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Cover of Prediction of Risk for Patients with Unstable Angina

Prediction of Risk for Patients with Unstable Angina

Evidence Reports/Technology Assessments, No. 31

Investigators: , MD, MS, Principal Investigator, , MD, MPH, , MS, , MD, , MM, , , PhD, and , MD.

Rockville (MD): Agency for Healthcare Research and Quality (US); .
Report No.: 01-E001ISBN-10: 1-58763-012-5

Structured Abstract

Objective:

Unstable angina comprises a broad spectrum of ischemic heart disease and is associated with varying levels of risk for unfavorable outcomes including myocardial infarction and death. Despite development of various diagnostic approaches, the evaluation of patients with chest pain suggestive of unstable angina or myocardial infarction remains a common, costly problem, with approximately 5 million people undergoing evaluation in emergency departments annually at an estimated cost of over $6 billion. The American College of Cardiology and the American Heart Association established a committee to develop guidelines for the diagnosis and treatment of unstable angina. Under a contract with the Agency for Health Care Policy and Research to assist the committee to evaluate the current ability to predict risk for patients with unstable angina, we performed three systematic reviews. The first review concerned the value of the electrocardiogram, physical examination, and clinical history in predicting outcome for patients with unstable angina. The second review examined the ability of troponin to predict outcome in patients with proven or suspected unstable angina. The third review examined the efficacy of chest pain units and emergency department protocols in patients who have suspected unstable angina or myocardial infarction.

Search Strategy:

We identified published studies (English language) through 1998 by searching the MEDLINE and EMBASE databases and by manually reviewing the bibliographies of identified articles.

Selection Criteria:

For the review of clinical and electrocardiographic predictors of outcome, we restricted our review to only those studies that performed a multivariate analysis of the clinical and/or electrocardiographic predictors of adverse clinical events in patients with either chest pain suggestive of ischemia or diagnosed unstable angina in the emergency department or hospital. For the review of troponin efficacy, we included reports of patient cohorts with unstable angina or suspected unstable angina that noted subsequent myocardial infarction, death, or revascularization. For the review of chest pain units and emergency department protocols, we included trials that were randomized. We also included controlled clinical trials of chest pain protocols used in the emergency department.

Data Collection and Analysis:

For the review of troponin studies, we pooled the data using odds ratios and relative risks for outcomes of death, subsequent myocardial infarction, and revascularization. Two independent reviewers abstracted each study.

Main Results:

Characteristics of patients with suspected unstable angina that were associated with worse outcomes included advanced age, male sex, prior myocardial infarction, and diabetes. In addition, congestive heart failure, hypertension, and smoking may also be important prognostic factors from the clinical history, but specific descriptors of the chest pain did not provide prognostic information. The strongest electrocardiographic predictor of adverse outcomes was ST-segment depression greater than 0.1 millivolt, whereas a completely normal electrocardiogram was a strong predictor of reduced risk. A positive troponin finding increased the risk of subsequent death 5.3-fold at 4 weeks (95 percent confidence interval: 3.6-7.9). A positive troponin finding also increased the risk of subsequent death or myocardial infarction 12.3-fold at 4 weeks (95 percent confidence interval: 6.4-23.8) in patients with diagnosed unstable angina. The absolute increase in mortality was 3.9 percent (95 percent confidence interval: 3.0-4.4) for patients with a positive troponin level. The predictive value of troponin T and troponin I was not significantly different. Data are insufficient at present to determine if rapid bedside troponin tests and laboratory-based measurements provide similar or different prognostic information. Although randomized trials of chest pain units are few, they consistently have shown decreased hospital costs compared with usual care. All studies included in this report apply to adult men and women.

Conclusions:

Several patient characteristics and electrocardiographic findings portend a worse prognosis in patients with suspected or diagnosed unstable angina including older age, male sex, past myocardial infarction, diabetes mellitus, and ST depression greater than 0.1 millivolt. Measurement of troponin T or troponin I provides additional independent prognostic information. Additional randomized trials of chest pain units are needed to determine more fully their health and economic benefits.

2101 East Jefferson Street, Rockville, MD 20852. www​.ahrq.gov

Prepared for: Agency for Healthcare Research and Quality, U.S. Department of Health and Human Services.1 Contract No. 290-97-0013. Prepared by: UCSF-Stanford Evidence-based Practice Center.

Suggested citation:

Heidenreich PA, Go A, Melsop KA, et al. Prediction of risk for patients with unstable angina. Evidence Report/Technology Assessment No. 31 (prepared by the UCSF-Stanford Evidence-based Practice Center under Contract No. 290-97-0013). AHRQ Publication No. 01-E001. Rockville, MD: Agency for Healthcare Research and Quality. December 2000.

On December 6, 1999, under Public Law 106-129, the Agency for Health Care Policy and Research (AHCPR) was reauthorized and renamed the Agency for Healthcare Research and Quality (AHRQ). The law authorizes AHRQ to continue its research on the cost, quality, and outcomes of health care and expands its role to improve patient safety and address medical errors.

This report may be used, in whole or in part, as the basis for development of clinical practice guidelines and other quality enhancement tools, or a basis for reimbursement and coverage policies. AHRQ or U.S. Department of Health and Human Services endorsement of such derivative products may not be stated or implied.

The authors of this report are responsible for its content. Statements in the report should not be construed as endorsement by the Agency for Healthcare Research and Quality or the U.S. Department of Health and Human Services of a particular drug, test, treatment, or other clinical service.

1

2101 East Jefferson Street, Rockville, MD 20852. www​.ahrq.gov

Bookshelf ID: NBK33602
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