Exercise testing: uses and limitations considering recent studies

Stress induced hypertensive response: should it be evaluated more carefully?

Various diagnostic methods have been used to evaluate hypertensive patients under physical and pharmacological stress. Several studies have shown that exercise hypertension has an independent, adverse impact on outcome; however, other prognostic studies have shown that exercise hypertension is a favorable prognostic indicator and associated with good outcome. Exercise hypertension may be encountered as a warning signal of hypertension at rest and future hypertensive left ventricular hypertrophy. The results of diagnostic stress tests support that hypertensive response to exercise is frequently associated with high rate-pressure product in hypertensives. In addition to the observations on high rate-pressure product and enhanced ventricular contractility in patients with hypertension, evaluation of myocardial contractility by Doppler tissue imaging has shown hyperdynamic myocardial function under pharmacological stress. These recent quantitative data in hypertensives suggest that hyperdynamic myocardial function and high rate-pressure product response to stress may be related to exaggerated hypertension, which may have more importance than that it has been already given in clinical practice.

Reliability of the assessment of the oxygen/heart rate relationship during a workday

The purpose of the present study was to evaluate the reliability of the oxygen consumption/heart rate (VO(2)/HR) relationship used to estimate energy expenditure during a workday. Before and after a 6-10 h work shift, the VO(2)/HR relationship was measured in 57 workers (28 female, 29 male) in our laboratory. VO(2) was similar before and after the shift at HR of 100 and 125 beats per minute (bpm). However, the VO(2)/HR relation and perceived exertion (RPE) became less accurate after a work shift as VO(2) and RPE were, respectively, increased at HR above 150 and 125 bpm. Increase of RPE for a same exercise intensity was higher in female subjects. Our results suggest good reliability of the VO(2)/HR relationship at HR usually found in workplaces.

Dobutamine stress echocardiography in women with systemic lupus erythematosus: increased occurrence of left ventricular outflow gradient

Dobutamine stress echocardiography (DSE) is an accurate noninvasive test used for the diagnosis and evaluation of patients with known or suspected coronary artery disease (CAD). The aim of this study was to determine the rate of positive findings in DSE, to define the echocardiographic and clinical characteristics of women with systemic lupus erythematosus (SLE) and to evaluate the safety of DSE in SLE patients. Thirty consecutive SLE patients were enrolled in the study and underwent DSE study. The mean age of patients was 44 years (range 20-76). Mean duration of SLE was 8.1 years and mean SLEDAI was 5.5. None of the DSE tests performed were positive for myocardial ischaemia. A left ventricular outflow gradient (LVOG) was found in 15/28 (54%) patients who completed the test, a result higher than the reported 20% prevalence of this finding in the literature. There were no significant differences in baseline characteristics between patients who developed a gradient and patients in whom a gradient was not found. There were no significant adverse effects during the study. In the general population, LVOG has been reported to be associated with an increased rate of chest discomfort and with a significantly lower prevalence of CAD. Whether this is true for SLE patients requires further study.

Gender-based differences in the prognostic value of coronary calcification

PURPOSE

To investigate the use of electron beam tomography (EBT) screening to predict all-cause mortality in a large cohort of asymptomatic women and men.

METHODS AND RESULTS

We obtained mortality information from the National Death Index in 10377 asymptomatic individuals (40% women) referred by primary care physicians for coronary calcification screening. The average follow-up period was 5 +/- 3.5 years. Univariable and multivariable Cox proportional hazard models were developed to predict all-cause mortality. Women had a lower prevalence of coronary calcification and smaller calcification scores than men (p < 0.0001). Death rates were higher among older, diabetic, hypertensive, and currently smoking individuals both in women and in men. In unadjusted (chi-square = 82, p < 0.0001) as well as risk-adjusted (chi-square = 7, p = 0.007) Cox survival models, women had a greater probability of death than men in each strata of calcification. Relative risk (RR) ratios were increased 3.0-fold, 5.5-fold, and 5.5-fold, respectively, for women compared with men with coronary calcification scores of 101-399, 400-1000, and >1000 (p < 0.0001). Using receiver operating characteristics (ROC) curve analyses to assess coronary calcification added incremental prognostic value to Framingham risk scores (p < 0.0001).

CONCLUSIONS

In this cohort of asymptomatic women, coronary calcification screening provided incremental prognostic information after adjustment for traditional risk factors. EBT may be a useful tool for risk stratification in women, where the early diagnosis of coronary heart disease (CHD) remains a strong challenge.

Hypertensive response to exercise: a potential cause for new wall motion abnormality in the absence of coronary artery disease

OBJECTIVES

We sought to characterize patients with a hypertensive response during exercise echocardiography and its effect on results of the test.

BACKGROUND

A hypertensive response to exercise has been shown to cause false-positive results in perfusion imaging, radionuclide angiography and exercise electrocardiography, but its influence on exercise echocardiography has not been reported.

METHODS

We identified 548 of 6,686 patients who had coronary angiography within four weeks after exercise echocardiography from 1992 through 1996. Echocardiographic results from 132 patients (24%) with a hypertensive response to exercise, defined as systolic blood pressure (SBP) >220 mm Hg for men and SBP >190 mm Hg for women or as an increase in diastolic blood pressure (DBP) >10 mm Hg or DBP >90 mm Hg during exercise echocardiography, were compared with those from 416 patients without a hypertensive response.

RESULTS

Of 132 patients with a hypertensive response to exercise, 108 patients had exercise echocardiographic results positive for ischemia. Of these patients, 24 (22%) were found to have no significant coronary artery disease (CAD). In contrast, of 320 patients with positive exercise echocardiographic results without a hypertensive response, 39 (12%) patients did not have significant CAD. Among the false-positive results, new wall motion abnormalities were extensive in 15 of 24 (63%) hypertensive responders involving >25% of segments compared with 14 of 39 non-hypertensive responders (36%, p = 0.012).

CONCLUSIONS

An excessive rise in blood pressure during exercise is associated with a greater likelihood of new or worsening abnormalities with exercise, which may be observed in the absence of angiographically significant coronary artery stenosis.

Potential use of Ca++ scanning to determine the need for and intensity of lipid-lowering therapy in asymptomatic adults

Deficiencies in traditional cardiovascular risk-factor assessment in asymptomatic individuals have led to the use of electron beam computed tomography (CT) scanning as a screening test for coronary artery disease. This novel approach is based on a secure pathologic foundation: the risk of coronary disease events is proportional to the severity and extent of underlying coronary atherosclerosis, and in middle-aged and elderly adults, calcified plaque is closely related to total plaque. Electron beam CT measures coronary calcium quickly, easily, accurately, and with a high degree of reproducibility. Coronary calcium is three to nine times higher in persons with fatal or nonfatal myocardial infarction than in age-matched controls, and four observational outcomes studies have demonstrated that the electron beam CT-derived coronary calcium score predicts fatal and nonfatal myocardial infarction. In symptomatic persons undergoing cardiac catheterization, electron beam CT is more closely associated with the severity of coronary atherosclerosis than are standard coronary risk factors. Preliminary evidence in asymptomatic persons indicates that the coronary calcium score also predicts coronary disease events more accurately than standard risk factors.

