The reproducibility of hemodynamic, electrocardiographic, and gas exchange data during treadmill exercise in patients with stable angina pectoris

Cardiopulmonary exercise testing as an integrative approach to explore physiological limitations in Duchenne muscular dystrophy

BACKGROUND

Cardiopulmonary exercise testing (CPET) is the gold-standard for quantification of peak oxygen uptake (VO2) and cardiorespiratory and muscle responses to exercise. Its application to Duchenne muscular dystrophy (DMD) has been scarce due to the notion that muscle weakness inherent to disease restricts the cardiorespiratory system from reaching maximal capacity.

OBJECTIVE

To investigate the utility of CPET in DMD by 1) establishing whether patients can perform maximal-effort exercise for valid VO2 peak assessment; 2) quantifying VO2 peak repeatability; 3) characterizing muscle and cardiorespiratory responses; 4) comparing VO2 peak to 6-min walk distance (6MWD).

METHODS

Twenty-seven DMD and eight healthy boys (6 years and older) underwent CPET using an incremental work-rate protocol for leg (ambulatory) or arm (non-ambulatory) cycling with measurement of heart rate (HR) and gas-exchange variables from rest to maximal-effort. The oxygen cost of work (ΔVO2/Δwork-rate) was calculated, and peak exercise parameters (VO2, HR, O2 pulse, ventilation (VE) and ventilatory threshold (VT)) were considered valid if the respiratory exchange ratio ≥1.01.

RESULTS

VO2 peak was valid (81.5% of patients), repeatable (intraclass correlation coefficient = 0.998) and low in ambulatory and non-ambulatory DMD compared to controls (19.0 ± 6.0; 10.7 ± 2; 35.2 ± 4.5 mL/kg/min respectively). VT was low (30.8 ± 10.7; 19.4 ± 3.0; 61.2 ± 6.9% VO2 peak) reflecting significant muscle metabolic impairment. Peak HR in ambulatory-DMD (172 ± 14 bpm) was similar to controls (183 ± 8.3 bpm), but O2 pulse was low (3.4 ± 1.0; 6.5 ± 1.1 mL/beat). Peak VE/VO2 (ambulatory = 42.1 ± 6.8; non-ambulatory = 42.2 ± 7.8; controls = 34.3 ± 4.6) and ΔVO2/Δwork-rate were elevated (ambulatory = 12.4 ± 4.9; non-ambulatory = 19.0 ± 9.7; controls = 10.1 ± 0.8) revealing ventilatory and mechanical inefficiency. Despite strong correlation between VO2 peak and 6MWD, severity of impairment was discordant.

CONCLUSION

Valid CPET is feasible in DMD, revealing low VO2 peak due to abnormal muscle metabolic and cardiorespiratory responses during dynamic exercise. CPET reveals cardiorespiratory limitations in DMD boys with unremarkable 6MWD, and should be considered an integrative approach in clinical care and assessment of emerging therapeutics.

Quantifying Improvement in V˙ o2peak and Exercise Thresholds in Cardiovascular Disease Using Reliable Change Indices

PURPOSE

Improving aerobic fitness through exercise training is recommended for the treatment of cardiovascular disease (CVD). However, strong justifications for the criteria of assessing improvement in key parameters of aerobic function including estimated lactate threshold (θ LT ), respiratory compensation point (RCP), and peak oxygen uptake (V˙ o2peak ) at the individual level are not established. We applied reliable change index (RCI) statistics to determine minimal meaningful change (MMC RCI ) cutoffs of θ LT , RCP, and V˙ o2peak for individual patients with CVD.

METHODS

Sixty-six stable patients post-cardiac event performed three exhaustive treadmill-based incremental exercise tests (modified Bruce) ∼1 wk apart (T1-T3). Breath-by-breath gas exchange and ventilatory variables were measured by metabolic cart and used to identify θ LT , RCP, and V˙ o2peak . Using test-retest reliability and mean difference scores to estimate error and test practice/exposure, respectively, MMC RCI values were calculated for V˙ o2 (mL·min -1. kg -1 ) at θ LT , RCP, and V˙ o2peak .

RESULTS

There were no significant between-trial differences in V˙ o2 at θ LT ( P = .78), RCP ( P = .08), or V˙ o2peak ( P = .74) and each variable exhibited excellent test-retest variability (intraclass correlation: 0.97, 0.98, and 0.99; coefficient of variation: 6.5, 5.4, and 4.9% for θ LT , RCP, and V˙ o2peak , respectively). Derived from comparing T1-T2, T1-T3, and T2-T3, the MMC RCI for θ LT were 3.91, 3.56, and 2.64 mL·min -1. kg -1 ; 4.01, 2.80, and 2.79 mL·min -1. kg -1 for RCP; and 3.61, 3.83, and 2.81 mL·min -1. kg -1 for V˙ o2peak . For each variable, MMC RCI scores were lowest for T2-T3 comparisons.

CONCLUSION

These MMC RCI scores may be used to establish cutoff criteria for determining meaningful changes for interventions designed to improve aerobic function in individuals with CVD.

Design and rationale of re-energize fontan: Randomized exercise intervention designed to maximize fitness in fontan patients

In this manuscript, we describe the design and rationale of a randomized controlled trial in pediatric Fontan patients to test the hypothesis that a live-video-supervised exercise (aerobic+resistance) intervention will improve cardiac and physical capacity; muscle mass, strength, and function; and endothelial function. Survival of children with single ventricles beyond the neonatal period has increased dramatically with the staged Fontan palliation. Yet, long-term morbidity remains high. By age 40, 50% of Fontan patients will have died or undergone heart transplantation. Factors that contribute to onset and progression of heart failure in Fontan patients remain incompletely understood. However, it is established that Fontan patients have poor exercise capacity which is associated with a greater risk of morbidity and mortality. Furthermore, decreased muscle mass, abnormal muscle function, and endothelial dysfunction in this patient population is known to contribute to disease progression. In adult patients with 2 ventricles and heart failure, reduced exercise capacity, muscle mass, and muscle strength are powerful predictors of poor outcomes, and exercise interventions can not only improve exercise capacity and muscle mass, but also reverse endothelial dysfunction. Despite these known benefits of exercise, pediatric Fontan patients do not exercise routinely due to their chronic condition, perceived restrictions to exercise, and parental overprotection. Limited exercise interventions in children with congenital heart disease have demonstrated that exercise is safe and effective; however, these studies have been conducted in small, heterogeneous groups, and most had few Fontan patients. Critically, adherence is a major limitation in pediatric exercise interventions delivered on-site, with adherence rates as low as 10%, due to distance from site, transportation difficulties, and missed school or workdays. To overcome these challenges, we utilize live-video conferencing to deliver the supervised exercise sessions. Our multidisciplinary team of experts will assess the effectiveness of a live-video-supervised exercise intervention, rigorously designed to maximize adherence, and improve key and novel measures of health in pediatric Fontan patients associated with poor long-term outcomes. Our ultimate goal is the translation of this model to clinical application as an "exercise prescription" to intervene early in pediatric Fontan patients and decrease long-term morbidity and mortality.

Measuring True Change in Individual Patients: Reliable Change Indices of Cardiac Rehabilitation Outcomes, and Implications for Quality Indicators

BACKGROUND

Mediated by outcomes such as improved exercise capacity, cardiac rehabilitation (CR) reduces morbidity and mortality. For accuracy, an individual CR patient's change must be measured reliably, an issue not typically considered in practice. Drawing from psychometric theory, we calculated reliable change indices (RCIs), to measure individual CR patients' true clinical change, apart from that from error and test practice/exposure, in exercise capacity, anxiety, and depression.

