Clinical and exercise test predictors of all-cause mortality: results from > 6,000 consecutive referred male patients

A clinical and echocardiographic score for assigning risk of major events after dobutamine echocardiograms

OBJECTIVES

We sought to develop and validate a risk score combining both clinical and dobutamine echocardiographic (DbE) features in 4890 patients who underwent DbE at three expert laboratories and were followed for death or myocardial infarction for up to five years.

BACKGROUND

In contrast to exercise scores, no score exists to combine clinical, stress, and echocardiographic findings with DbE.

METHODS

Dobutamine echocardiography was performed for evaluation of known or suspected coronary artery disease in 3156 patients at two sites in the U.S. After exclusion of patients with incomplete follow-up, 1456 DbEs were randomly selected to develop a multivariate model for prediction of events. After simplification of each model for clinical use, the models were internally validated in the remaining DbE patients in the same series and externally validated in 1733 patients in an independent series.

RESULTS

The following score was derived from regression models in the modeling group (160 events): DbE risk = (age.0.02) + (heart failure + rate-pressure product <15000).0.4 + (ischemia + scar).0.6. The presence of each variable was scored as 1 and its absence scored as 0, except for age (continuous variable). Using cutoff values of 1.2 and 2.6, patients were classified into groups with five-year event-free survivals >95%, 75% to 95%, and <75%. Application of the score in the internal validation group (265 events) gave equivalent results, as did its application in the external validation group (494 events, C index = 0.72).

CONCLUSIONS

A risk score based on clinical and echocardiographic data may be used to quantify the risk of events in patients undergoing DbE.

Fidedignidade intra e interdias do teste de exercício de quatro segundos

O teste de exercício de quatro segundos (T4s) é validado farmacologicamente para a avaliação da função vagal cardíaca e consiste em pedalar, o mais rápido possível, um cicloergômetro sem carga do quarto ao oitavo segundo de uma apnéia inspiratória máxima de 12 segundos. Um índice vagal cardíaco (IVC) adimensional é obtido pelo quociente entre a duração dos ciclos cardíacos (intervalos RR no eletrocardiograma) imediatamente antes e o mais curto do exercício. Objetivou-se determinar a fidedignidade inter e intradia do T4s e a necessidade de realizar duas tentativas, conforme descrito no protocolo original. No estudo 1, analisou-se prospectivamente a fidedignidade interdias dos resultados de 15 indivíduos assintomáticos (28 ± 6 anos) submetidos ao T4s por cinco dias seguidos, sendo realizadas duas tentativas a cada dia. Para determinar a fidedignidade intradia do IVC, foram realizadas, randomicamente em um dos dias, nove tentativas consecutivas do T4s. No estudo 2, calculou-se, retrospectivamente, a fidedignidade intradia do IVC de 1.699 indivíduos (47 ± 17 anos) em duas tentativas. O IVC apresentou elevada fidedignidade intradia e interdias (r i = 0,92; IC 95% = 0,84 a 0,97 e r i = 0,77; IC 95% = 0,49 a 0,92, respectivamente) no estudo 1, assim como, no estudo 2 (r i = 0,89; IC 95% = 0,88 a 0,90). Apesar da elevada fidedignidade, havia mínimas diferenças entre as médias (média ± EPM = 1,32 ± 0,01 vs. 1,37 ± 0,01; p < 0,001), sendo que em apenas 15% dos casos essa diferença foi maior do que 0,20, não representando, assim, maior relevância clínica. Verificou-se, ainda, que, em 65% das observações, a segunda tentativa foi considerada a melhor e que a realização de apenas uma induziria a erros de interpretação clínica em 27% dos dados. Em síntese, este estudo demonstrou a elevada fidedignidade do IVC avaliado pelo T4s, além de justificar a necessidade de realizar duas tentativas consecutivas em seu protocolo.

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.

Prognostic value of exercise tests in male veterans with chronic coronary artery disease

PURPOSE

The authors evaluate the prognostic value of treadmill testing in a large consecutive series of patients with chronic coronary artery disease. Exercise testing is widely performed, but analyses of the prognostic value of test results have largely concentrated on patients referred for the diagnosis of coronary artery disease, patients after an acute coronary event or procedure, or patients with congestive heart failure.