A basic approach to the interpretation of the exercise test

To interpret the exercise test, the following parameters need to be evaluated: the heart rate and blood pressure response, symptoms, dysrhythmias, aerobic capacity, and evidence for myocardial ischemia. When analyzing the ST segment for ischemia, the amount and type of ST depression and the time of onset and resolution are examined. The exercise test results are best used to determine a post-test probability that the patient has significant coronary disease, predict its severity, and provide a prognosis of the patient. The test allows primary care physicians to decide which patients with coronary artery disease can be safely managed medically and which high-risk patients need further evaluation and consideration for revascularization.

Prediction of coronary events with electron beam computed tomography

OBJECTIVES

We sought to determine the prognostic accuracy of electron beam computed tomographic (EBCT) scanning of the coronary arteries at three to four years.

BACKGROUND

Coronary artery calcium scores determined by EBCT correlate with the severity of coronary artery disease. However, previous reports of the prognostic accuracy of EBCT scanning for coronary events in asymptomatic individuals are conflicting.

METHODS

Asymptomatic men and women undergoing coronary EBCT completed initial and follow-up evaluations, which included past medical history, the Rose angina questionnaire and interim cardiovascular events. Reported coronary events (death, nonfatal myocardial infarction [MI] and revascularization procedures) were confirmed without knowledge of the scan results.

RESULTS

Information was obtained in 1,172 (99.6%) of 1,177 eligible subjects (baseline age 53 +/- 11 years, 71% men). During an average follow-up of 3.6 years, 39 subjects sustained coronary events: three coronary deaths, 15 nonfatal MIs and 21 coronary artery revascularization procedures. The mean coronary artery calcium score was 764 +/- 935 among subjects with events as compared with 135 +/- 432 among those without events (p < 0.0001). For the prediction of all coronary events and of nonfatal MIs and deaths, the areas under the receiver-operator characteristics curve were 0.84 and 0.86, respectively, and a coronary calcium score > or =160 was associated with odds ratios of 15.8 and 22.2, respectively. The odds ratios for all events remained high (14.3 to 20.2) after adjustment for self-reported cardiovascular risk factors.

CONCLUSIONS

In asymptomatic adults, EBCT of the coronary arteries predicts coronary death and nonfatal MI and the need for revascularization procedures.

Sympathetic reinnervation of the sinus node and exercise hemodynamics after cardiac transplantation

BACKGROUND

Sympathetic cardiac reinnervation occurs variably after cardiac transplantation (CT) in humans. We hypothesized that sinus node reinnervation would partially restore normal chronotropic response to exercise.

METHODS AND RESULTS

Thirteen recent CT recipients, 28 late CT recipients (> or =1 year after CT), and 20 control subjects were studied. Sinus node sympathetic reinnervation was determined by heart rate (HR) change after tyramine injection into the artery that perfused the sinus node. HR changes of <5 and > or =15 bpm were defined, respectively, as denervation and marked reinnervation. During treadmill exercise, HR, blood pressure, and expired O(2) and CO(2) were measured. All early transplant recipients exhibited features typical of denervation (basal HR, 88+/-2 bpm; peak HR, 132+/-4 bpm, peaking 1.8+/-0.3 minutes after exercise cessation and slowly declining after exercise). A similar pattern was found in the 12 late transplant recipients with persistent sinus node denervation. However, in patients with marked reinnervation, exercise HR rose more (peak HR, 142+/-4 and 141+/-2 bpm), peaked earlier after cessation of exercise (0.7+/-0.4 and 0. 3+/-0.1 minute), and fell more rapidly. Exercise duration and maximal oxygen consumption were not related significantly to reinnervation status, but a trend existed for longer exercise time in markedly reinnervated patients.

CONCLUSIONS

The present studies suggest that sympathetic reinnervation of the sinus node is accompanied by partial restoration of normal HR response to exercise. Both maximal oxygen consumption and exercise duration were markedly shorter in CT patients than in control subjects, and most of the difference was not related to innervation status.

Exercise endpoints in patients with chronic heart failure

BACKGROUND

Peak oxygen consumption (V(O(2))) is a powerful predictor of outcome in patients with chronic heart failure. This is not a test that is readily clinically available. We therefore sought to establish a method of assessing peak V(O(2)) from non-invasively acquired data.

METHODS

We analysed the results from incremental treadmill exercise tests in 60 patients [aged 59.0 (S.D. 12.4) years] with chronic heart failure or left ventricular dysfunction [left ventricular ejection fraction (29.6 (15.2)%)] and 52 control subjects [aged 36.7 (12.3)]. Metabolic gas exchange during exercise was measured with a respiratory mass spectrometer. Heart rate and blood pressure were measured.

RESULTS

Peak V(O(2)) was lower in patients than controls [19.9 (7.7) ml/kg/min vs. 38.3 (9.0), P<0. 001]. Exercise time (r=0.84, P<0.001), heart rate at peak exercise (r=0.63, P<0.0001), change in heart rate (r=0.72, P<0.0001), rate pressure product at peak exercise (r=0.64, P<0.0001) and change in systolic blood pressure (r=0.31, P=0.002) all correlated with peak V(O(2)). In a stepwise regression model, exercise time was the most powerful predictor of peak V(O(2)) (r(2)=0.79). The only additional independent variable was change in heart rate from rest to peak exercise, which increased r(2) to 0.80. In a survival analysis, measured peak V(O(2)) and the peak V(O(2)) estimated from exercise time and change in heart rate had similar predictive power.

CONCLUSIONS

In this preliminary study, peak V(O(2)) can be estimated from non-invasively acquired parameters. Estimated peak V(O(2)) and measured peak V(O(2)) have similar predictive power for outcome. Further work is necessary to see if estimated peak V(O(2)) is widely applicable in a clinical setting.

Is rest or exercise hypertension a cause of a false-positive exercise test?

STUDY OBJECTIVES

To determine if a history of hypertension or an exaggerated rise in exercise systolic BP is associated with a false-positive exercise ECG.

DESIGN, SETTING, AND PATIENTS

Retrospective analysis of the associations between exercise-induced ST-segment depression and a history of hypertension, exercise systolic BP, and several other clinical and exercise test variables. Among 20,097 patients referred for exercise tomographic thallium imaging in a nuclear cardiology laboratory at a tertiary care center, 1,873 patients met inclusion criteria for this study, which included no history of myocardial infarction or coronary artery revascularization, a normal resting ECG, and normal exercise thallium images.

RESULTS

False-positive ST-segment depression occurred in 20% of the population. A history of hypertension was actually associated with a lower likelihood of ST-segment depression (odds ratio, 0.70; 95% confidence interval [CI], 0.55 to 0.89; p = 0. 004). A higher peak exercise systolic BP was associated with a higher likelihood of ST-segment depression (odds ratio, 1.08 for each 10-mm Hg increase in systolic BP; 95% CI, 1.03 to 1.14; p < 0. 001). However, the association between peak exercise systolic BP and ST-segment depression was so weak that this measurement could not be predictive in the individual patient (R(2) = 0.2%). For every 20-mm Hg increase in peak exercise systolic BP, the percentage of patients with ST-segment depression increased by only 3%.

CONCLUSIONS

In patients with normal resting ECGs, we conclude the following: (1) a history of hypertension is not a cause of a false-positive exercise test, and (2) higher exercise systolic BP is a significant but weak predictor of ST-segment depression.