METHODS

Indirectly calculated exercise capacity (peak metabolic equivalents [METs]) and psychological symptoms were each measured twice, 1 week apart, by administering treadmill tests or the Hospital Anxiety and Depression Scale (HADS) to separate samples of 35 (mean age: 59.0 years; 6 women) and 96 (mean age: 64.4 years; 32 women) CR patients, respectively. Using test-retest reliability and mean difference scores from these samples to estimate error and practice/exposure effects, we calculated RCIs for a separate cohort (n = 2066; mean age: 62.0 years; 533 women) who completed 6-month CR, and compared change distributions (worsened/unchanged/improved) based on critical RCIs, mean and percent changes, cut-off scores, and standard deviations.

RESULTS

Practice/exposure effects were nonsignificant, except the mean HADS anxiety score decreased significantly (P ≤ 0.013; d = 0.17, small effect). Test-retest reliabilities were high (METs r = 0.934; HADS anxiety score r = 0.912; HADS depression score r = 0.90; P < 0.001). Among 2066 CR patients, RCI distributions differed (P < 0.001) from those of most other change criteria.

CONCLUSIONS

Change ascertainment depends on criterion choice. A Canadian Cardiovascular Society CR quality indicator of increase by 0.5 MET may be too small to assess individuals' functional capacity change. RCIs offer a pragmatic approach to benchmarking reliable change frequency, and pending further validation, could be used for feedback to individual patients.

Multi-trait analysis for genome-wide association study of five psychiatric disorders

We conducted a cross-trait meta-analysis of genome-wide association study on schizophrenia (SCZ) (n = 65,967), bipolar disorder (BD) (n = 41,653), autism spectrum disorder (ASD) (n = 46,350), attention deficit hyperactivity disorder (ADHD) (n = 55,374), and depression (DEP) (n = 688,809). After the meta-analysis, the number of genomic loci increased from 14 to 19 in ADHD, from 3 to 10 in ASD, from 45 to 57 in DEP, from 8 to 54 in BD, and from 64 to 87 in SCZ. We observed significant enrichment of overlapping genes among different disorders and identified a panel of cross-disorder genes. A total of seven genes were found being commonly associated with four out of five psychiatric conditions, namely GABBR1, GLT8D1, HIST1H1B, HIST1H2BN, HIST1H4L, KCNB1, and DCC. The SORCS3 gene was highlighted due to the fact that it was involved in all the five conditions of study. Analysis of correlations unveiled the existence of two clusters of related psychiatric conditions, SCZ and BD that were separate from the other three traits, and formed another group. Our results may provide a new insight for genetic basis of the five psychiatric disorders.

Test-Retest Reliability of Maximal and Submaximal Gas Exchange Variables in Patients With Coronary Artery Disease

PURPOSE

Gas exchange variables derived from cardiopulmonary exercise tests (CPETs) need to be reliable for evaluating interventions and clinical decision making. Whereas peak oxygen uptake ((Equation is included in full-text article.)O2) has shown to be a highly reliable parameter in patients with coronary artery disease (CAD), little is known about the reproducibility of these parameters in patients with CAD. Therefore, the purpose of this study was to confirm the reliability of peak (Equation is included in full-text article.)O2 and to investigate the reliability of submaximal CPET variables in patients with CAD.

METHODS

Eighty-five patients with CAD (57.6 ± 8.5 years; 79 males) performed 2 CPETs within 10 days before starting a rehabilitation program. Reliability of peak and submaximal exercise variables was assessed by using intraclass correlation coefficients (ICC), coefficients of variation, Pearson correlation coefficients, paired t tests, and Bland-Altman plots.

RESULTS

Maximal and submaximal exercise parameters showed adequate reliability. Overall, there was a good correlation across both testing occasions (r = 0.63-0.95; P < .05 for all). Peak (Equation is included in full-text article.)O2 (ICC, 0.95; 95% CI, 0.92-0.97) demonstrated excellent reliability. Of the submaximal exercise variables, oxygen uptake efficiency slope (OUES) was as reliable as peak (Equation is included in full-text article.)O2 (ICC, 0.97; 95% CI, 0.95-0.98). The ventilation/carbon dioxide production ((Equation is included in full-text article.)E/(Equation is included in full-text article.)CO2) slope showed very good test-retest reliability (ICC, 0.87; 95% CI, 0.80-0.91) and the (Equation is included in full-text article.)O2/work rate slope showed good reliability (ICC, 0.76; 95% CI, 0.64-0.85).

CONCLUSIONS

Both peak (Equation is included in full-text article.)O2 and OUES show excellent test-retest reliability. Accordingly, in the case of no or unreliable peak (Equation is included in full-text article.)O2 data, we suggest using OUES to evaluate cardiorespiratory fitness in patients with CAD.

How Accurate Is the Prediction of Maximal Oxygen Uptake with Treadmill Testing?

BACKGROUND

Cardiorespiratory fitness measured by treadmill testing has prognostic significance in determining mortality with cardiovascular and other chronic disease states. The accuracy of a recently developed method for estimating maximal oxygen uptake (VO2peak), the heart rate index (HRI), is dependent only on heart rate (HR) and was tested against oxygen uptake (VO2), either measured or predicted from conventional treadmill parameters (speed, incline, protocol time).

METHODS

The HRI equation, METs = 6 x HRI- 5, where HRI = maximal HR/resting HR, provides a surrogate measure of VO2peak. Forty large scale treadmill studies were identified through a systematic search using MEDLINE, Google Scholar and Web of Science in which VO2peak was either measured (TM-VO2meas; n = 20) or predicted (TM-VO2pred; n = 20) based on treadmill parameters. All studies were required to have reported group mean data of both resting and maximal HRs for determination of HR index-derived oxygen uptake (HRI-VO2).

RESULTS

The 20 studies with measured VO2 (TM-VO2meas), involved 11,477 participants (median 337) with a total of 105,044 participants (median 3,736) in the 20 studies with predicted VO2 (TM-VO2pred). A difference of only 0.4% was seen between mean (±SD) VO2peak for TM- VO2meas and HRI-VO2 (6.51±2.25 METs and 6.54±2.28, respectively; p = 0.84). In contrast, there was a highly significant 21.1% difference between mean (±SD) TM-VO2pred and HRI-VO2 (8.12±1.85 METs and 6.71±1.92, respectively; p<0.001).

CONCLUSION

Although mean TM-VO2meas and HRI-VO2 were almost identical, mean TM-VO2pred was more than 20% greater than mean HRI-VO2.

Observed change in peak oxygen consumption after aortic valve replacement and its predictors

Objective

To assess the change in peak oxygen consumption (pVO₂) and determine its outcome predictors after aortic valve replacement (AVR) for aortic stenosis (AS).

Methods

Patients with AS and preserved left ventricular ejection fraction who were referred for single AVR had cardiopulmonary exercise testing prior to and 9 months post-AVR. Predictors of outcome for pVO₂ were determined by multivariate linear and logistic regression analyses. A significant change in pVO₂ was defined as a relative change that was more than twice the coefficient of repeatability by test–retest (>10%).

