Lessons learned from studies of the standard exercise ECG test

Characteristics of Second-Line Investigations of Middle-Aged Athletes Who Failed Preparticipation Examinations

OBJECTIVE

The role of exercise testing during preparticipation examinations (PPEs) of middle-aged athletes is uncertain. This study examined the characteristics of disqualifications after an initial PPE that includes an exercise test in competitive athletes older than 30 years. We investigated disqualification rates and reasons, second-line investigations performed, and final decisions regarding competitive sports participation.

DESIGN

Chart review.

SETTING

Sports medicine clinic.

PARTICIPANTS

Athletes aged >30 years that performed an exercise test as part of their annual PPE at our sports medicine clinic (n = 866).

INDEPENDENT VARIABLES

Age, sex, height, weight, sport type, cardiovascular risk factors, and abnormal PPE findings.

MAIN OUTCOME MEASURES

Additional investigations performed, approval/disqualification regarding competitive sports participation.

RESULTS

The initial disqualification rate of athletes was 9.8%. Three (3.6%) athletes were disqualified following questionnaire and physical examination, 19 (22.4%) because of resting electrocardiogram findings, and 65 (76.5%) following the exercise test. After additional work-up, only 5 athletes (0.4%) were ultimately found ineligible for competitive sports. From those, only 2 athletes (0.2%) were disqualified because of exercise test findings, which were episodes of supraventricular tachycardia and not ischemia-related.

CONCLUSIONS

The addition of an exercise test to the PPE of middle-aged athletes is of limited value. If exercise testing of older athletes is performed, arrhythmias are probably of higher significance than ST-T changes.

Sudden Cardiac Death in Athletes

Physical activity confers substantial health benefits to healthy individuals and patients alike. Occasionally, however, exercise may act as a trigger for arrhythmic death in athletes who harbor an occult pathological substrate. The majority of sudden cardiac deaths (SCDs) in young athletes (≤35 years old) are secondary to inherited cardiac diseases, while ischaemic heart disease predominates in older athletes. In the absence of compulsory national or international registries of SCD in athletes, it is difficult to define the exact scale of the problem. In addition, the lack of post-mortem evaluation by pathologists with expertise in cardiac adaptation to exercise and inherited cardiac diseases casts doubt to the reliability of the reported causes. The proposed preventative strategies focus primarily on preventing deaths by cardiovascular evaluation of athletes and the use of automated external defibrillators in athletic venues. Cardiovascular screening of first-degree relatives, though often neglected, has the potential to avert further tragedies given the inherited nature of most conditions predisposing to SCD in the young. This article provides an overview of the epidemiology and causes of SCD in athletes and explores potential prevention strategies.

Angiographic Correlates of the Treadmill Scores in Non-High-Risk Patients with Unstable Angina

BACKGROUND

There has been no clear consensus regarding the optimum definition of a high-risk exercise ECG test. The aim of this study is to compare the diagnostic accuracy of several treadmill scores [American College of Cardiology/American Heart Association (ACC/AHA) High-Risk Criteria for exercise testing, Duke Treadmill Score, Veterans Affairs and West Virginia Prognostic Score, ST/Heart Rate Index] with the ST-segment depression analysis in the detection of significant and severe coronary disease as determined by coronary angiography.

METHODS

The study included a cohort of 248 consecutive patients admitted to hospital for unstable angina.

RESULTS

The sensitivities of the ACC/AHA High-Risk Criteria and the ST depression > or =1 mm were 89.02 and 76.83%, respectively, for the detection of significant coronary artery disease, and 96.15 and 86.54% for the detection of severe coronary artery disease. The specificities of the Duke Treadmill Score and the ST depression > or=1 mm were 96.43 and 73.81%, respectively, for the detection of significant coronary artery disease, and 81.63 and 47.45% for the detection of severe coronary artery disease.

CONCLUSIONS

The ACC/AHA High-Risk Criteria and Duke Treadmill Score provided relevant diagnostic information not available from the ST segment analysis alone.

Concomitant Detection of Systemic Atherosclerotic Disease while Screening for Abdominal Aortic Aneurysm

INTRODUCTION

Although population screening for abdominal aortic aneurysm (AAA) has/had a significant impact on disease-specific mortality, coexisting systemic atherosclerosis represents the major impediment to improved longevity. We examined the feasibility and yield of full cardiovascular assessment concomitant with screening for AAA detection.

