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Biomedical subjects

V Froelicher

Publications and source records attributed to V Froelicher.

At least 19 recordsLinked to original sources
PubMed2001

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

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

Adult↗
PubMed2001

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

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

Arrhythmias, Cardiac↗
PubMed2001

Validation of a specific activity questionnaire to estimate exercise tolerance in patients referred for exercise testing.

BACKGROUND: Physical activity and symptom questionnaires have been used as surrogates for exercise testing to estimate a patient's functional capacity and to individualize an exercise testing protocol in accordance with exercise testing guidelines. To validate these approaches, they must be compared with measured oxygen uptake (peak VO (2)). METHODS: Before exercise testing was performed, a brief, self-administered questionnaire (Veterans Specific Activity Questionnaire [VSAQ]) was given to 337 patients referred for exercise testing for clinical reasons. The VSAQ was used to estimate exercise tolerance on the basis of symptoms during daily activities to individualize ramp rates on the treadmill so that the test duration would be approximately 10 minutes. Clinical and demographic variables were added to the VSAQ responses in a stepwise regression model to determine their ability to predict both directly measured peak VO (2) and peak metabolic equivalents (METs) predicted from the treadmill workload. RESULTS: The mean exercise time was 9.6 +/- 3 minutes. Responses to the VSAQ and age were the strongest predictors of both measured and predicted exercise capacity. Small but significant contributions to the explanation of variance in both measured and estimated METs were made by resting heart rate, forced expiratory volume in 1 second expressed as a percentage of normal, exercise capacity predicted for age, and body mass index. The multiple R values from the regression equations for measured and estimated METs were 0.58 and 0.72, respectively. CONCLUSIONS: Estimating a patient's symptoms associated with daily activities along with age are the strongest predictors of a patient's exercise tolerance. The VSAQ, combined with pretest clinical data, predicts the estimated MET value from treadmill speed and grade better than directly measured METs do. When used for estimating a patient's symptom limits to individualize ramp rates on a treadmill, this approach yields an appropriate test duration in accordance with recent exercise testing guidelines.

Activities of Daily Living↗
PubMed2001

Assessing patients with possible heart disease using scores.

Multivariable analysis of clinical and exercise test data has the potential to become a useful tool for assisting in the diagnosis of coronary artery disease, assessing prognosis, and reducing the cost of evaluating patients with suspected coronary disease. Since general practitioners are functioning as gatekeepers and decide which patients must be referred to the cardiologist, they need to use the basic tools they have available (i.e. history, physical examination and the exercise test), in an optimal fashion. Scores derived from multivariable statistical techniques considering clinical and exercise data have demonstrated superior discriminating power compared with simple classification of the ST response. In addition, by stratifying patients as to probability of disease and prognosis, they provide a management strategy. While computers, as part of information management systems, can run complicated equations and derive these scores, physicians are reluctant to trust them. Thus, these scores have been represented as nomograms or simple additive tables so physicians are comfortable with their application. Their results have also been compared with physician judgment and found to estimate the presence of coronary disease and prognosis as well as expert cardiologists and often better than nonspecialists. However, the discriminating power of specific variables from the medical history and exercise test remains unclear because of inadequate study design and differences in study populations. Should expired gases be substituted for estimated metabolic equivalents (METs)? Should ST/heart rate (HR) index be used instead of putting these measurements separately into the models? Should right-sided chest leads and HR in recovery be considered? There is a need for further evaluation of these routinely obtained variables to improve the accuracy of prediction algorithms especially in women. The portability and reliability of these equations must be demonstrated since access to specialised care must be safe-guarded. Hopefully, sequential assessment of the clinical and exercise test data and application of the newer generation of multivariable equations can empower the clinician to assure the cardiac patient access to appropriate and cost-effective cardiological care.

Adult↗
PubMed2000

Exercise testing in clinical medicine.

Exercise-induced changes in the electrocardiogram have been used to identify coronary artery disease for almost a century. Over the past decade, however, clinicians have increasingly focused on more expensive diagnostic tools believing them to offer improved diagnostic accuracy. In fact, by incorporating historical data, the simple exercise test can in most cases outperform the newer tests. The use of prediction equations and non-staged exercise protocols can improve the test still further, while advances in the use of the test for prognosis, with the discovery of novel risk factors and the addition of gas analysis, may in the future shift the primary emphasis away from diagnosis. Brief, inexpensive, and done in most cases without the presence of a cardiologist, the exercise test offers the highest value for predictive accuracy of any of the non-invasive tests for coronary artery disease.