Results

The pre-AVR characteristics of the 37 study patients included the following: median age (range) 72 (46–83) years, aortic valve area index (AVAI) 0.41 (SD 0.11) cm²/m², mean gradient (MG) 49.1 (SD 15.3) mm Hg and New York Heart Association (NYHA)≥II 27 (73%). Pre-AVR and post-AVR mean pVO₂ was 18.5 and 18.4 mL/kg/m² (87% of the predicted), respectively, but the change from pre-AVR was heterogeneous. The relative change in pVO₂ was positively associated with the preoperative MG (β=0.50, p=0.001) and negatively associated with brain natriuretic peptide > upper level of normal according to age and gender (β=−0.40, p=0.009). A relative increase in pVO₂ exceeding 10% was found in 9 (24%), predicted by lower pre-AVR AVAI (OR 0.18; 95% CI 0.04 to 0.82, p=0.027) and lower peak O₂ pulse (OR 0.94; 95% CI 0.88 to 0.99, p=0.045). Decreases in pVO₂ exceeding 10% were found in 11 (30%) and predicted by lower MG (OR 0.93; 95% CI 0.86 to 0.99, p=0.033).

Conclusions

Change in pVO₂ was heterogeneous. Predictors of favourable and unfavourable outcomes for pVO₂ were identified.

Reliability of peak exercise testing in patients with heart failure with preserved ejection fraction

Exercise intolerance is the primary symptom in patients with heart failure and preserved ejection fraction (HFpEF), a major determinant of their decreased quality of life, and an important outcome in clinical trials. Although cardiopulmonary exercise testing (CPET) provides peak and submaximal diagnostic indexes, the reliability of peak treadmill CPET in patients >55 years of age with HFpEF has not been examined. Two CPETs were performed in 52 patients with HFpEF (70 ± 7 years old). The 2 tests were separated by an average of 23 ± 13 days (median 22) and performed under identical conditions, with no intervention or change in status between visits except for initiation of a placebo run-in. A multistep protocol for patient screening, education, and quality control was used. Mean peak oxygen consumption was similar on tests 1 and 2 (14.4 ± 2.4 vs 14.3 ± 2.3 ml/kg/min). Correlation coefficients and intraclass correlations from the testing days were determined (oxygen consumption, r = 0.85, p <0.001, intraclass correlation 0.855; ventilatory anaerobic threshold, r = 0.79, p <0.001, intraclass correlation 0.790; ventilation per carbon dioxide slope, r = 0.87, p <0.001, intraclass correlation 0.864; heart rate, r = 0.94, p <0.001, intraclass correlation 0.938). These results challenge conventional wisdom that serial baseline testing is required in clinical trials with exercise-capacity outcomes. In conclusion, in women and men with HFpEF and severe physical dysfunction, key submaximal and peak ET variables exhibited good reliability and were not significantly altered by a learning effect or placebo administration.

Assessment of exercise capacity in African patients with chronic heart failure using six minutes walk test

BACKGROUND

The purpose of this study was to assess the functional capacity during a 6-minute corridor walk and a 6-minute bicycle ergometry exercise in patients with chronic heart failure (CHF).

METHOD

Thirty five patients with stable CHF were recruited for the study. Each subject performed six minutes corridor walk and 6-minute bicycle ergometry testing. The 6-minute walk required the subjects to walk at a self selected speed on a 20 meter marked level ground for 6-minute. All the subjects also performed a 6-minute exercise on a stationary bicycle ergometer with initial resistance of 20 watts and increased by 10 watts after 3-minutes. The perceived rate of exertion was assessed using a modified Borg Scale after each exercise mode. The maximum oxygen consumption was derived using American College of Sport Medicine equations.

RESULTS

Result showed high positive correlation between distance walked in the 6-minute and the maximum volume of oxygen (VO(2) max) (r = 0.65, P < 0.01). The average distance walked was 327 m +/- 12.03 m. The VO(2) max estimated during bicycle ergometry was higher (13.7 +/- 1.9 L) than during the six minutes walk (8.9 +/- 1.2 L).

CONCLUSION

Six minutes walk could be useful to evaluate exercise tolerance in patients with chronic heart failure, while the bicycle ergometer could be more appropriate in the assessment of maximum functional capacity in these patients.

WITHDRAWN: Aerobic exercise training programmes for improving physical and psychosocial health in adults with Down syndrome

BACKGROUND

Although physical fitness has been suggested to improve physical and psychosocial health for a variety of population profiles, there is a lack of information about the safety and effectiveness of aerobic exercise for adults with Down syndrome.

OBJECTIVES

To evaluate the effectiveness and safety of aerobic exercise training programmes for physiological and psychosocial outcomes in adults with Down syndrome.

SEARCH STRATEGY

Search terms and synonyms for "aerobic exercise" and "Down syndrome" were used within the following databases: CENTRAL (2007, Issue 1); MEDLINE via PUBMED (1966 to March 2007); EMBASE (2005 to April 2007); CINAHL (1982 to March 2007); LILACS (1982 to March 2007); PsycINFO (1887 to March 2007); ERIC (1966 to March 2007); CCT (March 2007); Academic Search Elite (to March 2007), C2- SPECTR (to March 2007 ), NRR (2007 Issue 1), ClinicalTrials.gov (accessed March 2007) and within supplements of Medicine and Science in Sports and Exercise.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials using supervised aerobic exercise training programmes with behavioral components accepted as co-interventions.

DATA COLLECTION AND ANALYSIS

Two reviewers selected relevant trials, assessed methodological quality and extracted data. Where appropriate, data was pooled using meta-analysis with a random effects model

MAIN RESULTS

The two studies included in this trial used different kinds of aerobic activity: walking/jogging and rowing training. One included study was conducted in the USA, the other in Portugal. In the meta-analyses, only maximal treadmill grade, a work performance variable, was improved in the intervention group after aerobic exercise training programmes (-4.26 [95% CI -6.45, -2.06]) grade. The other outcomes in the meta-analysis showed no significant differences between intervention and control groups, as expressed by weighted mean difference: VO(2) peak -0.30 (95% CI -377, 3.17) mL.Kg.min(-1); peak heart rate, -2.84 (95% CI -10.73, 5.05) bpm; respiratory exchange ratio, 0.01 (95% CI -0.04, 0.06); pulmonary ventilation, -5.86 (95% CI -16.06, 4.34) L.min(-1). 30 other measures including work performance, oxidative stress and body composition variables could not be combined in the meta-analysis. Apart from work performance, trials reported no significant improvements in these measures.

AUTHORS' CONCLUSIONS

There is insufficient evidence to support improvement in physical or psychosocial outcomes of aerobic exercise in adults with Down syndrome. Although evidence exists which supports improvements in physiological and psychological aspects from strategies using mixed physical activity programmes, well-conducted research which examines long-term physical outcomes, adverse effects, psychosocial outcomes and costs are required before informed practice decisions can be made.

Do regression-based computer algorithms for determining the ventilatory threshold agree?

The determination of the ventilatory threshold has been a persistent problem in research and clinical practice. Several computerized methods have been developed to overcome the subjectivity of visual methods but it remains unclear whether different computerized methods yield similar results. The purpose of this study was to compare nine regression-based computerized methods for the determination of the ventilatory threshold. Two samples of young and healthy volunteers (n = 30 each) participated in incremental treadmill protocols to volitional fatigue. The ventilatory data were averaged in 20-s segments and analysed with a computer program. Significant variance among methods was found in both samples (Sample 1: F = 11.50; Sample 2: F = 11.70, P < 0.001 for both). The estimates of the ventilatory threshold ranged from 2.47 litres.min(-1) (71% VO2max) to 3.13 litres.min(-1) (90% VO2max) in Sample 1 and from 2.37 litres.min(-1) (67% VO2max) to 3.03 litres.min(-1) (83% VO2max) in Sample 2. The substantial differences between methods challenge the practice of relying on any single computerized method. A standardized protocol, likely based on a combination of methods, might be necessary to increase the methodological consistency in both research and clinical practice.