METHODS

A total of 1032 asymptomatic men over the age of 50 years (328 were >60 years) underwent a detailed cardiac health questionnaire, sphygmomanometry, body mass index calculation, fasting lipid profiling, ultrasonographic (US) examination of their infrarenal aorta and carotid arteries, and treadmill exercise stress testing. Framingham and SCORE project estimations of the 10-year risk of ischemic heart disease (IHD) and fatal cardiovascular disease (CVD) of any cause were calculated for the men with an AAA and in those>60 years but with neither AAA nor known cardiac disease.

RESULTS

Overall, we detected an AAA>3 cm in 30 men (2.9%). Unaddressed obesity, smoking, hypertension, impaired glucose metabolism, and hypercholesterolemia were commonly identified in individuals both with and without an AAA, being notably frequent in those>60 years without an AAA. The 10-year risk of IHD and CHD in those>60 years was similar regardless of whether an AAA was present. Doppler screening for significant carotid stenosis had detection rates similar to those for aortic US scanning, being most useful in those>65 years of age. Exercise stress testing, however, was of only limited value when used nonselectively.

CONCLUSIONS

Modifiable atherosclerotic disease and cardiovascular risk can be readily detected in individuals presenting for AAA screening and are present to a significant degree at an earlier age. Consideration of selected, additional investigations is required to maximize the value of generalized screening programs.

Validation of the accuracy of pretest and exercise test scores in women with a low prevalence of coronary disease: the NHLBI-sponsored Women's Ischemia Syndrome Evaluation (WISE) study

BACKGROUND

Recently revised American College of Cardiology/American Heart Association guidelines have suggested that exercise test scores be used in decisions concerning patients with suspected coronary artery disease (CAD). Pretest and exercise test scores derived for use in women without known CAD have not been tested in women with a low prevalence of CAD.

METHODS

Within the Women's Ischemia Syndrome Evaluation (WISE) study, we evaluated 563 women undergoing coronary angiography for suspected myocardial ischemia. The prevalence of angiographic CAD was 26%. Overall, 189 women underwent treadmill exercise testing. Prognostic end points included death, myocardial infarction, stroke, and revascularization.

RESULTS

Each score stratified women into 3 probability groups (P <.001) according to the prevalence of coronary disease: Pretest: low 20/164 (12%), intermediate 53/245 (22%), high 75/154 (49%); Exercise test: low 11/83 (13%), intermediate 22/74 (30%), high 17/32 (53%). However, the Duke score did not stratify as well: low 7/46 (15%), intermediate 36/126 (29%), high 6/17 (35%); P =.44. When pretest and exercise scores were considered together, the best stratification with the exercise test score was in the intermediate pretest group (P <.03). The Duke score did not stratify this group at all (P =.98). Pretest and exercise test scores also stratified women according to prognostic end points: pretest--low 7/164 (4.3%), intermediate 28/245 (11.4%), high 27/154 (17.5%), P <.01; exercise test--low 4/83 (4.8%) and intermediate-high 17/106 (16%), P =.014.

CONCLUSION

Both pretest and exercise test scores performed better than the Duke score in stratifying women with a low prevalence of angiographic CAD. The exercise test score appears useful in women with an intermediate pretest score, consistent with American College of Cardiology/American Heart Association guidelines.

Exercise capacity and the risk of death in women: the St James Women Take Heart Project

BACKGROUND

Cardiovascular disease is the leading cause of death among women and accounts for more than half of their deaths. Women have been underrepresented in most studies of cardiovascular disease. Reduced physical fitness has been shown to increase the risk of death in men. Exercise capacity measured by exercise stress test is an objective measure of physical fitness. The hypothesis that reduced exercise capacity is associated with an increased risk of death was investigated in a cohort of 5721 asymptomatic women who underwent baseline examinations in 1992.

METHODS AND RESULTS

Information collected at baseline included medical and family history, demographic characteristics, physical examination, and symptom-limited stress ECG, using the Bruce protocol. Exercise capacity was measured in metabolic equivalents (MET). Nonfasting blood was analyzed at baseline. A National Death Index search was performed to identify all-cause death and date of death up to the end of 2000. The mean age of participants at baseline was 52+/-11 years. Framingham Risk Score-adjusted hazards ratios (with 95% CI) of death associated with MET levels of <5, 5 to 8, and >8 were 3.1 (2.0 to 4.7), 1.9 (1.3 to 2.9), and 1.00, respectively. The Framingham Risk Score-adjusted mortality risk decreased by 17% for every 1-MET increase.

CONCLUSIONS

This is the largest cohort of asymptomatic women studied in this context over the longest period of follow-up. This study confirms that exercise capacity is an independent predictor of death in asymptomatic women, greater than what has been previously established among men. The implications for clinical practice and health care policy are far reaching.

