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Biomedical subjects

V F Froelicher

Publications and source records attributed to V F Froelicher.

At least 19 recordsLinked to original sources
PubMed1992

Usefulness of exercise-induced ST-segment depression in the inferior leads during exercise testing as a marker for coronary artery disease.

Multiple lead systems are shown to have a higher sensitivity than that of single leads for detecting coronary artery disease (CAD) during exercise testing, but the value of ST-segment depression isolated to the inferior leads is questionable. To ascertain the diagnostic accuracy of inferior limb lead II compared with that of precordial lead V5, a retrospective analysis of 173 men was performed (108 in a training population and 65 in a validation cohort). All patients had a standard exercise test and underwent diagnostic coronary angiography within 15 days of the exercise test (range 1 to 65). Sixty-three patients had greater than or equal to 1 coronary stenoses greater than or equal to 70%, or left main lesion greater than or equal to 50%, whereas 45 patients in the training population did not. Exclusion criteria were female sex, left ventricular hypertrophy, left bundle branch block or resting ST-segment depression on the baseline electrocardiogram, previous myocardial infarction or revascularization procedures, and any significant valvular or congenital heart disease. Lead V5 had a better combination of sensitivity (65%) and specificity (84%) (chi-square = 24.11; p less than 0.001) than that of lead II (sensitivity 71%, specificity 44%) (chi-square = 2.25; p = 0.13) at a single cut point, and this improved specificity was substantial (95% confidence interval for observed difference 22 to 58%). Receiver-operating characteristic curve analysis also revealed that lead V5 (area = 0.759) was markedly superior to lead II (area = 0.582) over multiple cut points (z = 3.032; 2p = 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Impact of left ventricular hypertrophy on blood pressure responses to exercise.

It is claimed that exaggerated blood pressure (BP) responses to exercise are predictive of future hypertension and may also be indicative of left ventricular (LV) hypertrophy. The relation between LV hypertrophy and maximal exercise BP was examined in 35 normal male volunteers and 65 untreated hypertensive male patients. Multiple stepwise regression analysis revealed that preexercise systolic BP was the major determinant of maximal exercise systolic BP (r = 0.52; p less than or equal to 0.0001), indicating that higher baseline BP predicted higher exercise BP. However, hypertensive patients with LV hypertrophy had the smallest increases in systolic BP with exercise. Accordingly, there was an inverse relation between LV muscle mass and systolic BP responses to exercise in these patients (r = -0.34; p = 0.005). When compared with normotensive subjects, hypertensive patients had lower measures of maximal oxygen uptake and exercise heart rates (p = 0.01). This may indicate lower cardiac performance at maximal exercise and explain the reduced capacity of hypertensive patients with LV hypertrophy to increase systolic BP with exercise. Neither baseline nor exercise BPs correlated with LV mass; instead, the model of regression analysis indicated that body weight was the principal determinant of LV mass. Contrary to previous reports, exaggerated exercise BPs were not associated with LV hypertrophy in hypertensive or normotensive patients.

Adult↗
PubMed1992

Ventilatory mechanisms of exercise intolerance in chronic heart failure.