Reproducibility of peak oxygen uptake and other cardiopulmonary exercise testing parameters in patients with heart failure (from the Heart Failure and A Controlled Trial Investigating Outcomes of exercise traiNing)

Peak oxygen uptake (pVo2) is an important parameter in assessing the functional capacity and prognosis of patients with heart failure. In heart failure trials, change in pVo2 was often used to assess the effectiveness of an intervention. However, the within-subject variability of pVo2 on serial testing may limit its usefulness. This study was designed to evaluate the within-subject variability of pVo2 over 2 baseline cardiopulmonary exercise tests. As a substudy of the HF-ACTION trial, 398 subjects (73% men, 27% women; mean age 59 years) with heart failure and left ventricular ejection fraction < or =35% underwent 2 baseline cardiopulmonary exercise tests within 14 days. Mean pVo2 was unchanged from test 1 to test 2 (15.16 +/- 4.97 vs 15.18 +/- 4.97 ml/kg/min; p = 0.78). However, mean within-subject absolute change was 1.3 ml/kg/min (10th, 90th percentiles 0.1, 3.0), with 46% of subjects increasing and 48% decreasing on the second test. Other parameters, including the ventilation-to-carbon-dioxide production slope and Vo2 at ventilatory threshold, also showed significant within-subject variation with minimal mean differences between tests. In conclusion, pVo2 showed substantial within-subject variability in patients with heart failure and should be taken into account in clinical applications. However, on repeated baseline cardiopulmonary exercise tests, there appears to be no familiarization effect for Vo2 in patients with HF. Therefore, in multicenter trials, there is no need to perform >1 baseline cardiopulmonary exercise test.

The Clinical Significance of Aerobic Exercise Testing and Prescription: From Apparently Healthy to Confirmed Cardiovascular Disease

Aerobic exercise testing clearly provides valuable clinical information in apparently healthy adults as well as a number of patient populations. Maximal aerobic capacity, either estimated from workload or measured directly, is perhaps the most frequently analyzed variable ascertained from such testing. This practice is warranted given the consistent prognostic significance of maximal aerobic capacity. Other variables obtained from the aerobic exercise test, such as the heart rate response during exercise and into recovery, the systolic and diastolic blood pressure responses during exercise, oxygen consumption at anaerobic threshold, and the ventilatory response to exercise, also provide important insight into an individual's health and prognosis. Furthermore, the aerobic exercise test is highly valuable in developing an individualized and safe exercise prescription. Aerobic exercise training goals, with respect to frequency, duration, frequency, and mode of exercise, are well established for the apparently healthy population as well as individuals at risk for or diagnosed with cardiovascular disease. Adherence to these physical activity recommendations clearly provides numerous health benefits, perhaps most important of which is a significant decrease in the risk for cardiovascular events and mortality. This review addresses concepts of aerobic exercise testing and training and discusses their clinical implications.

Association of functional and health status measures in heart failure

BACKGROUND

A wide variety of instruments have been used to assess the functional capabilities and health status of patients with chronic heart failure (HF), but it is not known how well these tests are correlated with one another, nor which one has the best association with measured exercise capacity.

METHODS AND RESULTS

Forty-one patients with HF were assessed with commonly used functional, health status, and quality of life measures, including maximal cardiopulmonary exercise testing, the Duke Activity Status Index (DASI), the Veterans Specific Activity Questionnaire (VSAQ), the Kansas City Cardiomyopathy Questionnaire (KCCQ), and 6-minute walk distance. Pretest clinical variables, including age, resting pulmonary function tests (forced expiratory volume in 1 s and forced vital capacity), and ejection fraction (EF) were also considered. The association between performance on these functional tools, clinical variables, and exercise test responses including peak VO2 and the VO2 at the ventilatory threshold, was determined. Peak oxygen uptake (VO2) was significantly related to VO2 at the ventilatory threshold (r = 0.76, P < .001) and estimated METs from treadmill speed and grade (r = 0.72, P < .001), but had only a modest association with 6-minute walk performance (r = 0.49, P < .01). The functional questionnaires had modest associations with peak VO2 (r = 0.37, P < .05 and r = 0.26, NS for the VSAQ and DASI, respectively). Of the components of the KCCQ, peak VO2 was significantly related only to quality of life score (r = 0.46, P < .05). Six-minute walk performance was significantly related to KCCQ physical limitation (r = 0.53, P < .01) and clinical summary (r = 0.44, P < .05) scores. Among pretest variables, only age and EF were significantly related to peak VO2 (r = -0.58, and 0.46, respectively, P < .01). Multivariately, age and KCCQ quality of life score were the only significant predictors of peak VO2, accounting for 72% of the variance in peak VO2.

CONCLUSION

Commonly used functional measures, symptom tools, and quality of life assessments for patients with HF are poorly correlated with one another and are only modestly associated with exercise test responses. These findings suggest that exercise test responses, non-exercise test estimates of physical function, and quality of life indices reflect different facets of health status in HF and one should not be considered a surrogate for another.

Exercise performance in young and middle-aged female patients with subclinical hyperthyroidism

Subclinical hyperthyroidism (SH) may be responsible for many cardiovascular changes, including an impaired exercise performance. The aim of our study was to evaluate the response to the treadmill cardiopulmonary test in patients with SH. We studied 14 female patients from our endocrine clinic with exogenous SH, free from cardiovascular diseases, with mean age of 38.6 +/- 10.2 years, body mass index (BMI) of 24.4 +/- 4.0 kg/m(2), and disease duration of 4.9 +/- 4.9 years. The mean serum thyrotropin (TSH) was 0.03 +/- 0.03 mU/L, serum free thyroxine (FT(4)), 1.72 +/- 0.21 ng/dL, and serum triiodothyronine level, 137 +/- 32 ng/dL. The control group comprised 15 euthyroid, healthy women, with mean age of 35.4 +/- 7.4 years and BMI of 27.3 +/- 5.9 kg/m(2). Both groups had a sedentary lifestyle and underwent the cardiopulmonary test using a treadmill with the Balke protocol. Gas concentrations and the respiratory outflow were measured and the electrocardiogram (ECG) was registered in real time. We calculated the minute ventilation (V(E)), the oxygen consumption (peak VO(2)), the carbonic gas exhalation (peak VCO(2)) and the anaerobic threshold (AT). The heart rate (HR) at rest (90.9 +/- 15.7 versus 78.9 +/- 8.7 beats per minute; p = 0.03) was higher in the patients from our clinic. There was no difference between groups regarding age, BMI, fat percentage, blood pressure, peak HR, exercise duration, mean treadmill peak inclination, V(E), peak VO(2), peak VCO(2), and AT. There was no correlation between peak VO(2) and FT(4), TSH, or disease duration. Our results show that exercise capacity in young and middle-aged female patients is not significantly affected by exogenous SH.

Aerobic exercise training programmes for improving physical and psychosocial health in adults with Down syndrome

BACKGROUND

Although physical fitness has been suggested to improve physical and psychosocial health for a variety of population profiles, there is a lack of information about the safety and effectiveness of aerobic exercise for adults with Down syndrome.