Coronary Disease↗
PubMed2000

Exercise training and myocardial remodeling in patients with reduced ventricular function: one-year follow-up with magnetic resonance imaging.

BACKGROUND: Exercise training is now an accepted therapeutic intervention in patients with reduced ventricular function after a myocardial infarction. However, there are conflicting reports on the effects of training on the remodeling process of the heart, and previous studies have only assessed short-term effects of training. METHODS AND RESULTS: Twenty-five patients with reduced ventricular function after myocardial infarction were randomly assigned to an intensive 2-month exercise training program or to a control group (control group: n = 13, aged 55 +/- 7 years, ejection fraction 33.3% +/- 6%; exercise group: n = 12, aged 56 +/- 5 years, ejection fraction 31.5% +/- 7%) and followed up for 1 year. Measures of left ventricular size, function, and wall thickness in the infarct and noninfarct areas were made by magnetic resonance imaging at baseline, after the 2-month training period, and 1 year later. Maximal oxygen uptake increased in the trained group, from 19.7 +/- 3 mL/kg per minute at baseline to 25.1 +/- 5 and 24.2 +/- 5 mL/kg per minute after 2 months and 1 year, respectively (P <.05 vs baseline for both), whereas the control group did not change significantly. Ejection fraction, end-diastolic volumes, and end-systolic volumes did not change at any measurement point throughout the study period in either the trained or control groups. Myocardial wall thickness measurements at end-diastole and end-systole and their differences determined by magnetic resonance imaging yielded no significant interactions between groups. When myocardial wall thickness measurements were classified by infarct or noninfarct areas, no differences were observed between groups over the study period. CONCLUSIONS: Intensive exercise training in patients with reduced ventricular function resulted in a significant improvement in exercise capacity after 2 months, and this improvement was sustained over 1 year. In contrast to some recent reports, training had no deleterious effects on left ventricular volume, function, or wall thickness regardless of infarct area.

Exercise Test↗
PubMed1998

Can computerization of the exercise test replace the cardiologist?

BACKGROUND: The type of practitioners who use the standard exercise test is changing. Once a tool of the cardiologist, the standard exercise test is now being performed by internists and other noncardiologists. Because this change could be facilitated by computerization similar to the computerized interpretation programs available for the resting electrocardiograph (ECG), we performed this analysis. A secondary aim was to demonstrate the effects of medication status and resting ECG abnormalities on test diagnostic characteristics because these factors affect utility of the exercise test by the generalist. METHODS AND RESULTS: A retrospective analysis was performed of consecutive patients referred at 2 university-affiliated Veteran's Affairs Medical Centers and a Hungarian Hospital for evaluation of chest pain and possible ischemic heart disease. There were 1384 consecutive male patients without a prior myocardial infarction with complete data who had exercise tests and coronary angiography between 1987 and 1997. Measurements included clinical, exercise test data, and visual interpretation of the ECG recordings as well as more than 100 computed measurements from the digitized ECG recordings and compilation of angiographic data from clinical reports. The computer measurements had similar diagnostic power compared with visual interpretation. Computerized measurements from maximal exercise or recovery were equivalent or superior to all other measurements. Prediction equations applied by computer were superior to single ECG measurements. Beta-blockers had no effect on test characteristics, whereas resting ST depression was associated with decreased specificity and increased sensitivity. CONCLUSIONS: Computerized exercise ST measurements are comparable to visual ST measurements by a cardiologist; computerized scores that included clinical and exercise test results exhibited the greatest diagnostic power. Applying scores with a computer allows the practicing physician to improve the diagnostic characteristics of the standard exercise test. This approach is successful even when there is resting ST depression, thus lessening the need for more expensive nuclear or imaging studies.

Adult↗
PubMed1998

Effect of spinal cord injury on the heart and cardiovascular fitness.

