The ventilatory threshold: quantitative analysis of reproducibility and relation to arterial lactate concentration in normal subjects and in patients with chronic congestive heart failure

Assessment of cardiopulmonary capacity in deconditioned athletes because of knee injury

BACKGROUND

An athlete's career inevitably goes through periods of forced physical exercise interruption like a knee injury. Advanced echocardiographic methods and cardiopulmonary exercise testing (CPET) are essential in evaluating athletes in the period elapsing after the injury. However, the feasibility of a maximal pre-surgery CPET and the capacity of resting advanced echocardiographic techniques to predict cardiorespiratory capacity still need to be clarified.

METHODS

We evaluated 28 non-professional athletes aged 18-52, involved in prevalently aerobic or alternate aerobic/anaerobic sports activities, affected by a knee pathology with indications for surgical treatment. The evaluation was performed at rest by trans-thoracic echocardiography, including global longitudinal strain (GLS) and myocardial work (MW) assessment, and during exercise by CPET.

RESULTS

The percent-predicted peak oxygen consumption (peak VO2%) was 82.8±13.7%, the mean respiratory exchange ratio was 1.16±0.08, and the mean ventilation/carbon dioxide (VE/VCO2) slope was 24.23±3.36. Peak VO2% negatively correlated with GLS (r=-0.518, P=0.003) and global wasted work (GWW) (r =-0.441, P=0.015) and positively correlated with global work efficiency (GWE) (r=0.455, P=0.012). Finally, we found that the VE/VCO2 slope during exercise was negatively correlated with GWE (r=-0.585, P=0.001) and positively correlated with GWW (r=0.499, P=0.005).

CONCLUSIONS

A maximal CPET can be obtained in deconditioned athletes because of a knee injury, allowing a comprehensive functional pre-surgery evaluation. In these patients, peak VO2 is reduced due to decreased physical activity after injury; however, a lower cardiopulmonary efficiency may be a concause of the injury itself. In addition, we demonstrated that the MW indexes obtained at rest could predict exercise capacity and ventilatory efficiency as evaluated by CPET.

Cardiopulmonary Exercise Testing in Heart Failure With Preserved Ejection Fraction: Technique Principles, Current Evidence, and Future Perspectives

Heart failure with preserved ejection fraction (HFpEF) is a multifactorial clinical syndrome involving a rather complex pathophysiologic substrate and quite a challenging diagnosis. Exercise intolerance is a major feature of HFpEF, and in many cases, diagnosis is suspected in subjects presenting with exertional dyspnea. Cardiopulmonary exercise testing (CPET) is a noninvasive, dynamic technique that provides an integrative evaluation of cardiovascular, pulmonary, hematopoietic, neuropsychological, and metabolic functions during maximal or submaximal exercise. The assessment is based on the principle that system failure typically occurs when the system is under stress, and thus, CPET is currently considered to be the gold standard for identifying exercise intolerance, allowing the differential diagnosis of underlying causes. CPET is used in observational studies and clinical trials in HFpEF; however, in most cases, only a few from a wide variety of CPET parameters are examined, while the technique is largely underused in everyday cardiology practice. This article discusses the basic principles and methodology of CPET and studies that utilized CPET in patients with HFpEF, in an effort to increase awareness of CPET capabilities among practicing cardiologists.

Cardiopulmonary exercise testing in patients with end-stage kidney disease: principles, methodology and clinical applications of the optimal tool for exercise tolerance evaluation

Chronic kidney disease (CKD), especially end-stage kidney disease (ESKD), is associated with an increased risk for cardiovascular events and all-cause mortality. Exercise intolerance as well as reduced cardiovascular reserve is extremely common in patients with CKD. Cardiopulmonary exercise testing (CPET) is a non-invasive, dynamic technique that provides an integrative evaluation of cardiovascular, pulmonary, neuropsychological and metabolic function during maximal or submaximal exercise, allowing the evaluation of functional reserves of these systems. This assessment is based on the principle that system failure typically occurs when the system is under stress and thus CPET is currently considered to be the gold standard for identifying exercise limitation and differentiating its causes. It has been widely used in several medical fields for risk stratification, clinical evaluation and other applications, but its use in everyday practice for CKD patients is scarce. This article describes the basic principles and methodology of CPET and provides an overview of important studies that utilized CPET in patients with ESKD, in an effort to increase awareness of CPET capabilities among practicing nephrologists.

Exercise training as part of multidisciplinary rehabilitation in cancer survivors: an observational study on changes in physical performance and patient-reported outcomes

PURPOSE

To describe changes in physical performance and patient-reported outcomes in cancer survivors who participated in an exercise program as part of usual-care multidisciplinary rehabilitation and the influence of training adaptations during the coronavirus-19 (COVID-19) pandemic.

METHODS

In an observational cohort study, cancer survivors underwent usual-care multidisciplinary rehabilitation including a 10-week exercise program. During the COVID-19 pandemic, the exercise program was adapted with reduced training time and frequency. Mean changes and 95% confidence intervals in physical performance (peak oxygen uptake (VO2peak), peak work rate during a steep ramp test (SRT-WRpeak), 6-min walking distance, muscle strength) and patient-reported outcomes (health-related quality of life, fatigue, anxiety, and depression) were assessed between the start and the end of the exercise program. Linear regression analysis, adjusting for baseline levels of outcomes, was used to investigate differences in changes in outcomes between participants who underwent the original and the adapted program.

RESULTS

All outcomes statistically significantly improved over time, regardless of adaptations in the exercise program. VO2peak increased with 9.6% and 7.7% in the original and adapted program, respectively. Significant smaller improvements were observed in SRT-WRpeak (- 3.9%) and upper body muscle strength (- 10.8%) after participation in the adapted compared to the original program. No significant between-group differences were observed for other outcomes.

CONCLUSION

Physical performance and patient-reported outcomes statistically and clinically significantly improved in cancer survivors who participated in an exercise program as part of usual-care multidisciplinary rehabilitation. Improvements of performance outcomes were smaller since the training adaptations, though only significant for SRT-WRpeak and upper body strength.