OBJECTIVES

To evaluate the effectiveness and safety of aerobic exercise training programmes for physiological and psychosocial outcomes in adults with Down syndrome.

SEARCH STRATEGY

Search terms and synonyms for "aerobic exercise" and "Down syndrome" were used within the following databases:CENTRAL (2005, Issue 2); MEDLINE (1966 to March 2005); EMBASE (2005 to April 2005); CINAHL (1982 to March 2005); LILACS (1982 to March 2005); PsycINFO (1887 to March 2005); ERIC (1966 to March 2005); CCT (March 2005); Academic Search Elite (to March 2005), C2- SPECTR (to March 2005 ), NRR (2005 Issue 1), ClinicalTrials.gov (accessed March 2005)and within supplements of Medicine and Science in Sports and Exercise.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials using supervised aerobic exercise training programmes with behavioral components accepted as co-interventions.

DATA COLLECTION AND ANALYSIS

Two reviewers selected relevant trials, assessed methodological quality and extracted data. Where appropriate, data was pooled using meta-analysis with a random effects model

MAIN RESULTS

The two studies included in this trial used different kinds of aerobic activity: walking/jogging and rowing training. One included study was conducted in the USA, the other in Portugal. In the meta-analyses, only maximal treadmill grade, a work performance variable, was improved in the intervention group after aerobic exercise training programmes (-4.26 [95% CI -6.45, -2.06]) grade. The other outcomes in the meta-analysis showed no significant differences between intervention and control groups, as expressed by weighted mean difference: VO(2) peak -0.30 (95% CI -377, 3.17) mL.Kg.min(-1); peak heart rate, -2.84 (95% CI -10.73, 5.05) bpm; respiratory exchange ratio, 0.01 (95% CI -0.04, 0.06); pulmonary ventilation, -5.86 (95% CI -16.06, 4.34) L.min(-1). 30 other measures including work performance, oxidative stress and body composition variables could not be combined in the meta-analysis. Trials reported no significant improvements in these measures.

AUTHORS' CONCLUSIONS

There is insufficient evidence to support improvement in physical or psychosocial outcomes of aerobic exercise in adults with Down syndrome. Although evidence exists which supports improvements in physiological and psychological aspects from strategies using mixed physical activity programmes, well-conducted research which examines long-term physical outcomes, adverse effects, psychosocial outcomes and costs are required before informed practice decisions can be made.

Reproducibility of Cardiopulmonary Exercise Measurements in Patients With Pulmonary Arterial Hypertension

BACKGROUND AND OBJECTIVES

As part of a recent study, cardiopulmonary exercise tests (CPETs) were used to evaluate and follow up patients with pulmonary arterial hypertension (PAH). These patients were more impaired than those in other published series evaluating CPET reproducibility. We used these patient tests to assess patient performance variability and evaluate reading variability. To achieve this end, six independent evaluators graded key CPET measurements in patients with PAH who underwent duplicate CPETs within 3 days of each other.

SETTING AND PATIENTS

Over a 15-month period at two tertiary-care teaching hospitals, 42 patients with PAH underwent repeated, paired CPETs using cycle ergometry.

INTERVENTIONS AND MEASUREMENTS

Each patient underwent one to six pairs of cycle ergometry tests to maximal tolerance. Each pair of tests was separated by 3 months, with each test in the pair separated by 1 to 3 days. Specific guidelines were given to the independent evaluators for the key measurements assessed from each CPET study: peak O(2) uptake (Vo(2)), peak heart rate, peak O(2) pulse, anaerobic threshold (AT), and end-tidal Po(2), end-tidal Pco(2), and the ventilatory equivalent for CO(2) at the AT (Ve/Vco(2)@AT).

RESULTS

There were no fatalities or complications occurring among the 242 tests performed on 42 patients. The mean peak Vo(2) was 722 mL/min or 41% of predicted; 34 patients were Weber class C or D. Using the specific guidelines to measure the variability of measurements made by the six independent evaluators, the coefficients of variation were < 2.2% for peak Vo(2), peak heart rate, peak O(2) pulse, end-tidal values at the AT, and Ve/Vco(2)@AT, while for the AT, it was 8.5%. There were no significant differences in these measurements between the first and second tests of any pair or between the earlier and later sets of pairs.

CONCLUSIONS

Using specific guidelines, key CPET measurements can be safely, reliably, and reproducibly assessed even in patients with severe exercise intolerance.

A broader paradigm for understanding and treating heart failure

Several recent clinical trials in heart failure have failed to demonstrate improvements in survival, suggesting that new approaches must be adopted if there are to be further improvements in heart failure treatment. We propose a broader paradigm for heart failure care based on a chronic rather than an acute illness model. This approach recognizes a broader range of outcomes including patient-perceived health status, expanded populations of interest that more closely reflect the changing epidemiology of heart failure, and a wider scope of interventions that address co-morbidity and health behavior. This approach will require a rationally designed health care delivery system that applies the best available evidence to the care of individual patients with heart failure.

Effects of combined aerobic and resistance training versus aerobic training alone in cardiac rehabilitation

PURPOSE

This study examined the effects of performing combined resistance and aerobic training, versus aerobic training alone, in patients with coronary artery disease.

METHODS

Thirty-six patients with coronary artery disease were randomized to either an aerobic-only training group (AE) or a combined aerobic and resistance training group (AE + R). Both groups performed 30 minutes of aerobic exercise 3 days/week for 6 months. In addition, AE + R group performed two sets of resistance exercise on seven different Nautilus machines after completion of aerobic training each day. Twenty patients (AE: n = 10; AE + R: n = 10) completed the training protocol with > 70% attendance.

RESULTS

Strength gains for AE + R group were greater than for AE group on six of seven resistance machines (P < 0.05). VO2peak increased after training for both AE and AE + R (P < 0.01) with no difference in improvement between the groups. Resting and submaximal exercise heart rates and rate-pressure product were lower after training in the AE + R group (P < 0.01), but not in the AE group. AE + R increased lean mass in arm, trunk, and total body regions (P < 0.01), while AE increased lean mass in trunk region only (P < 0.01). Percent body fat was reduced for AE + R after training (P < 0.05) with a between group trend toward reduced body fat (P = 0.09). Lean mass gain significantly correlated with strength increase in five of seven resistance exercises for AE + R.

CONCLUSIONS

Resistance training adds to the effects of aerobic training in cardiac rehabilitation patients by improving muscular strength, increasing lean body mass, and reducing body fat.

