Chapter 25 Percutaneous coronary intervention in saphenous vein graft disease
INTRODUCTION
Since first implantation of coronary grafts in 1967 the success of venous conduits in relieving myocardial ischaemia has been limited by their temporal attrition. Although internal mammary grafts have unsurpassed long term patency, utilisation is limited by scarcity. The use of gastroepiploic and radial arteries has been shown to be less than optimal.1 Consequently, in spite of declining surgical revascularization rates worldwide, the use of venous grafts seems unlikely to diminish and treatment of symptomatic patients with degenerated venous grafts will remain a problem for interventional cardiologists.
Vein graft disease progression and its timing
Three interlinked pathological processes – thrombosis, neointimal hyperplasia and atherosclerosis, which are temporally distinct, contribute to vein graft disease.2,3 Awareness of the processes and their timing may help in optimising outcome from intervention.
Atherosclerosis is the main pathological process that contributes to vein graft occlusion one year and beyond after surgery.2 The predisposing factors and the basic process of atheroma development are similar to those documented in native coronary arteries. However, there are a few distinct topographic, temporal, and histological differences in the pathology of vein graft disease.
The distinct morphological difference seen in vein grafts compared to native coronary arteries is that vein graft atheroma is diffuse, concentric, and friable with poorly developed or absent fibrous cap with little calcification. Intravascular ultrasound studies reveal the absence of focal compensatory enlargement (‘Glagov’s law’) of diseased vein graft segments.3,4 Late graft thrombosis triggers recurrent ischaemia and is frequently seen in old degenerating grafts with advanced atherosclerotic disease.5
REVASCULARISATION FOR VEIN GRAFT DISEASE
Redo surgery
Recurrence of anginal symptoms is seen in up to 20% of patients within one year following surgical revascularisation followed by 4% of patients annually during the next 5 years, 19% at 10 years and 31% at 12 years.6
There are limited data comparing percutaneous revascularisation to repeat surgery in patients with angina recurrence. Repeat surgery achieves complete revascularisation in 92% of patients compared to 38% in the percutaneous intervention group. However, in-hospital complications are more common in surgical patients: death (7.3 % vs. 0.3%), Q-wave MI (6.1% vs. 0.9%), and low output syndromes (24% vs. 9%). Both procedures result in equal survival rates at one and six years with equal relief of angina but repeat intervention and/or revascularisation is more frequent in the percutaneous group (64% vs. 8%) at six years.7,8
Given the high morbidity and mortality of re-operation reduced symptomatic benefit as compared to first bypass surgery,8,9 percutaneous revascularisation should be the preferred first route for post surgery angina recurrence.
Percutaneous coronary intervention
Balloon angioplasty for vein graft disease has moderate procedural success limited by high periprocedural complication rate, high incidence of restenosis (35%) and high repeat revascularisation rate.10,11 Clinical trials show BMS to be superior to balloon angioplasty in vein graft lesions. The use of stents is associated with a high procedural success, superior clinical outcome, and reduced TLR. However, as compared to native vessels the restenosis rate remains high12,13 coupled with higher periprocedural complications.
The significant problems associated with vein graft intervention are:
The use of DES in native coronary arteries has shown promising results with significant reduction in restenosis rates.14,15 Limited data is available on the long term efficacy of DES in patients with vein graft disease. Most studies confirm a high procedural success rate but there is conflicting data on how DES would affect the clinical outcome. Two nonrandomized trials have shown a trend towards a reduction in MACE at six to nine months follow up.16,17 The use of DES was associated with a lower restenosis rate (10% vs. 26.7%, P=0.03) and TVR (4.9% vs. 23.1%, P <0.01) at six to nine months. However, one study showed similar clinical outcome at 30 days, 60 days and 1 year.18
Diffuse SVG disease
Unlike focal graft lesions, diffusely degenerative graft disease with large ulcerated fragile plaques with associated thrombus is associated with a low procedural success, higher complication rates and low long term patency rate.19
Endoluminal reconstruction by stenting of diffuse lesions (‘full metal jacket’) is a possible option and clinical trials reveal a high procedural success for stenting of diffuse lesions. However, it has been associated with a high incidence of death (11.1%) or myocardial infarction (9.4%) and frequent need for repeat angioplasty.20