Isocapnic buffering period: From physiology to clinics

Background

During cardiopulmonary exercise test, the isocapnic buffering period ranges between anaerobic threshold (AT) and respiratory compensation point (RCP). We investigated whether oxygen uptake (VO2) increase during the isocapnic buffering period (ΔVO2AT-RCP) is related to heart failure severity and prognosis.

Methods

We retrospectively analysed reduced ejection fraction heart failure patients who attained RCP at cardiopulmonary exercise test. The study endpoint was the composite of cardiovascular mortality and urgent heart transplantation/left ventricular assist device implantation. Hazard ratio was assessed to identify the increase of risk associated with ΔVO2AT-RCP (below and above the median of ΔVO2AT-RCP).

Results

AT and RCP were both identified in 782 (39.2%) out of 1995 reduced ejection fraction heart failure cases. Left ventricular ejection fraction and peak VO2 were 33 ± 9% and 16.5 ± 4.5 mL/kg per min (61 ± 16% of predicted value), suggesting moderate heart failure. At five years, endpoint did not vary between patients below and above the median ΔVO2AT-RCP (3.85 mL/min per kg (25–75th interquartile range = 2.69–5.46)). ΔVO2AT-RCP correlated with several parameters associated to heart failure prognosis, such as peak VO2, VE/VCO2 slope, brain natriuretic peptide and left ventricular ejection fraction. The ΔVO2AT-RCP value was associated with prognosis at univariate but not at multivariable analysis, where only VE/VCO2 slope endured.

Conclusion

ΔVO2AT-RCP correlates with several parameters linked to heart failure severity. Isocapnic buffering period stratifies heart failure patients, but not more than other prognostic indices.

Test-retest reliability and four-week changes in cardiopulmonary fitness in stroke patients: evaluation using a robotics-assisted tilt table

BACKGROUND

Exercise testing devices for evaluating cardiopulmonary fitness in patients with severe disability after stroke are lacking, but we have adapted a robotics-assisted tilt table (RATT) for cardiopulmonary exercise testing (CPET). Using the RATT in a sample of patients after stroke, this study aimed to investigate test-retest reliability and repeatability of CPET and to prospectively investigate changes in cardiopulmonary outcomes over a period of four weeks.

METHODS

Stroke patients with all degrees of disability underwent 3 separate CPET sessions: 2 tests at baseline (TB1 and TB2) and 1 test at follow up (TF). TB1 and TB2 were at least 24 h apart. TB2 and TF were 4 weeks apart. A RATT equipped with force sensors in the thigh cuffs, a work rate estimation algorithm and a real-time visual feedback system was used to guide the patients' exercise work rate during CPET. Test-retest reliability and repeatability of CPET variables were analysed using paired t-tests, the intraclass correlation coefficient (ICC), the coefficient of variation (CoV), and Bland and Altman limits of agreement. Changes in cardiopulmonary fitness during four weeks were analysed using paired t-tests.

RESULTS

Seventeen sub-acute and chronic stroke patients (age 62.7 ± 10.4 years [mean ± SD]; 8 females) completed the test sessions. The median time post stroke was 350 days. There were 4 severely disabled, 1 moderately disabled and 12 mildly disabled patients. For test-retest, there were no statistically significant differences between TB1 and TB2 for most CPET variables. Peak oxygen uptake, peak heart rate, peak work rate and oxygen uptake at the ventilatory anaerobic threshold (VAT) and respiratory compensation point (RCP) showed good to excellent test-retest reliability (ICC 0.65-0.94). For all CPET variables, CoV was 4.1-14.5 %. The mean difference was close to zero in most of the CPET variables. There were no significant changes in most cardiopulmonary performance parameters during the 4-week period (TB2 vs TF).

CONCLUSIONS

These findings provide the first evidence of test-retest reliability and repeatability of the principal CPET variables using the novel RATT system and testing methodology, and high success rates in identification of VAT and RCP: good to excellent test-retest reliability and repeatability were found for all submaximal and maximal CPET variables. Reliability and repeatability of the main CPET parameters in stroke patients on the RATT were comparable to previous findings in stroke patients using standard exercise testing devices. The RATT has potential to be used as an alternative exercise testing device in patients who have limitations for use of standard exercise testing devices.

Very Early Lactate Threshold in Healthy Young Men as Related to Oxygen Uptake Kinetics

We assessed the correspondence between the V-slope ventilatory threshold (VT) and the lactate threshold (LT) by using a distinctive slow submaximal ramp protocol to ensure that sufficient data points exist around the threshold. Twenty healthy young men participated. A submaximal test based on a prior maximal test (25 watt/min, medium ramp) was performed with an individual slow-ramp protocol (6-17 watt/min, slow ramp), in which the time to reach the VT workload was estimated to be 10 minutes. The LT was determined visually by detecting a rise above the resting value, without or with log-log transformation (LT1, LT2). The point at which the blood lactate exceeded the minimal difference (LMD) of 2 resting values was also calculated. The VT appeared significantly earlier under the slow-ramp protocol compared to the medium-ramp protocol (from 19.3 ± 3.9 to 15.0 ± 4.0 mL/kg/min VO2, P < 0.001). The mean LT1 and LT2 values appeared even earlier than the VT (LT1, P = 0.004; LT2, P = 0.002) (LT1, 11.9; LT2, 13.4; LMD, 17.0; VT, 15.0 mL/kg/min VO2). As the mean % of peak VO2, each occurred at 29.9%, 33.7%, 42.5%, and 37.8%. The VT correlated significantly with LT1, LT2, and LMD (r = 0.61, 0.64, 0.80; P = 0.004, 0.002, <0.001). Mean blood lactate showed a similar trend (1.30, 1.43, 1.81, 1.68 mmol/L, respectively). Furthermore, the ΔVO2/Δ work rate slope increased (from 10.8 ± 0.9 to 11.5 ± 0.9; P = 0.01) with the slow ramp, and the lower LT was associated with the greater increase in slope (LT1, r = -0.47, P = 0.03; LT2, r = -0.59, P =  .005), that is, the lower LT was an indication that on the faster medium ramp the slope would decrease. The LMD and VT did not show this relation. Under slow-ramp exercise testing in healthy young men, the VT appeared earlier than under medium-ramp exercise testing. In addition, the LT appeared even earlier (at approximately 30% of peak VO2) than the VT, although they correlated. This very early onset of LT was, however, associated with evidence of reduced oxygen uptake kinetics.

