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Methodologic problems of exercise testing for coronary artery disease: groups, analysis and bias.

To determine why exercise testing remains controversial as a diagnostic test for coronary artery disease, a methodologic review was undertaken of 33 studies comprising 7,501 patients who had undergone both exercise tests and coronary angiography. Of seven methodologic standards for research design, only one received general compliance: the requirement for an adequate variety of anatomic lesions. Less than half of the studies complied with any of the remaining six standards: adequate identification of the groups selected for study; adequate analysis for relevant chest pain syndromes; avoidance of a limited challenge group; and avoidance of work-up bias, diagnostic review bias and test review bias. Only one study met as many as five standards. These methodologic problems may explain the wide range of sensitivity (35 to 88 percent) and specificity (41 to 100 percent) found for exercise testing, because the variations could not be attributed to the usual explanations: definition of anatomic abnormality, stress test technique or definition of an abnormal test. Determining the true value of exercise testing requires methodologic improvements in patient selection, data collection and data analysis.

Coronary Disease↗

The current value of exercise testing soon after acute myocardial infarction.

We performed exercise testing in 236 of 289 survivors of acute myocardial infarction to test the hypothesis that exercise-related parameters contribute to cardiac prognosis. Beta-blockers and/or calcium antagonists were used by 50% and 55% respectively of the study population. Of the 236 patients 67 had received thrombolytic therapy during the acute event. By either univariate or multivariate analysis, we found that exercise-related parameters were poor predictors of cardiac prognosis. Therefore, in our population, exercise testing performed 3 weeks after myocardial infarction provides little information of prognostic value.

Academic Medical Centers↗

Comparison of exercise test scores and physician estimation in determining disease probability.

BACKGROUND: The recent American College of Cardiology/American Heart Association exercise testing guidelines provided equations to calculate treadmill scores and recommended their use to improve the predictive accuracy of the standard exercise test. However, if physicians can estimate the probability of coronary artery disease as well as the scores can, there would be no reason to add this complexity to test interpretation. To compare the exercise test scores with physician's estimation of disease probability, we used clinical, exercise test, and coronary angiographic data to compute the recommended scores and print patient summaries and treadmill reports. OBJECTIVE: To determine whether exercise test scores can be as effective as expert cardiologists in diagnosing coronary disease. METHODS: Five hundred ninety-nine consecutive male patients without previous myocardial infarction with a mean +/- SD age of 59 +/- 11 years were considered for this analysis. With angiographic disease defined as any coronary lumen occlusion of 50% or more, 58% had disease. The clinical/treadmill test reports were sent to expert cardiologists and to 2 other groups, including randomly selected cardiologists and internists, who classified the patients as having high, low, or intermediate probability of disease and estimated a numerical probability from 0% to 100%. RESULTS: Forty-five expert cardiologists returned estimates on 336 patients, 37 randomly chosen practicing cardiologists returned estimates on 129 patients, 29 randomly chosen practicing internists returned estimates on 106 patients, 13 academic cardiologists returned estimates on 102 patients, and 27 academic internists returned estimates on 174 patients. When probability estimates were compared, the scores were superior to all physician groups (0.76 area under the receiver operating characteristic curve to 0.70 for experts [P=.046], 0.73 to 0.58 for cardiologists [P=.003], and 0.76 to 0.61 for internists [P=.006]). Using a probability cut point of greater than 70% for abnormal, predictive accuracy was 69% for scores compared with 64% for experts, 63% to 62% for cardiologists, and 70% to 57% for internists. CONCLUSION: Although most similar to the disease estimates of the presence of clinically significant angiographic coronary artery disease provided by the expert cardiologists, the scores outperformed the nonexpert physicians.

Adult↗

Cardiopulmonary exercise testing. The clinical value of gas exchange data.