Cardiorespiratory fitness and physical activity as risk predictors of future atherosclerotic cardiovascular diseases

Physical fitness and activity status are well-documented risk predictors of cardiovascular and total mortality. The purpose of this article is to show how cardiorespiratory fitness predicts atherosclerotic cardiovascular diseases. Measurement of maximum oxygen consumption (VO(2max)), defined with or without ventilatory gas analysis during exercise testing, can provide a good estimate for cardiorespiratory fitness, which is an independent marker of the early disease. Low VO(2max) has been shown to be comparable with elevated systolic blood pressure, smoking, obesity, and diabetes in importance as a risk factor for mortality, as well as a predictor of coronary artery disease and the progression of atherosclerosis. Cardiorespiratory fitness represents one of the strongest predictors of mortality, emphasizing the importance of exercise testing in everyday clinical practice. In the future, well-defined, disease-specific training programs for exercise prescriptions in different risk groups are needed as a clinical tool.

Heart rate recovery after treadmill exercise testing and risk of cardiovascular disease events (The Framingham Heart Study)

A delayed heart rate (HR) recovery after graded exercise testing has been associated with increased all-cause mortality in clinic-based samples. No prior study has examined the association of HR recovery after exercise with the incidence of coronary heart disease (CHD) and cardiovascular disease (CVD) events. We evaluated 2,967 Framingham study subjects (1,400 men, mean age 43 years) who were free of CVD and underwent a treadmill exercise test (Bruce protocol) at a routine examination. We examined the relations of HR recovery indexes (decrease in HR from peak exercise) to the incidence of a first CHD or CVD event and all-cause mortality, adjusting for established CVD risk factors. During follow-up (mean 15 years), 214 subjects experienced a CHD event (156 men), 312 developed a CVD event (207 men), and 167 died (105 men). In multivariable models, continuous HR recovery indexes were not associated with the incidence of CHD or CVD events, or with all-cause mortality. However, in models evaluating quintile-based cut points, the top quintile of HR recovery (greatest decline in HR) at 1-minute after exercise was associated with a lower risk of CHD (hazards ratio vs bottom 4 quintiles 0.54, 95% confidence interval [CI], 0.32 to 0.93) and CVD (hazards ratio 0.61, 95% CI 0.41 to 0.93), but not all-cause mortality (hazards ratio 0.99, 95% CI 0.60 to 1.62). In our community-based sample, HR recovery indexes were not associated with all-cause mortality. A very rapid HR recovery immediately after exercise was associated with lower risk of CHD and CVD events. These findings should be confirmed in other settings.

Exercise capacity and mortality among men referred for exercise testing

BACKGROUND

Exercise capacity is known to be an important prognostic factor in patients with cardiovascular disease, but it is uncertain whether it predicts mortality equally well among healthy persons. There is also uncertainty regarding the predictive power of exercise capacity relative to other clinical and exercise-test variables.

METHODS

We studied a total of 6213 consecutive men referred for treadmill exercise testing for clinical reasons during a mean (+/-SD) of 6.2+/-3.7 years of follow-up. Subjects were classified into two groups: 3679 had an abnormal exercise-test result or a history of cardiovascular disease, or both, and 2534 had a normal exercise-test result and no history of cardiovascular disease. Overall mortality was the end point.

RESULTS

There were a total of 1256 deaths during the follow-up period, resulting in an average annual mortality of 2.6 percent. Men who died were older than those who survived and had a lower maximal heart rate, lower maximal systolic and diastolic blood pressure, and lower exercise capacity. After adjustment for age, the peak exercise capacity measured in metabolic equivalents (MET) was the strongest predictor of the risk of death among both normal subjects and those with cardiovascular disease. Absolute peak exercise capacity was a stronger predictor of the risk of death than the percentage of the age-predicted value achieved, and there was no interaction between the use or nonuse of beta-blockade and the predictive power of exercise capacity. Each 1-MET increase in exercise capacity conferred a 12 percent improvement in survival.

CONCLUSIONS

Exercise capacity is a more powerful predictor of mortality among men than other established risk factors for cardiovascular disease.

Effects of adjustment for referral bias on the sensitivity and specificity of single photon emission computed tomography for the diagnosis of coronary artery disease

PURPOSE

Referral bias, in which the result of a diagnostic test affects the subsequent referral for a more definitive test, influences the accuracy of noninvasive tests for coronary artery disease. This study evaluates the effect of referral bias on the apparent accuracy of single photon emission computed tomography (SPECT).