Cardiopulmonary exercise testing for risk prediction in major abdominal surgery

Reduced exercise capacity is associated with increased postoperative morbidity. Cardiopulmonary exercise testing variables can be used to risk stratify patients. This information can be used to help guide the choice of surgical procedure and to decide on the most appropriate postoperative care environment. Thus CPET can aid collaborative decision making and improve the process of informed consent. In the future, CPET may be combined with other risk predictors to improve outcome prediction. Furthermore early evidence suggests that CPET can be used to guide prehabilitation training programs, improving fitness and thereby reducing perioperative risk.

Cardiopulmonary exercise testing, prehabilitation, and Enhanced Recovery After Surgery (ERAS)

PURPOSE

This review evaluates the current and future role of cardiopulmonary exercise testing (CPET) in the context of Enhanced Recovery After Surgery (ERAS) programs.

PRINCIPAL FINDINGS

There is substantial literature confirming the relationship between physical fitness and perioperative outcome in general. The few small studies in patients undergoing surgery within an ERAS program describe less fit individuals having a greater incidence of morbidity and mortality. There is evidence of increasing adoption of perioperative CPET, particularly in the UK. Although CPET-derived variables have been used to guide clinical decisions about choice of surgical procedure and level of perioperative care as well as to screen for uncommon comorbidities, the ability of CPET-derived variables to guide therapy and thereby improve outcome remains uncertain. Recent studies have reported a reduction in CPET-defined physical fitness following neoadjuvant therapies (chemo- and radio-therapy) prior to surgery. Preliminary data suggest that this effect may be associated with an adverse effect on clinical outcomes in less fit patients. Early reports suggest that CPET-derived variables can be used to guide the prescription of exercise training interventions and thereby improve physical fitness in patients prior to surgery (i.e., prehabilitation). The impact of such interventions on clinical outcomes remains uncertain.

CONCLUSIONS

Perioperative CPET is finding an increasing spectrum of roles, including risk evaluation, collaborative decision-making, personalized care, monitoring interventions, and guiding prescription of prehabilitation. These indications are potentially of importance to patients having surgery within an ERAS program, but there are currently few publications specific to CPET in the context of ERAS programs.

Cardiopulmonary exercise testing, prehabilitation, and Enhanced Recovery After Surgery (ERAS)

PURPOSE

This review evaluates the current and future role of cardiopulmonary exercise testing (CPET) in the context of Enhanced Recovery After Surgery (ERAS) programs.

PRINCIPAL FINDINGS

There is substantial literature confirming the relationship between physical fitness and perioperative outcome in general. The few small studies in patients undergoing surgery within an ERAS program describe less fit individuals having a greater incidence of morbidity and mortality. There is evidence of increasing adoption of perioperative CPET, particularly in the UK. Although CPET-derived variables have been used to guide clinical decisions about choice of surgical procedure and level of perioperative care as well as to screen for uncommon comorbidities, the ability of CPET-derived variables to guide therapy and thereby improve outcome remains uncertain. Recent studies have reported a reduction in CPET-defined physical fitness following neoadjuvant therapies (chemo- and radio-therapy) prior to surgery. Preliminary data suggest that this effect may be associated with an adverse effect on clinical outcomes in less fit patients. Early reports suggest that CPET-derived variables can be used to guide the prescription of exercise training interventions and thereby improve physical fitness in patients prior to surgery (i.e., prehabilitation). The impact of such interventions on clinical outcomes remains uncertain.

CONCLUSIONS

Perioperative CPET is finding an increasing spectrum of roles, including risk evaluation, collaborative decision-making, personalized care, monitoring interventions, and guiding prescription of prehabilitation. These indications are potentially of importance to patients having surgery within an ERAS program, but there are currently few publications specific to CPET in the context of ERAS programs.

Changes in exercise capacity in subjects with cardiac asymptomatic hereditary hemochromatosis during a follow-up after 5 yrs

OBJECTIVE

A long-term effect of hereditary hemochromatosis (HH) on aerobic exercise capacity (AEC) has not been well described.

DESIGN

Forty-three HH and 21 volunteer control subjects who were asymptomatic underwent cardiopulmonary exercise testing using the Bruce protocol. AEC was assessed with minute ventilation (V(E)), oxygen uptake (V(O)(2)), and carbon dioxide production (V(CO)(2)) at baseline and at a follow-up assessment after 5 yrs. A paired t test was used for analyses of normality data; otherwise, Wilcoxon's signed rank-sum test was used.

RESULTS

Thirty-three HH subjects and 18 volunteer control subjects returned for a repeat cardiopulmonary exercise testing at the fifth-year follow-up (80% overall return rate). At the fifth-year follow-up, AEC was not different between the two groups. Compared with baseline measurements, exercise time, peak V(O)(2), and the V(E)/V(CO)(2) slope did not differ statistically at the fifth-year follow-up between both groups. Iron depletion through phlebotomy for 5 yrs did not significantly affect AEC in newly diagnosed HH subjects at baseline (n = 14) and cardiac arrhythmias during exercise tended to decrease after 5 yrs of therapy in this group.

CONCLUSIONS

The AEC of asymptomatic HH subjects treated using conventional therapy is not statistically affected by the disease during a 5-yr period.

The role of exercise training in heart failure

Exercise training in patients with systolic heart failure (HF) is an accepted adjunct to an evidence-based management program. This review describes the pathophysiologic features that are thought to be responsible for the exercise intolerance experienced in the HF patient. Significant research has expanded our appreciation of the interplay of hemodynamic, ventilatory, and skeletal myopathic processes in this common, chronic condition. Randomized, controlled exercise trials designed to measure endothelial function, inflammatory markers, sympathetic neural activation, and skeletal muscle metabolism and structure have further defined the pathophysiology, documented the impact of exercise training on these processes, and confirmed the benefit of this therapy. Consistent with prior clinical research and patient experience are the recently published results of the HF-ACTION (Heart Failure-A Controlled Trial Investigating Outcomes of exercise TraiNing), which demonstrated a modest improvement in exercise capacity, reduction of symptoms, and improved self-reported measures of quality of life without adverse events. Consideration is given in this review to the benefits of variable intensity programs and the addition of resistance exercise to a standard aerobic prescription. Despite increasing validation of the role exercise training plays in the modification of exercise intolerance, challenges remain in its routine therapeutic application, including acceptance and use as an adjunctive intervention in the management of the patient with HF, limited insurance coverage for HF patients in cardiac rehabilitation, tailoring of exercise programs to best address the needs of subgroups of patients, and improved short- and long-term adherence to exercise training and a physically active lifestyle.