Mechanisms that have been suggested to underlie the abnormal ventilatory response to exercise in patients with chronic congestive heart failure (CHF) include high pulmonary pressures, ventilation-perfusion mismatching, early metabolic acidosis, and abnormal respiratory control. To evaluate the role that ventilation and gas exchange play in limiting exercise capacity in patients with CHF, data from 33 patients with CHF and 34 normal subjects of similar age who underwent maximal exercise testing were analyzed. Maximal oxygen uptake was higher among normal subjects (31.7 +/- 6 ml/kg/min) than among patients with CHF (17.7 +/- 4 ml/kg/min; p less than 0.001). The ventilatory equivalent for oxygen, expressed as a percentage of maximal oxygen uptake, was 25% to 35% higher among patients with CHF compared with normal subjects throughout exercise (p less than 0.01). A steeper component effect of ventilation on maximal oxygen uptake was observed among normal subjects compared with patients with CHF, which suggests that a significant portion of ventilation in CHF is wasted. Maximal oxygen uptake was inversely related to the ratio of maximal estimated ventilatory dead space to maximal tidal volume (VD/VT) in both groups (r = -0.73, p less than 0.001). Any given oxygen uptake at high levels of exercise among patients with CHF was accompanied by a higher VD/VT, lower tidal volume, and higher respiratory rate compared with normal subjects (p less than 0.01). Relative hyperventilation in patients with CHF started at the beginning of exercise and was observed both below and above the ventilatory threshold, which suggests that the excess ventilation was not directly related to earlier than normal metabolic acidosis. Thus abnormal ventilatory mechanisms contribute to exercise intolerance in CHF, and excess ventilation is associated with both a higher physiologic dead space and an abnormal breathing pattern. The high dead space is most likely due to ventilation-perfusion mismatching in the lungs, which is related to poor cardiac output, and the abnormal breathing pattern appears to be an effort to reduce the elevated work of breathing that is caused by high pulmonary pressures and poor lung compliance.

Adult↗
PubMed1992

Prediction of severe coronary artery disease using computerized ECG measurements and discriminant function analysis.

This study tested the hypothesis that discriminant function analysis of clinical and exercise-test variables including computerized ST measurements could improve the prediction of severe coronary artery disease. Secondary objectives were to demonstrate the effect of digoxin and/or resting electrocardiographic (ECG) abnormalities, and to evaluate the relative importance of ST measurements made during the recovery phase and in the three lead group areas. The design was a retrospective analysis of data collected during exercise testing and coronary angiography. The ECG data were gathered and stored in digital format on optical discs and all ST measurements were made off-line using the authors' own software. Univariate and multivariate analytic methods were used to analyze all pretest characteristics as well as hemodynamic and computerized ECG responses to exercise. A 1,000-bed Veterans Affairs Medical Center served as the setting. The study included 446 male veterans who underwent a sign or symptom limited treadmill exercise test and coronary angiography. Analysis was also performed on a subset of this population formed by excluding patients receiving digoxin or with resting ECGs exhibiting left ventricular hypertrophy or ST depression (n = 328). In the total study population, the authors derived a treadmill score using discriminant function analysis. This score included: (1) the time-slope area in lead V5 during recovery; (2) delta heart rate; (3) angina pectoris during the exercise test; and (4) presence of diagnostic Q waves on the resting ECG. This score was effective in predicting triple vessel/left main disease and outperformed exercise-induced ST depression for predicting severe coronary artery disease. After exclusion of patients with ECGs exhibiting left ventricular hypertrophy or resting ST depression and patients receiving digoxin, discriminant function analysis chose: (1) the time-slope area in lead V5 during recovery and (2) delta heart rate. Exclusion of these patients resulted in a nonsignificant decrease in specificity of all ST criteria. ST-segment amplitude or slope in lead V5 at 3.5 minutes in recovery clearly outperformed the maximal exercise measurements in both groups. Summing the depressions or selecting the most depression in the three areas (ie, lateral-V5, inferior-II, anterior-V2) did not improve test performance. Leads other than V5 did not contain significant diagnostic information. A quantitative approach to exercise testing using discriminant function analysis enhanced the tests' performance for predicting severe coronary disease. The inclusion of patients taking digoxin or with resting ECG abnormalities nonsignificantly decreases the specificity of all ST criteria.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

Angiographic patterns and severe coronary artery disease. Exercise test correlates.

In a Veterans Affairs Medical Center, we studied 607 male patients to determine whether patterns and severity of coronary artery disease could be predicted by means of standard clinical and exercise test data. We found significant differences in clinical, hemodynamic, and electrocardiographic measurements among patients with progressively increasing disease severity determined by angiography. Left main disease produced responses significantly different from those of three-vessel disease only when accompanied by a 70% or greater narrowing of the right coronary artery. Discriminant function analysis revealed that the maximum amount of horizontal or downsloping ST depression in exercise and/or recovery was the most powerful predictor of disease severity, with 2-mm ST depression yielding a sensitivity of 55% and a specificity of 80% for prediction of severe coronary artery disease (three-vessel disease plus left main disease). Patients with increasingly severe disease also demonstrated a greater frequency of abnormal hemodynamic responses to exercise.