METHODS

All patients referred for evaluation at two university-affiliated Veterans Affairs Medical Centers who underwent exercise treadmill tests for clinical indications between 1987 and 2000 were determined to be dead or alive using the Social Security Death Index after a mean 5.8-year follow-up. Patients without established heart disease and those with congestive heart failure were excluded, leaving the target population of those with a history myocardial infarction or coronary intervention. Clinical and exercise test variables were collected prospectively according to standard definitions; testing and data management were performed in a standardized fashion using a computer-assisted protocol. All-cause mortality was used as the endpoint for follow-up. Standard survival analysis was performed including Kaplan Meier curves and the Cox Hazard Model.

RESULTS

Of the 1,473 patients with coronary artery disease who had exercise testing, 273 (19%) patients had a revascularization procedure (Revascularization group); 813 (55%) had a history of myocardial infarction, diagnostic Q waves (MI group), or both; and 387 (26%) had a history of myocardial infarction or Q wave and revascularization (Combined group). Mean age of the patients was 61.8 +/- 9 years. A total of 401 deaths occurred during a mean follow-up of 5.8 years with an annual mortality rate of 4.5%. Only two variables, age and maximal exercise capacity, were independently and statistically associated with time to death in all three groups and were the strongest predictors of all cause mortality.

CONCLUSION

A simple score based on METs, age, and history of myocardial infarction or diagnostic Q waves can stratify prognosis in patients with chronic coronary artery disease. The score enabled the identification of a group at low risk (32% of the cohort) with an annual mortality rate of 2%, a group at intermediate risk (42% of the cohort) with an annual mortality rate of about 4%, and a group at high risk (26% of the cohort) with an average annual mortality rate of approximately 7%.

Exercise testing scores as an example of better decisions through science

INTRODUCTION

The application of common statistical techniques to clinical and exercise test data has the potential to become a useful tool for assisting in the diagnosis of coronary artery disease, assessing prognosis, and reducing the cost of evaluating patients with suspected coronary disease. Since general practitioners function as gatekeepers and decide which patients must be referred to the cardiologist, they need to optimally use the basic tools they have available (i.e., history, physical exam, and the exercise test).

METHODS

Review of the literature with a focus on the scientific techniques for aiding the decision-making process.

RESULTS

Scores derived from multivariable statistical techniques considering clinical and exercise data have demonstrated superior discriminating power when compared using receiver-operating-characteristic curves with the ST segment response. In addition, by stratifying patients as to probability of disease and prognosis, they provide a management strategy. While computers as part of information management systems can calculate complicated equations to provide scores, physicians are reluctant to trust them. Thus, these scores have been represented as nomograms or simple additive tables so physicians are comfortable with their application. Scores have also been compared with physician judgment and been found to estimate the presence of coronary disease and prognosis as well as expert cardiologists, and often better than nonspecialists.

CONCLUSION

Multivariate scores can empower the clinician to assure the cardiac patient with access to appropriate and cost-effective cardiological care.

The prognostic value of body mass index and standard exercise testing in male veterans with congestive heart failure

OBJECTIVE

To evaluate the prognostic characteristics of body mass index (BMI) and standard exercise test variables in a consecutive series of patients with mild to moderate congestive heart failure (CHF) referred for standard exercise tests.

BACKGROUND

Controversy exists regarding the prognostic importance of BMI, etiology, and exercise test variables in patients with CHF.

METHODS

All patients referred for evaluation at two university-affiliated Veterans Affairs Medical Centers who underwent treadmill tests for clinical indications between 1987 and 2000 were determined to be dead or alive using the Social Security Death Index after a mean 6 years follow-up. Clinical and exercise test variables were collected prospectively according to standard definitions; testing and data management were performed in a standardized fashion using a computer-assisted protocol. Survival analysis was performed using all-cause mortality as the endpoint for follow-up.

RESULTS

A total of 522 patients with a history and clinical findings of CHF underwent exercise testing. Forty-two percent died during the follow-up period, for an average annual mortality of 6.7%. Cox proportional hazards model chose peak metabolic equivalents (METs), BMI, age, and ischemic etiology in rank order as independently and significantly associated with time to death. A score based on these variables classified patients into low (2% annual mortality), medium (5.2%), and high-risk groups (7% annual mortality).

