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Exercise echocardiography does not greatly enhance diagnostic accuracy among people with low pre-test probability of coronary artery disease
PROGNOSIS
Exercise echocardiography does not greatly enhance diagnostic accuracy among people with low pre-test probability of coronary artery disease Abstracted from: Elhendy A, Shub C, McCully RB, Mahoney DW, Burger KN, Pellikka PA. Exercise echocardiography for the prognostic stratification of patients with low pretest probability of coronary artery disease. Am J Med 2001;111:18 ^23.
BACKGROUND A person’s risk of cardiac events can be estimated as ‘low’, ‘medium’ or ‘high’ on the basis of factors such as age, sex, smoking, hypertension, diabetes, hypercholesterolemia, symptoms or abnormal electrocardiogram ¢ndings. People found to be at medium or high risk in these ‘pre-tests’ may be referred for exercise echocardiography, which is helpful in re¢ning the risk classi¢cation. OBJECTIVE To assess the prognostic value of exercise echocardiography among people with‘low’ pre-test probabilities of coronary artery disease. SETTING USA; date not speci¢ed. METHOD Prospective cohort study. PARTICIPANTS 1618 people with estimated pre-test probability of coronary artery disease of 25% or less. People with history of ischemic heart disease or typical angina symptoms were excluded. 35% were men aged under 40, 65% were women aged under 60. Mean age 55 years. Risk factors considered were chest pain, sex, age, blood pressure, smoking, diabetes, cholesterol and resting ST segment appearance on electrocardiogram. The following groups were considered as low risk: men under 40 with atypical chest pain; women under 60 with atypical chest pain; all women without chest pain; men without chest pain and less than three other risk factors; men under 50 without chest pain and less than four other risk factors. INTERVENTION Symptom-limited treadmill exercise echocardiography test. An index score was calculated using the number of abnormal segments divided by the number of visualized segments. For each participant a rest wall motion score index, exercise wall motion score index and a change in wall motion score index during exercise was calculated. A risk prediction 54
Evidence-based Cardiovascular Medicine (2002) 6, 54 ^55 doi:10.1054/ebcm.451, available online at http://www.idealibrary.com.on
model was constructed on the basis of these indices and exercise electrocardiographic variables. Test operators were blinded to clinical characteristics. Median followup was 3 years (maximum 7.8 years).
OUTCOMES Contribution made by exercise echocardiographic variables compared with clinical variables to a multivariate risk prediction model for cardiac events (cardiac death, non-fatal myocardial infarction or revascularization).
MAIN RESULTS There were few events during follow-up in the ‘low-risk’ population, with one cardiac death and 2.5 non-fatal myocardial infarctions per 1000 person-years. Among clinical, exercise echo and exercise electrocardiographic characteristics in a multivariate model, electrocardiographic variables were signi¢cantly associated with cardiac events. Echocardiography added only 5% to the accuracy of outcome prediction based on clinical characteristics. Sensitivity of change in wall motion score with exercise was low for predicting events, although speci¢city was higher (seeTable 1). Nine out of 19 patients with a cardiac event were identi¢ed with the stress test.
AUTHORS’ CONCLUSIONS The cost of exercise echocardiography, including further investigation of false-positive results, is not justi¢ed by the small additional accuracy achieved in low-risk populations.
Table 1 E¡ectiveness of exercise echocardiograph for predicting cardiac events (cardiac death, non-fatal myocardial infarction or revascularization) for low-risk patients
Predicted by echocardiography Not predicted by echocardiography
Cardiac event
No cardiac event
36% 64%
16% 84%
1361-2611/02/$ - see front matter & 2002 Elsevier Science Ltd. All rights reserved
NOTES The echocardiography ¢ndings were known to the physicians deciding to revascularize, which could
introduce bias by selectively removing more severely a¡ected patients.
Commentary
lines, in common with the present study, do not recommend exercise echocardiography for screening for late events in people with a low clinically estimated pre-test probability of coronary artery disease.
This study found that in patients with a low pre-test probability of coronary artery disease, exercise echocardiography does not enhance accuracy for the prediction of cardiac events.The study also highlights the effects of disease prevalence on the predictive value of a positive test. In a previous study by Marwick and colleagues,1 the prognostic value of exercise echocardiography was assessed in a group of 500 patients with known or suspected coronary artery disease. In this high-risk group, 37% of participants had an abnormal test result (fixed wall motion abnormalities or ischemia during exercise), compared with19% in the present study.The annual cardiac event rate was 4.7% compared to only 0.3% in the present study. In Marwick’s study, the presence of ischemia during exercise echocardiography was associated with a relative risk of late cardiac events of 4.8, compared to 2.1 in the present study. The influence of disease prevalence on the predictive value of a test is discussed in US guidelines for exercise testing.2 The guide-
Don Poldermans Erasmus University Rotterdam The Netherlands
Literature cited 1. Marwick TH, Mehta R, Arheart K, Lauer MS. Use of exercise echocardiography for prognostic evaluation of patients with known or suspected coronary artery disease. J Am Coll Cardiol 1997; 30: 83^90. 2. Gibbons RJ, Balady GJ, Beasley JW, et al. ACC/AHA guidelines for exercise testing. J Am Coll Cardiol 1997; 30: 260 ^315.