Chi-Square Distribution↗
PubMed1992

Individualized ramp treadmill. Observations on a new protocol.

The many different approaches to exercise testing have hindered the consistent interpretation of hemodynamic, electrocardiographic, and ventilatory gas exchange responses. One of the most influential approaches is the choice of the exercise protocol. Recent data suggest that the protocol can have an important impact on test sensitivity, the reason for test termination, the ST/HR slope calculation, the interpretation of gas exchange responses, and the accuracy with which oxygen uptake is predicted from work rate. Recent recommendations for optimizing the test have focused on the test duration, reducing the increments in work rate, and individualizing the test relative to the purpose of the test and the subject tested. We describe a treadmill test which considers these recommendations for optimizing exercise testing.

Adult↗
PubMed1991

Hemodynamic determinants of exercise capacity in chronic heart failure.

PURPOSE: To synthesize information on hemodynamic determinants of exercise capacity in patients with chronic heart failure. DATA IDENTIFICATION: Relevant studies published from the mid-1960s to the present were identified by a manual search of the English-language literature and by bibliographic review of pertinent articles. STUDY SELECTION: Both controlled and observational studies that reported measures of either exercise time or oxygen uptake and hemodynamic variables in patients with heart failure were reviewed for quality and included when relevant to the discussion. DATA EXTRACTION: Key conclusions or data, or both, were extracted from each article and described. DATA SYNTHESIS: Exercise intolerance is a hallmark of chronic congestive heart failure. Studies have emphasized central factors and indices of systolic ventricular function, but poor relations have been consistently found between these measurements and exercise capacity. Recent data suggest that diastolic function (that is, ventricular filling and compliance) is an important factor affecting the ability to increase cardiac output and determining exercise capacity, but this issue needs further study. A clearer picture of histologic and biochemical abnormalities in skeletal muscle has recently emerged; patients with heart failure show greater glycolysis, reduced oxidative phosphorylation, and reduced oxidative enzyme activity. Vasodilatory abnormalities in heart failure were first described more than 20 years ago, and such abnormalities may underlie recently reported reductions in skeletal muscle blood flow during exercise. Relative hyperventilation is commonly observed during exercise in patients with heart failure and is related to ventilation-perfusion mismatching in the lung due to a higher-than-normal fraction of physiologic dead space. Neurohumoral abnormalities include reductions in beta-receptor density and sensitivity and contribute to reduced inotropic and chronotropic responses to exercise. CONCLUSIONS: Systolic function and exercise capacity are unrelated in patients with chronic heart failure, but many hemodynamic abnormalities (including those in the heart, lung, and skeletal muscle) overlap, which leads to exercise intolerance in these patients.

Heart Failure↗
PubMed1991

Correlation between resting ST segment depression, exercise testing, coronary angiography, and long-term prognosis.