The use of various FES protocols to encourage increases in physical activity and to augment physical fitness and reduce heart disease risk is a relatively new, but growing field of investigation. The evidence so far supports its use in improving potential health benefits for patients with SCI. Such benefits may include more efficient and safer cardiac function; greater stimulus for metabolic, cardiovascular, and pulmonary training adaptations; and greater stimulus for skeletal muscle training adaptations. In addition, the availability of relatively inexpensive commercial FES units to elicit muscular contractions, the ease of use of gel-less, reusable electrodes, and the increasing popularity of home and commercial upper body exercise equipment mean that such benefits are likely to be more accessible to the SCI population through increased convenience and decreased cost. The US Department of Health and Human Services has identified those with SCI as a "special population" whose health problems are accentuated, and so need to be specifically addressed. FES presents "a clear opportunity.... For health promotion and disease prevention efforts to improve the health prospects and functional independence of people with disabilities." As a corollary to this, the Centers for Disease Control and Prevention have recommended the development of techniques to prevent or ameliorate secondary disabilities in persons with a SCI. Patients with SCI have an increased susceptibility to cardiac morbidity and mortality in the acute and early stages of their injury. Most of these patients make an excellent adaptation except when confronted with infection or hypoxia. SCI by itself does not promote atherosclerosis; however, in association with multiple secondary conditions related to SCI, along with advancing age, patients with SCI are predisposed to relatively greater risk of heart disease. The epidemiologic significance of this is reflected in demographic studies that indicate an increasing number of SCI patients becoming aged. Currently 71,000 (40%) of the total 179,000 patients with SCI living in the United States are older than 40 years, and 45,000 have injuries sustained more than 20 years earlier. In addition, new injuries in the older population are increasing (currently 11% of all injuries), and some of these new patients with SCI already have pre-existing cardiac disease. Studies have demonstrated that improved lifestyle, physical activity, lipid management, and dietary restrictions can affect major risk factors for coronary artery disease. Therefore an aggressive cardiac prevention program is appropriate for patients with SCI as part of their rehabilitation. At a given submaximal workload, arm exercise is performed at a greater physiologic cost than is leg exercise. At maximal effort, however, physiologic responses are generally greater in leg exercise than arm exercise. Arm exercise is less efficient and less effective than lower body exercise in developing and maintaining both central and peripheral aspects of cardiovascular fitness. The situation is further compounded in SCI because of poor venous return as a result of lower-limb blood pooling, as a result of lack of sympathetic tone, and a diminished or absent venous "muscle pump" in the legs. This latter mechanism perhaps contributes the greatest diminution in the potential for aerobic performance in the SCI population. Obtaining a cardiopulmonary training effect in individuals with SCI is quite possible. Current studies indicate decreases in submaximal HR, respiratory quotient, minute ventilation, and oxygen uptake, with increases in maximal power output, oxygen uptake, minute ventilation, and lactic acid. Individuals with SCI have been shown to benefit from lower limb functional electrical stimulation (FES)-induced exercise. Studies have consistently reported increases in lower limb strength and cycle endurance performance with these protocols, as well as improvements in metabolic and

Autonomic Nervous System Diseases↗
PubMed1998

Predicting severe angiographic coronary artery disease using computerization of clinical and exercise test data.

Currently the standard exercise test is shifting from being a tool for the cardiologist to utilization by the nonspecialist. This change could be facilitated by computerization similar to the interpretation programs available for the resting ECG. Therefore, we sought to determine if computerization of both exercise ECG measurements and prediction equations can substitute for visual analysis performed by cardiologists to predict which patients have severe angiographic coronary artery disease. We performed a retrospective analysis of consecutive patients referred for evaluation of possible or known coronary artery disease who underwent both exercise testing with digital recording of their exercise ECGs and coronary angiography at two university-affiliated Veteran's Affairs medical centers and a Hungarian hospital. There were 2,385 consecutive male patients with complete data who had exercise tests between 1987 and 1997. Measurements included clinical and exercise test data, and visual interpretation of the ECG paper tracings and > 100 computed measurements from the digitized ECG recordings and compilation of angiographic data from clinical reports. The computer measurements had similar diagnostic power compared with visual interpretation. Computerized ECG measurements from maximal exercise or recovery were equivalent or superior to all other measurements. Prediction equations applied by computer were only able to correctly classify two or three more patients out of 100 tested than ECG measurements alone. beta-Blockers had no effect on test characteristics while ST depression on the resting ECG decreased specificity. By setting probability limits using the scores from the equations, the population was divided into high-, intermediate-, and low-probability groups. A strategy using further testing in the intermediate group resulted in 86% sensitivity and 85% specificity for identifying patients with severe coronary disease. We conclude that computerized exercise ST measurements are comparable to visual ST measurements by a cardiologist and computerized scores only minimally improved the discriminatory power of the test. However, using these scores in a stratification algorithm allows the nonspecialist physician to improve the discriminatory characteristics of the standard exercise test even when resting ST depression is present. Computerization permitted accurate identification of patients with severe coronary disease who require referral.