Test-retest reliability of the oxygen uptake efficiency slope in surgical patients

The oxygen uptake efficiency slope is a measure of cardiopulmonary fitness, that can be obtained from a sub-maximal cardiopulmonary exercise test. It has been evaluated in medical patients but its reliability in surgical populations remains uncertain. We conducted a test-retest study with the aim of establishing the reliability of the oxygen uptake efficiency slope in relation to that of the anaerobic threshold and peak oxygen uptake, in general surgical patients. Twenty-six patients over 60 years old completed two symptom-limited, incremental cycle ergometry tests within 7 days. The mean (SD) anaerobic threshold was 13.0 (3.0) mlO(2) .kg(-1) .min(-1) . There were no significant differences between mean test and retest values of anaerobic threshold (p = 0.50), peak oxygen uptake (p = 0.76) or oxygen uptake efficiency slope (p = 0.42). Reliability coefficients (95% CI) for the anaerobic threshold, oxygen uptake efficiency slope and peak oxygen uptake were 66.7% (45.3-87.9%), 89.0% (81.0-96.9%) and 91.7% (85.7-97.8%), respectively. The oxygen uptake efficiency slope was determined easily in all patients and found to have excellent reliability. Its clinical utility in determining pre-operative fitness warrants further evaluation.

Does left atrial volume affect exercise capacity of heart transplant recipients?

BACKGROUND

Heart transplant (HT) recipients demonstrate limited exercise capacity compared to normal patients, very likely for multiple reasons. In this study we hypothesized that left atrial volume (LAV), which is known to predict exercise capacity in patients with various cardiac pathologies including heart failure and hypertrophic cardiomyopathy is associated with limited exercise capacity of HT recipients.

METHODS

We analyzed 50 patients [age 57 ±2 (SEM), 12 females] who had a post-HT echocardiography and cardiopulmonary exercise test (CPX) within 9 weeks time at clinic follow up. The change in LAV (ΔLAV) was also computed as the difference in LAV from the preceding one-year to the study echocardiogram. Correlations among the measured parameters were assessed with a Pearson's correlation analysis.

RESULTS

LAV (n = 50) and ΔLAV (n = 40) indexed to body surface area were 40.6 ± 11.5 ml·m-2 and 1.9 ± 8.5 ml·m-2·year-1, data are mean ± SD, respectively. Indexed LAV and ΔLAV were both significantly correlated with the ventilatory efficiency, assessed by the VE/VCO2 slope (r = 0.300, p = 0.038; r = 0.484, p = 0.002, respectively). LAV showed a significant correlation with peak oxygen consumption (r = -0.328, p = 0.020).

CONCLUSIONS

Although our study is limited by a retrospective study design and relatively small number of patients, our findings suggest that enlarged LAV and increasing change in LAV is associated with the diminished exercise capacity in HT recipients and warrants further investigation to better elucidate this relationship.

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.

Cardiopulmonary exercise testing and its application

Cardiopulmonary exercise testing (CPET) has become an important clinical tool to evaluate exercise capacity and predict outcome in patients with heart failure and other cardiac conditions. It provides assessment of the integrative exercise responses involving the pulmonary, cardiovascular and skeletal muscle systems, which are not adequately reflected through the measurement of individual organ system function. CPET is being used increasingly in a wide spectrum of clinical applications for evaluation of undiagnosed exercise intolerance and for objective determination of functional capacity and impairment. This review focuses on the exercise physiology and physiological basis for functional exercise testing and discusses the methodology, indications, contraindications and interpretation of CPET in normal people and in patients with heart failure.

Exercise Capacity of Cardiac Asymptomatic Hereditary Hemochromatosis Subjects

PURPOSE

The exercise capacity of cardiac asymptomatic subjects with hereditary hemochromatosis (HH) has not been well described. In this study, we tested whether the iron overload associated with HH affected exercise capacity with a case control study design.

METHODS

Forty-three HH and 21 normal control subjects who were New York Heart Association functional class I underwent metabolic stress testing using the Bruce protocol at the clinical center of the National Institutes of Health. Exercise capacity was assessed with minute ventilation (.VE), oxygen uptake (.VO2), and carbon dioxide production (.VCO2) using a breath-by-breath respiratory gas analyzer.

RESULTS

The exercise capacity of HH subjects was not statistically different from that of control subjects (exercise time 564 +/- 135 vs 673 +/- 175 s, P = 0.191; peak .VO2 29.6 +/- 6.4 vs 32.5 +/- 6.7 mL.kg(-1).min(-1), P = 0.109; ventilatory threshold 19.0 +/- 3.4 vs 21.0 +/- 5.0 mL.min(-1).kg(-1), P = 0.099; data are for HH vs control subjects). Ventilatory efficiency was comparable between groups (.VE/.VCO2 slope 23.7 +/- 3.2 vs 23.4 +/- 4.2, P = 0.791). No significant correlation between the markers of iron levels and the markers of exercise capacity was noted. Iron depletion by 6-month phlebotomy therapy in 18 subjects who were newly diagnosed did not affect exercise testing variables (exercise time 562 +/- 119 vs 579 +/- 118 s, P = 0.691; peak .VO2 29.5 +/- 3.7 vs 29.1 +/- 4.7 mL.kg(-1).min(-1), P = 0.600; ventilatory threshold 18.5 +/- 2.8 vs 17.9 +/- 3.8 mL.kg(-1).min(-1), P = 0.651; data are from before and after phlebotomy therapy). Abnormal ischemic electrocardiographic responses and complex arrhythmias were more frequently seen in HH subjects.

