Underuse of cardioprotective medications in patients prior to acute myocardial infarction

Abstract

S prevention in coronary heart disease (CHD) improves survival and reduces recurrent events.1–4 National clinical guidelines and organizational performance measures recommend the use of hydroxymethylglutaryl coenzyme A reductase inhibitors (statins), blockers, angiotensin-converting enzyme (ACE) inhibitors, and aspirin in most patients after acute myocardial infarction (AMI).5–8 However, many high-risk patients do not receive them.9,10 We sought to determine whether patients with known CHD admitted for AMI to hospitals in the Veterans Administration (VA) system had indications for pharmacologic secondary prevention before admission and the extent to which these therapies were begun in the period immediately after discharge from the hospital. • • • We conducted a before–after study of patients with documented CHD who had an AMI to compare their cardioprotective medications during the 6 months before admission for AMI and during the 3 months after hospital discharge. We identified established male patients who had a diagnosis of CHD registered from April 1 to June 30, 2000, and were admitted with a primary diagnosis of AMI between July 1, 2000, and June 30, 2001, to any of the 8 VA medical centers in the Veterans Integrated Service Network (VISN) 20. A diagnosis of CHD was defined as an in-patient primary discharge diagnosis or an outpatient diagnosis for any of the following International Classification of Diseases, 9th revision (ICD9-CM) codes: 410 (AMI), 411 (unstable angina pectoris), 412 (past AMI), and 414 (coronary atherosclerosis). We defined an established patient as having visited a VA primary or specialty care clinic (including internal medicine, primary care, geriatric, cardiology, endocrinology, diabetes, hypertension, pulmonary, and mental health) between April 1, 2000, and June 30, 2000, and having made at least 1 visit within 13 to 24 months before April 1, 2000. Only patients who were alive on June 30, 2000, and alive at discharge were included. Patient, pharmacy, co-morbidity, and laboratory data were extracted from the VISN 20 data warehouse (CHIPS). CHIPS is a relational database that contains data from the clinical information systems of each of the 8 VA medical facilities in VISN 20 of the Veterans Health Administration. The main variables of interest were prescriptions dispensed for 4 drug classes: statins, blockers, ACE inhibitors/angiotensin II receptor blockers (ARBs), and aspirin. We included ARBs because a growing body of published reports supports treatment with ARBs in patients intolerant to ACE inhibitors.11,12 Drug data were extracted for from January 1, 2000, to September 30, 2001. We compared the proportion of CHD patients with filled prescriptions of each drug class 6 months before the AMI admission date and 3 months after hospital discharge. We also compared the proportion of prescription fills for each of the 4 drug classes based on the history of cardiac risk factors before admission. Risk factors included ICD9-CM documentation of hypertension, diabetes, and congestive heart failure, and laboratory documentation of elevated low-density lipoprotein (LDL) cholesterol. Data on risk factors were extracted from January 1, 1990, to June 30, 2001. We defined an LDL cholesterol 120 mg/dl (3.11 mmol/L) as elevated based on the Veterans Health Administration guidelines for management of dyslipidemia. LDL cholesterol data were extracted for 15 months before the admission date. The most recent documented LDL cholesterol before admission was used in our analyses. We used McNemar’s test to assess the statistical significance of the changes in the proportion of patients with medication fills before admission and after discharge. We identified 13,767 male veterans with a history of CHD during April 1 and June 30, 2000. Of these men, 239 were admitted to a VISN 20 facility with a primary diagnosis of AMI from July 1, 2000, to June 30, 2001. Eight patients died in the hospital and were excluded from study. The remaining 231 patients (mean age 69 years) were predominantly white (94%) and married (55%). Cardiac risk factors were common (Table 1). After discharge for AMI, we observed significant (p 0.05) increases in the percentage of patients receiving a prescription for 3 of the 4 drug classes: from 50% to 68% for statins, from 53% to 82% for blockers, and from 50% to 66% for ACE inhibitors/ARBs (Table 2). The amount of increase From Health Services Research and Development Center of Excellence, VA Puget Sound Health Care System, Seattle; and the Departments of Health Services and Medicine, University of Washington, Seattle, Washington. This work was funded by VA HSR & D Grant IHD 98-001 from the VA Health Services Research and Development Service, Seattle, Washington. Dr. Miller’s address is: HSR & D Center of Excellence, VA Puget Sound Health Care System (152), 1660 South Columbian Way, Seattle, Washington 98108. E-mail: Rosalie.Miller@med.va.gov. Manuscript received January 30, 2003; revised manuscript received and accepted April 3, 2003.