Authors' objectives:

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.

Authors' results and conclusions: 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.

Authors' recommendations: 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.

Authors' methods: Systematic review

Project Status: Completed

URL for project: http://www.ahrq.gov/clinic/epcsums/unstabsum.htm

Year Published: 2000

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: United States

Organisation Name: Agency for Healthcare Research and Quality

Contact Address: Center for Outcomes and Evidence Technology Assessment Program, 540 Gaither Road, Rockville, MD 20850, USA. Tel: +1 301 427 1610; Fax: +1 301 427 1639;

Contact Name: martin.erlichman@ahrq.hhs.gov

Contact Email: martin.erlichman@ahrq.hhs.gov

Copyright: Agency for Healthcare Research and Quality (AHRQ)