Cardiopulmonary exercise testing is a noninvasive tool whose clinical value is not yet widely recognized. The technique involves breath-by-breath measurement of respiratory gas exchange during a symptom-limited exercise test, with determination of maximal oxygen uptake and anaerobic threshold. These measurements serve as objective, reproducible indices of exercise capacity that can be applied to the management of various clinical problems. In addition, by permitting simultaneous assessment of circulatory and ventilatory reserves, the test can be especially helpful in the differential diagnosis of exertional dyspnea and fatigue. This paper reviews the physiology of gas exchange, the limitations of standard exercise tests, and the methodology and clinical applications of cardiopulmonary exercise testing.

Carbon Dioxide↗

Change point in VCO2 during incremental exercise test: a new method for assessment of human exercise tolerance.

The main purpose of this study was to present a new method to determine the level of power output (PO) at which VCO2 during incremental exercise test (IT) begins to rise non-linearly in relation to power output (PO) - the change point in VCO2 (CP-VCO2). Twenty-two healthy non-smoking men (mean +/- SD: age 22.0 +/- 0.9 years; body mass 74.5 +/- 7.5 kg; height 181 +/- 7 cm; VO2max 3.753 +/- 0.335 l min-1) performed an IT on a cycloergometer. The IT started at a PO of 30 W, followed by gradual increases of 30 W every 3 min. Antecubital venous blood samples were taken at the end of each step and analysed for plasma lactate concentration [La]pl, blood PO2, PCO2 [HCO3-]b and [H+]b. In the detection of the change-point VCO2 (CP-VCO2), a two-phase model was assumed for the 'third-minute-data' of each step of the test. In the first phase, a linear relationship between VCO2 and PO was assumed, whereas in the second, an additional increase in VCO2 was allowed, above the values expected from the linear model. The PO at which the first phase ends is called the change point in VCO2. The identification of the model consists of two steps: testing for the existence of the change point, and estimating its location. Both procedures are based on suitably normalized recursive residuals (see Zoladz et al. 1998a. Eur J Appl Physiol 78, 369-377). In the case of each of our subjects it was possible to detect the CP-VCO2 and the CP-VO2 as described in our model. The PO at the CP-VCO2 amounted to 134 +/- 42 W. The CP- VO2 was detected at 136 +/- 32 W, whereas the PO at the LT amounted to 128 +/- 30 W and corresponded to 49 +/- 11, 49 +/- 8 and 47 +/- 8.6% VO2max, respectively, for the CP-VCO2, CP-VO2 and the LT. The [La]pl at the CP-VCO2 (2.65 +/- 0.76 mmol L-1), at the CP-VO2 (2.53 +/- 0. 56 mmol L-1) and at the LT (2.25 +/- 0.49 mmol L-1) were already significantly higher (P < 0.01, Students t-test) than the value reached at rest (1.86 +/- 0.43 mmol L-1). Our study illustrates that the CP-VCO2 and the CP-VO2 occur at a very similar power output as the LT. We therefore postulate that the CP-VCO2 and the CP-VO2 be applied as an additional criterion to assess human exercise tolerance.

Adult↗

Effects of two successive maximal exercise tests on pulmonary gas exchange in athletes.

Pulmonary extravascular water accumulation may be involved in exercise-induced hypoxaemia in highly aerobically trained athletes. We hypothesized that if such an alteration were present in elite athletes performing a maximal exercise test, the impairment of gas exchange would be worse during a second exercise test following the first one. Eight male athletes performed two incremental exercise tests separated by a 30-min recovery period. Pulmonary gas exchange and ventilatory data were measured during exercise tests performed in normoxia. Arterial blood samples were drawn each minute during rest, exercise, and recovery. Pulmonary diffusing capacity for CO (DLCO) was measured at rest, after the first (T1) and the second (T2) test. All the subjects underwent a spirometric test at rest and after T2. Maximal and recovery data for O2 uptake and minute ventilation were not statistically different between T1 and T2. Partial pressure of arterial O2 (PaO2) decreased during both tests but was lower during T2 for rest, 60 W, and 120 W (P < 0.02). Alveolar-arterial difference in partial pressure of O2 (PA-aO2) increased during both the tests but was significantly larger during T2 for rest, 60 W, and 120 W (P < 0.01). The PaO2 and PA-aO2 data at maximal exercise were not significantly different between T1 and T2. Compared to rest, PA-aO2 remained significantly larger during recovery for both T1 and T2 (P < 0.0001). The PA-aO2 during T2 recovery was larger than T1 recovery (P < 0.008). Spirometric data did not change. The DLCO measurements after T1 and T2 were not significantly different from rest. These results showed an alteration of PaO2 and PA-aO2 during T1, which tended to be worse during and after T2; however, these data do not allow us to make a definitive statement as to the cause of the hypoxaemia. Our study confirmed that exhausting exercise caused hypoxaemia. It also demonstrated that the disturbance in pulmonary gas exchange persisted for at least 30 min following the end of the exercise period and became worse during submaximal intensities of the following incremental exercise test.