CONCLUSIONS

The aerobic exercise capacity of asymptomatic HH subjects seems not to be statistically different from that of normal subjects. The iron levels do not seem to affect exercise capacity in asymptomatic HH subjects.

Impaired chronotropic and vasodilator reserves limit exercise capacity in patients with heart failure and a preserved ejection fraction

BACKGROUND

Nearly half of patients with heart failure have a preserved ejection fraction (HFpEF). Symptoms of exercise intolerance and dyspnea are most often attributed to diastolic dysfunction; however, impaired systolic and/or arterial vasodilator reserve under stress could also play an important role.

METHODS AND RESULTS

Patients with HFpEF (n=17) and control subjects without heart failure (n=19) generally matched for age, gender, hypertension, diabetes mellitus, obesity, and the presence of left ventricular hypertrophy underwent maximal-effort upright cycle ergometry with radionuclide ventriculography to determine rest and exercise cardiovascular function. Resting cardiovascular function was similar between the 2 groups. Both had limited exercise capacity, but this was more profoundly reduced in HFpEF patients (exercise duration 180+/-71 versus 455+/-184 seconds; peak oxygen consumption 9.0+/-3.4 versus 14.4+/-3.4 mL x kg(-1) x min(-1); both P<0.001). At matched low-level workload, HFpEF subjects displayed approximately 40% less of an increase in heart rate and cardiac output and less systemic vasodilation (all P<0.05) despite a similar rise in end-diastolic volume, stroke volume, and contractility. Heart rate recovery after exercise was also significantly delayed in HFpEF patients. Exercise capacity correlated with the change in cardiac output, heart rate, and vascular resistance but not end-diastolic volume or stroke volume. Lung blood volume and plasma norepinephrine levels rose similarly with exercise in both groups.

CONCLUSIONS

HFpEF patients have reduced chronotropic, vasodilator, and cardiac output reserve during exercise compared with matched subjects with hypertensive cardiac hypertrophy. These limitations cannot be ascribed to diastolic abnormalities per se and may provide novel therapeutic targets for interventions to improve exercise capacity in this disorder.

Statement on cardiopulmonary exercise testing in chronic heart failure due to left ventricular dysfunction: recommendations for performance and interpretation. Part I: definition of cardiopulmonary exercise testing parameters for appropriate use in chronic heart failure

Cardiopulmonary exercise testing (CPET) provides a global assessment of the integrated response to exercise involving the pulmonary, cardiovascular, haematopoietic, neuropsychological, and skeletal muscle systems. This information cannot be obtained through investigation of the individual organ systems in isolation. The non-invasive, dynamic physiological overview permits the evaluation of both submaximal and peak exercise responses, providing the physician with relevant information for clinical decision making. The use of CPET in management of the chronic heart failure patient is increasing with the understanding that resting pulmonary and cardiac function testing cannot reliably predict exercise performance and functional capacity and that, furthermore, overall health status and prognosis are predicted better by indices of exercise tolerance than by resting measurements. Our aim is to produce a statement which provides recommendations on the interpretation and clinical application of CPET in heart failure, based on contemporary scientific knowledge and technical advances: the focus is on clinical indications, issues of standardization, and interpretative strategies for CPET.

Is Functional Capacity Related to Left Atrial Contractile Function in Nonobstructive Hypertrophic Cardiomyopathy?

The mechanisms underlying reduced exercise capacity in patients with nonobstructive hypertrophic cardiomyopathy (NHCM) could include perturbations of ventricular relaxation, diastolic compliance, or compensatory atrial systolic function. We hypothesized that a loss of atrial contractility in NHCM patients leads to reduced functional capacity. To test this hypothesis, we compared resting noninvasive left atrial ejection phase indices in 49 consecutive patients with NHCM (ages 36+/-10 years; 41% female) and normal left ventricular ejection fraction (mean, 68%+/-8%) with objective metabolic exercise parameters. Left atrial active emptying fraction, ejection force, and kinetic energy failed to predict exercise capacity. Only left atrial total and active emptying volumes correlated weakly with minute volume/CO2 production slope (r=0.31 and r=0.33; p<0.05 for both). Furthermore, when subjects were stratified by New York Heart Association symptomatology, exercise parameters--but not atrial contractility--differed between groups. These data, obtained at rest, fail to suggest that NHCM-related heart failure symptoms are due to an atrial myopathy.

Influence of Permanent Right Ventricular Pacing on Cardiorespiratory Exercise Parameters in Chronic Heart Failure Patients With Implanted Cardioverter Defibrillators

STUDY OBJECTIVES

Patients with chronic heart failure and implanted cardioverter-defibrillators (ICDs) may have a higher incidence of new-onset or worsening heart failure requiring hospitalization with dual-chamber ICDs compared with single-chamber ICDs.

DESIGN AND SETTING

The purpose of this study was to show the impact of permanent right ventricular (RV) pacing on exercise capacity and related cardiorespiratory parameters in patients with chronic heart failure and ICDs.

PATIENTS AND INTERVENTIONS

Seventeen patients with chronic heart failure and a dual-chamber ICD performed cardiopulmonary exercise testing (CPX) on 3 different days. After CPX 1, patients were randomized either to back-up pacing or permanent RV pacing. After 3 months, CPX 2 was performed and patients changed groups (crossover design); CPX 3 was performed after 3 additional months.

MEASUREMENTS AND RESULTS

Maximal values for workload (108 +/- 46 W vs 117 +/- 48 W, p < 0.01), oxygen uptake (Vo(2)) [21.0 +/- 5.3 mL/min/kg vs 22.5 +/- 6.4 mL/min/kg, p < 0.05], oxygen pulse (13 +/- 3.7 mL vs 14 +/- 4.0 mL, p < 0.05), and metabolic equivalent (6.0 +/- 1.5 vs 6.4 +/- 1.8, p < 0.05) were significantly lower with permanent RV pacing compared to back-up pacing. Workload, Vo(2), and oxygen pulse were significantly reduced at the ventilatory anaerobic threshold, while workload and Vo(2) were significantly lower at the respiratory compensation point. No differences were found for maximal heart rate, minute ventilation Ve, and respiratory exchange ratio. The Ve/carbon dioxide production slope was significantly steeper with permanent RV pacing compared to back-up pacing.

