CABG has been the traditional Rx for patients with amenable coronary occlusions and suitable operative candidates.
recently, the introduction of drug-eluting stents is increasingly challenging the role of CABG in patients suitable for stent and who are likely to tolerate and comply with long term antithrombotic medications such as clopidogrel.
long term outcomes
the mortality benefit of CABG is most evident in the first decade after surgery and then falls off significantly due to failure of SVG grafts and advancement of native coronary disease
the cardiac mortality is about 1 percent per year with arterial grafts and 2.0 to 2.5 percent per year with venous grafts, but these will vary with population studied.
CABG is of particular benefit in patients with ischemic left ventricular dysfunction, a reduced left ventricular ejection fraction, and evidence of hibernating myocardium.
although high-risk patients (three vessel disease and reduced left ventricular ejection fraction) had a better outcome with CABG compared to medical therapy at 10 years, there was no difference by 22 years.
graft patency
saphenous vein grafts
saphenous vein grafts (SVGs) begin to deteriorate within 5-7 years:
65-80% remain patent at 5 years
50-60% at 7-10 years
50% at 15 years
deterioration is dependent upon:
target vessel diameter < 2mm
smoking, hypertension, dyslipidaemia
stenosis occurs in 3 phases:
early - prior to discharge from hospital - occurs in 10%
intermediate - between 1 month and 1 year - occurs in 10-20%
late - after 1 year - between 1 and 6 years, annual stenosis rate is 2% per year, rising to 4-5% per year
internal mammary artery grafts
internal mammary artery grafts (IMA grafts) are much better than SVGs but more difficult to perform:
early patency rates of 99% (left IMA) and 94% (right IMA)
LIMA patency rates: 98% at 5yrs, 95% at 10yrs (up to 98-99% if not a right coronary artery, 83% if RCA), 88% at 15 yrs
RIMA patency rates: 96% at 5yrs, 81% at 10yrs, 88% at 15 yrs
radial artery grafts
4-10% develop immediate arterial spasm
patency rates: up to 96% at 1yr, 89% at 4yrs
recurrent angina
recurrent angina during the postoperative period is usually due to a technical problem with a graft or with early graft closure. It is an indication for prompt coronary angiography with catheter revascularization, if feasible.
recurrent angina after the first few months is caused by both graft disease and by progression of atherosclerosis in nonbypassed vessels. Progression of native disease is the more likely cause after internal mammary artery grafts, whereas graft disease is more likely after SVGs.
general medical Rx
aggressive risk factor reduction is recommended in all patients with CHD.
among patients undergoing CABG or PCI, progression of disease in previously untreated vessels accounted for two-thirds of the increase in myocardium at risk at five years.
non-compliance with medical Rx post-CABG such as aspirin (lifelong), clopidogrel (1st 9-12months post-op) and statins, doubles the rate of death or MI at 2 years post-CABG.
predictors of mortality
include:
perioperative MI - increases short-term and long-term mortality
cardiovascular risk factors:
age: RR 1.54 per decade
total cholesterol: RR 1.11 for each 1.3mmol/L increase
diabetes mellitus: RR 1.45
systemic hypertension: RR 1.28
cigarette smoking: RR 1.33
metabolic syndrome /insulin resistance syndrome
incomplete revascularisation
presence of un-grafted coronary artery disease almost halves 20 year survival (reduces survival from 75% to ~43%)
chronic renal disease with reduced GFR even if mild, increases perioperative mortality and long-term mortality