts 1
• Comment on left ventricular function if ventriculography is performed 1

Critical Pitfalls to Avoid

• Do not rely solely on a single angiographic view - obtain multiple projections to fully visualize the graft course and anastomoses 1
• Do not miss subtle anastomotic narrowing that may cause early graft failure 1, 2
• Do not overlook competitive flow as a cause of arterial graft failure, particularly in grafts to non-critically stenosed vessels 5
• Be aware that thrombus may be overdiagnosed on some imaging modalities but should still be reported when suspected 2
• In patients >5 years post-CABG, graft disease accounts for 85% of acute ischemic presentations, making thorough graft evaluation essential 3