CONCLUSION

Standard exercise testing and BMI can be used to estimate prognosis in outpatients with heart failure. A score incorporating METs, BMI, age, and etiology efficiently stratified these patients. BMI was chosen by the survival analysis, confirming its surprising inverse relationship to prognosis in CHF patients (i.e., heavier patients do better).

Better decisions through science: exercise testing scores

Statistical tools can be used to create scores for assisting in the diagnosis of coronary artery disease and assessing prognosis. General practitioners and internists frequently function as gatekeepers, deciding which patients must be referred to the cardiologist. Therefore, they need to use the basic tools they have available (ie, history, physical examination and the exercise test) in an optimal fashion. Scores derived from multivariable statistical techniques considering clinical and exercise data have demonstrated superior discriminating power compared with diagnosis only using the ST segment response. In addition, by stratifying patients as to probability of disease and prognosis, they provide a more practical management strategy than a response of normal or abnormal. Although computers, as part of information management systems, can calculate complicated equations and derive these scores, physicians are reluctant to trust them. However, when represented as nomograms or simple additive discrete pieces of information, scores are more readily accepted. The scores have been compared with physician judgment and have been found to estimate the presence of coronary disease and prognosis as well as expert cardiologists and often better than nonspecialists. However, the discriminating power of specific variables from the medical history and exercise test remains unclear because of inadequate study design and differences in study populations. Should expired gases be substituted for estimated METs? Should ST/heart rate index be used instead of putting ST depression and heart rate separately into the models? Should right-sided chest leads and heart rate in recovery be considered? There is a need for further evaluation of these easily obtained variables to improve the accuracy of prediction algorithms, especially in women. The portability and reliability of scores must be ensured because access to specialized care must be safeguarded. Assessment of the clinical and exercise test data and application of the newer scores can empower the clinician to assure the cardiac patient access to appropriate and cost-effective cardiologic care.

Diagnostic exercise tests on 4000 consecutive men

OBJECTIVE

Our purpose was to report the prevalence of abnormal treadmill test responses and their association with mortality in a large consecutive series of patients referred for standard diagnostic exercise tests, with testing performed and reported in a standardized fashion.

BACKGROUND

Exercise testing is widely performed, but an analysis of responses has not been presented for a large number of consecutive tests performed on patients referred for diagnosis of cardiac disease.

METHODS

All patients referred for evaluation at 2 university-affiliated Veterans Affairs Medical Centers who underwent exercise treadmill tests for clinical indications between 1987 and 2000 were determined to be dead or alive according to the Social Security Death Index after a mean 5.9-year follow-up. Patients with established heart disease (ie, prior coronary bypass surgery, myocardial infarction, or congestive heart failure) were excluded from analyses. Clinical and exercise test variables were collected prospectively according to standard definitions; testing and data management were performed in a standardized fashion with a computer-assisted protocol. All-cause mortality was used as the end point for follow-up. Standard survival analysis was performed, including Kaplan-Meier curves and a Cox hazard model.

RESULTS

After the exclusions, 3974 men (mean age 57.5 +/- 11 years) had standard diagnostic exercise testing over the study period with a mean of 5.9 (+/-3.7) years of follow-up (64% of all tested). There were no complications of testing in this clinically referred population, 82% of whom were referred for chest pain, risk factors, or signs and symptoms of ischemic heart disease. Five hundred forty-nine (14%) had a history of typical angina. Indications for testing were in accordance with published guidelines. A total of 545 died, yielding an annual mortality rate of 1.8%. The Cox hazard model chose the following variables in rank order as independently associated with time to death: change in rate pressure product, age greater than 65 years, METs less than 5, and electrocardiographic left ventricular hypertrophy. A score based on these variables classified patients into low-, medium-, and high-risk groups. The high-risk group with a score greater than 3 has a hazard ratio of 4 (95% confidence interval 3.82-4.27) and an annual mortality rate of 4%.

CONCLUSION

This comprehensive analysis provides rates of various abnormal responses that can be expected in men referred for diagnostic exercise testing at typical Veterans Administration Medical Centers. Four simple variables combined as a score predict all-cause mortality after clinical decisions for therapy are prescribed.