Exercise-induced silent myocardial ischemia and future cardiac events in healthy, sedentary, middle-aged and older men

OBJECTIVES

Before men older than age 45 participate in vigorous exercise programs, the American Heart Association and the American College of Sports Medicine recommend they undergo a screening maximal exercise treadmill test. We examined the predictive value for subsequent cardiac events of exercise-induced silent myocardial ischemia (SI) during the exercise treadmill test in healthy, sedentary, obese, middle-aged and older men recruited for research studies.

DESIGN

A cohort study with 7 years of follow-up.

SETTING

Out-patient research at a tertiary hospital.

PARTICIPANTS

170 healthy, sedentary, obese, middle-aged and older (ages 45-79 years) men with no prior history of coronary artery disease (CAD) recruited for research studies.

MEASUREMENTS

Cardiac risk factors, exercise-induced SI (ST segment depression on the electrocardiogram during a maximal exercise treadmill test), maximal aerobic capacity (VO2max), and 7- year follow-up data on incident CAD.

RESULTS

At baseline, 37 of the men (22%) had exercise-induced SI on their treadmill tests. Seven-year follow-up data was obtained in 97% of the patients. In the interim, 31 men had cardiac endpoints (sudden cardiac death, myocardial infarction, angioplasty, coronary artery bypass graft surgery, angina), and four had noncardiac deaths. Seventeen of the 37 men (46%) with exercise-induced SI on their baseline exercise tests had cardiac endpoints compared with 14 of 133 (11%) men with normal exercise tests (P < .001). Compared with the men with no cardiac endpoints, the men with subsequent cardiac endpoints were older (63 +/- 1 vs 58 +/- 1 years, mean +/- SEM, P < .001) and had a lower maximal aerobic capacity (VO2max) (24 +/- 1 vs 29 +/- 1 mL/kg/min, P < .001). In Cox proportional hazards analysis, exercise-induced SI and a low VO2max were independent predictors of subsequent cardiac endpoints.

CONCLUSION

In a healthy population of obese, sedentary, middle-aged and older men, exercise-induced SI and low VO2max were predictors of incident CAD. This suggests that exercise treadmill testing is beneficial in assessing risk for future cardiac events in obese, sedentary individuals.

The Women's Ischemia Syndrome Evaluation (WISE) study: protocol design, methodology and feasibility report

OBJECTIVES

The Women's Ischemia Syndrome Evaluation (WISE) is a National Heart, Lung and Blood Institute-sponsored, four-center study designed to: 1) optimize symptom evaluation and diagnostic testing for ischemic heart disease; 2) explore mechanisms for symptoms and myocardial ischemia in the absence of epicardial coronary artery stenoses, and 3) evaluate the influence of reproductive hormones on symptoms and diagnostic test response.

BACKGROUND

Accurate diagnosis of ischemic heart disease in women is a major challenge to physicians, and the role reproductive hormones play in this diagnostic uncertainty is unexplored. Moreover, the significance and pathophysiology of ischemia in the absence of significant epicardial coronary stenoses is unknown.

METHODS

The WISE common core data include demographic and clinical data, symptom and psychosocial variables, coronary angiographic and ventriculographic data, brachial artery reactivity testing, resting/ambulatory electrocardiographic monitoring and a variety of blood determinations. Site-specific complementary methods include physiologic and functional cardiovascular assessments of myocardial perfusion and metabolism, ventriculography, endothelial vascular function and coronary angiography. Women are followed for at least 1 year to assess clinical events and symptom status.

RESULTS

In Phase I (1996-1997), a pilot phase, 256 women were studied. These data indicate that the WISE protocol is safe and feasible for identifying symptomatic women with and without significant epicardial coronary artery stenoses.

CONCLUSIONS

The WISE study will define contemporary diagnostic testing to evaluate women with suspected ischemic heart disease. Phase II (1997-1999) is ongoing and will study an additional 680 women, for a total WISE enrollment of 936 women. Phase III (2000) will include patient follow-up, data analysis and a National Institutes of Health WISE workshop.

Exercise tolerance in asymptomatic elderly men with fluoroscopically detected coronary artery calcification

STUDY OBJECTIVE

The value of detecting coronary artery calcification (CAC), by cardiac imaging, for the diagnosis of coronary artery disease (CAD) in asymptomatic middle-aged men has been demonstrated. However, the incidence of CAC increases with age. The functional significance of CAC remains unknown in asymptomatic elderly men. The purpose of this study is to explore whether CAC in asymptomatic aging men signifies the presence of cardiovascular dysfunction during exercise.

DESIGN

This study was designed to address whether elderly asymptomatic men, selected because they have CAC, have reduced exercise tolerance due to functionally significant CAD.

PARTICIPANTS AND SETTING

Thirty-eight asymptomatic male volunteers (ages 50 to 75 years, mean [+/-SD] 64+/-7 years) with a normal resting ECG and at least one coronary risk factor, in a population study. Nineteen subjects had CAC detected by digital subtraction fluoroscopy in at least two major coronary arteries, and 19 subjects had no identifiable CAC.

METHODS AND RESULTS

Each subject underwent a symptom-limited incremental exercise test with 12-lead ECG monitoring and respiratory gas analysis. Four indexes of exercise oxygen transport were evaluated: peak oxygen uptake (VO2), lactic acidosis threshold, peak VO2/heart rate ratio, and VO2 relative to a work rate increase. Eleven of 38 subjects (28%) were found to have reduced oxygen transport, which was defined as an abnormal reduction in more than two of the above four indexes of oxygen transport. Five of the 11 subjects with reduced oxygen transport had CAC, and 6 subjects did not (not significant). Only one subject with CAC had exercise ST depression.

CONCLUSION

Significant CAC in asymptomatic men over age 50 does not signify exercise limitation due to CAD.

Independent prognostic significance of ischemic ST-segment response limited to recovery from treadmill exercise in asymptomatic subjects

BACKGROUND

Although exercise-induced ST depression is an independent predictor of future coronary events in asymptomatic populations, the predictive value of ST depression beginning after exercise cessation is unknown.

METHODS AND RESULTS

We analyzed the treadmill exercise tests of 825 healthy volunteers who were 22 to 89 years of age from the Baltimore Longitudinal Study of Aging. All subjects were free from coronary heart disease by history, physical examination, and resting ECG. From 825 participants, 611 (group 0) had no ischemic ST-segment changes during or after treadmill exercise, while 214 subjects developed > or = 1-mm flat or downsloping ST depression: 151 (group 1) had ST changes starting during exercise, and 63 (group 2) had changes limited to recovery. Groups 1 and 2 were similar in age, sex, smoking status, hypertension prevalence, fasting plasma glucose, and serum cholesterol (CHOL). However, both groups were older and had higher CHOL and prevalence of hypertension than group 0. Treadmill exercise duration, peak oxygen consumption, and maximal heart rate were similar between groups 1 and 2 but were lower than in group 0 (each P < 0.05). During a mean follow-up time of 9 years, 55 subjects developed coronary events (angina pectoris, myocardial infarction, or coronary death): 21 of 611 (3.4%) in group 0, 22 of 151 (14.6%) in group 1, and 12 of 63 (19%) in group 2 (P = 0.001). By survival analysis, the risk of coronary events was similar in groups 1 and 2 but significantly higher than in group 0 (P < 0.0001). Multiple logistic regression showed that age (odds ratio [OR] = 1.07 per year, P = 0.00001), CHOL (OR = 1.02 per 1 mg, P = 0.0001), and presence of ST-segment depression (OR = 2.59, P = 0.007 and OR = 2.38, P = 0.04 for groups 1 and 2, respectively) were independent predictors of events.