Adult↗

The use of preoperative exercise testing to predict cardiac complications after arterial reconstruction.

To assess the value of exercise testing in the prediction of cardiac risk, 100 patients requiring arterial reconstructive surgery had either treadmill testing or arm ergometry before operation. Thirty-four patients then had abdominal aortic aneurysm repair, 48 had reconstructions for aortoiliac occlusive disease, and 18 had infrainguinal revascularization procedures. Cardiac complications included myocardial infarction in 10%, acute congestive failure in 5%, malignant ventricular arrhythmias in 7%, and cardiac death in 7%. Contingency table analysis showed that patients who achieved less than 85% of their predicted maximum heart rate (PMHR) during exercise testing had a complication rate of 24%, whereas patients who achieved more than 85% of PMHR had a 6% complication rate (p = 0.0396). The degree of ST segment depression during exercise testing was not a significant predictor of cardiac complications. However, patients who had a positive stress test (ST depression more than 1 mm) and achieved less than 85% of their PMHR had a complication rate of 33%, whereas patients with a positive stress test who achieved more than 85% of their PMHR had no complications (p = 0.048). Statistical analysis with a logistic regression model showed two factors to be significant. Patients who achieved a high maximum heart rate during exercise testing had a low probability of developing postoperative cardiac complications (p = 0.04), as did patients who achieved high cardiac work load maximal oxygen uptake (p = 0.03). We conclude that preoperative exercise testing is useful to predict cardiac complications after arterial reconstruction. Patients who are able to achieve more than 85% of their PMHR and a high maximal oxygen uptake represent a low-risk group.

Aorta, Abdominal↗

Some common abnormal responses to exercise testing: what to do when you see them.

This article reviews the role of exercise testing in the assessment of patients with suspected coronary disease. To accomplish this, four major topics are considered: the general concept of risk stratification; the estimation of outcomes using data from the initial evaluation of the patient; diagnostic assessment with the exercise test; and prognostic assessment with the exercise test. This review focuses on the standard treadmill exercise test.

Arrhythmias, Cardiac↗

Exercise testing in children with Wolff-Parkinson-White syndrome.

Exercise testing using a modified Bruce treadmill protocol was performed by 17 children with Wolff-Parkinson-White (WPW) syndrome. All had intracardiac electrophysiology studies as well. Endurance time, heart rate and blood pressure were normal during exercise. Ventricular premature complexes were seen with exercise in 2 patients and supraventricular tachycardia with exercise testing was seen in 2. Disappearance of the delta wave with exercise correlated with a long anterograde effective refractory period of the Kent bundle (360 to 390 ms). Children with partial normalization of the QRS during exercise had a longer anterograde effective refractory period of the Kent bundle than those in whom preexcitation persisted. In 1 patient, disappearance of the delta wave with exercise confirmed the diagnosis of WPW syndrome. Preexcitation was seen only after exercise in 1 patient. Exercise testing is of value in the evaluation of children with WPW syndrome; children with WPW syndrome who have total normalization of the QRS interval during exercise and few or no symptoms of tachycardia do not require electrophysiologic study.

