Patients who adhered to their medical therapy for up to eight years after undergoing CABG or PCI had significantly fewer major adverse cardiac events compared with those who did not adhere to their treatment, according to a retrospective, observational study.

For patients who did not adhere to their medications, CABG was superior to PCI in terms of complications-free survival rates. For patients who adhered to their medications, the revascularization strategies yielded similar outcomes.

The researchers defined major adverse cardiac events as all-cause mortality, nonfatal MI and reintervention.

Lead researcher Paul Kurlansky, MD, of Columbia University in New York, and colleagues published their results online Oct. 24 in Circulation.

“Adherence can have a dramatic impact on the long-term outcome of both heart bypass and angioplasty patients, and that impact may be more compelling in angioplasty than in bypass patients,” Kurlansky said in a news release. “We know enough from this study to seriously ask the question—are patients unwilling to adhere to medication schedules better off choosing heart bypass over angioplasty—but the answer needs to come from larger more contemporary trials.”

The researchers analyzed data on 973 patients who underwent CABG and 2,255 patients who underwent PCI from Feb. 1, 2004, to July 31, 2004. The patients were part of the CARE (Coronary Artery Revascularization Evaluation) registry, which included data on revascularization procedures from eight community hospitals.

The CABG group had a higher incidence of smoking, cerebral and peripheral vascular disease, triple-vessel disease, reduced ejection fraction and nonelective status, while the PCI group had a higher incidence of prior procedures. The mean follow-up time was 67 months in the CABG group and 61.8 months in the PCI group.

For both groups, patients who received antiplatelet medications, lipid-lowering therapies and beta-blockers had significant benefits in major adverse cardiac event-free survival. A Cox regression analysis found that compliance to optimal medical therapy was a better predictor of major adverse cardiac event-free survival than the choice of therapy.

“From the perspective of outcomes research, these findings suggest that any long-term comparison of these two therapeutic approaches cannot be fully or appropriately evaluated without information on medication adherence,” the researchers wrote. “Although the literature is replete with such studies, the effect of adherence to appropriate medical therapy on comparative outcomes has not been previously defined. The results of this observational study suggest both a dramatic effect of medication adherence on the long-term outcomes of each approach and a differential influence when these two approaches to [coronary artery revascularization] are compared. These findings strongly suggest that future investigations of different approaches to [coronary artery revascularization] should directly address the issue of adherence to [optimal medical therapy] in the interpretation of findings.”

The researchers mentioned a few limitations of the study, including its observational design, which meant they could not determine the reasons behind medical decisions or why patients were selected for CABG or PCI. They also based medication history on patient recall and did not know the status of medical therapy between discharge and the two follow-up periods.

“Results warrant confirmation in larger, more contemporary databases,” the researchers wrote. “If corroborated, a patient’s ability to adhere to a medical regimen may affect the selection of optimal therapy for patients requiring coronary revascularization.”