CONCLUSIONS

Thus, ischemic ST-segment changes developing during recovery from treadmill exercise in apparently healthy individuals have adverse prognostic significance similar to those appearing during exercise.

Unstable angina: are we able to recognize high-risk patients?

It is difficult to identify characteristics of patients with unstable angina that are predictive of a high likelihood of developing clinical events. However, several features have been recognized. Patients with a clinical history of previous stable exertional angina symptoms who began to experience rest pain appear to be at risk and tend to have more extensively underlying coronary disease. When the ischemic episodes are accompanied by rates, a new or worsening mitral regurgitation murmur, or hypotension, there is a high likelihood of significant coronary artery disease and one should triage these patients to early cardiac catheterization and prompt revascularization. An angiographic feature that carries a high risk is a lesion in the proximal left anterior descending or in the left main coronary artery. Certain typical ECG patterns are very suggestive for a critical narrowing in these coronary arteries. If chest pain and ST-segment changes recur on vigorous medical management, early invasive evaluation should be strongly considered. Even so, the left ventricular function is very important prognostically. According to serologic tests, the level of C-reactive protein and serum amyloid A protein suggesting that there may be active inflammation predicts an early poor outcome. However, these serologic abnormalities do not have much clinical value. An increased platelet activation and a reduced fibrinolytic capacity play a role in the pathogenesis of unstable angina, but thrombolytic therapy does not improve the prognosis in patients with unstable angina.

Impaired heart rate response to graded exercise. Prognostic implications of chronotropic incompetence in the Framingham Heart Study

BACKGROUND

Previous reports have suggested that an attenuated exercise heart rate response may be associated with coronary heart disease risk and with mortality. These observations may parallel the association between reduced heart rate variability during normal activities and adverse outcome. This investigation was designed to look at the prognostic implications of exercise heart rate response in a population-based sample.

METHODS AND RESULTS

In this prospective cohort investigation, 1575 male participants (mean age, 43 years) in the Framingham Offspring Study who were free of coronary heart disease, who were not taking beta-blockers, and who underwent submaximal treadmill exercise testing (Bruce protocol) were studied. Heart rate response was assessed in three ways: (1) failure to achieve 85% of the age-predicted maximum heart rate, which has been the traditional definition of chronotropic incompetence; (2) the actual increase in heart rate from rest to peak exercise; and (3) the ratio of heart rate to metabolic reserve used by stage 2 of exercise ("chronotropic response index"). Proportional hazards analyses were used to evaluate the associations of heart rate responses with all-cause mortality and with coronary heart disease incidence during 7.7 years of follow-up. Failure to achieve target heart rate occurred in 327 (21%) subjects. During follow-up there were 55 deaths (14 caused by coronary heart disease) and 95 cases of incident coronary heart disease. Failure to achieve target heart rate, a smaller increase in heart rate with exercise, and the chronotropic response index were predictive of total mortality and incident coronary heart disease (P <.01). Failure to achieve target heart rate remained predictive of incident coronary heart disease even after adjusting for age, ST-segment response, physical activity, and traditional coronary disease risk factors (adjusted hazard ratio, 1.75; 95% confidence interval, 1.11 to 2.74; P=.02). After adjusting for the same factors, the increase in exercise heart rate remained inversely predictive of total mortality (P=.04) and coronary heart disease incidence (P=.0003). The chronotropic response index also was predictive of total mortality (P=.05) and incident coronary heart disease (P=.001) after adjusting for age and other risk factors.

CONCLUSIONS

An attenuated heart rate response to exercise, a manifestation of chronotropic incompetence, is predictive of increased mortality and coronary heart disease incidence.

Influence of left ventricular hypertrophy on detection of coronary artery disease using exercise echocardiography

OBJECTIVES

This study examined the influence of left ventricular hypertrophy on the accuracy of exercise electrocardiography and echocardiography for detection of coronary artery disease.

BACKGROUND

Electrocardiographic repolarization abnormalities caused by left ventricular hypertrophy compromise the diagnostic accuracy of exercise electrocardiography but not of exercise echocardiography. The relative merits of these investigations are less well defined in patients with hypertrophy but without electrocardiographic (ECG) changes.

METHODS

We prospectively evaluated 147 consecutive patients without prior myocardial infarction undergoing both exercise echocardiography and coronary arteriography. Coronary stenoses > 50% diameter were present in 62 patients (42%). Positive test results were defined by a new or worsening wall motion abnormality or > 0.1 mV of ST depression. Echocardiographic left ventricular hypertrophy (mass > 131 g/m2 in men, > 100 g/m2 in women) was identified in 68 patients. A subgroup with clinically suspected hypertrophy was defined according to the presence of ECG evidence of hypertrophy, hypertension or aortic stenosis.

RESULTS

The overall sensitivity of exercise echocardiography exceeded that of exercise electrocardiography (71% vs. 54%, p = 0.06). Echocardiographic hypertrophy had no significant effect on the sensitivity of either test. The specificity of exercise echocardiography exceeded that of exercise electrocardiography (91 vs. 74%, p = 0.01). In patients with hypertrophy, the specificity of exercise echocardiography exceeded that of exercise electrocardiography (95% vs. 69%, p < 0.01), whereas among patients without hypertrophy, the specificities (respectively, 87% and 78%) were more comparable. The accuracy of exercise echocardiography exceeded that of the exercise ECG in the overall group (82% vs. 65%, p = 0.002) and in patients with hypertrophy (85% vs. 60%, p = 0.004), but this difference was less prominent in patients without hypertrophy (80% vs. 69%, p = NS). In patients with clinically suspected hypertrophy, exercise echocardiography demonstrated a higher sensitivity, specificity and accuracy than exercise electrocardiography. The cost incurred in the identification of coronary disease was least with a strategy involving use of the exercise echocardiogram instead of routine exercise testing in patients with known or clinically suspected left ventricular hypertrophy.

CONCLUSIONS

Exercise echocardiography is more accurate than exercise electrocardiography for the detection of coronary artery disease in patients with known or clinically suspected left ventricular hypertrophy.

Relation between myocardial fractional flow reserve calculated from coronary pressure measurements and exercise-induced myocardial ischemia

BACKGROUND

Myocardial fractional flow reserve (FFRmyo) is a functional index of stenosis severity that can be derived from intracoronary pressure measurements performed during maximal vasodilatation. It is defined as the maximal myocardial perfusion during hyperemia in the presence of a stenosis in the epicardial artery expressed as a fraction of its normal maximal expected value. To determine threshold values of FFRmyo, of hyperemic translesional pressure gradient (delta P(max)), and of resting translesional pressure gradient (delta P(rest)) that are uniformly associated with exercise-induced ischemia, we studied the relation between these pressure-derived indexes and the results of exercise ECG.