Resting ST segment depression has been identified as a marker for adverse cardiac events in patients with and without known coronary artery disease. To correlate this with exercise testing, coronary angiography, and how it impacts on long-term prognosis, a retrospective study was performed on 476 patients, of whom 223 had no clinical or electrocardiographic evidence of prior myocardial infarction while 253 were survivors of an infarction. All patients performed a standard exercise test and underwent diagnostic coronary angiography within an average of 32 days of their exercise test (range 0 to 90 days). Exclusions were women, those with left bundle branch block, left ventricular hypertrophy, use of digoxin, previous revascularization procedures, or significant valvular or congenital heart disease. Long-term follow-up was carried out for an average of 45 months (+/- 17). Of the patients without prior infarction, 23 (10%) had persistent resting ST segment depression, and of those with a prior history of infarction, 37 (15%) also had resting ST segment depression. Patients with resting ST segment depression and no prior myocardial infarction had a higher prevalence of severe coronary disease (three-vessel and/or left main) (30%) than those without resting ST segment depression (16%) (95% confidence interval [CI] for observed difference -5.0% to 33.9%, p = 0.12). The criterion of greater than or equal to 2 mm of additional exercise-induced ST segment depression was a particularly useful marker in these patients for the diagnosis of any coronary disease (likelihood ratio 3.35, 95% CI 0.56 to 19.93, p = 0.06). Patients with resting ST segment depression and a prior myocardial infarction had a 2.5 times higher prevalence of severe coronary artery disease compared with patients without resting ST segment depression (43% versus 17% prevalence, respectively, 95% CI for observed difference 9.38% to 42.8%, p less than 0.001) and also had larger left ventricles postinfarction (left ventricular end-diastolic volume index 102 ml/m2 compared with 96 ml/m2, p less than 0.001).(ABSTRACT TRUNCATED AT 400 WORDS)

Coronary Angiography↗
PubMed1991

Effect of beta-blockade on the interpretation of the exercise ECG: ST level versus delta ST/HR index.

The diagnostic value of exercise-induced ST segment depression is considered to be decreased in patients receiving beta-blockers. One approach to improving predictive accuracy has been to use the ratio of maximal change in exercise-induced ST segment depression to the corresponding maximal change in heart rate (delta ST/HR index). The present study compared these two ECG methods. The records of exercise tests performed on 3047 male veterans were screened to exclude patients with prior revascularization procedures or myocardial infarction, those receiving digoxin, and those with certain resting ECG abnormalities; the use of beta-blocker drugs at the time of testing was also noted. All exercise tests were sign/symptom limited. Significant angiographic coronary disease was defined as greater than or equal to 75% reduction in luminal diameter of at least one coronary artery. Disease severity was evaluated in an expanded study group that included patients with prior myocardial infarction. Mean maximal heart rate was 21 beats.min-1 lower for those receiving beta-blockers (p less than 0.05), but there was no difference in mean metabolic equivalent (MET) level achieved. The diagnostic accuracy of an abnormal test result for determination of the presence or absence of coronary artery disease was not significantly different in the subgroup taking beta-blockers versus the subgroup not taking beta-blockers (N = 200), and use of the delta ST/HR index did not improve test performance. For discrimination of severe disease, test accuracy was also unaffected by beta-blockers and was not improved by the delta ST/HR index (N = 454).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1991

The prognostic value of exercise capacity: a review of the literature.

While there is still much debate in the literature regarding the specific MET levels at which there are differences in survival, the following points have become clear with the growing body of reports in the literature. Exercise capacity seems to be an independent predictor of mortality, and when it is combined with other clinical, exercise, or angiographic data, it becomes very powerful in this regard. This relates to both overall mortality and to that from cardiovascular disease. There is still a need for the establishment of mortality data related to MET levels adjusted for age and activity status. A low exercise capacity of less than 6 METs indicates a higher mortality group, probably regardless of the underlying extent of coronary disease or left ventricular function. Analysis of the CASS data has indicated that these patients benefit from coronary artery bypass surgery with respect to survival. An exercise capacity of greater than 10 METs designates an excellent survival group, again despite the extent of coronary artery disease or left ventricular function. If 10 METs truly exerts a "protective effect" that obviates any survival benefit from coronary artery bypass surgery, this has enormous implications for cost containment and medical care. It is nonetheless important to remember that this level of exercise capacity does not imply the absence of either coronary disease or triple-vessel coronary disease. Exercise capacity is related to more than just cardiovascular fitness and integrity. It is dependent upon a combination of other physiologic components as well, including pulmonary function, health status of other organ systems, nitrogen balance, nutritional status, medications, orthopedic limitations, and others.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular Diseases↗
PubMed1991

The ventilatory threshold: method, protocol, and evaluator agreement.

