Methods

The present study was a retrospective, single-center, observational study comparing the outcomes of DES and CABG performed in patients with chronic LV systolic dysfunction. The institutional review board approved the present study, and informed consent was waived. The patients were recruited from the cardiovascular catheterization and surgery databases of Samsung Medical Center (Seoul, South Korea). Patients with a LV ejection fraction <50% who had undergone PCI with DES or CABG from January 2003 to December 2010 were included. The patients who presented with acute myocardial infarction within 4 weeks of PCI were excluded.

The LV ejection fraction was evaluated using echocardiography in all patients within 4 weeks before the procedure. The baseline clinical, laboratory, and angiographic characteristics were collected from the databases and medical records. The follow-up clinical status was documented by a review of the hospital records, telephone interviews, or interviewing the general practitioners.

DES or CABG was selected according to patient preference and the preference of their physician. Coronary interventions were performed according to current standard procedural guidelines. All patients undergoing PCI were prescribed aspirin (300 mg loading dose) and clopidogrel (300 to 600 mg loading dose) before PCI. The treatment strategy and the use of glycoprotein IIb/IIIa receptor inhibitors or intravascular ultrasonography were left to the operator’s discretion. DESs were used without restriction. After the procedure, aspirin was continued indefinitely, and clopidogrel was recommended for ≥12 months. In the CABG group, an arterial graft with off-pump coronary artery bypass was the preferred technique, when possible. We did not limit the use of aspirin or heparin before or after surgery.

All-cause death was defined as any death during or after the procedure. Recurrent myocardial infarction (MI) was defined as the recurrence of ischemic symptoms or electrocardiographic changes accompanied by elevated cardiac enzymes. Periprocedural MI was not considered recurrent MI in the present study. Cerebrovascular accident was defined as ischemic neurologic deficits that persisted >24 hours. Any coronary revascularization was defined as revascularization of either target or nontarget vessels using PCI or CABG. A significant lesion was defined as stenosis of ≥50% of the diameter of a vessel with a reference diameter of >2.0 mm by visual estimation. Complete revascularization was considered to have been accomplished when all vessels with a significant lesion were successfully revascularized.

The primary outcome was all-cause death during follow-up. The secondary outcomes included all-cause death, recurrent MI, cerebrovascular accident, coronary revascularization with PCI or CABG, and major adverse cardiac and cerebrovascular events, defined as a composite event of all-cause death, recurrent MI, cerebrovascular accident, and coronary revascularization during follow-up.

Continuous variables were compared using the t test or Wilcoxon rank sum test, where applicable. Categorical data were tested using the chi-square test or Fisher’s exact test, as appropriate. Survival curves were constructed using Kaplan-Meier estimates and compared using the log-rank test. The Cox proportional hazard model was used to compare the risk of adverse cardiac events between the DES and CABG groups. Propensity scores were estimated using multiple logistic regression analysis. A full nonparsimonious model was developed that included age; gender; diabetes mellitus; hypertension; dyslipidemia; smoking; chronic kidney disease; history of MI, PCI, CABG, or cerebrovascular accident; New York Heart Association functional classification III or greater; LV ejection fraction; N-terminal pro-B-type natriuretic peptide; clinical manifestations; aspirin use; use of renin-angiotensin system blockers, β blockers, and statins at discharge; European System for Cardiac Operative Risk Evaluation score; an artery with significant stenosis; number of coronary arteries narrowed; and complete revascularization ( Tables 1 and 2 ). The discrimination and calibration ability of the propensity score model were assessed using the c-statistic and Hosmer–Lemeshow statistic. Cox regression analysis using pairs matched by a greedy algorithm and the nearest available pair-matching method among patients with an individual propensity score was also performed to evaluate the reduction in outcomes risk. The covariate balance achieved by matching was assessed by calculating the absolute standardized differences in covariates between the DES and CABG groups. In the propensity score–matched population, continuous variables were compared using a paired t test or the Wilcoxon sign rank test, as appropriate. Categorical variables were compared using the McNemar or Bowker test of symmetry, as appropriate. The reduction in the risk of an adverse outcome was compared using a stratified Cox regression model adjusted by the synergy between PCI with Taxus and cardiac surgery (SYNTAX) score. The cumulative incidence rates of individual clinical outcomes and composite outcomes were estimated using the Kaplan-Meier method and compared using the paired Prentice-Wilcoxon test. Statistical analyses were performed using Statistical Analysis Systems, version 9.2 (SAS Institute, Cary, North Carolina). All tests were 2 tailed, and p <0.05 was considered statistically significant.