CONCLUSIONS

Permanent RV pacing significantly reduced maximal and submaximal measures of exercise. For patients with chronic heart failure and sufficient atrioventricular conduction, every effort should be made to minimize permanent right ventricular pacing.

Effect of high-volume and -intensity endurance training in heart transplant recipients

BACKGROUND

A recommended component of heart transplant recipients (HTR) is endurance-oriented exercise therapy. However, the trainability of HTR after transplantation is vague. We examined the effect of high-volume and -intensity exercise training on exercise performance in HTR, compared with HTR undergoing regular rehabilitation training, and sedentary healthy subjects (SHS).

METHODS

We studied four groups of individuals; of those, three groups were HTR. Subjects were a regularly trained HTR group of denervated (HTR-D; N = 15), reinnervated (HTR-R; N = 26) hearts, a high-volume and -intensity endurance-training group (training time 7-20 h.wk(-1); HTR-ET; N = 12), and a group of sedentary healthy subjects (SHS; N = 21). All participants performed cardiopulmonary exercise testing.

RESULTS

The HTR-ET achieved a significantly higher performance (255 +/- 47 W, VO(2max) of 45.2 +/- 6.9 mL.kg(-1).min(-1)) in contrast to all other groups (HTR-D: 119 +/- 17 W, VO(2max) of 17.4 +/- 4.5 mL.kg(-1).min(-1); HTR-R: 119 +/- 17 W, VO(2max) of 16.9 +/- 3.7 mL.kg(-1).min(-1); SHS: 184 +/- 19 W, VO(2max) of 35.0 +/- 6.9 mL.kg(-1).min(-1)). The HR at maximal power output in the HTR-ET was 169 +/- 17 bpm and similar to SHS (164 +/- 17 bpm), but significantly higher than HTR-D (125 +/- 16) and HTR-R (142 +/- 10). Maximal lactate concentration (LAmax) of HTR-ET was 9.9 +/- 2.2 mmol.L(-1), comparable to SHS (9.2 +/- 2.1 mmol.L(-1)), and significantly higher than HTR-D (5.5 +/- 1.5 mmol.L(-1)) and HTR-R (5.1 +/- 1.0 mmol.L(-1)).

CONCLUSIONS

Data suggest that HTR can perform high-volume and -intensity exercise training, reaching exercise performance comparable to or even exceeding values of sedentary or moderately trained healthy subjects.

Oxygen uptake efficiency slope, a new submaximal parameter in evaluating exercise capacity in chronic heart failure patients

BACKGROUND

The oxygen uptake efficiency slope (OUES) is a new submaximal parameter which objectively predicts the maximal exercise capacity in children and healthy subjects. However, the usefulness of OUES in adult patients with and without advanced heart failure remains undetermined. The present study investigates the stability and the usefulness of OUES in adult cardiac patients with and without heart failure.

METHODS

Forty-five patients with advanced heart failure (group A) and 35 patients with ischemic heart disease but normal left ventricular ejection fraction (group B) performed a maximal exercise test. PeakVO2 and percentage of predicted peakVO2 were markers of maximal exercise capacity, whereas OUES, ventilatory anaerobic threshold (VAT), and slope VE/VCO2 were calculated as parameters of submaximal exercise.

RESULTS

Group A patients had lower peakVO2 (P < .001), lower percentage of predicted peakVO2 (P = .001), lower VAT (P < .05), steeper slope VE/VCO2 (P < .001), and lower OUES (P < .02). Within group A, significant differences were found for VAT, slope VE/VCO2, and OUES (all P < .01) between patients with peakVO2 above and below 14 mL O2/kg/min. Of all the submaximal parameters, VAT correlated best with peakVO2 (r =.814, P < .01) followed by OUES/kg (r = .781, P < .01), and slope VE/VCO2 (r = -.492, P < .001). However, VAT could not be determined in 18 (23%) patients.

CONCLUSIONS

OUES remains stable over the entire exercise duration and is significantly correlated with peakVO2 in adult cardiac patients with and without impaired LVEF. Therefore, OUES could be helpful to assess exercise performance in advanced heart failure patients unable to perform a maximal exercise test. Further studies are needed to confirm our hypothesis.

Influence of beta-blocker use on percentage of target heart rate exercise prescription

BACKGROUND

Exercise is recommended for cardiac patients irrespective of beta-blockers. Percentages of maximal heart rate (%HRmax) and heart rate reserve (%HRR) are widely used to determine training intensities. The purpose of this study was to investigate the influence of chronic cardioselective beta blockade on the %HRmax and %HRR model.

METHODS

Ten healthy male subjects randomly received oral placebo or beta-blocker bisoprolol (5 mg/day) for 2 weeks using a double-blind, crossover design. In the second week, the subjects performed a cardiopulmonary exercise test until exhaustion to determine the aerobic (AeT) and anaerobic (AnT) threshold.

RESULTS

No significant differences were found for absolute and relative values of oxygen consumption, power output and ratings of perceived exertion at AeT, AnT and maximum workload. Mean HR was significantly (P<0.05) lower at rest (-15 +/- 5 bpm), AeT (-19 +/- 8 bpm), AnT (-22 +/- 10 bpm) and maximal workload (-19 +/- 11 bpm) with bisoprolol compared to placebo. Percentage of maximal heart rate (%HRmax) was significantly (P<0.05) reduced at rest (43 versus 39%), AeT (64 versus 60%) and AnT (86 versus 82%), a trend for a reduction was found for %HRR at AnT (75 versus 71%, P=0.07).

CONCLUSIONS

Exercise prescription using %HRmax or %HRR methods are of limited accuracy for patients taking beta-blockers. Although %HRmax and %HRR are easy to determine and therefore attractive, we suggest that the most precise exercise prescription would depend on AeT and AnT. Percentages of maximal oxygen consumption or maximal workload or ratings of perceived exertion may be suggested as a substitute. Alternatively, upper limits for %HRmax and %HRR should be lower for patients taking beta-blockers.