Exercise stress testing. An overview of current guidelines

Exercise stress testing (ET) is an inexpensive noninvasive tool that provides valuable cardiopulmonary information in healthy and diseased populations. It is most commonly used for diagnosing coronary artery disease (CAD) and developing appropriate exercise prescriptions (EP). With its widespread use and application, it is imperative that safe and appropriate guidelines and procedures are used, as there are a number of risks associated with testing in a population with or suspected of having CAD. The focus should be on the patient's safety: personnel must be properly trained and aware of all emergency procedures, contra-indications for ET and indications for test termination must be strictly adhered to. Three main types of testing are prevalent: submaximal, maximal and maximal utilising gas exchange. The maximal test is most commonly used, and the submaximal is appropriate for hospitalised patients. Gas exchange data is essential when assessing congestive heart failure and timing for heart transplantation. ET is commonly performed using a treadmill or a bicycle ergometer. The treadmill provides a more familiar exercise modality and has been shown to have greater diagnostic sensitivity than the bicycle ergometer; it is, however, more expensive and requires more space in the testing room. The bicycle ergometer is more appropriate for those individuals who are severely obese or have problems with extended periods of walking. Regardless of the modality used, an appropriate exercise protocol should be used. In North America, the Bruce protocol is the most common. However, the Bruce protocol, and others that estimate exercise capacity based on equations, tend to overestimate exercise capacity. They may be too demanding for those with limited exercise capacity, and too long for those with high exercise capacity. For these people, an exercise protocol that reaches maximal capacity in 8 to 12 minutes using smaller increments in workload should be considered. Once completed, the results of ET needs to be correctly interpreted. This includes reviewing the test results while considering the patient's history, medications and indication for the test. ET can also be used to develop an EP for the participant. An EP should take into account the intensity, modality of exercise, frequency and duration, as well as being realistic for the individual and the goals to be achieved. All the information from the test results and the pre-test examination should be presented in a report that also includes the advised EP.

Heterogeneity among cardiac ischemic and anginal responses to exercise, mental stress, and daily life

The objectives of this study were to compare and contrast indicators of ischemia in a well-characterized group of 196 patients with coronary artery disease, documented angiographically or by verified history of myocardial infarction, and a positive exercise test result. Myocardial ischemia occurs frequently in response to everyday stressors in patients with coronary artery disease. The Psychophysiological Interventions in Myocardial Ischemia study provides a unique opportunity to study neuroendocrine and psychological manifestations of ischemia. Patients with exercise-induced ischemia underwent exercise radionuclide ventriculography and electrocardiographic monitoring and 2 laboratory mental stressors (Speech and Stroop) after being withdrawn from cardiac medications. In addition, 48-hour ambulatory electrocardiograms were recorded during routine daily activities. Patients with a history of angina within the past 3 months reported angina during the bicycle or treadmill test with a much higher frequency than patients without such an anginal history (77% vs 26%). Ejection fraction (EF) responses to the Stroop test were abnormal in 48% of patients with an abnormal EF response to the Speech task, versus 17% in patients with a normal EF response (p <0.01). Seventy-six percent of patients had an abnormal EF response to bicycle exercise. Three indicators of ischemia (ST-segment depression, wall motion abnormality, and EF response) were compared during the same laboratory stressor and across different types of stress tests. Presence of the 3 indicators was only moderately associated during exercise, and only weak or nonsignificant associations occurred among the presence of the 3 ischemic markers during mental stress. Occurrence of the same ischemic markers was moderately associated between the 2 mental stress tasks, but few associations were found between the occurrence of the same ischemic marker during exercise and mental stress. There is a marked heterogeneity of responses to psychological and exercise stress testing using electrocardiography, ambulatory electrocardiography, or radionuclide criteria for ischemia during stress. The heterogeneity may be related to differences in the magnitude or types of physiologic responses provoked and to differences in the sensitivity and specificity of the different tests used to identify ischemia.

Dangerous curves. A perspective on exercise, lactate, and the anaerobic threshold

A number of general observations can be made from these recent studies. Lactate is a ubiquitous substance that is produced and removed from the body at all times, even at rest, both with and without the availability of oxygen. It is now recognized that lactate accumulates in the blood for several reasons, not just the fact that oxygen supply to the muscle is inadequate. Lactate production and removal is a continuous process; it is a change in the rate of one or the other that determines the blood lactate level. Rather than a specific threshold, there is most likely a period of time during which lactate production begins to exceed the body's capacity to remove it (through buffering or oxidation in other fibers). It may be appropriate to replace the term "anaerobic threshold" to a more functional description, since the muscles are never entirely anaerobic nor is there always a distinct threshold ("oxygen independent glycolysis" among others has been suggested) Lactate plays a major role as a metabolic substrate during exercise, is the preferred fuel for slow-twitch muscle fibers, and is a precursor for liver gluconeogenesis. The point at which lactate begins to accumulate in the blood, causing an increase in ventilation, is important to document clinically. Irrespective of the underlying mechanism or specific model that describes the process, the physiologic changes associated with lactate accumulation have significant import for cardiopulmonary performance. These include metabolic acidosis, impaired muscle contraction, hyperventilation, and altered oxygen kinetics, all of which contribute to an impaired capacity to perform work. Thus, any delay in the accumulation of blood lactate which can be attributed to an intervention (drug, exercise training, surgical, etc) may add important information concerning the efficacy of the intervention. A substantial body of evidence is available demonstrating that lactate accumulation occurs later (shifting to a higher percentage of Vo2max) after a period of endurance training. In athletes, the level of work that can be sustained prior to lactate accumulation, visually determined, is an accurate predictor of endurance performance. Presumably, these concepts have implications related to vocation/disability among patients with cardiovascular and pulmonary disease, but few such applied studies have been performed outside the laboratory. Blood lactate during exercise and its associated ventilatory changes maintain useful and interesting applications in both the clinical exercise laboratory and the sport sciences. However, the mechanism, interpretation, and application of these changes continue to rely more on tradition and convenience than science.

Development and evaluation of the Seattle Angina Questionnaire: a new functional status measure for coronary artery disease

OBJECTIVES

This study sought to establish the validity, reproducibility and responsiveness of the Seattle Angina Questionnaire, a 19-item self-administered questionnaire measuring five dimensions of coronary artery disease: physical limitation, anginal stability, anginal frequency, treatment satisfaction and disease perception.

BACKGROUND

Assessing the functional status of patients is becoming increasingly important in both clinical research and quality assurance programs. No current functional status measure quantifies all of the important domains affected by coronary artery disease.

METHODS

Cross-sectional or serial administration of the Seattle Angina Questionnaire was carried out in four groups of patients: 70 undergoing exercise treadmill testing, 58 undergoing coronary angioplasty, 160 with initially stable coronary artery disease and an additional 84 with coronary artery disease. Evidence of validity was sought by comparing the questionnaire's five scales with the duration of exercise treadmill tests, physician diagnoses, nitroglycerin refills and other validated instruments. Reproducibility and responsiveness were assessed by comparing serial responses over a 3-month interval.

RESULTS

All five scales correlated significantly with other measures of diagnosis and patient function (r = 0.31 to 0.70, p < or = 0.001). Questionnaire responses of patients with stable coronary artery disease did not change over 3 months. The questionnaire was sensitive to both dramatic clinical change, as seen after successful coronary angioplasty, and to more subtle clinical change, as seen among outpatients with initially stable coronary artery disease.

CONCLUSIONS

The Seattle Angina Questionnaire is a valid and reliable instrument that measures five clinically important dimensions of health in patients with coronary artery disease. It is sensitive to clinical change and should be a valuable measure of outcome in cardiovascular research.

Functional capacity before and after cardioversion of atrial fibrillation: a controlled study

OBJECTIVE

To evaluate the effect of cardioversion on peak oxygen consumption (peak VO2) in patients with long-standing atrial fibrillation, to assess the importance of underlying heart disease with respect to the response to exercise, and to relate functional capacity to long-term arrhythmia outcome.

DESIGN

Prospective controlled clinical trial.

SETTING

Tertiary referral centre.

PATIENTS

63 consecutive patients with chronic atrial fibrillation accepted for treatment with electrical cardioversion. Before cardioversion all patients were treated with digoxin, verapamil, or a combination of both to attain a resting heart rate < or = 100 beats per minute.

INTERVENTIONS

Electrical cardioversion.