METHODS

Over a 10-year period, 14,273 patients without known coronary artery disease underwent stress SPECT. Coronary angiography was performed within 3 months after the stress test in 1853 patients (13%). The apparent sensitivity, specificity, and likelihood ratios of SPECT were determined in these patients, and then adjusted for referral bias using two different formulas.

RESULTS

The overwhelming majority (95%) of patients who underwent angiography had abnormal SPECT images. Apparent values for test indices were a sensitivity of 98%, a specificity of 13%, a likelihood ratio for a positive test of 1.1, and a likelihood ratio for a negative test of 0.15. Test indices adjusted for referral bias (using the two methods) were a sensitivity of 65% or 67%, a specificity of 67% or 75%, a likelihood ratio for a positive test of 2.0 or 2.7, and a likelihood ratio for a negative test of 0.44 or 0.52.

CONCLUSION

Referral bias has a marked effect on the apparent accuracy of stress SPECT for the diagnosis of coronary disease. Adjustment for referral bias yields estimates for sensitivity and specificity and likelihood ratios that better reflect the accuracy of the technique.

Exercise testing in the new millennium

In the changing economic times, internists and family physicians are becoming the main performers of the standard exercise test. The education of those noncardiologists who wish to perform exercise testing is quite important. In the new millennium, the American College of Cardiology/American Heart Association evidence-based guidelines on exercise testing continue to have a large impact. Used for diagnosis or prognosis, exercise scores such as the Duke exercise score will be applied to each test. Increased computerization and the internet will bring inexpensive web-enabled devices for sophisticated exercise testing into the doctor's office and allow remote over-reading services.

Computer applications in the interpretation of the exercise electrocardiogram

The exercise electrocardiogram remains the noninvasive diagnostic test of first choice in patients with coronary artery disease. While new technology offers novel diagnostic possibilities and the ability to assess patients unsuitable for exercise testing, no other investigation has to this point furnished the quality of functional information and value-for-predictive accuracy of exercise electrocardiography. In this article, we describe how this central position in the work up of the cardiac patient has been secured through the evolution of the microprocessor. Particularly important has been its ability to harness and present large volumes of raw data, to derive and manipulate multivariate equations for diagnostic prediction, and to run 'expert' systems which can pool demographic and exercise test data, calculate risk scores, and prompt the nonexpert with advice on current management. These key features explain the pivotal role of the exercise test in the diagnostic, and increasingly prognostic, armoury of the cardiovascular clinician.

Are the American College of Cardiology/American Heart Association guidelines for exercise testing for suspected coronary artery disease correct?

BACKGROUND

Recently published American College of Cardiology (ACC)/American Heart Association (AHA) guidelines state that patients with suspected coronary disease and an intermediate pretest probability are appropriate candidates for exercise ECG, while those with low or high pretest probability are not.

METHODS

From 5,103 consecutive patients with symptoms of suspected coronary disease, we evaluated 872 patients who underwent coronary angiography following exercise ECG. Differences in test performance were determined using receiver operating characteristic curve area analysis. A score using age, gender, symptoms, and risk factors was used to classify patients into low, intermediate, and high pretest probability groups.

RESULTS

When patients with inadequate exercise tests were excluded, overall sensitivity and specificity were 70% and 66%, respectively. Only the intermediate pretest probability group demonstrated significant incremental value: pretest vs posttest intermediate, 70 +/- 3 vs 79 +/- 3 (p < 0.0001); low, 71 +/- 6 vs 76 +/- 7 (p = 0.39); and high, 69 +/- 8 vs 75 +/- 7 (p = 0.12). From the low- to the high-probability groups, there was a progressive increase in positive predictive value (21%, 62%, and 92%) and decrease in negative predictive value (94%, 72%, and 28%), respectively. The frequencies of abnormal exercise ECGs were lower in the unselected groups compared with the angiography groups (low, 13% vs 36%; intermediate, 22% vs 53%; high, 36% vs 63%).

CONCLUSIONS

Based on the information added by exercise testing to clinical data, these results confirm the ACC/AHA guideline assignments for test selection. However, despite these guidelines, patients with a low pretest probability can be selected for exercise testing with the knowledge that a positive result is infrequent and a negative result carries a very high negative predictive value. Intermediate-probability patients on average carry a significant false-negative rate, suggesting that exercise ECG alone may not be a sufficient screening test in all intermediate-probability patients. Because of poor negative predictive value and a large percentage of negative tests, high-probability patients should undergo coronary angiography as the initial strategy, unless the goal of exercise testing is to assess prognosis.