To evaluate the effects of different methods of detection, exercise modes, protocols, and reviewers on oxygen uptake (VO2) at the ventilatory threshold (ATge), 17 men with heart disease (mean age 59 +/- 6 years) and six healthy men (mean age 60 +/- 11 years) underwent six exercise tests on different days. Each subject performed three treadmill tests (Bruce, Balke, and ramp) and three bicycle ergometer tests (50 W/stage, 25 W/stage, and ramp) in random order. The ventilatory threshold was determined for each of the six exercise tests by three independent, blinded reviewers by means of graphic plots of three commonly used methods of determination: (1) changes in the ventilatory equivalents for VO2 and VCO2, (2) changes in end-tidal oxygen and carbon dioxide pressures, and (3) the intersection of the slope of VCO2 and VO2 (V slope). The largest variability in the ATge was observed with changes in the exercise protocol. The greatest absolute (ml/min) and percentage differences in oxygen uptake at the ATge as a result of changes in protocol, method of determination, and observers were 336 (36%), 125 (12%), and 70 (7%), respectively. The overall intraclass correlation coefficient for VO2 at the ATge among the three reviewers was 0.60 and among the three protocols was 0.85 (p less than 0.01). The V slope method of detection had consistently good agreement among reviewers and was least affected by the protocol. The variance in the ATge (excluding intersubject and error variance) accounted for by differences in protocol, method, and reviewer was 82%, 14%, and 4%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaerobic Threshold↗
PubMed1991

Post-myocardial infarction exercise testing. Non-Q wave versus Q wave correlation with coronary angiography and long-term prognosis.

BACKGROUND: The presence or absence of baseline diagnostic Q waves has been believed to compromise the accuracy of standard exercise electrocardiography in identifying severe coronary artery disease (three-vessel and/or left main disease); therefore, a retrospective analysis was performed using a personal computer data base of exercise test responses and cardiac catheterization results to evaluate this premise, and follow-up was performed to observe how Q waves and/or severe coronary disease impacted on survival. METHODS AND RESULTS: Two hundred fifty-three male patients who had survived a myocardial infarction were studied. Patients on digitalis, those with left bundle branch block or left ventricular hypertrophy on their baseline electrocardiogram, those with previous revascularization procedures, and those with significant valvular or congenital heart disease were excluded. All patients performed either a low-level predischarge or a sign/symptom limited exercise test and underwent diagnostic coronary angiography within 32 days of each test (range, 0-90 days). Long-term follow-up on patients was performed for an average of 45 months (+/- 17 months). Group NQMI comprised 103 post-myocardial infarction patients lacking Q waves at the time of exercise testing and group QMI comprised 150 patients who developed Q waves with their myocardial infarction. The cut points of greater than or equal to 1 mm (chi 2 = 14.39, p less than 0.001) and greater than or equal to 2 mm (chi 2 = 26.11, p less than 0.001) of exercise-induced ST segment depression were reliable markers of severe coronary disease in Q wave infarct survivors. This was also true for non-Q wave infarct survivors as greater than or equal to 1 mm (chi 2 = 6.02, p = 0.01) and greater than or equal to 2 mm (chi 2 = 4.37, p = 0.04) of ST segment depression were reliable markers of severe coronary disease. Receiver operating characteristic curve analysis revealed that exercise-induced ST segment depression had discriminating power for the identification of severe coronary artery disease in both the Q wave myocardial infarction patients (area = 0.735, z = 4.47, p less than 0.001) and the non-Q wave infarct patients (area = 0.700, z = 3.20, p less than 0.001). After 4.4 years of cumulative follow-up, patients with severe coronary disease had an infarct-free survival rate of 72% (95%, CI, 50.0-86.0%), whereas those without severe disease had an 86% (95% CI, 76.5-91.5%) infarct-free survival rate (Cox chi 2 = 4.00, p = 0.045). Non-Q wave patients had an infarct-free survival rate of 81% (95% CI, 66.0-89.5%), whereas those with Q waves had an infarct-free survival rate of 85% (95% CI, 73.9-91.3%) (Cox chi 2 = 0.0005, p = NS). CONCLUSIONS: The presence or absence of diagnostic Q waves has no significant effect on the ability of the exercise electrocardiogram to identify severe coronary artery disease in survivors of myocardial infarction. Long-term infarct-free survival of patients with myocardial infarction is more related to the presence of severe coronary disease rather than if they suffered a non-Q wave or Q wave infarction.