METHODS AND RESULTS

We studied 60 patients with an isolated lesion in one major epicardial coronary artery, normal left ventricular function, and no left ventricular hypertrophy. Maximal exercise ECG (off anti-ischemic medication) was performed within 6 hours before catheterization. Intracoronary pressure measurements were taken at rest and during hyperemia with a pressure monitoring guide wire. ST-segment depressions at peak exercise (considered abnormal when > or = 0.1 mV) were compared with FFRmyo, delta P(max), and delta P(rest). Thirty-seven patients had an abnormal and 23 patients a normal exercise ECG. A significant linear correlation was found between the magnitude of ST-segment depressions and both FFRmyo and delta P(max) (r = -.75, SEE = 0.53; r = .71, SEE = 0.56). A weaker correlation was noted between ST-segment depressions and delta P(rest) (r = .53, SEE = 0.67). Sensitivity and specificity curves were constructed for the prediction of an abnormal exercise ECG for the three pressure-derived indexes. The values that most accurately predicted an abnormal exercise ECG were 66% for FFRmyo, 31 mm Hg for delta P(max), and 12 mm Hg for delta P(rest). No patient with a FFRmyo value > 72% showed an abnormal exercise ECG. In addition, receiver operating characteristic curves demonstrated a greater accuracy of FFRmyo and of delta P(max) than of delta P(rest) for predicting the results of the exercise ECG.

CONCLUSIONS

In the present study, cutoff values of FFRmyo and translesional pressure gradients are established from the relation between intracoronary pressure-derived indexes and ECG signs of myocardial ischemia during maximal exercise. These values can be helpful for clinical decision making in cases with dubious angiographic results. Furthermore, our data support the concept that stenosis physiology is better reflected by hyperemic than by basal measurements.

Chronotropic incompetence in chronic heart failure

BACKGROUND

The exercise limitation of patients with chronic heart failure may be due in part to an inability to increase heart rate as normal, a limitation sometimes referred to as chronotropic incompetence. This may be due to down regulation of beta receptors.

METHODS

Fifty-seven patients with chronic heart failure and 14 age-matched controls underwent symptom limited treadmill exercise tests with metabolic gas exchange measurements. Heart rate and blood pressure responses were also recorded.

RESULTS

Peak oxygen consumption was reduced in the heart failure patients (19.6 (S.D. +/- 7.6) vs. 35.0 (+/- 9.9); P < 0.001). Heart rate at peak exercise (r = 0.47, P < 0.001), and change in heart rate from rest to peak exercise (r = 0.59; P < 0.001) and rate pressure product at peak exercise (r = 0.56, P < 0.001) all correlated with peak oxygen consumption. The percentage of predicted maximal heart rate at peak exercise correlated poorly with peak oxygen consumption (r = 0.29; P > 0.05). Peak systolic and diastolic blood pressures did not correlate with peak oxygen consumption. Sixteen patients had chronotropic incompetence. There was no significant difference between this group and those without chronotropic incompetence in the intensity of exercise performed, underlying diagnosis, drug therapy or prevalence of atrial fibrillation. There was a trend towards shorter exercise times in the incompetent group (430 (+/- 251) vs. 545 (+/- 216) s; P = 0.08) compared to the other patients.

CONCLUSIONS

Chronotropic incompetence was seen in < 30% of patients with chronic heart failure. However, there are few differences between the group with chronotropic incompetence and the group without. Chronotropic incompetence is thus unlikely to be a major factor limiting exercise capacity in unselected patients with chronic heart failure and is likely to be the major factor limiting exercise in a much smaller proportion of patients.

Duration and magnitude of ST-segment depression during exercise and recovery: a symmetric relation

The pattern of appearance and disappearance of ST depression on 12-lead electrocardiographic exercise testing in subjects with coronary artery disease (> or = 70% stenosis) and its relation to the severity of disease were prospectively explored in 34 consecutive patients. The first lead to show positivity during exercise also developed maximum ST depression in 73% of patients and was the last lead to lose positivity in recovery (94%). The last lead to show positivity during exercise was first to lose positivity in recovery (92%). Greater ST depression was associated with a greater number of positive leads (p < 0.001; r = 0.7). The duration of ST depression during exercise, maximum ST depression, and recovery time were related (p = 0.001, r = 0.6; p = 0.006, r = 0.5; p < 0.001, r = 0.6, respectively, for the three interactions). However, the correlations of ST depression and recovery time with the severity of vessel disease and with rate-pressure product at initial ST depression were poor, suggesting that the degree of ST-segment depression and recovery time may depend more on the duration and intensity of myocardial ischemia solicited with exercise rather than on the ischemic threshold or on the severity of coronary artery disease.

Limited value of exercise testing in the detection of silent restenosis after successful coronary angioplasty

We studied the diagnostic value of exercise electrocardiographic (ECG) testing in 191 patients who were completely asymptomatic 6 months after a successful percutaneous transluminal coronary angioplasty procedure. With > 70%- and > 50%-diameter stenosis at follow-up as restenosis criteria, the sensitivities of exercise ECG testing were 29% and 21%; the specificities 89% and 91%; the positive predictive values 20% and 52%; the negative predictive values 93% and 70%; the accuracies 83% and 68%; and the risk ratios 2.8 and 1.7, for prevalences of 9% and 33%, respectively. There were no significant differences in the diagnostic value of exercise ECG testing between men and women, patients receiving or not receiving beta-blocking agents, and the presence or absence of pathologic Q waves. Significant differences in systolic blood pressure and the rate-pressure product at peak exercise were found between patients with and without restenosis. For individual patients, however, no practical conclusions can be drawn from these values. In conclusion, the diagnostic value of exercise ECG testing for silent restenosis is low, and supplementation with other techniques seems to be warranted.

Synergistic value of simultaneous stress dobutamine sestamibi single-photon-emission computerized tomography and echocardiography in the detection of coronary artery disease

The relative value of exercise electrocardiography, simultaneous dobutamine technetium 99m-sestamibi (MIBI) single-photon-emission computerized tomography (SPECT), and echocardiography were evaluated for the diagnosis of coronary artery disease in patients with chest pain. Sixty-one consecutive patients underwent exercise electrocardiography and simultaneous graded dobutamine echocardiography and MIBI imaging. All patients underwent coronary arteriography. The exercise electrocardiogram was found to be a poor predictor of coronary artery disease (p not significant). Individually, MIBI SPECT and echocardiography were significantly predictive of coronary artery disease (p < 0.001). According to logistic regression analysis, the combined imaging modalities significantly increased the prediction of coronary artery disease for any vessel (p < 0.001), for multiple vessels (p < 0.001), and for the left anterior descending (p < 0.001), for right coronary artery (p < 0.001), and for left circumflex arteries (p < 0.01), compared with either MIBI SPECT or echocardiography alone. The results suggest a synergism in the detection of coronary artery disease when MIBI SPECT and echocardiography are combined during dobutamine stress.

Comparative ability of dobutamine and exercise stress in inducing myocardial ischaemia in active patients

OBJECTIVE

To compare the ability of dobutamine and exercise stress to induce myocardial ischaemia and perfusion heterogeneity under routine clinical circumstances.

DESIGN

86 active patients without previous myocardial infarction were studied by dobutamine and exercise stress protocols and coronary angiography. During both tests patients underwent electrocardiography, digitised echocardiography, and perfusion scintigraphy using Tc-99m methoxybutylisonitrile (MIBI) single photon emission computed tomography.

MAIN OUTCOME MEASURE

Coronary disease defined as an ST segment depression of > or = 0.1 mV, a resting or stress induced perfusion defect, or a resting or stress induced wall motion abnormality on exercise and dobutamine stress testing.

