The prognostic value of the exercise test

Exercise treadmill test may predict clinical outcome among working-aged patients suspected of coronary heart disease in general practice

OBJECTIVE

To specify the diagnostic value of treadmill tests conducted in primary health care by trained GPs for working-aged patients.

DESIGN

A two-year follow-up study.

SETTING

Kangasala Health Centre, Finland.

SUBJECTS

All patients under the age of 60 (n = 348) examined by exercise treadmill test carried out by trained GPs during a period of three years.

MAIN OUTCOME MEASURES

The number of patients having a diagnosis of coronary heart disease at the end of two years' follow-up. Predictive values of the exercise test.

RESULTS

During the two years' follow-up period CHD was diagnosed in six of the patients who did not yield a positive finding in the test. A negative finding in the test was very reliable; coronary heart disease manifested in only 2% of these cases. Almost half of the patients yielding a positive finding ended up having coronary angiography and 1 in 10 underwent coronary bypass surgery.

CONCLUSION

Among working-aged patients suspected of coronary heart disease an exercise treadmill test may predict clinical outcome in general practice.

An overview of risk assessment in coronary artery disease

Risk assessment is a central activity in virtually all aspects of the examination and treatment of patients. Methods to standardize this process and improve its accuracy can only improve the quality of medical care. Since health care is undergoing reform in this country, it seems likely that physicians will increasingly need objective justification for their decision making. Risk assessment models offer a potentially useful tool. The Duke Treadmill Score is well-validated and clinically useful for risk assessment in patients with either established or suspected coronary artery disease for whom the desirability of additional invasive testing must be determined. One of the major goals of risk assessment is to identify the low-risk patients for whom no additional testing is required. Whereas multiple valid strategies for accomplishing this exist, there is no consensus on the optimal approach. Cost-containment pressures may indicate the use of exercise testing as the preferred initial strategy in patients who are able to exercise and have an interpretable electrocardiogram. Exercise nuclear testing could thus be reserved for patients in the intermediate-risk group for whom the additional accuracy of these latter tests would provide a more precise risk-stratification estimate. For patients unable to exercise, a pharmacologic stress test (such as echocardiography with dobutamine or an adenosine isonitrile study) would be an acceptable alternative.

Issues in contemporary cardiac rehabilitation: a historical perspective

Cardiac rehabilitation consists of exercise, psychosocial support and education and is prescribed most often for patients with coronary heart disease. Its purpose is to facilitate readaptation to normal life through the achievement of maximal functional capability and to reduce heart disease risk factors. It began historically with progressive ambulation after myocardial infarction and by 1980 became a standardized inpatient therapy performed according to a stepped procedure. Predischarge exercise testing was added and has become a meaningful contribution to the concept of risk stratification after an acute coronary event. Rehabilitation has subsequently become part of the outpatient environment and is delivered by multiple models. Meta-analyses have shown that rehabilitation reduces overall and cardiovascular deaths by about 20% and sudden death by about 37% during the year after an acute myocardial infarction. The significance of this, however, must now be modulated by the dynamic role of aggressive coronary intervention. Selection for such intervention has become an important adjunctive aspect of rehabilitation. Newer findings suggest that those stratified at low risk will benefit most by the modification of coronary risk factors, and that patients previously thought to be poor candidates for rehabilitation (such as those with significant left ventricular dysfunction and low work capacity) may experience substantial relative functional benefit. Beyond risk stratification, important contemporary issues include surveillance of patients after angioplasty, the effectiveness of rehabilitation in the attenuation or reversal of both native and vein graft atherosclerosis and consideration of such currently emphasized end points as quality of life and economic evaluation.