Coronary Angiography↗
PubMed1991

Cardiovascular benefits of physical activity.

Animal studies have consistently shown increased heart strength, size, and vascularity in wild animals compared to domestic animals. While exercise has not been shown to decrease atherosclerosis in either animals or humans, it has been theorized that exercise makes the heart more resistant to ischemia through stimulation of collateral vessel formation and enlargement of already existent coronary arteries. In humans, the benefits and dangers of exercise have been researched with morphological, hemodynamic, and epidemiological studies. Many of these are discussed here as well as the national fitness recommendations made by various health organizations. A summary of the cardiovascular benefits of exercise as supported by the literature is then presented.

Animals↗
PubMed1979

Profiles of radionuclide left ventricular ejection fraction changes induced by supine bicycle exercise in normals and patients with coronary heart disease.

This paper presents the profiles of left ventricular ejection fraction (EF) during and following supine bicycle exercise in normal subjects and in patients with coronary heart disease, as well as the relationship of the described patterns to clinical parameters. Twenty normal men and 40 patients with coronary artery disease were studied using gated equilibrium radionuclide angiography (EQ-EF). In the normals, during exercise, EF increased by a mean of 25% of the resting value, with an increase of no less than 11%. The exercise-limiting symptom in patients with coronary artery disease was angina pectoris in 20 and fatique in the other 20 patients. In the angina patients, there was a mean decrease in EF of 20%, and in the other coronary artery disease patients ejection fraction change little. Only two patients with coronary artery disease increased from a normal resting value to peak exercise by more than 11%, and they had isolated right coronary lesions. An "overshoot" elevation of ejection fraction above resting levels was demonstrated following termination of exercise in most patients. The patients with a significant fall in exercise ejection fraction more frequently had abnormal exercise-induced ECG changes as well as abnormal left ventriculograms and more severe coronary artery disease at cardiac catheterization than the patients with little change in ejection fraction. We conclude that 1) normals could be separated from most patients with significant coronary artery disease in this study population; 2) ejection fraction must be measured at maximal exercise for it to have diagnostic value, since there could be normal rise before and after peak exercise and an abnormal response missed; and 3) the ejection fraction response to exercise reflects the severity of the underlying coronary artery disease. The described patterns of exercise-induced changes in left ventricular ejection fraction are important to consider when using this new technique to diagnose and evaluate patients with coronary artery disease.

Adult↗
PubMed1979

Normal electrocardiographic waveform characteristics during treadmill exercise testing.

Forty asymptomatic male patients at low risk for cardiovascular disease completed maximal treadmill testing. Electrocardiograms from leads CC5, CM5, V5, Yh and Z were recorded across multiple pretest, exercise and recovery conditions. ECG waveforms were subsequently digitized, averaged and processed to provide Q-, R-, S- and T-wave amplitudes, ST-segment means and slopes, and QS- and RT-interval durations. Average R-wave amplitude increased during early exercise and then dramatically decreased to maximum effort. Average S-wave amplitude became greater as exercise progressed. Average J junction was slightly positive before exercise, became negative during exercise (except lead Z) and returned to zero after exercise. The ST-segment slope increased dramatically with progressive exercise. The response of T-wave amplitude, RT and QS intervals are also described. Separately, 22 asymptomatic male subjects each completed two maximal treadmill tests 2 weeks apart. ECG data acquisition and processing were similar to those noted above. Pooled, within-subject estimates of variability were computed for the ECG leads, ECG measurements and protocol conditions. These variability estimates are useful for interpreting ECG responses to exercise testing.

Adult↗