RESULTS

Dobutamine stress was submaximal in 51 patients because of ingestion of beta adrenoceptor blocking agents on the day of the test (n = 25) or failure to attain the peak dose owing to side effects (n = 28). Exercise was limited in 23 patients by non-cardiac symptoms. The peak heart rate with dobutamine was less than that attained with exercise (105 (25) v 132 (24) beats/min, P < 0.0001); the response to maximal dobutamine stress significantly exceeded that to submaximal stress. Peak blood pressure was greatest with exercise (206 (27) v 173 (25) mm Hg, P < 0.001), values at maximal and submaximal dobutamine stress being comparable. Electrocardiographic evidence of ischaemia was induced less frequently by dobutamine than exercise (32% v 77% of the 56 patients with significant coronary disease, P < 0.01), as was abnormal wall motion (54% v 88%, P < 0.001). Ischaemia was induced more readily with maximal stress of either type; thus the sensitivities of dobutamine and exercise echocardiography were comparable only in patients undergoing a maximal dobutamine testing (73% v 77%, NS). Perfusion heterogeneity was induced in 58% of patients with coronary disease at submaximal dobutamine stress, 73% at maximal dobutamine stress, and 73% at exercise stress (NS). Among 30 patients without coronary stenoses, normal function was obtained in 83% of echocardiography studies with dobutamine and in 80% with exercise (NS). Normal perfusion was identified in 70% of these patients at exercise MIBI, and 68% at dobutamine stress (NS).

CONCLUSIONS

In a group of patients studied under normal clinical circumstances antianginal treatment and inability to complete the stress protocol are frequent and compromise the capacity of dobutamine stress to induce ischaemia. In contrast, the induction of perfusion heterogeneity is less susceptible to submaximal stress.

Concerning falsely negative and falsely positive electrocardiographic responses to exercise

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Heart rate variability from 24-hour electrocardiography and the 2-year risk for sudden death

BACKGROUND

Low heart rate variability has been implicated as a risk factor for sudden death. However, no large epidemiological studies using sudden death as an outcome event have been reported.

METHODS AND RESULTS

A total of 6,693 consecutive patients who underwent 24-hour ambulatory ECG were followed up for 2 years; of these, 245 patients died suddenly. Clinical data at the time of 24-hour ambulatory ECG were collected for all patients who died suddenly and for a random sample of 268 patients from the study cohort. In all patients in sinus rhythm with or without occasional supraventricular arrhythmias at the 24-hour ECG (193 patients who died suddenly and 230 patients from the sample), heart rate variability parameters were derived. Patients with low short-term RR interval variability (mean during 24 hours of per-minute standard deviations [SD] of RR intervals < 25 msec) had a 4.1-fold higher risk (95% confidence interval [CI], 2.6, 8.1) for sudden death than patients with high short-term variability (> or = 40 msec); after adjustment for age, evidence of cardiac dysfunction, and history of myocardial infarction, the relative risk was 2.6 (95% CI, 1.4, 5.1). The crude relative risk of long-term RR interval variability (SD during 24 hours of per-minute means of RR intervals < 8 msec) was 4.4 (95% CI, 2.6, 7.7); after adjustment for the same risk factors, it was 2.2 (95% CI, 1.2, 4.1). Patients with a minimum heart rate > or = 65 beats per minute had a double risk of sudden death compared with those with a minimum heart rate < 65 beats per minute (adjusted relative risk, 2.1; 95% CI, 1.3, 3.6).

CONCLUSIONS

These findings support the theory that patients with low parasympathetic activity (low short-term RR interval variability) have an increased risk for sudden death independent of other risk factors.

Emergency cardiac stress testing in the evaluation of emergency department patients with atypical chest pain

STUDY OBJECTIVES

To determine the feasibility, safety, and reliability of emergency cardiac treadmill exercise stress testing (CTEST) in the evaluation of emergency department patients with atypical chest pain.

DESIGN

Thirty-two patients with atypical chest pain, normal ECGs, and risk factor stratification having low-probability of coronary artery disease were evaluated prospectively using outpatient, emergency CTEST. Study patients were compared with a retrospectively selected sample of admitted patients diagnosed with atypical chest pain who met the study criteria and were evaluated with CTEST as inpatients. All patients had follow-up at three and six months after evaluation.

SETTING

University-affiliated community teaching hospital with 65,000 annual ED visits.

RESULTS

All patients had normal CTEST. No patient had evidence of coronary artery disease, myocardial infarction, or sudden death during the follow-up period. The average length of stay was 5.5 hours for emergency CTEST patients versus two days for inpatients. The average patient charge was $467 for ED evaluation with emergency CTEST versus $2,340 for inpatient evaluation.

CONCLUSION

Emergency CTEST is a safe, efficient, cost-effective, and practical method of evaluating selected ED patients with chest pain. It is a useful aid for clinical decision making and may help to prevent unnecessary hospital admissions.

Early and late exercise testing. Usefulness after percutaneous transluminal coronary angioplasty

Seventy-five patients 36 to 68 years of age were studied after undergoing successful single-vessel percutaneous transluminal coronary angioplasty (PTCA). In all cases exercise tests (ETs) were made prior to the procedure and 2 to 4 days and 6 months thereafter. Angiographic controls were performed on patients with positive ET. Both early and late ET carried out after dilatation lasted significantly longer. Patients were able to tolerate greater work loads and their heart rates and arterial blood pressures also were higher. The ETs conducted prior to PTCA were positive in 62 patients. After dilatation, the early test was positive in 18 and the late test, in 10. Angiographic controls revealed restenosis in 75 percent of patients with single-vessel disease and positive ET. Thus, the results of ETs in patients with single-vessel disease tend to become negative after successful PTCA. Early and late positive ETs are associated with restenosis, while negative ETs indicate a good prognosis.

The importance of assessing time-course behaviour of abnormal ST/T changes after exercise

Routine stress electrocardiography has been criticised for yielding too many so-called 'false-positive' results because ST/T changes that develop during and after exercise are prevalent. Recent studies in our institution indicate, however, that the time-course behaviour patterns of these ST/T configurational 'abnormalities' after exercise are different from those reflecting myocardial ischaemia due to epicardial coronary artery disease (CAD). Time-course analysis increases the predictive value of exercise testing and has dramatically decreased the number of asymptomatic subjects or symptomatic patients at low risk of having CAD being subjected to coronary arteriography in our institution. Our method of assessing post-exercise time course patterns of abnormal ST/T are described in detail. Ischaemic ST/T abnormalities have late onset, early offset or early onset, late offset whereas those ST/T changes associated with normal epicardial coronary arteries have late onset, late offset or early onset, early offset post-exercise time course patterns.

