CABG Better in Elderly, PCI Better in Young?

Abstract & Commentary

By Andrew J. Boyle, MBBS, PhD, Assistant Professor of Medicine, Interventional Cardiology, University of California, San Francisco.

Source: Flather M, et al. The effect of age on outcomes of coronary artery bypass surgery compared with balloon angioplasty or bare-metal stent implantation among patients with multivessel coronary disease. A collaborative analysis of individual patient data from 10 randomized trials. J Am Coll Cardiol 2012;60:2150-2157.

As our population ages and outcomes from revascularization also improve, more elderly patients are being referred for coronary artery bypass graft surgery (CABG) and for percutaneous coronary intervention (PCI). Current guidelines do not include age-specific recommendations for the choice of revascularization technique. Although there are several clinical trials comparing CABG and PCI, the effects of age on the outcomes remain uncertain. Therefore, Flather and colleagues performed a meta-analysis using data from 10 randomized controlled trials that compared CABG with PCI to ascertain the effects of age on outcomes from these procedures. Notably, all of the studies included only used balloon angioplasty or bare-metal stents; none of these studies used drug-eluting stents. The authors used individual patient-level data from 7812 patients and divided them into tertiles of age (≤ 56.2 years, 56.3-65.1 years, and ≥ 65.2 years). The primary outcome was all-cause mortality. Secondary outcomes were the composite of death or myocardial infarction (MI), repeat coronary revascularization, and angina at 1 year of follow-up.

There were significant baseline differences between the age groups, as expected. Older patients were more likely to be female and to have diabetes, hypertension, peripheral vascular disease, heart failure, and triple vessel disease, but were less likely to be smokers or to have a history of MI (all P < 0.001). However, within each age tertile, the baseline characteristics were well matched between those randomized to CABG or PCI.

Younger patients randomized to PCI had lower mortality than CABG (8% vs 11%), whereas older patients randomized to PCI had higher mortality than CABG (24% vs 20%). The CABG-to-PCI adjusted hazard ratio [HR] for all-cause mortality was described for each tertile of age, with values greater than 1.0 signifying that CABG was associated with a higher mortality than PCI, whereas values lower than 1.0 indicated CABG had lower mortality. The HR was 1.23 in the young (95% CI, 0.95-1.59), 0.89 in the middle tertile (95% CI, 0.73-1.10), and 0.79 in the oldest tertile of age (95% CI, 0.67-0.94). This relationship was the same for the combined secondary endpoint of death or MI. Of note, the CABG-to-PCI HR for mortality decreased with age and crossed 1.0 at age 59 years, suggesting that CABG is associated with lower mortality than PCI in patients > 59 years of age, but PCI is associated with lower mortality in patients < 59 years of age. The relationship between age and outcomes was similar when stratified by diabetes. The CABG-to-PCI HR for mortality was < 1.0 (i.e., favored CABG) among patients > 63 years without diabetes and among patients > 47 years with diabetes. In all age groups, PCI was associated with a higher rate of repeat revascularization than CABG. The rate of stroke was only available in six studies, but increased significantly with age and assignment to CABG. The authors conclude that patient age modifies the comparative effectiveness of CABG and PCI on hard cardiac events, with CABG favored at older ages and PCI favored at younger ages.

Commentary

The debate continues about which revascularization strategy, CABG or PCI, is best. The recently presented FREEDOM trial suggests that diabetics fare better with CABG than PCI. The SYNTAX trial suggested that those with more anatomically complex coronary disease have better outcomes with CABG. The current study suggests that aging may also play a role in selecting the most appropriate subsets of patients for a particular treatment. It should be noted that this is an observational study and not a randomized trial, and as such there may be selection bias for either treatment that cannot be fully accounted for by statistical adjustment.

It may be somewhat counterintuitive that older patients have better outcomes with CABG and younger patients have lower mortality with PCI. CABG has traditionally been thought of as a superior long-term treatment option. Therefore, one would expect that younger patients have longer to live and longer to gain the benefits of CABG. One explanation may be that age acts as a surrogate for more extensive coronary artery disease. Although the authors corrected for the presence of triple vessel disease, they were unable to get further detail of anatomical extent of atherosclerosis, such as the SYNTAX score. Outcomes with PCI or CABG are worse with extensive, complex coronary disease and this may be influencing the results with age presented in this paper.

These results will not change guidelines, as they are observational in nature. However, they may help clinicians steer toward a particular strategy if clinical equipoise exists in parameters other than age. Further prospective studies are needed to elucidate the effects of aging on PCI and CABG outcomes, particularly in the era of drug-eluting stents, and taking into account parameters other than death and MI, such as cost-effectiveness and quality-of-life measures.