Incidence of Secondary Stroke and Myocardial Infarction Based on Managed Care Administrative Data

Abstract

32 Background: Little data exist on the incidence of subsequent acute ischemic events in persons with established atherosclerotic vascular disease in managed care plans. Objective: To estimate the incidence of secondary stroke and myocardial infarction (MI) over 3 years. Methods: Patients were identified as having atherosclerotic vascular disease (either stroke, MI, or peripheral arterial disease {PAD}) using administrative data from 11 UnitedHealthcare plans (3 with Medicare) from 1995–98. The stroke cohort includes patients ≥ 40 years old hospitalized with a primary or secondary ICD-9-CM code of either 434 or 436, and length of stay ≥ 1 day. Patients with a carotid endarterectomy or claims consistent with cardioembolic strokes were excluded. Persons age ≥ 40 with a primary ICD-9-CM code of 410 and a length of stay ≥ 2 days were included in the MI cohort. The PAD cohort included patients ≥ 40 with a hospital admission or an office visit with an ICD-9-CM code of 440.2x or 440.3. Cumulative incidences of subsequent stroke or MI were estimated for each cohort using Kaplan-Meier survival analysis. Results: For stroke, MI, and PAD cohorts, 3527 (49% Medicare), 9039 (26% Medicare), and 10,925 (46% Medicare) members were identified, respectively. Nearly 96% of MI and 89% of stroke patients were discharged alive. During an average follow-up period of 12 months in the stroke cohort, the cumulative incidences of stroke or MI were 4%, 7%, 12% and 14% at 0.5, 1, 2, and 3 years, respectively. Incidences in the MI cohort were 4%, 6%, 8% and 11% at 0.5, 1, 2, and 3 years (mean follow-up=15 months). In the PAD cohort with a mean follow-up of 15 months, the cumulative percentages with subsequent AMI or stroke were 2%, 3%, 5% and 8% after 0.5, 1, 2, and 3 years. Stroke accounted for 79%, 16%, and 39% of the secondary events in the stroke, MI, and PAD cohorts, respectively. Conclusions: Among persons with atherosclerotic vascular disease enrolled in managed care plans around the US, the incidence of subsequent ischemic events is consistent with a significant burden of symptomatic disease. Among stroke patients who have a subsequent ischemic event, stroke is the secondary event in the vast majority of cases.