Evidence-based Cardiovascular Medicine (2002) 6, 54 ^55
55
Exercise echocardiography does not greatly enhance diagnostic accuracy among people with low pre-test probability of coronary artery disease Abstracted from: Elhendy A, Shub C, McCully RB, Mahoney DW, Burger KN, Pellikka PA. Exercise echocardiography for the prognostic stratification of patients with low pretest probability of coronary artery disease. Am J Med 2001;111:18 ^23.
BACKGROUND A person’s risk of cardiac events can be estimated as ‘low’, ‘medium’ or ‘high’ on the basis of factors such as age, sex, smoking, hypertension, diabetes, hypercholesterolemia, symptoms or abnormal electrocardiogram ¢ndings. People found to be at medium or high risk in these ‘pre-tests’ may be referred for exercise echocardiography, which is helpful in re¢ning the risk classi¢cation. OBJECTIVE To assess the prognostic value of exercise echocardiography among people with‘low’ pre-test probabilities of coronary artery disease. SETTING USA; date not speci¢ed. METHOD Prospective cohort study. PARTICIPANTS 1618 people with estimated pre-test probability of coronary artery disease of 25% or less. People with history of ischemic heart disease or typical angina symptoms were excluded. 35% were men aged under 40, 65% were women aged under 60. Mean age 55 years. Risk factors considered were chest pain, sex, age, blood pressure, smoking, diabetes, cholesterol and resting ST segment appearance on electrocardiogram. The following groups were considered as low risk: men under 40 with atypical chest pain; women under 60 with atypical chest pain; all women without chest pain; men without chest pain and less than three other risk factors; men under 50 without chest pain and less than four other risk factors. INTERVENTION Symptom-limited treadmill exercise echocardiography test. An index score was calculated using the number of abnormal segments divided by the number of visualized segments. For each participant a rest wall motion score index, exercise wall motion score index and a change in wall motion score index during exercise was calculated. A risk prediction 54
Evidence-based Cardiovascular Medicine (2002) 6, 54 ^55 doi:10.1054/ebcm.451, available online at http://www.idealibrary.com.on
model was constructed on the basis of these indices and exercise electrocardiographic variables. Test operators were blinded to clinical characteristics. Median followup was 3 years (maximum 7.8 years).
OUTCOMES Contribution made by exercise echocardiographic variables compared with clinical variables to a multivariate risk prediction model for cardiac events (cardiac death, non-fatal myocardial infarction or revascularization).
MAIN RESULTS There were few events during follow-up in the ‘low-risk’ population, with one cardiac death and 2.5 non-fatal myocardial infarctions per 1000 person-years. Among clinical, exercise echo and exercise electrocardiographic characteristics in a multivariate model, electrocardiographic variables were signi¢cantly associated with cardiac events. Echocardiography added only 5% to the accuracy of outcome prediction based on clinical characteristics. Sensitivity of change in wall motion score with exercise was low for predicting events, although speci¢city was higher (seeTable 1). Nine out of 19 patients with a cardiac event were identi¢ed with the stress test.
AUTHORS’ CONCLUSIONS The cost of exercise echocardiography, including further investigation of false-positive results, is not justi¢ed by the small additional accuracy achieved in low-risk populations.
Table 1 E¡ectiveness of exercise echocardiograph for predicting cardiac events (cardiac death, non-fatal myocardial infarction or revascularization) for low-risk patients
Predicted by echocardiography Not predicted by echocardiography
Cardiac event
No cardiac event
36% 64%
16% 84%
1361-2611/02/$ - see front matter & 2002 Elsevier Science Ltd. All rights reserved
NOTES The echocardiography ¢ndings were known to the physicians deciding to revascularize, which could
introduce bias by selectively removing more severely a¡ected patients.
Commentary
lines, in common with the present study, do not recommend exercise echocardiography for screening for late events in people with a low clinically estimated pre-test probability of coronary artery disease.
This study found that in patients with a low pre-test probability of coronary artery disease, exercise echocardiography does not enhance accuracy for the prediction of cardiac events.The study also highlights the effects of disease prevalence on the predictive value of a positive test. In a previous study by Marwick and colleagues,1 the prognostic value of exercise echocardiography was assessed in a group of 500 patients with known or suspected coronary artery disease. In this high-risk group, 37% of participants had an abnormal test result (fixed wall motion abnormalities or ischemia during exercise), compared with19% in the present study.The annual cardiac event rate was 4.7% compared to only 0.3% in the present study. In Marwick’s study, the presence of ischemia during exercise echocardiography was associated with a relative risk of late cardiac events of 4.8, compared to 2.1 in the present study. The influence of disease prevalence on the predictive value of a test is discussed in US guidelines for exercise testing.2 The guide-
Don Poldermans Erasmus University Rotterdam The Netherlands
Literature cited 1. Marwick TH, Mehta R, Arheart K, Lauer MS. Use of exercise echocardiography for prognostic evaluation of patients with known or suspected coronary artery disease. J Am Coll Cardiol 1997; 30: 83^90. 2. Gibbons RJ, Balady GJ, Beasley JW, et al. ACC/AHA guidelines for exercise testing. J Am Coll Cardiol 1997; 30: 260 ^315.
Evidence-based Cardiovascular Medicine (2002) 6, 54 ^55
55