The Incidence of Unrecognized Myocardial Infarction in Women with Coronary Heart Disease

The Incidence of Unrecognized Myocardial Infarction in Women with Coronary Heart Disease

Michael G. Shlipak, MD, MPH;
Darryl A. Elmouchi, MD;
David M. Herrington, MD, MHS;
Feng Lin, MS;
Deborah Grady, MD, MPH;
Mark A. Hlatky, MD; and
for the Heart and Estrogen/progestin Replacement Study Research Group

From the University of California, San Francisco, Veterans Affairs Medical Center, San Francisco, and Stanford University School of Medicine, Stanford, California; and Wake Forest University School of Medicine, Winston-Salem, North Carolina.

Abstract

Background: Several cohort studies in populations without coronary heart disease have demonstrated that up to 40% of incident myocardial infarctions are clinically unrecognized.

Objective: To determine the incidence of unrecognized myocardial infarction in women with coronary heart disease in the Heart and Estrogen/progestin Replacement Study (HERS).

Design: Randomized, double-blind, placebo-controlled trial of conjugated estrogens plus medroxyprogesterone or identical placebo with 4.1 years of follow-up.

Settings: Outpatient and community settings at 20 U.S. clinical centers.

Patients: 2763 postmenopausal women younger than 80 years of age with coronary heart disease and an intact uterus.

Measurements: Annual electrocardiograms were obtained for all participants during follow-up (mean, 4.1 years) and were evaluated by using the NOVACODE computer algorithm and visual confirmation. A total of 13 715 electrocardiograms were obtained. Suspected unrecognized myocardial infarctions were investigated by comparing a participant's previous surveillance electrocardiograms with the electrocardiograms obtained from all of her intervening hospitalizations. Characteristics of patients with recognized and unrecognized myocardial infarction were compared.

Results: Among the 256 nonfatal myocardial infarctions, 11 were unrecognized (4.3% [95% CI, 2.2% to 7.6%]). Seven occurred in women assigned to placebo and 4 occurred in women assigned to hormone therapy (P > 0.2). Women with unrecognized myocardial infarction were less likely to have diabetes mellitus or previous angina and were more likely to have had previous bypass surgery compared with women who had clinically recognized myocardial infarction.

Conclusion: The incidence of unrecognized myocardial infarction in women with coronary disease was far lower than that observed in previous studies of populations without coronary heart disease.

Article and Author Information

Grant Support: This study and the HERS trial were funded by Wyeth-Ayerst Research, Radnor, Pennsylvania. Dr. Shlipak is a recipient of the Veterans Administration Research Career Development Award (99-314-1) from the Division of Health Services Research and Development.
Requests for Single Reprints: Michael Shlipak, MD, MPH, General Internal Medicine Section (111A-1), Veterans Affairs Medical Center, 4150 Clement Street, San Francisco, CA 94121; e-mail, shlip{at}itsa.ucsf.edu.
Current Author Addresses: Drs. Shlipak, Elmouchi, and Grady: General Internal Medicine Section (111A-1), Veterans Affairs Medical Center, 4150 Clement Street, San Francisco, CA 94121.
Dr. Herrington: Department of Medicine, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157-1045.
Ms. Lin: University of California, San Francisco, Prevention Sciences Group, 74 New Montgomery Street, Suite 600, San Francisco, CA 94105.
Dr. Hlatky: Stanford University School of Medicine, HRP Redwood Building, Stanford, CA 94305-5405.
Author Contributions: Conception and design: M.G. Shlipak, D. Grady, M.A. Hlatky.
Analysis and interpretation of the data: M.G. Shlipak, D.A. Elmouchi, D.M. Herrington, F. Lin, D. Grady, M.A. Hlatky.
Drafting of the article: M.G. Shlipak, D.A. Elmouchi.
Critical revision of the article for important intellectual content: M.G. Shlipak, D.A. Elmouchi, D.M. Herrington, F. Lin, D. Grady, M.A. Hlatky.
Final approval of the article: M.G. Shlipak, D.A. Elmouchi, D.M. Herrington, F. Lin, D. Grady, M.A. Hlatky.
Provision of study materials or patients: D.M. Herrington.
Statistical expertise: F. Lin.
Obtaining of funding: D. Grady.
Administrative, technical, or logistic support: D. Grady.
Collection and assembly of data: D. Grady.