ABSTRACT & COMMENTARY

By Jeffrey Zimmet, MD, PhD

Associate Professor of Medicine, University of California, San Francisco, Director, Cardiac Catheterization Laboratory, San Francisco VA Medical Center

Dr. Zimmet reports no financial relationships relevant to this field of study.

SOURCE: Hannan EL, et al. Coronary artery bypass graft surgery versus drug-eluting stents for patients with isolated proximal left anterior descending disease. J Am Coll Cardiol 2014;64:2717-2726.

Among patients with obstructive coronary disease requiring revascularization, guidelines would suggest a clear preference for coronary artery bypass grafting (CABG) over percutaneous coronary intervention (PCI) only in certain defined subsets, including those with left main disease and in diabetics with multi-vessel disease. Patients with isolated proximal LAD disease represent a unique high-risk subset of those with single-vessel disease, in that the size of the affected territory and associated ischemic risk makes CABG a viable option. In fact, U.S. guidelines currently assign a slight advantage to CABG with a left internal mammary graft to the left anterior descending (LAD) for such patients, rating this as a IIa indication vs a IIb recommendation for PCI. This is despite a relative paucity of data on this subset of patients, at least using contemporary treatments. In fact, of the nine randomized, controlled trials forming the basis for 17 published studies examining this question, most are quite small, and all but one were performed using bare-metal stents; the single small RCT incorporating drug-eluting stents (DES) used first-generation devices that are no longer part of the treatment landscape.

Hannan and colleagues contribute to this important topic with an observational study based on New York state registry data. For the period from the beginning of 2008 and the end of 2010, all patients who received CABG or PCI with DES for isolated proximal LAD disease were identified. Of the 6064 patients in this set, 5340 received PCI with DES and 724 underwent CABG. Based on available data, 715 CABG patients were propensity matched to 715 PCI patients, after which the characteristics of the matched patients were found to be similar. To maximize chances that downstream events would be captured in the database, only New York state residents were included. Three-year outcomes for the matched sets were reported.

Prior to propensity matching, unadjusted mortality and the combined endpoint of mortality, MI, and/or stroke were lower in the overall slightly healthier PCI group (4.3% vs 5.9%, P < 0.04 and 6.1% vs 8.3%, P < 0.03, respectively), but repeat revascularization was significantly higher among DES patients (12.2% vs 6.5%, P < 0.0001). Among the propensity-matched pairs, there were no significant differences in 3-year mortality rates or mortality, myocardial infarction (MI), and/or stroke rates. However, the rates for repeat revascularization remained significantly lower for CABG patients (adjusted hazard ratio, 0.54; 95% confidence interval, 0.36-0.81).

The study concludes that the majority (88%) of patients with isolated proximal

LAD disease undergo PCI. While there were no differences between CABG and DES in mortality or the combined outcome of mortality, MI, and stroke, repeat revascularization rates were significantly higher among PCI patients. The authors suggest that the preference for CABG in U.S. guidelines is discordant with their data, although they note that randomized trials involving large cohorts are needed to fully answer this question.

COMMENTARY

It should come as no surprise that PCI procedures greatly outnumber CABG for patients with isolated disease of the proximal LAD. The majority of such patients are diagnosed in the cardiac catheterization laboratory, where PCI may be performed in an ad hoc fashion without the involvement of the cardiac surgical team. Patients and cardiologists alike will most often elect the less-invasive revascularization option when given a choice. In this light, the current study gives support and reassurance that real-world patients are not being harmed with respect to the all-important hard outcomes of death, MI, and stroke.

On the other hand, the repeat revascularization data from this study are relatively compelling. The investigators found an absolute difference of nearly 5% between the two revascularization strategies, favoring CABG, which agrees with older studies. This advantage held up even when examining unadjusted data from the entire dataset, in which PCI patients had lower rates of important comorbidities, including prior MI, cerebrovascular and peripheral vascular disease, chronic obstructive pulmonary disease, and congestive heart failure. The accompanying editorial by cardiac surgeon Friedrich-Wilhelm Mohr of Leipzig University touts this benefit (Left Internal Mammary to LAD Artery Still Rules the Roost), and further points out that additional advantage may be gained through use of novel surgical techniques such as minimally invasive direct coronary artery bypass surgery. Such minimally invasive procedures are not done well or even offered at every heart center; however, knowledge of the local landscape must figure into practical decision-making.

The most notable factors that are routinely left out of analyses such as these are lesion and vessel characteristics that concretely affect the choice of revascularization. Features such as lesion length, vessel tortuosity and calcification, and involvement of significant sidebranches all increase PCI complexity, while the quality of the downstream anastomotic target and the distal coronary tree affect the projected success of bypass. In day-to-day practice, PCI is performed immediately for proximal LAD lesions that are anatomically suitable. Cardiologists would do well to think beyond the immediate procedure and to involve the Heart Team for optimal decision-making when appropriate.