Elsevier

American Heart Journal

Volume 169, Issue 1, January 2015, Pages 78-85.e4
American Heart Journal

Clinical Investigation
Acute Ischemic Heart Disease
National trends in stroke after acute myocardial infarction among Medicare patients in the United States: 1999 to 2010

https://doi.org/10.1016/j.ahj.2014.06.011Get rights and content

Background

Stroke is a common and important adverse event after acute myocardial infarction (AMI) in the elderly. It is unclear whether the risk of stroke after AMI has changed with improvements in treatments and outcomes for AMI in the last decade.

Methods

To assess trends in risk of stroke after AMI, we used a national sample of Medicare data to identify Fee-for-Service patients (n = 2,305,441) aged ≥65 years who were discharged alive after hospitalization for AMI from 1999 to 2010.

Results

We identified 57,848 subsequent hospitalizations for ischemic stroke and 4,412 hospitalizations for hemorrhagic stroke within 1 year after AMI. The 1-year rate of ischemic stroke decreased from 3.4% (95% CI 3.3%-3.4%) to 2.6% (2.5%-2.7%; P < .001). The risk-adjusted annual decline was 3% (hazard ratio, 0.97; [0.97-0.98]) and was similar across all age and sex-race groups. The rate of hemorrhagic stroke remained stable at 0.2% and did not differ by subgroups. The 30-day mortality for patients admitted with ischemic stroke after AMI decreased from 19.9% (18.8%-20.9%) to 18.3% (17.1%-19.6%) and from 48.3% (43.0%-53.6%) to 45.7% (40.3%-51.2%) for those admitted with hemorrhagic stroke. We observed a decrease in 1-year mortality from 37.8% (36.5%-39.1%) to 35.3% (33.8%-36.8%) for ischemic stroke and from 66.6% (61.4%-71.5%) to 60.6% (55.1%-65.9%) for hemorrhagic stroke.

Conclusions

From 1999 to 2010, the 1-year risk for ischemic stroke after AMI declined, whereas the risk of hemorrhagic stroke remained unchanged. However, 30-day and 1-year mortality continued to be high.

Introduction

Elderly patients have an elevated risk of acute myocardial infarction (AMI) and stroke. The vast majority of AMI and strokes occur in the Medicare population, and AMI is a key risk factor for subsequent stroke.1, 2 As the population in the United States ages, the risk of stroke after AMI could be expected to increase. However, other factors may counterbalance the effect of this demographic change. Extensive national efforts to improve processes of care and outcomes for AMI, which resulted in reductions in AMI hospitalization and mortality rates,3, 4 might also reduce the risk of stroke after AMI. Improved secondary prevention with statins and antiplatelet therapy to avoid adverse events after AMI could also contribute to risk reduction.5, 6, 7, 8, 9, 10, 11, 12 Moreover, the trends in revascularization treatments, such as the increase in rates of percutaneous coronary intervention (PCI) and the decline in rates of coronary artery bypass graft (CABG) surgery,13, 14 may impact the risk of stroke. Conversely, the greater use of antiplatelet agents recommended by recent guidelines intended to reduce the risk of ischemic stroke, such as clopidogrel and aspirin, could increase the risk of hemorrhagic stroke.15, 16, 17, 18 Surveillance studies using contemporary national data are needed to evaluate whether the risk of stroke after AMI has changed over the last decade.19

To better understand changes in the incidence of stroke after AMI, we used 100% Medicare Fee-For-Service inpatient data from the Centers for Medicare & Medicaid Services (CMS) to characterize temporal trends in the risk for ischemic and hemorrhagic stroke within 1 year after hospitalization for AMI from 1999 to 2010. We also evaluated whether these trends varied by patient age, sex, race, and major surgical treatment subgroups (ie, PCI and CABG). Because of the remarkably high incidence of stroke in the southeastern United States, known as the Stroke Belt, we also examined whether patients who resided in that region also had high risk for strokes after AMI.

Section snippets

Study sample

We used CMS Medicare Provider Analysis and Review files to identify all Medicare Fee-For-Service patients, aged ≥65 years, who were discharged alive from acute care hospitals with a principal discharge diagnosis of AMI (International Classification of Diseases, Ninth Revision, Clinical Modification [ICD-9-CM] codes 410.xx except 410.x2) between January 1, 1999, and December 31, 2010. If a patient had ≥1 AMI hospitalization within a year, we randomly selected 1 of these hospitalizations. We used

Patient characteristics

Our study sample included 2,305,441 patients discharged alive from a hospitalization for AMI. The mean age (SD) remained stable from 78.6 (7.8) years in 1999 to 78.8 (8.6) years in 2010. Several comorbidities increased by ≥5 absolute percentage points, including atherosclerosis, respiratory failure, hypertension, and renal failure (Table I and online Appendix Supplementary Table I). The 3 most common comorbidities in 2010 were atherosclerosis, hypertension, and diabetes. The mean length of stay

Discussion

In this study of contemporary trends in the occurrence and outcomes of stroke after AMI from 1999 to 2010, we found that the rates of ischemic stroke had a relative decline of 23.5%, whereas rates of hemorrhagic stroke remained stable. The improvements represent a nontrivial decline, suggesting 1 fewer subsequent ischemic stroke for every 125 hospitalizations for AMI.

Our findings are consistent with those from European studies.29 In addition, a meta-analysis by Witt et al 30that found the

Conclusions

Among Medicare beneficiaries from 1999 to 2010, we observed a marked reduction in hospitalizations for ischemic stroke after AMI, possibly related to improved treatment and outcomes associated with AMI. Hemorrhagic stroke after AMI remained rare with persistent rates of high mortality despite the availability of more potent antiplatelet regimens.

Disclosures

Drs Ross and Krumholz work under contract with the CMS to develop and maintain performance measures; they are also recipients of research grants from Medtronic and from Johnson & Johnson, through Yale University, to develop methods of clinical trial data sharing. Dr Krumholz is the chair of a cardiac scientific advisory board for UnitedHealth, and Dr Ross is a member of a scientific advisory board for FAIR Health. Dr Masoudi has contracts with the Oklahoma Foundation for Medical Quality and the

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