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Left Main PCI vs. CABG: Five-year Follow-up of Two Registries
Abstract & Commentary
By Andrew J. Boyle, MBBS, PhD
Sources: Park D-W, et al. Long-term safety and efficacy of stenting versus coronary artery bypass grafting for unprotected left main coronary artery disease. 5-year results from the MAIN-COMPARE (Revascularization for Unprotected Left Main Coronary Artery Stenosis: Comparison of Percutaneous Coronary Angioplasty Versus Surgical Revascularization) Registry. J Am Coll Cardiol. 2010;56:117-124; Chieffo A, et al. 5-year outcomes following percutaneous coronary intervention with drug-eluting stent implantation versus coronary artery bypass graft for unprotected left main coronary artery lesions: The Milan Experience. J Am Coll Cardiol Intv. 2010;3:595-601.
The evolution of percutaneous coronary intervention (PCI) techniques has resulted in PCI becoming a reasonable alternative to coronary artery bypass graft (CABG) surgery in selected patients with unprotected left-main coronary artery (ULMCA) stenosis. This was reflected in a change in the ACC/AHA guidelines upgrading left-main PCI to a class-IIb indication. However, there is a paucity of long-term outcome data comparing PCI to CABG in the treatment of ULMCA disease. Two recent publications now extend the outcome data to five years following PCI vs. CABG.
Results: Park and colleagues studied 2,240 patients with ULMCA disease and compared outcomes between those who underwent PCI (n = 1,102) with drug-eluting stents (DES; n = 784) or bare-metal stents (BMS; n=318) and those who underwent CABG (n = 1,138). The short- and medium-term data from this non-randomized multicenter registry have previously been reported but, in this paper, the authors report the longer-term outcomes 3-9 years after the index procedure (median 5.2 years).
Patients undergoing CABG were considered high risk: they were slightly older, more likely to have diabetes, dyslipidemia, peripheral arterial disease, unstable presentation, and prior myocardial infarction (MI), and were more likely to smoke. Furthermore, CABG patients had a higher prevalence of triple-vessel disease. PCI patients were more likely to have had prior PCI. Unadjusted mortality was lower in patients receiving DES than CABG (p = 0.02), as was the combined endpoint of death, stroke, and Q-wave MI (p = 0.02). There was no difference between BMS and CABG for these endpoints. However, the need for target-vessel revascularization (TVR) was significantly higher in both PCI groups than CABG. After propensity-score matching, there were no differences between PCI and CABG in total mortality or in the combined endpoint. This was consistent in both BMS and DES patient cohorts. However, increased rates of target-vessel revascularization continued to be seen in the PCI groups.
Chieffo et al present the results of a smaller cohort of 249 patients with ULMCA disease. In this single-center non-randomized registry, 107 patients were treated with DES and 142 with CABG. Again, in this registry, CABG patients were higher risk: they were older, more likely to have hypertension, renal failure, and concomitant disease in the right coronary artery. Unadjusted mortality (15.9% vs. 18.3%) and cardiac death (7.5% vs. 11.9%) were not different between PCI and CABG, respectively. PCI resulted in lower-composite endpoint of cardiac death, MI, and stroke compared to CABG (OR 0.38; p = 0.02). However, TVR rates were higher after PCI than CABG (28% vs. 8.4%, p = 0.0001). After propensity-score adjustment, there was no difference between PCI and CABG in total mortality, the composite of death and MI, or in MACCE (death + stroke + MI + TVR).
CABG remains the standard of care in patients with ULMCA disease in the United States. However, a growing body of literature suggests that PCI may be an acceptable alternative in selected patients. These two registry studies extend our current knowledge of PCI vs. CABG for left-main disease out to five years of follow-up, allaying some fears of a later "catch-up" phenomenon with PCI. Both registries show that PCI is associated with similar outcomes to CABG, in terms of death and MI, but with lower stroke rates and higher revascularization rates. These data will help clinicians and patients individualize their choice of revascularization strategy. However, the longer-term results beyond five years remain unknown.
These two studies are limited by their observational, retrospective nature. There is inherent selection bias in the clinician's decision to pursue either CABG or PCI for individual patients, and even sophisticated statistical analysis cannot account for all the unmeasured biases here. Furthermore, we are not told if the long-term medical therapy is the same in the PCI and CABG groups, which may contribute to differences between the two arms. Thus, these data should not change our current practice paradigm. However, despite these limitations, Park et al and Chieffo et al provide some reassurance that the upgrade of PCI for ULMCA disease to a IIb indication in the latest ACC/AHA guidelines should be safe at least out to five years.