MAIN OUTCOME MEASURES

Peak VO2 measured before and 1 month after electrical cardioversion to compare patients who were in sinus rhythm and those in atrial fibrillation at these times. Maintenance of sinus rhythm for a mean follow up of 19 (7) months.

RESULTS

Mean (1SD) peak VO2 in patients in sinus rhythm after 1 month (n = 37) increased from 21.4 (5.8) to 23.7 (6.4) ml/min/kg (+11%, P < 0.05), whereas in patients with a recurrence of atrial fibrillation 1 month after cardioversion (n = 26) peak VO2 was unchanged. In patients who were in sinus rhythm both those with and without underlying heart disease improved, and improvement was not related to functional capacity or left ventricular function before cardioversion. Baseline peak VO2 was not a predictive factor for long-term arrhythmia outcome.

CONCLUSION

Restoration of sinus rhythm improved peak VO2 in patients with atrial fibrillation, irrespective of the presence of underlying heart disease. Peak VO2 was not a predictive factor for long-term arrhythmia outcome after cardioversion of atrial fibrillation. These findings suggest that cardioversion is the best method of improving functional capacity in patients with atrial fibrillation, whether or not they have underlying heart disease and whatever their functional state.

Effects of sublingual nitroglycerin on the gas exchange response to exercise in stable angina pectoris

To quantitate changes in gas exchange variables that occur after administration of sublingual nitroglycerin in patients with stable angina pectoris, a randomized double-blind 2-period crossover study was performed with continuous expired gas exchange analysis and progressive exercise using individualized ramp treadmill protocols. Significant reductions in minute ventilation and respiratory rate were observed at 5 minutes of exercise during nitroglycerin therapy. Gas exchange variables i.e., minute ventilation, carbon dioxide production and oxygen uptake were significantly increased at the onset of angina after nitroglycerin administration. When techniques for optimizing the assessment of cardiopulmonary function were used, significant improvements in gas exchange variables were demonstrated in stable angina pectoris after administration of sublingual nitroglycerin.

Evaluation of breath-by-breath measurement of respiratory gas exchange in pediatric exercise testing

In adults, breath-by-breath analysis has been used for measuring respiratory gas exchange during exercise. The present study evaluates the validity and reproducibility of this method in children. In 21 patients with various types of congenital heart disease, steady state exercise testing was performed on a motor-driven treadmill. Based on simultaneous measurements of VO2, VCO2, VE and R, comparisons were made between the breath-by-breath and Douglas bag methods. No significant differences were found between both methods for any of the variables. In seven other patients the reproducibility of cardiorespiratory variables during exercise was assessed. No significant difference was found for the cardiorespiratory variables during any of the tests and the coefficients of variation were comparable to data obtained in adults. It is concluded that the breath-by-breath method for measuring respiratory values can be applied in children with an acceptable degree of validity and reproducibility.

Comparison of ischemic and physiologic responses during exercise tests in men using the standard and modified Bruce protocols

The importance of low-level (warm-up) exercise for reducing exercise-induced myocardial ischemic symptoms in patients with coronary artery disease is well-recognized by clinicians. Whether altering the abruptness of exercise, such as that which occurs during different frequently used testing protocols, affects myocardial ischemic variables and maximal exercise capacity has not been resolved. This study seeks to determine the effects of altering the increment of work-rate change per exercise stage on both the ischemic threshold and maximal exercise capacity using 2 frequently used exercise testing protocols. Thirty-two patients with documented coronary artery disease and previously positive exercise tests (ischemic ST depression greater than or equal to 1.0 mm) performed symptom-limited exercise tests using both the standard and modified Bruce protocols in random order, 1 hour apart. Exercise electrocardiograms were analyzed to determine the ischemic threshold, defined as heart rate at onset of greater than or equal to 1.0 mm ischemic ST depression. Patients achieved a higher peak heart rate (124 +/- 19 vs 117 +/- 21 beats/min; p less than 0.0001), rate-pressure product (21.4 +/- 3.9 vs 19.8 +/- 4.1 beats/min x mm Hg x 10(3); p less than or equal to 0.0001) and oxygen consumption (VO2) (18.5 +/- 3.7 vs 16.5 +/- 4.4 ml/kg/min; p less than or equal to 0.001) with the standard than with the modified Bruce protocol. At matched submaximal exercise stages there were no differences in VO2, heart rate or oxygen pulse between protocols. Time to ischemic threshold was significantly reduced with the standard compared with the modified Bruce protocol (312 +/- 107 vs 607 +/- 221 seconds; p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

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)

Comparison of the ramp versus standard exercise protocols

To compare the hemodynamic and gas exchange responses of ramp treadmill and cycle ergometer tests with standard exercise protocols used clinically, 10 patients with chronic heart failure, 10 with coronary artery disease who were asymptomatic during exercise, 11 with coronary artery disease who were limited by angina during exercise and 10 age-matched normal subjects performed maximal exercise using six different exercise protocols. Gas exchange data were collected continuously during each of the following protocols, performed on separate days in randomized order: Bruce, Balke and an individualized ramp treadmill; 25 W/stage, 50 W/stage and an individualized ramp cycle ergometer test. Maximal oxygen uptake was 16% greater on the treadmill protocols combined (21.4 +/- 8 ml/kg per min) versus the cycle ergometer protocols combined (18.1 +/- 7 ml/kg per min) (p less than 0.01), although no differences were observed in maximal heart rate (131 +/- 24 versus 126 +/- 24 beats/min for the treadmill and cycle ergometer protocols, respectively). No major differences were observed in maximal heart rate or maximal oxygen uptake among the various treadmill protocols or among the various cycle ergometer protocols. The ratio of oxygen uptake to work rate, expressed as a slope, was highest for the ramp tests (slope +/- SEE ml/kg per min = 0.80 +/- 2.5 and 0.78 +/- 1.7 for ramp treadmill and ramp cycle ergometer, respectively). The slopes were poorest for the tests with the largest increments in work (0.62 +/- 4.0 and 0.59 +/- 2.8 for the Bruce treadmill and 50 W/stage cycle ergometer, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Optimizing the exercise test for pharmacological investigations

Exercise trials in cardiology are often hindered by inconsistent approaches to exercise testing. These inconsistencies include the choice of exercise protocol, exercise end points, points of analysis, and absence or misuse of gas exchange data. Gas exchange techniques greatly enhance the accuracy with which cardiopulmonary function is assessed by exercise. Commonly used protocols are not always appropriate for all patients or all studies. Both cardiovascular disease and the exercise protocol can have an important impact on the relation between changes in work rate and oxygen uptake. Ramp protocols appear to offer the greatest promise for assessing cardiopulmonary function. Analyzing hemodynamic and gas exchange responses at several points submaximally, in addition to those at peak exercise, can add important information concerning the efficacy of a drug. A great deal of confusion continues to hinder the application of the gas exchange anaerobic threshold, and many of the commonly used testing end points are not reliable.

