CHICAGO — Patients for whom an optimal panel of secondary-prevention drugs was not prescribed following coronary bypass surgery had a significantly higher risk of death or myocardial infarction than did patients who got all of their appropriate medications, according to an observational study with almost 3,000 bypass patients.
To improve the long-term outcomes of coronary bypass, “health-care systems must focus on using the appropriate discharge treatments and other secondary-prevention strategies” rather than relying on improved intraoperative care, Dr. Abhinav Goyal said at the annual scientific sessions of the American Heart Association. “If a health care system is to improve outcomes, it [should not] rely on [the actions of] individual physicians.”
Dr. Goyal, a cardiologist at Duke University in Durham, N.C, and associates reviewed data on 2,970 patients who enrolled in the Project of Ex Vivo Vein Graft Engineering via Transfection (PREVENT) IV trial, which was designed to test the efficacy of ex vivo treatment of vein grafts with edifoligide before coronary bypass surgery. The drug had no effect on vein graft survival at 1 year after surgery, the study's primary end point (JAMA 2005;294:2446–54).
The researchers' post hoc analysis had a completely different focus than the primary goal of the PREVENT IV study. It used patient records to estimate which of the participants were ideal candidates for each of four categories of secondary prevention drugs that are often prescribed to patients with coronary artery disease, to determine what percentage of patients actually received these drugs at the time of their hospital discharge and at 1 year after surgery, and then to assess the link between drug use and clinical outcomes after 2 years of follow-up.
The four drug classes were antiplatelet drugs, specifically aspirin and clopidogrel; β-blockers; ACE inhibitors and angiotensin-receptor blockers (ARBs); and lipid-lowering drugs, including statins. The researchers defined the ideal recipients of each of the four categories, based on the absence of any absolute or relative contraindications for the drug class and on certain clinical criteria. For example, patients were considered ideal candidates for β-blocker treatment if they had a history of a myocardial infarction or symptomatic reduced left ventricular ejection fraction. Similar clinical criteria also defined patients as ideal candidates for treatment with an ACE inhibitor or ARB.
Of all patients evaluated, 98% were identified as ideal candidates for an antiplatelet drug, 29% were identified as ideal candidates for a β-blocker, 41% were ideal recipients of an ACE inhibitor or ARB, and 81% were ideal candidates to get at least one lipid-lowering drug. Because most were ideal candidates for more than one of these drug classes, the analysis also examined the total pattern of drug prescribing. Overall, 65% of patients received all of their appropriate prescriptions at hospital discharge, 19% received prescriptions for more than half but less than all of their appropriate medications, and 16% received prescriptions for no more than half of their appropriate drugs.
In patients who were ideal candidates, the rates of prescribing at hospital discharge and at 1 year after discharge were generally high: about 95% for antiplatelet drugs, about 80% for β-blockers, and more than 80% for lipid-lowering drugs. (See box.) But prescribing rates were “suboptimal” for ACE inhibitors and ARBs, with prescriptions written to about half of the ideal recipients.
Data also suggested a link between prescriptions for these drugs and 2-year outcomes. The 2-year incidence of death or myocardial infarction was 4% in patients who received all of the medications for which they were ideal candidates, 5% in patients who received more than half but less than 100% of their drugs, and 8% in patients who were prescribed half or less of their ideal medications.
In a multivariate analysis that controlled for age, gender, diabetes, renal function, and several other clinical features, bypass surgery patients who received no more than half of their appropriate medications were 69% more likely to die or have a myocardial infarction, compared with patients who received all of their appropriate medications, a statistically significant difference.
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