Usefulness of ambulatory silent myocardial ischemia added to the prognostic value of exercise test parameters in predicting risk of cardiac death in patients with stable angina pectoris and exercise-induced myocardial ischemia

The prognostic significance of ambulatory silent ischemia detected by Holter monitoring during daily life was prospectively evaluated and compared with several exercise test parameters in 86 patients with stable angina and positive exercise tests. Forty-seven patients (group 1) had no evidence of ischemia and 39 (group 2) had 1 or more episodes of silent ischemia during the monitoring period. During mean follow-up of 24 +/- 8 months there were only 2 cardiac deaths (nonsudden) in group 1 (4% mortality) compared with 9 (3 sudden and 6 nonsudden) in group 2 (23% mortality). Kaplan-Meier actuarial analysis revealed worse survival (p less than 0.008) for patients in group 2. The Cox regression analysis of clinical variables, electrocardiographic and exercise parameters, angiographic data and Holter monitoring results revealed silent ischemia during daily life as the most powerful predictor of cardiac mortality (p = 0.003). These results demonstrate that in patients with chronic stable angina and abnormal exercise tests, ambulatory ischemia detected by Holter monitoring provides significant additional prognostic information to that derived from evaluation of exercise test parameters alone.

Prognostic value of a treadmill exercise score in outpatients with suspected coronary artery disease

BACKGROUND

The treadmill exercise test identifies patients with different degrees of risk of death from cardiovascular events. We devised a prognostic score, based on the results of treadmill exercise testing, that accurately predicts outcome among inpatients referred for cardiac catheterization. This study was designed to determine whether this score could also accurately predict prognosis in unselected outpatients.

METHODS

We prospectively studied 613 consecutive outpatients with suspected coronary disease who were referred for exercise testing between 1983 and 1985. Follow-up was 98 percent complete at four years. The treadmill score was calculated as follows: duration of exercise in minutes--(5 x the maximal ST-segment deviation during or after exercise, in millimeters)--(4 x the treadmill angina index). The numerical treadmill angina index was 0 for no angina, 1 for nonlimiting angina, and 2 for exercise-limiting angina. Treadmill scores ranged from -25 (indicating the highest risk) to +15 (indicating the lowest risk).

RESULTS

Predicted outcomes for the outpatients, based on their treadmill scores, agreed closely with the observed outcomes. The score accurately separated patients who subsequently died from those who lived for four years (area under the receiver-operating-characteristic curve = 0.849). The treadmill score was a better discriminator than the clinical data and was even more useful for outpatients than it had been for inpatients. Approximately two thirds of the outpatients had treadmill scores indicating low risk (greater than or equal to +5), reflecting longer exercise times and little or no ST-segment deviation, and their four-year survival rate was 99 percent (average annual mortality rate, 0.25 percent). Four percent of the outpatients had scores indicating high risk (less than -10), reflecting shorter exercise times and more severe ST-segment deviation; their four-year survival rate was 79 percent (average annual mortality rate, 5 percent).

CONCLUSIONS

The treadmill score is a useful and valid tool that can help clinicians determine prognosis and decide whether to refer outpatients with suspected coronary disease for cardiac catheterization. In this study, it was a better predictor of outcome than the clinical assessment.

Use of the exercise test to predict prognosis after coronary artery bypass grafting

The objective of this study was to predict the prognosis of patients who become symptomatic after having undergone coronary artery bypass grafting (CABG) using clinical and exercise test responses. A retrospective analysis was performed of all veterans referred for clinical indications to a Veterans Administration Medical Center for a treadmill test after having undergone CABG. Of 2,044 patients who were exercise tested from April 1984 to May 1987, 296 had previously undergone CABG. Clinical data considered included age, sex, medication and symptom status, history of myocardial infarction, type of myocardial infarction and time from CABG. The exercise test responses considered were MET level, maximal heart rate, maximal systolic blood pressure, chest pain pattern and ST-segment response. During a 2-year follow-up after exercise testing, there were 15 deaths, 11 nonfatal myocardial infarctions, 6 repeat CABGs and 3 percutaneous transluminal coronary angioplasties. Although MET level and maximal heart rate were significantly related to prognosis and no patient who exceeded 8 METs died, the predictive power of these exercise test responses was low and ST-segment depression was not predictive at all. The inability of the exercise electrocardiogram to predict cardiac events in patients after CABG requires the use of other methods of testing to identify those who need invasive studies and intervention.