Diagnosis of coronary artery disease using exercise echocardiography and positron emission tomography: comparison and analysis of discrepant results

Both exercise echocardiography and rubidium-82 positron emission tomography are used in the detection and characterization of coronary artery disease. This study compared results of both in 74 patients with known coronary anatomy, by use of exercise echocardiography before and after treadmill exercise and positron emission tomography with intravenous dipyridamole-handgrip stress. Significant (greater than 50%) coronary stenoses were present in 70 patients; exercise echocardiography and positron emission tomography each identified 63 patients (sensitivity 90%). Significant stenoses without previous myocardial infarction were present in 34 patients; 29 (85%) were identified by exercise echocardiography and 28 by positron emission tomography (82%, p = NS). Four patients had no significant coronary disease, and were all identified as normal by both methods. Segments were classified as either normal or showing stress or resting abnormalities, and the diagnoses were compared in the territories of the three major coronary arteries. Results were concordant with respect to the presence or absence of coronary disease in 185 of 222 territories (83%). The remaining 37 regions had abnormalities by exercise echocardiography or positron emission tomography but not both. Stress defects were identified by only one of the tests in 24 areas (in 12 [50%], angiographic findings correlated with positron emission tomography). Resting defects were diagnosed by only one modality in 13 regions (angiographic findings correlated with the results of positron emission tomography in 9 [69%] of these). Both exercise echocardiography and positron emission tomography are sensitive for the identification of coronary artery disease, although on a regional basis, positron emission tomography appears to be more specific for the diagnosis of resting perfusion defects.

Accuracy of ST/heart rate index in the diagnosis of coronary artery disease

The accuracy of ST/heart rate (ST HR) index was evaluated in patients presenting for exercise electrocardiography with suspected coronary disease. In all, 420 patients (235 men and 185 women) with normal electrocardiograms at rest underwent exercise testing, followed within 3 months by coronary angiography. The sensitivity and specificity for standard ST criteria (greater than or equal to 1 mm horizontal or downsloping depression) were 48% (78 of 162) and 81% (208 of 258), respectively. An ST HR-index threshold of 1.86 microV/beta/min had the exact same specificity with a sensitivity of 44% (71 of 162; p = not significant). Consideration of greater than or equal to 1.5 mm upsloping depression had no significant impact on the aforementioned results. Using multivariate logistic regression analysis, age, sex, symptoms, cigarette smoking, diabetes mellitus, qualitative ST slope, rate-pressure product, METs achieved and exercise angina were evaluated with and without ST HR index and ST depression. According to this analysis, age, sex, symptoms and ST slope were good predictors of presence or absence of disease. Neither ST HR index nor ST depression had significance in the multivariate analysis. However, when a separate analysis was performed in men and women, the 2 quantitative ST variables showed significance in men, but not in women. Comparisons of discriminative accuracy using receiver-operating characteristic curves demonstrated differences between men and women, but no difference between ST HR index and ST depression. Therefore, concerning questions of coronary disease diagnosis, consideration of ST HR index was not better than standard ST criteria, and added nothing to multivariate analysis of other available variables.

Assessment of myocardial ischemia by 12-lead electrocardiography and Frank vector system during coronary angioplasty: value of a new orthogonal lead system for quantitative ST segment monitoring

The optimal number and placement of electrocardiographic (ECG) leads to detect myocardial ischemia induced by coronary balloon inflation was assessed by analyzing ST segment changes in the standard 12-lead ECG and Frank X, Y, Z leads at 90-s intervals during 34 consecutive coronary angioplasty procedures. Mean occlusion time during angioplasty was 218 +/- 65 s. Myocardial ischemia, defined as transient angina or ST segment deviation greater than or equal to 1 mm in at least one lead, occurred in 33 (97%) of the 34 procedures. The most sensitive single leads (V2 or V3) detected 17 (51%) of 33 ischemic episodes. The best dual-lead combinations (leads V2 and V5, leads a VF and V3 and leads V3 and Y) increased the sensitivity of 69% (23 of 33). The three-lead combination V2, V5, Y had the highest detecting power (78% [26 of 33]). The X, Y, Z leads by themselves had a sensitivity of only 60% (20 of 33). From this proposed orthogonal lead system (V2, V5, Y), which combines anteroposterior (V2), left to right (V5) and inferosuperior (Y) forces, the spatial ST vector magnitude was calculated and monitored during balloon inflations. A good correlation was observed between this ST vector magnitude and the sum of ST deviations on the standard ECG (r = 0.940, p less than 0.00001), and these data were reproducible over sequential balloon inflations. The results of the study suggest that this orthogonal lead system is of considerable value in the detection and quantification of acute myocardial ischemia and, in this respect, is more useful than the Frank orthogonal vector system.

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.

Effect of the degree of effort on exercise echocardiography for the detection of restenosis after coronary artery angioplasty

To determine whether the accuracy of exercise echocardiography is affected by the degree of effort during exercise, we examined 101 patients who had 6 months earlier undergone successful coronary artery angioplasty, with resting and immediate postexercise echocardiography and same-day coronary angiography. A positive exercise echocardiographic response was defined as the development of a new or worsening wall motion abnormality postexercise, compared with resting wall motion. Significant coronary disease (greater than 50% diameter stenosis) was present in 48 patients, 38 of whom had single-vessel disease and 10 of whom had two-vessel disease. Exercise echocardiography correctly identified 32 patients with significant disease (sensitivity 67%) and 44 patients without significant disease (specificity 83%). The effect of the degree of exercise effort on the sensitivity and specificity of the test was evaluated by three criteria; (1) the percentage of maximum predicted heart rate (MHR), (2) the duration of exercise (DUR), and (3) the double product (DP). To determine the influence of the degree of effort upon sensitivity and specificity, the effort criteria were compared between patients with true positive (TP) tests to those with false negative tests (FN), and in patients with true negative (TN) tests compared with those with false positive (FP) tests. No significant differences were detected in MHR, DUR, or DP between TP versus FN patients or between TN versus FP patients. These results indicate that for symptom-limited exercise echocardiography in postangioplasty patients, neither sensitivity nor specificity is significantly affected by the degree of effort during exercise.

Duration of ST segment depression after exercise-induced myocardial ischemia is influenced by body position during recovery but not by type of exercise

To assess whether the duration of ischemic ST segment depression after exercise can be modified by changes in body position during recovery or with different types of exercise, 18 patients with chronic stable angina, positive exercise test results, and documented coronary artery disease were prospectively studied. Every patient underwent testing with three different exercise protocols: (1) Bruce (Bruce-standing recovery), (2) abrupt onset of exercise (abrupt), and (3) modified Bruce protocol preceded by a 10-minute warm-up period (warm-up). After exercise test patients recovered in a sitting position. In addition, all patients performed a fourth exercise (Bruce protocol), but this time they recovered in the supine position (Bruce-supine recovery). Time and heart rate-blood pressure product at 1 mm ST segment depression were similar for Bruce-standing recovery, abrupt, and Bruce-supine recovery protocols (5.1 +/- 2, 4.4 +/- 2, and 5.2 +/- 2 minutes and 20.8 +/- 4, 21.3 +/- 4, and 20.4 +/- 4 beats/min x mm Hg x 10(-3), respectively. Heart rate and heart rate-blood pressure product at peak exercise did not differ in Bruce-standing recovery, abrupt, and Bruce-supine recovery. Maximal ST segment depression was -2.0, -1.9, and -2.0 mm with Bruce-standing recovery, abrupt, and Bruce-supine recovery exercise, respectively, and -1.5 mm with warm-up exercise (p less than 0.05). Duration of ST segment depression into recovery was significantly prolonged after Bruce-supine recovery exercise (9.4 + 5 minutes) compared with Bruce-standing recovery, abrupt, and warm-up protocols (6.8 + 3, 5.9 + 4, and 5.0 + 3 minutes, respectively; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Accuracy of exercise electrocardiography in detecting physiologically significant coronary arterial lesions