The effect of complete and incomplete revascularization on exercise variables in patients undergoing coronary angioplasty

To investigate the effects of complete and incomplete revascularization on the response to exercise, 25 patients underwent symptom-limited exercise testing with continuous assessment of gas exchange a mean of 5 +/- 4 days prior to and 18 +/- 12 days following percutaneous transluminal coronary angioplasty. All antianginal medications were discontinued for testing. Revascularization was considered complete if all stenoses were reduced to less than 50% diameter (13 patients), and incomplete if one or more stenoses remained (12 patients). Consistent improvements in ST-segment depression were observed after angioplasty at matched submaximal exercise levels (mean range 0.5-0.8 mm; p less than 0.05), and were accompanied by a reduction in angina. Significant increases in heart rate and systolic blood pressure were observed at peak exercise following angioplasty in both groups. Gas exchange variables were significantly improved at maximal exercise, with a similar increase in oxygen uptake observed in both groups following angioplasty (mean increase 3.3-3.7 ml/kg/min; p less than 0.01). Thus, incomplete revascularization following coronary angioplasty resulted in hemodynamic, electrocardiographic, symptomatic, and gas exchange responses to exercise that were comparable to complete revascularization.

Effects of glutamate on exercise tolerance and circulating substrate levels in stable angina pectoris

The effects of glutamate on exercise tolerance, ischemic threshold and venous substrate concentrations were studied in 20 patients with stable angina pectoris and positive stress tests. Each patient underwent 4 upright bicycle exercise tests on consecutive days. The first and fourth tests were performed without medication while the second and third tests were preceded by a low and high bolus dose of monosodium glutamate, either 0.8 and 1.5 mg/kg body weight intravenously (10 patients) or 40 and 80 mg/kg orally (10 patients). Comparison of the first and fourth tests revealed good reproducibility of electrocardiographic, hemodynamic and metabolic data. Glutamate increased exercise duration (p less than 0.05) in a dose-related way when given intravenously (59 +/- 14 and 153 +/- 14 seconds) and when given orally (53 +/- 21 and 90 +/- 23 seconds; all data are mean +/- standard error of the mean). It also delayed the onset of ST-segment depression (p less than 0.05) by 73 +/- 19, 120 +/- 23, 62 +/- 27 and 80 +/- 30 seconds, respectively. Hemodynamics were not changed by glutamate at rest or at comparable workloads, but at onset of ST-segment depression the heart rate-blood pressure product was increased (p less than 0.05). Glutamate administration induced dose-related 1.5- to 10-fold elevations in plasma glutamate, 15 to 50% decreases in plasma free fatty acids (p less than 0.05) and 5 to 30% increases in plasma alanine contents. Circulating levels of glucose, lactate, citrate and albumin were not modified by glutamate.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of cardioversion on maximal exercise capacity in patients with chronic atrial fibrillation

To evaluate the effect of cardioversion on exercise capacity, 11 male patients (59 +/- 8 years) with chronic atrial fibrillation underwent maximal exercise testing using gas exchange techniques before and after successful cardioversion to normal sinus rhythm. Testing was conducted 1 day prior to and a mean of 39 (range 10 to 95) days following cardioversion. Heart rate, blood pressure, and respiratory gas exchange responses were evaluated at rest, at a standard submaximal workload (3.0 mph/0% grade), at the gas exchange anaerobic threshold, and at maximal exertion. Cardioversion resulted in a mean decrease in resting heart rate of 37 beats/min (113 +/- 16 versus 76 +/- 10 beats/min, p less than 0.001). While mean heart rate was approximately 50 beats/min lower following cardioversion at both submaximal stages of exercise p less than 0.001), oxygen uptake was not different. At maximal exercise, heart rate was markedly reduced (192 +/- 24 to 144 +/- 21 beats/min, p less than 0.001) and maximal oxygen uptake was higher (1.86 +/- 0.5 to 2.06 +/- 0.5 L/min, p less than 0.05) after cardioversion. In addition, an improved efficiency of ventilation was observed at exercise levels exceeding 60% of maximal oxygen uptake.

Increased exercise capacity after digoxin administration in patients with heart failure

Failure to objectively assess the effect of digitalis on exercise capacity has resulted in controversy regarding its use in patients with chronic congestive heart failure. To clarify this situation, maximal treadmill testing with respiratory gas exchange analysis was performed on 11 patients (mean age 57 +/- 9 years) with chronic congestive heart failure with and without digoxin therapy. Ten of the 11 had a consistent third sound gallop, and the mean ejection fraction of the group was 24 +/- 10%. Rest heart rate was significantly higher (91 +/- 16 versus 102 +/- 16 beats/min; p less than 0.05) and rest systolic blood pressure was significantly reduced in the absence of digoxin (130 +/- 23 versus 121 +/- 15 mm Hg; p less than 0.05). No differences in heart rate or blood pressure were observed during exercise. Significant increases in ventilatory oxygen uptake were observed with digoxin submaximally (3.0 mph, 0% grade), at the gas exchange anaerobic threshold and at maximal exercise (mean increase of 2.6 ml/kg per min; p less than 0.02). An improvement in the estimated ratio of ventilatory dead space to tidal volume (VD/VT), an index of physiologic efficiency, occurred throughout exercise during digoxin therapy, and there was a significant negative correlation between the change in maximal oxygen uptake and change in maximal estimated VD/VT (r = -0.63; p less than 0.05). Thus, digoxin therapy is associated with a significant improvement in exercise capacity in patients with chronic heart failure, most likely due to an improved matching of ventilation to perfusion.

Variability of indexes for myocardial ischemia: a comparison of exercise treadmill test, ambulatory electrocardiographic monitoring and symptoms of myocardial ischemia

Fifty-four patients with chronic stable angina were studied to determine and compare weekly variability of indexes for the detection of myocardial ischemia. All patients underwent three single-blind placebo periods, each lasting 1 week. An exercise treadmill test, 24 h ambulatory electrocardiographic (Holter) monitoring (analyzed blindly) and an accurate diary of anginal attacks and nitroglycerin use were obtained at the end of each placebo period. An unbalanced, completely random component of variance analysis was used to calculate a component for within subject variability and a component for among subject variability. The coefficient of variation and percent variation (within subjects) of onset of chest pain during exercise were 19% and 30%, respectively; the corresponding values were 28% and 33% for onset of 1 mm ST depression, 15% and 15% for exercise duration, 44% and 27% for number of ischemic episodes/24 h, 56% and 43% for anginal frequency and 55% and 27% for nitroglycerin consumption, respectively. With use of this statistical method and variation within subjects, the change in the value of each variable necessary to exceed those attributable to spontaneous variation was determined. The trade-off between repeated measurements and number of subjects, the sample size estimated for planning studies and the minimal sample size for using various designs were also determined. Although the data indicate that all indexes for myocardial ischemia, both during exercise and during daily activity, vary considerably, but the exercise variables have less variability and are more reproducible.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise time: a possible source of misleading results during long-term pharmacological studies by multiple stress testings in coronary artery disease

The assessment of chronic pharmacological treatment of stable angina requires serial exercise stress testings. It is well known that exercise tolerance can be improved by the training effect of performing repeated testings. Our study investigated the values of heart rate, systolic blood pressure, rate-pressure product, and duration of exercise at 0.1 mV ST depression during exercise and the same parameters plus the maximal ST-segment depression at peak exercise, collected from three different tests. The first and second were performed at one-week intervals before, and the third (75 days after the first), was performed after a double-blind study with a drug versus placebo. We found a significant increase of exercise duration at 0.1 mV ST depression and at peak exercise, while 6 of 12 patients increased exercise duration from the second to the third test. Individual variability of exercise duration showed increasing values, ranging from 0 to 71% (first vs. third test). In contrast, the ratio of heart rate and systolic blood pressure did not differ between the tests. Our data criticized the use of mean values of exercise time for pharmacological studies; moreover, individual variability could affect results independently of drug or placebo administration. These findings should be taken into account in order to exclude misleading results.