Occurrence of Secondary Ischemic Events Among Persons with Atherosclerotic Vascular Disease
Published in: Stroke, v. 33, no. 4, Apr. 2002, p. 901-906
Posted on RAND.org on December 31, 2001
BACKGROUND AND PURPOSE: Few data exist for large managed care populations on the occurrence of subsequent acute ischemic events in persons with established atherosclerotic vascular disease. We estimated the occurrence of secondary stroke, acute myocardial infarction (AMI), and vascular deaths among 2 large, managed care samples. METHODS: With the use of International Classification of Diseases, Ninth Revision, Clinical Modification codes, patients aged > or =40 years and with stroke, AMI, or peripheral arterial disease (PAD) were identified from administrative data of United Healthcare plans during 1995-1998. Stroke, AMI, and PAD cohorts were identified within a commercial insurance sample and a Medicare sample. Cumulative occurrences of subsequent stroke, AMI, or vascular death were estimated by survival analysis. RESULTS: In the stroke commercial cohort (n=1631; mean age, 62.1 years), cumulative occurrence of subsequent events was 4.2%, 6.5%, 9.8%, and 11.8% at 0.5, 1, 2, and 3 years, respectively; cumulative secondary event occurrence in the AMI commercial cohort (n=6458; mean age, 56.0 years) was 3.5%, 4.8%, 7.3%, and 8.5% and in the PAD commercial cohort (n=5813; mean age, 59.2 years) was 1.5%, 2.8%, 4.8%, and 6.5%, respectively. Cumulative secondary event occurrences were even higher in stroke (n=1518; mean age, 79.5 years), AMI (n=2197; mean age, 76.2 years), and PAD (n=5033; mean age, 76.6 years) cohorts of the Medicare sample: 18.1%, 17.0%, and 8.7%, respectively, at 3 years. More than 75% of each stroke cohort's secondary events were strokes; more than 75% of each AMI cohort's secondary events were AMIs. Of the PAD cohorts' secondary events, 27% to 39% were strokes, 48% to 57% were AMIs, and 13% to 16% were vascular deaths. CONCLUSIONS: Among these managed care enrollees with existing atherosclerotic vascular disease, subsequent ischemic events represent a significant symptomatic disease burden. Given these findings, it is very important to determine whether secondary prevention strategies are being effectively used to manage patients with diagnosed atherosclerosis.