Comparison of Coronary Artery Bypass Grafting (CABG) and Percutaneous Coronary Intervention (PCI)

The ideal treatment for ischemic coronary artery disease (CAD) remains a subject of debate. The two primary revascularization modalities are coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI). Throughout this article, we discuss the history, indications, applications and outcomes of these revascularization procedures. Both PCI and surgical revascularization are advancing rapidly, and it is likely that such advances will continue in the years to come.

Several studies have shown that mechanical revascularization by either CABG or PCI is more effective in relieving angina and improving quality of life.

The ORBITA (Objective Randomised Blinded Investigation with optimal medical Therapy of Angioplasty in stable angina) trial randomized PCI with placebo in patients with stable coronary artery disease due to single-vessel CAD in the presence of moderate angina. This study outlined that symptomatic relief in that cohort might be at least partly due to placebo effect and, importantly, it emphasized the role of optimal medical therapy (OMT).

While bioabsorbable stents have not lived up to the promise and have been pulled out of the market, bioabsorbable stents continue to hold promise. Bioabsorbable magnesium stents are being evaluated. The advantages of biodegradable polymers include high drug-loading capacity, controlled long-term drug release, and full degradation of the polymer over a defined period, resulting in full release of the drug during a well-controlled time interval.

Thromboresistant polymer coatings based on biologic substances such as fibrin, collagen, hyaluronic acid, and biologic oils are being tested. These polymers serve as drug delivery reservoirs for drugs that inhibit neointimal hyperplasia through suppression of platelet activation and the inflammatory response and through inhibition of smooth muscle cell migration and proliferation.

The effect of variable dose and release kinetics of drugs on neointimal hyperplasia is also being studied. Multiple drugs may be delivered at timed intervals through newly designed stents.

Gene-eluting stents are undergoing experimental and clinical trials; these will be usable either alone or in conjunction with other drug-eluting stents (DESs) and may further reduce in-stent restenosis (ISR). The ABSORB trial studied the safety of the bioabsorbable everolimus-eluting stent. At 2 years, the stent was bioabsorbed, with vasomotion restored and restenosis prevented, and was clinically safe, suggesting freedom from late thrombosis.

The TRITON-TIMI 38 trial showed that in patients with acute coronary syndromes with scheduled PCI, prasugrel therapy was associated with significantly reduced rates of ischemic events, including stent thrombosis, but with an increased risk of major bleeding, including fatal bleeding. Overall mortality did not differ significantly between treatment groups. Prasugrel has been approved by the US Food and Drug Administration (FDA). Other antithrombotics are in the pipeline.

Most acute coronary syndromes are caused by rupture of unstable plaques of mild-to-moderate stenosis (< 50%). Stenting of such vulnerable lesions might result in stabilization and prevention of plaque rupture. Likewise, rapid advances have been made in surgical techniques. In the future, PCI and CABG may come to be seen as complementary techniques for myocardial revascularization.
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Source: Arun Kalyanasundaram, MD, MPH Interventional Cardiology Fellow, Department of Cardiology, Cleveland Clinic