The accuracy of exercise electrocardiography in detecting a physiologically significant coronary artery stenosis has been assessed previously by comparing the exercise test with a coronary arteriogram. The inherent inaccuracy of visually determined percent diameter stenosis measurements might have lead to the conclusion that the exercise electrocardiogram was less accurate than it truly was. To determine the accuracy of the exercise electrocardiography in detecting a physiologically significant coronary stenosis, we studied 40 patients with one-vessel, one-lesion coronary artery disease, a normal resting electrocardiogram, and no hypertrophy or prior infarction. Each patient underwent exercise electrocardiography (Bruce protocol) that was interpreted as abnormal if the ST segment developed 0.1-mV or greater depression 80 msec after the J point. The physiological significance of each coronary stenosis was assessed by measuring of coronary flow reserve (peak divided by resting blood flow velocity) in the stenotic artery using a Doppler catheter and intracoronary papaverine (normal, 3.5 or greater peak/resting velocity). The percent diameter and percent area stenosis produced by each lesion were determined using quantitative angiography (Brown/Dodge method). Of the 17 patients with reduced coronary flow reserve (3.5 or greater peak/resting blood flow velocity) in the stenotic artery, 14 had an abnormal exercise electrocardiogram (sensitivity, 0.82; 95% confidence interval, 0.70-0.94). Conversely, 20 of 23 patients with normal coronary flow reserves had normal exercise tests (specificity, 0.87; 95% confidence interval, 0.77-0.97). The exercise electrocardiogram was abnormal in each of 11 patients with markedly reduced coronary flow reserve (less than 2.5 peak/resting velocity) and in three of six patients with moderately reduced reserve (2.5-3.4 peak/resting velocity). The products of systolic blood pressure and heart rate at peak exercise were significantly correlated with coronary reserve in patients with truly abnormal exercise tests. In comparison, the sensitivity (0.61; 95% confidence interval, 0.46-0.76) and specificity (0.73; 95% confidence interval, 0.60-0.86) of exercise electrocardiography in detecting a 60% or greater diameter stenosis may be significantly lower (p less than 0.05). Exercise electrocardiography, therefore, was a good predictor of the physiological significance (assessed by coronary flow reserve) of a coronary stenosis in patients with a normal resting electrocardiogram and no hypertrophy or prior infarction. Its value in a broader and larger patient population will require further study. These results, however, underscore the importance of a physiological gold standard in assessing the accuracy of noninvasive studies for detecting coronary artery disease.

Assessment of "silent" restenosis and long-term follow-up after successful angioplasty in single vessel coronary artery disease: the value of quantitative exercise electrocardiography and quantitative coronary angiography

Exercise electrocardiographic (ECG) testing during follow-up after coronary angioplasty is widely applied to evaluate the efficacy of angioplasty, even in asymptomatic patients. One hundred forty-one asymptomatic patients without previous myocardial infarction underwent quantitative exercise ECG testing and quantitative coronary angiography 1 to 6 months after successful angioplasty in single vessel coronary artery disease to 1) determine the value of exercise ECG testing to detect "silent" restenosis, and 2) assess the long-term prognostic value of exercise ECG testing and coronary angiography. The prevalence of restenosis (defined as greater than or equal to 50% luminal narrowing at the dilation site) was 12% in this selected study group. Of 26 patients with an abnormal exercise ECG (ST segment depression greater than or equal to 0.1 mV), only 4 (15%) showed recurrence of stenosis. Sensitivity and specificity for detection of restenosis were 24% and 82%, respectively. One hundred thirty-four patients (95%) were followed up 1 to 64 months (mean 35) after exercise ECG testing and coronary angiography. Thirty-two patients (24%) experienced a cardiac event: in 25 patients (78%) the initial event was recurrent angina pectoris (New York Heart Association class III or IV) and in 7 patients (22%) it was myocardial infarction, although cardiac death did not occur. The mean interval between exercise ECG testing and the initial cardiac events was 14 months (range 1 to 55), whereas 47% of the initial events took place less than or equal to 6 months after exercise ECG testing.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic utility of predischarge dipyridamole-thallium imaging compared to predischarge submaximal exercise electrocardiography and maximal exercise thallium imaging after uncomplicated acute myocardial infarction

The prognostic value of predischarge dipyridamole-thallium scanning after uncomplicated myocardial infarction was determined by comparison with submaximal exercise electrocardiography and 6-week maximal exercise thallium imaging and by correlation with clinical events. Two endpoints were defined: cardiac events and severe ischemic potential. Of the 40 patients studied, 8 had cardiac events within 6 months (1 died, 3 had myocardial infarction and 4 had unstable angina requiring hospitalization). The finding of any redistribution on dipyridamole-thallium scanning was common (77%) in these patients and had poor specificity (29%). Redistribution outside of the infarct zone, however, had equivalent sensitivity (63%) and better specificity (75%) for events (p less than 0.05). Both predischarge dipyridamole-thallium and submaximal exercise electrocardiography identified 5 of the 8 events (p = 0.04 and 0.07, respectively). The negative predictive accuracy for events for both dipyridamole-thallium and submaximal exercise electrocardiography was 88%. In addition to the 8 patients with events, 16 other patients had severe ischemic potential (6 had coronary bypass surgery, 1 had inoperable 3-vessel disease and 9 had markedly abnormal 6-week maximal exercise tests). Predischarge dipyridamole-thallium and submaximal exercise testing also identified 8 and 7 of these 16 patients with severe ischemic potential, respectively. Six of the 8 cardiac events occurred before 6-week follow-up. A maximal exercise thallium test at 6 weeks identified 1 of the 2 additional events within 6 months correctly. Thallium redistribution after dipyridamole in coronary territories outside the infarct zone is a sensitive and specific predictor of subsequent cardiac events and identifies patients with severe ischemic potential.(ABSTRACT TRUNCATED AT 250 WORDS)

How to detect silent myocardial ischemia

Anginal pain alone is not a sensitive marker of ischemia. In one study of 2,014 completely asymptomatic men, 2.5% were found to have silent ischemia when they underwent treadmill exercise testing. Another method of detection, ambulatory electrocardiographic monitoring, can be used in patients who cannot exercise or may be used to clarify results of exercise testing. Many investigators believe that the two tests provide complementary information on the patient's response to high demand and to daily-living activities. Other methods for determining necessary treatment and prognosis include dipyridamole with thallium perfusion scanning, nuclear exercise testing, coronary angiography, and catheterization. The cost, required frequency of retesting, and incidence of false results should be considered before screening is started.

Long term survival of class IV heart failure patients treated with oral amrinone

The purpose of this study was to evaluate the effect of amrinone on the survival of a group of 51 Class IV congestive heart failure patients as well as changes in exercise capacity, hemodynamics, and clinical status. In those 22 patients able to exercise before treatment with amrinone, exercise duration increased from 4.15 minutes to 6.58 minutes on the treadmill. In those 19 patients first treated with intravenous amrinone, there was an increase in cardiac index from 1.9 to 2.6 L/min/m2. Thirty seven patients (72%) died in the follow-up period, most in the first four months. In this group of Class IV heart failure patients, there were two subsets of patients: one with a stable course (Group I) and one with a malignant course (Group II). The Group II patients accounted for much of the mortality in the follow-up. Patients with coronary artery disease did worse than patients with idiopathic dilated cardiomyopathies. There was no evidence that amrinone shortened or prolonged the survival of these Class IV patients.