A refined technique for determining the respiratory gas exchange responses to anaerobic metabolism during progressive exercise - repeatability in a group of healthy men

The respiratory gas exchange and ventilation during an incremental cycle exercise test were analysed in a group of 19 healthy, moderately fit men. Different computer algorithms were used to estimate the VO2 values where: (i) the rate of VCO(2) increase just exceeds the rate of VO(2) increase (DX, derivative crossing), (ii) VCO(2)/VO(2) = 1.00 (PX, point of crossing) and (iii) ventilation (VE) increases disproportionately in relation to VCO(2) (PQ, point of VCO(2) equivalent rise). The DX and PQ measurements were analysed using a new approach employing polynomial regression and the value of PX was determined following low-pass filtration of raw data. The repeatability of the measurements was evaluated with a 5-6 week interval between the tests. The correlations between tests were 0.75 at DX, 0.85 at PX and 0.62 at PQ. The mean differences between the repeated tests were not statistically significant. The repeatability of VO2, in absolute values expressed as +/-2 SD of the differences between the tests, had values of 5.0, 6.1 and 9.5 ml min(-1) kg(-1) for DX, PX and PQ, respectively. The mean value of VO(2) for each measurement point expressed as a percentage of VO(2 max) was 54% at DX, 68% at PX and 70% at PQ. The most common sequence of the measured values was DX < PX < PQ, but the sequence DX < PQ < PX was also observed. It is concluded that the gas exchange responses to developing anaerobic metabolism during progressive exercise can be characterized by a series of thresholds. However, the considerable variation in absolute values in the two testing occasions requires further attention.

Cardiopulmonary exercise testing in children with heart failure secondary to idiopathic dilated cardiomyopathy

STUDY OBJECTIVE

To determine and compare the cardiopulmonary responses of healthy children and children with heart failure due to idiopathic dilated cardiomyopathy (IC) to progressive treadmill exercise testing.

SETTING

University teaching hospital specializing in cardiology.

PATIENTS OR PARTICIPANTS

Twenty-six children with stable, chronic heart failure (left ventricular ejection fraction < 45%) caused by IC (IC group) and 12 healthy children (control group).

INTERVENTIONS

After 12-lead resting ECG, all children underwent progressive treadmill exercise testing using a modified Naughton protocol. Tests were performed in a controlled-temperature exercise facility, at least 2 h after a light meal.

MEASUREMENTS AND RESULTS

Cardiopulmonary parameters were assessed at rest, at anaerobic threshold (AT), and at peak exercise. At rest, the tidal volume (VT) and O(2) consumption (VO(2)) for heart rate (O(2) pulse) were lower, while the heart rate, respiratory rate, and ventilatory equivalent for O(2) (minute ventilation [VE]/VO(2)) were higher in the IC group compared with the control group. At AT, the systolic BP, O(2) pulse, VT, exercise duration, VO(2), CO(2) production (VCO(2)), and VE were lower, while the VE/VO(2) and ventilatory equivalent for CO(2) (E/CO(2)) were higher in the IC group (p < 0.05). At peak exercise, the IC group had a significantly lower systolic BP, O(2) pulse, VE, VT, exercise duration, VO(2), and VCO(2), but higher VE/VO(2) and VE/VCO(2) than the control group (p < 0.05). The VE/VCO(2) slope was significantly higher for the IC group. No correlation existed between variables evaluated at rest vs during exercise.

CONCLUSIONS

Gas exchange analysis performed during exercise successfully differentiated children with heart failure from healthy children.

Heart rate at the estimated lactate threshold in patients with chronic obstructive pulmonary disease: effects on the target intensity for dynamic exercise training

BACKGROUND

Physical training at the range of exercise intensities associated with sustained blood lactate accumulation seems to rapidly improve aerobic performance in both healthy subjects and patients with chronic obstructive pulmonary disease (COPD). However, it is still unclear whether patients' heart rate (HR) at the estimated lactate threshold (HR [symbol: see text]L)--as expressed in percent attained peak HR (AHR), predicted peak HR (PHR) and HR reserve (HRR)--are comparable with the ranges of intensity that are commonly used for target exercise training in control subjects.

METHODS

The authors evaluated 26 patients with stable COPD (forced expiratory volume in 1 second = 1.17 +/- 0.28 L) who were submitted for spirometric evaluation, and, after familiarization, to a symptom-limited ramp-incremental cardiopulmonary exercise testing on a cycle ergometer.

RESULTS

The authors were able to identify [symbol: see text]L in only 18 patients (69%). The HR [symbol: see text]L corresponded to wide range of exercise intensities according to the three methods (ranging from 70-95% AHR, 50-90% PHR, and 35-60% HRR). However, most of the subjects would be trained within +/- 5% HR [symbol: see text]L if they had been exercised at 80 to 85% AHR and 40 to 45% HRR; these values correspond to higher (AHR) and lower (HRR) intensities than usually recommended for healthy subjects.

CONCLUSIONS

Considering that [symbol: see text]L was not identified in approximately one third of the patients and there was ample variability on HR [symbol: see text]L as %AHR, %PHR, and %HRR, the use of HR and [symbol: see text]L targets for routine exercise prescription does not seem to be clinically justifiable in patients with COPD submitted to pulmonary rehabilitation.

Change in left atrial and ventricular dimensions during and immediately after exercise

PURPOSE

The aim of this study was to evaluate differences in the left atrial (LAD), total ventricular end-diastolic (TEDD), end-systolic diameters (TESD), and left ventricular shortening fraction (SF) compared with heart rate (HR) and systolic blood pressure (SBP) during exercise and recovery.

METHODS

Healthy young male (N = 15) and female (N = 16) subjects performed an incremental cycle ergometer test in upright position, and three phases of energy supply were defined by means of blood lactate concentration (LA) and respiratory gas exchange variables (I: aerobic; II: aerobic-anaerobic transition; III: anaerobic). Subjects were required to rest their arms on a steering bar and to lean their upper body forward; two dimensional (2-D) echocardiograms were obtained over the left parasternal area at rest (R), at the end of each phase, immediately within 15 s post, and 6 min after exercise (6 min). By using VINGMED's "Anatomical M-Mode," it was possible to extract M-Mode Sweeps from stored 2-D-Loops and perform the M-Mode measurement.