Adolescent↗

Comparison of the electrocardiographic changes induced by maximam exercise testing with treadmill and cycle ergometer.

Maximum exercise testing using treadmill walking and cycle ergometry was compared in 40 male patients who had suffered a myocardial infarction in the preceeding twelve months. Maximum oxygen uptake was on average 17% greater in the treadmill than the cycle test and maximum heart rate was also higher, but the rate pressure product (RPP) was a similar due to a higher blood pressure in the cycle ergometer test. Eleven subjects showe ST-segment depression greater than 1 min and eight subjects showed ST-segment elevation greater than 1 mm. There was a close relationship (r2 = 0.96) between the magnitude of ST-segment changes in the two tests. Four subjects showing ST depression of 1 mm in the treadmill test showed depression during the cycle ergometer test which was less than this conventionally "positive" value. In these subjects RPP was lower during cycling than in treadmill walking. With both tests maximum ST-segment changes were measured immediately on stopping exercise: resolution of ST depression was more rapid than ST elevation. The two exercise testing modes are closely comparable in their ability to reveal changes of myocardial ischemia.

Adult↗

[The value of exercise tests in the diagnosis of ischemic heart disease].

New knowledges of contemporary cardiology have created possibilities for critically reevaluation of current criteria in exercise testing and have shown its new diagnostic and prognostic value. A multifactorial approach to exercise testing includes an analysis of ECG criteria and hemodynamic parameters obtained during exercise testing. This approach increases the value of stress testing in diagnosis, assessment of the severity and prognosis of coronary artery disease. The inclination toward arrhythmias, detection of asymptomatic ischemia and early detection of a dysfunction of the left ventricle have been emphasized. The indications for use and termination of exercise testing absolute and relative contraindications for exercise testing are critically discussed. The sensitivity of exercise testing is 60 to 80 percent and specificity level ranges between 85 to 90 percent. The incidence of serious complications is decreased about 50 percent by a careful screening of patients and appropriate safety level.

Exercise Test↗

Comparative evaluation of dopamine infusion & treadmill exercise tests in the diagnosis of coronary artery disease.

Dopamine infusion test (DIT) was compared with treadmill exercise test (TMT) in 20 patients of chronic stable angina (TMT +ve) for inducing reversible myocardial ischaemia so as to assess its efficacy as an alternative to TMT in patients who cannot perform exercise test due to certain non-cardiac diseases. DIT was positive in 15 of the 20 patients studied; five patients in whom DIT was negative had late onset, early offset changes in TMT. Haemodynamically the increase in heart rate (HR) was less but rise in systolic blood pressure (SBP) was more with dopamine infusion in comparison to the corresponding stage of TMT. However, evidence of myocardial ischaemia (ST segment depression) appeared at a lower rate pressure product (RPP) with dopamine infusion compared to exercise test. The test was tolerated well, in higher doses (stages III & IV) side effects like ventricular ectopic beats, palpitation and angina not warranting stoppage of test, were seen in some patients. Dopamine infusion is a good chemical stress test, and can be used as an alternative to TMT especially in situations where the latter cannot be performed. The test is simple, cost effective, non-invasive and well tolerated.

Angina Pectoris↗

[Frequency of life-threatening complications associated with exercise testing (author's transl)].

Most of the statistics on complications of ergometric exercise tests come from the United States and are largely related to treadmill ergometry. A questionnaire was sent in the summer of 1978 to 198 investigative units in the German-speaking regions. The results of 1065 923 person-tests were made available. Exercise testing of 353 638 sports-persons revealed no serious complications. On the other hand, testing of 712 285 patients, predominantly with coronary heart disease, lead to 17 deaths and a total of 96 life-threatening complications. The result of this survey indicates that one must expect one such complication for every 7500 ergometry tests. The danger of pulmonary oedema on exercise in recumbency is about five times higher than that on sitting or standing. The most frequent complication was ventricular fibrillation. A defibrillator should therefore always be immediately available during exercise tests.