Coronary Angiography↗
PubMed1997

An agreement approach to predict severe angiographic coronary artery disease with clinical and exercise test data.

OBJECTIVE: To demonstrate that an agreement approach to applying equations on the basis of clinical and exercise test variables is an accurate, self-calibrating, and cost-efficient method for predicting severe coronary artery disease in clinical populations. DESIGN: Retrospective analysis of consecutive patients with complete data from exercise testing and coronary angiography referred for evaluation of possible coronary artery disease. After developing an equation in a training set, this equation and two other equations developed by other investigators were validated in a test set. The study was performed at two university-affiliated Veteran's Affairs medical centers. PATIENTS: 1080 consecutive men studied between 1985 and 1995 who had coronary angiography within 3 months of the treadmill test. The population was randomly divided into a training set of 701 patients and a test set of 379 patients. Patients with previous coronary artery bypass surgery, valvular heart disease, marked degrees of resting ST depression, and left bundle branch block were excluded. MEASUREMENTS: Recording of clinical and exercise test data along with visual interpretation of the electrocardiogram recordings on standardized forms and abstraction of visually interpreted angiographic data from clinical catheterization reports. RESULTS: Simple clinical and exercise test variables improved the standard application of exercise-induced ST criteria for predicting severe coronary artery disease. By setting probability thresholds for severe disease of <20% and >40% for the three prediction equations, the agreement approach divided the test set into three groups: low risk (patients with all three equations predicting <21% probability of severe coronary disease), no agreement, and high risk (all three equations with >39% probability) for severe coronary artery disease. Because the patients in the no agreement group would be sent for further testing and would eventually be correctly classified, the sensitivity of the agreement approach was 89% and the specificity was 96%. The agreement approach appeared to be unaffected by disease prevalence, missing data, variable definitions, or even angiographic criteria. CONCLUSIONS: Requiring diagnosis of severe coronary disease to be dependent on agreement between these three equations has made them likely to function in all clinical populations. The agreement approach should be an efficient method for the evaluation of populations with varying prevalence of coronary artery disease, limiting the use of more expensive noninvasive and invasive testing to patients with a higher probability of left main or triple-vessel coronary artery disease. This approach provides a strategy that can be applied by inputting the results of basic clinical assessment into a programmable calculator or a computer to assist the practitioner in deciding when further evaluation is appropriate, thus assuring patients access to subspecialty care.

Confounding Factors, Epidemiologic↗
PubMed1997

A consensus approach to diagnosing coronary artery disease based on clinical and exercise test data.

OBJECTIVE: To demonstrate that a consensus approach for combining prediction equations based on clinical and exercise test variables derived from different populations can stratify patients referred for possible coronary artery disease (CAD) into low-, intermediate-, and high-risk groups. DESIGN: Retrospective analysis of consecutive patients with complete data from exercise testing and coronary angiography referred for evaluation of possible CAD. After derivation of a logistic equation in our own training set of patients, this equation, along with two other equations developed independently by other investigators, was validated in a test set. The validation strategy for the consensus approach included the following: (1) calculation of probability scores for each patient using each logistic equation independently; (2) determination of probability thresholds in the training set to divide the patients into three groups-low risk (prevalence CAD <5%), intermediate risk (5 to 70%), and high risk (>70% prevalence of CAD); (3) using agreement among at least two of three of the prediction equations to generate "consensus" for each patient; and (4) application of the consensus approach thresholds to the test set of patients. SETTINGS: Two university-affiliated Veteran's Affairs medical centers. PATIENTS: We studied 718 consecutive men between 1985 and 1995 who had coronary angiography within 3 months of an exercise treadmill test for suspected CAD. The population was randomly divided into a training set of 429 patients and a test set of 289 patients. Patients with previous myocardial infarction or coronary artery bypass surgery, valvular heart disease, left bundle branch block, or any Q waves present on their resting ECG were excluded from the study. MEASUREMENTS: Recording of clinical and exercise test data along with visual interpretation of the ECG recordings on standardized forms and abstraction of visually interpreted angiographic data from clinical catheterization reports. RESULTS: We demonstrated that by using simple clinical and exercise test variables, we could improve on the standard use of ECG criteria during exercise testing for diagnosing CAD. Using the consensus approach divided the test set into populations with low, intermediate, and high risk for CAD. Since the patients in the intermediate group would be sent for further testing and would eventually be correctly classified, the sensitivity of the consensus approach is 94% and the specificity is 92%. The consensus approach controls for varying disease prevalence, missing data, inconsistency in variable definition, and varying angiographic criterion for stenosis severity. The percent of correct diagnoses increased from the 67% for standard exercise ECG analysis and from the 80% for multivariable predictive equations alone to >90% correct diagnoses for the consensus approach. CONCLUSIONS: The consensus approach has made population-specific logistic regression equations portable to other populations. Excellent diagnostic characteristics can be obtained using simple data and measurements. The consensus approach is best applied utilizing a programmable calculator or a computer program to simplify the process of calculating the probability of CAD using the three equations.

