What are the technical considerations for stent sizing, predilatation, and post-dilation in a patient with a history of coronary artery bypass grafting (CABG) undergoing percutaneous coronary intervention (PCI) for lesions in their grafts?

Technical Aspects of Graft PCI: Stent Sizing, Predilatation, and Post-Dilation

For saphenous vein graft (SVG) PCI, use distal embolic protection devices, perform direct stenting when feasible to minimize plaque disruption, size stents to match the graft diameter (typically 3.5-5.0mm), and reserve aggressive post-dilation for suboptimal results given the high risk of distal embolization. 1, 2

Mandatory Technical Requirements

Distal Embolic Protection

• Distal embolic protection devices must be used when technically feasible in all SVG interventions - this is a Class I recommendation from ACC/AHA guidelines 1, 2
• Protection devices significantly reduce complications from embolization, which occurs more frequently in grafts with diffuse atherosclerotic involvement, visible thrombus, irregular/ulcerative surfaces, and long lesions with large plaque volume 1
• Without embolic protection, SVG PCI carries substantially higher rates of slow-flow, distal embolization, and periprocedural MI 1

Stent Sizing Strategy

Saphenous Vein Grafts

• Size stents to match the reference graft diameter, which is typically larger than native vessels (3.5-5.0mm range) 1
• SVG diameter varies by location: ostial and mid-shaft segments are often larger than distal anastomotic regions 1
• Avoid undersizing, as this increases risk of stent thrombosis and restenosis in the friable, atherosclerotic graft tissue 1

Internal Mammary Artery Grafts

• IMA grafts are smaller caliber vessels (2.5-3.5mm typically) requiring appropriately downsized stents 1
• Balloon dilation alone may suffice for distal anastomotic IMA stenoses, with stenting reserved for suboptimal results 1

Predilatation Approach

When to Predilate

• Minimize or avoid predilatation in friable, atherosclerotic SVGs (>3 years old) to reduce distal embolization risk 1
• Direct stenting is preferred when technically feasible in degenerated vein grafts to minimize plaque disruption 1
• Predilatation is reasonable for:
  • Tight, fibrotic lesions preventing stent delivery 1
  • Early perianastomotic stenoses (1-12 months post-CABG) due to intimal hyperplasia, which respond well to balloon dilation 1
  • Calcified ostial lesions requiring lesion preparation 1

Predilatation Technique

• Use undersized balloons (balloon-to-artery ratio 0.8-1.0) at low pressures initially 1
• In acute graft thrombosis (<30 days post-CABG), balloon dilation across suture lines has been accomplished safely 1
• Consider mechanical thrombectomy before balloon dilation in thrombotic lesions to reduce embolic burden 1

Post-Dilation Strategy

Conservative Approach Recommended

• Use selective, cautious post-dilation in SVG PCI due to high embolization risk from friable plaque 1
• Post-dilate only for:
  • Significant stent underexpansion (>20% residual stenosis) 1
  • Edge dissection requiring coverage 1
  • Suboptimal apposition documented by imaging 3

Post-Dilation Technique

• Use non-compliant balloons sized 1:1 to the stent diameter (not oversized) 1
• Employ short inflation times at moderate pressures to minimize plaque disruption 1
• Have vasodilators ready (adenosine, diltiazem, nitroprusside, verapamil) for slow-flow management 1

Lesion-Specific Technical Considerations

Distal Anastomotic Stenoses

• Respond well to balloon dilation alone with favorable long-term prognosis 1
• Stenting enhances immediate results but may not be mandatory for all cases 1
• Can safely dilate across suture lines even within days of surgery 1

Mid-Shaft and Ostial SVG Lesions

• Require stent deployment for optimal results 1
• Ostial lesions may benefit from ablative technologies (directional atherectomy, excimer laser) to facilitate stent delivery 1
• Mid-shaft lesions have higher restenosis rates than distal anastomotic lesions 1

Timing-Based Approach

• Early ischemia (<30 days post-CABG): Usually graft thrombosis - consider mechanical thrombectomy, cautious balloon dilation, and stenting 1, 2
• Intermediate period (1-12 months): Typically perianastomotic intimal hyperplasia - balloon dilation often sufficient, stenting for suboptimal results 1
• Late disease (>3 years): Atherosclerotic degeneration - mandatory embolic protection, direct stenting preferred, drug-eluting stents over bare-metal 1, 4

Drug-Eluting vs Bare-Metal Stents

Use drug-eluting stents (DES) as first choice for graft PCI - they reduce mortality and MACE rates compared to bare-metal stents, particularly in SVG interventions 4

• DES show significantly fewer MACEs (29.0% vs 52.1%) and less target vessel revascularization than BMS in graft lesions 4
• The safety and efficacy profile of DES is superior across all graft types 4

Imaging Guidance

While not specifically addressed in graft PCI guidelines, the iPSP strategy (imaging-guided pre-dilation, stent sizing, and post-dilation) demonstrated superior 3-year outcomes in complex lesions, with adjusted hazard ratio of 0.71 for cardiac events 3

• This approach is particularly relevant for complex graft lesions given their high-risk nature 3
• Intravascular ultrasound can optimize stent sizing in large-caliber SVGs where angiography may be misleading 3

Critical Pitfalls to Avoid

• Never attempt PCI on chronic total vein graft occlusions - associated with high complication rates and low sustained patency 1, 2
• Avoid aggressive manipulation in degenerated SVGs (>3 years old) without embolic protection 1, 2
• Do not use intracoronary fibrinolysis in the first week post-CABG due to hemorrhage risk - mechanical thrombectomy is safer 1
• Consider IABP support when treating grafts in patients with systemic hypotension or severe LV dysfunction, as vein graft flow is pressure-dependent 1

Alternative Strategy: Native Vessel PCI

When feasible, prioritize native vessel PCI over graft PCI - it demonstrates superior long-term outcomes with higher MACE-free and revascularization-free survival rates 4

• Native vessel PCI should be considered first-line treatment when the native vessel is accessible 4
• SVGs can serve as conduits to facilitate complex native vessel interventions rather than being the primary target 5
• If both graft and native vessel stenoses are present, attempt PCI of both when technically feasible, particularly if stents can be deployed successfully 1