Coronary Disease↗

Long-term prognostic value of exercise testing in men and women from the Coronary Artery Surgery Study (CASS) registry.

Many prior studies involving a predominantly male population have demonstrated the importance of exercise test results in determining the outcome of patients with coronary artery disease. The prognostic significance of exercise testing in women is unknown. In our study, a total of 3,086 men and 747 women underwent maximal treadmill exercise testing, coronary angiography, and were prospectively followed for up to 16 years. They were divided into 3 groups (high, intermediate, and low risk) on the basis of exercise testing. Sixteen-year survival based on exercise test groups ranged from 38% to 61% in men and from 44% to 79% in women (p < 0.001). Among men, 12-year survival was enhanced by coronary artery bypass surgery versus medical therapy in the high-risk subgroup (69% vs 55%, respectively, p = 0.0025), but the 2 therapies were similar in the intermediate- and low-risk subgroups. Among women, neither medical nor surgical therapy resulted in improved 12-year survival rates in any of the 3 subgroups. These results suggest that exercise testing is helpful in assessing long-term survival in men and women. However, only exercise testing in men could identify a high-risk subset whose survival was enhanced by coronary artery bypass graft surgery.

Adult↗

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.

Coronary Angiography↗

Exercise testing to stratify risk in aortic stenosis.

AIMS: The aims of this study were to assess the accuracy of exercise testing in predicting symptom onset within 12 months in patients with asymptomatic aortic stenosis and to establish the criteria that define a positive test. METHODS AND RESULTS: A total of 125 patients with aortic stenosis [effective orifice area (EOA) 0.9+/-0.2 cm2] were assessed by Specific Activity Scale (SAS) classification, transthoracic echocardiography, and treadmill exercise testing using the modified Bruce protocol. During follow-up, 36 patients (29%) developed spontaneous symptoms within 12 months. Of these, 26 (72%) had had symptoms revealed by exercise testing and 24 (67%) had severe stenosis (EOA < or = 0.8 cm2). Exercise-limiting symptoms were the only independent predictors of outcome at 12 months, and an abnormal blood pressure response or ST segment depression did not improve the accuracy of the exercise test. The positive predictive accuracy for exercise-induced symptoms was 57% in the whole population and 79% for patients aged <70 in SAS Class I. The negative predictive accuracy was 87% in the whole population and 86% in the subgroup. CONCLUSION: A significant proportion of patients with apparently asymptomatic aortic stenosis experience limiting symptoms on treadmill exercise testing. The subsequent development of spontaneous symptoms is strongly related to the severity of stenosis and to limiting symptoms on exercise testing, but less so to an abnormal blood pressure response or ST segment depression.

Aged↗

Exercise testing in the assessment of pulmonary disease.

In this chapter, the different types of exercise tests and the indications for requesting a particular type of test have been discussed. The normal physiological responses to exercise have been reviewed and examples of the abnormal responses seen in a variety of disease states that have been discussed. The relatively small number of these responses limits the specificity of exercise tests in actually establishing a diagnosis, but can be helpful in narrowing the differential diagnosis. Perhaps exercise tests are most valuable in cases where the patient's symptoms are mainly limited to exercise and where investigations done at rest have failed to resolve a diagnostic question. When exercise testing is used under these circumstances, it serves a unique function in the diagnosis and management of pulmonary disease.

Asthma, Exercise-Induced↗

[Predictive role of exercise tests in development of restenosis in patients after coronary stent implantation].

Bicycle exercise tests were carried out in 2 weeks -- 9 months after successful stent implantation in 1463 patients. Result of exercise test was positive in 472 and negative -- in 991 patients. At control angiography which was performed within 1 week after exercise test binary in-stent restenosis >50% was found in 326 of 1463 patients. Sensitivity, specificity, predictive value of positive and negative results of exercise test for the presence of restenosis were 85, 83, 59 and 5%, respectively.

Adult↗