Coronary Angiography↗
PubMed1994

Prediction of atherosclerotic cardiovascular death in men using a prognostic score.

Treadmill and clinical data were gathered prospectively on consecutive patients who underwent exercise testing for evaluation for coronary artery disease in a 1,200 bed Veterans Affairs Medical Center. From 3,609 men referred for exercise testing from 1984 to 1990, 3,134 patients remained after excluding those with significant valvular heart disease and those with prior coronary artery bypass surgery. Of these, 588 were selected for clinical reasons to undergo cardiac catheterization within 3 months of evaluation leaving 2,546 who were not selected. Over 3 years, there were 158 cardiovascular deaths, 99 nonfatal myocardial infarcts and 183 patients who underwent coronary artery bypass surgery. In the total population, the Cox proportional-hazards model demonstrated the following characteristics to be statistically significant independent predictors of time until cardiovascular death: a history of congestive heart failure and/or taking digoxin, exercise-induced ST depression, the change in systolic blood pressure during exercise, and exercise capacity in METs. Using the Cox model coefficients to weight the variables, a simple score (the Veterans Affairs Prognostic Score) was constructed based on these items. Average annual cardiovascular mortality was plotted against the score enabling its estimation for any given patient. In the subgroup selected for cardiac catheterization (n = 588), the mean score was greater, consistent with a poorer prognosis, compared with the total population; 53% (n = 312) had a score < -2 associated with an annual mortality < 2%. Thus, in over half of the patients selected for catheterization, the catheterization was unnecessary if performed to lessen their chance of cardiovascular death, since no intervention could improve their prognosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Increase in blood lactate during ramp exercise: comparison of continuous and threshold models.

Controversy persists regarding the mechanism underlying the lactate threshold. It has recently been argued that there is in fact no "threshold" and that blood lactate increases as a continuous function during exercise (Hughson J. Appl. Physiol. 62:1975-1981, 1987). In comparing continuous and threshold models, questions have been raised regarding the ramp rate, data sampling, and the mathematical models employed (Morton J. Appl. Physiol. 67:885-888, 1989). To address some of these concerns, we evaluated 61 subjects (mean age 45 +/- 15), who underwent maximal ramp treadmill tests with the ramp rate individualized such that test duration was approximately 10 min for each subject. The relationship between changes in blood lactate and oxygen uptake were evaluated using a modification of the log-log transformation model described by Beaver (J. Appl. Physiol. 59:1936-1940, 1985) and a continuous exponential plus constant model described by Hughson et al. (J. Appl. Physiol. 62:1975-1981, 1987). Model fitting, using mean squared error (MSE) and coefficient of determination (CD) for each method were as follows: [table: see text] The modified log-log model had a better fit as indicated by the lower MSE and higher CD, suggesting the change in lactate was better described by this model. However, the differences were so slight as to suggest: 1) a meaningful difference does not exist between the two; or 2) these methods may not be capable of detecting a difference, if one exists.

Adult↗
PubMed1994

Special considerations in exercise testing. Protocols, equipment, and testing athletes.

A growing number of physicians are performing exercise tests in their offices for the purposes of diagnosing cardiopulmonary disease and assessing exercise capacity in patients with heart disease. Methodology of testing is important in making the most effective use of the information gathered from the test. Selecting an approach that fits the objectives of the test and the individual being tested is essential for accurate and reproducible results. This article discusses the various exercise protocols and equipment used in exercise testing.

Exercise Test↗