RESULTS

In contrast to the significant decrease in TEDD and TESD from III to 15 s up to resting values and the significant increase in SF from III to 15 s, the moderate decrease in HR immediately post exercise (15 s) was not significant. The SBP showed a significantly decrease from III to 15 s; in contrast to TEDD, TESD, and SF, the values at 15 s were comparable with the values at II. For LAD, significant increase during exercise and a decrease during recovery were observed. Sex-specific differences of changes in measured variables could not be found.

CONCLUSION

We concluded that post exercise measurement of left ventricular and atrial dimensions or SF were not valid to describe heart function at maximal exercise although immediately post exercise HR was near maximal level.

The 6-min walk and peak oxygen consumption in advanced heart failure: aerobic capacity and survival

BACKGROUND

This study sought to determine to what extent the 6-min walk (6MW) distance in advanced heart failure predicts aerobic capacity and provides comparable information regarding survival. Peak oxygen uptake ( VO(2)) and the 6MW both describe function and predict outcome over a wide range of heart failure, but their determinants and implications may differ within a narrower clinical spectrum. This study compared 6MW with aerobic capacity both at peak exercise and during low-level cycling.

METHODS AND RESULTS

Both the 6MW and symptom-limited cycle ergometry were performed by 307 patients of whom 264 patients additionally performed 6 min of 20-W cycling to estimate aerobic capacity during sustained low-level activity. In the first 198 patients, multivariate analysis of survival was performed with the 6MW and peak VO (2). Patients achieved the 6MW of 393 +/- 104 m and peak VO (2) of 14 +/- 5 mL/kg per minute. Although low peak VO (2) was more likely with the shorter 6MW, the relation was weak within peak VO (2) range of 10 to 20 mL/kg per minute (n = 213, 69% of patients, r = 0.28). During 20-W exercise, VO (2) was 9.2 +/- 2.0 mL/kg per minute, with respiratory exchange ratio poorly correlated with the 6MW. In contrast to peak VO (2), the 6MW in meters did not predict survival. Division into short, medium, and long walks, however, supplemented simple clinical description.

CONCLUSIONS

Although helpful in broader populations for identification of patients with obvious clinical compromise, the 6MW distance is not a surrogate for peak VO (2) in assessing aerobic capacity or prognosis for individuals with advanced heart failure.

How high can a correlation coefficient be? Effects of limited reproducibility of common cardiological measures

In clinical studies the linear correlation coefficient is commonly used to quantify the strength of the association between two variables, such as height and weight: the value of r indicates whether the relationship is a strong one. However, actual clinical data includes an underlying physical variable plus an inevitable measurement error component that represents the reproducibility of the test used. If test reproducibility is poor, then even if the underlying physical variables are perfectly correlated, the actual observed correlation coefficient cannot be one but must be somewhat less. We present a method for calculating the reduction in correlation coefficient due to limited reproducibility, and discuss its implications with respect to experimental design and interpretation.

Reproducibility of cardiopulmonary exercise testing in elderly patients with congestive heart failure

Elderly patients with congestive heart failure, including those with preserved systolic function, underwent maximal cardiopulmonary exercise testing. Maximal exercise oxygen consumption, exercise time, heart rate, respiratory exchange ratio, and ventilatory anaerobic threshold showed good reproducibility.

Maximal and submaximal exercise testing in heart failure

Although reduced exercise capacity is the main complaint of patients with congestive heart failure (CHF), the best method to measure it remains controversial. Peak VO2, obtained using maximal exercise testing, is the most accurate measure of maximal functional capacity. It is related to peak exercise cardiac output and is one of the most important independent variables for the prognostic assessment of patients with CHF. It has, however, a low sensitivity for measurement of changes induced by therapy and is poorly related to everyday physical activity, patient symptoms, and quality of life. The anerobic threshold may also be regarded as a parameter of maximal functional capacity. Its value is mainly indirect, because it shows that the patient is performing a maximal effort limited by the cardiovascular system. The VO2 kinetics at the start and at the end of exercise are probably more related to patient symptoms, but it is unresolved which protocols and parameters might best be used to study this aspect of exercise performance. Duration of a submaximal exercise at a constant work rate and the distance walked during a 6-min walking test are gaining wide popularity as parameters of submaximal performance. However, when these exams are carried out up to exhaustion in patients with severe functional limitation, they may involve attainment of the anerobic threshold and therefore their clinical meaning may be similar to the one of a maximal exercise test. Moreover, tests based on the assessment of submaximal exercise capacity have been useful for assessment of therapy in single-center trials but have been often inadequate in multicenter trials.

Exertional dyspnea in heart failure: a symptom unrelated to pulmonary function at rest or during exercise. Duke University Clinical Cardiology Studies (DUCCS) Exercise Group

BACKGROUND

Exertional dyspnea is a common symptom in patients with heart failure, and the mechanisms responsible for the symptom are unknown. The purpose of this study was to identify factors responsible for the symptom of exertional dyspnea in patients with heart failure.

METHODS

Resting pulmonary-function tests and maximal cardiopulmonary exercise tests were performed in 71 patients with New York Heart Association functional class II-IV symptoms (mean ejection fraction 30.6%; mean age, 68 years).

RESULTS

The severity of dyspnea at peak exercise, which patients rated as 3 to 10 on a 1 to 10 severity scale, did not correlate with rest or exercise hemodynamic, spirometric, or metabolic variables, including peak oxygen uptake (VO2), minute ventilation (Ve), and respiratory rate, or with derived variables including Ve/VO2, Ve/VCO2, and the dyspnea index (Ve/maximum voluntary ventilation). Additionally, these variables did not differ between patients who reported limitation of exercise by dyspnea and those who were limited by fatigue.

CONCLUSIONS

The symptom of exertional dyspnea in patients with heart failure is not determined by abnormalities in ventilatory function or demand.

Improvement in the mechanical efficiency of walking: an explanation for the "placebo effect" seen during repeated exercise testing of patients with heart failure. Duke University Clinical Cardiology Studies (DUCCS) Exercise Group

To determine the mechanism responsible for the "placebo effect" seen during serial exercise testing of patients with heart failure, we examined metabolic variables for 81 patients who underwent five baseline exercise tests as part of a multicenter drug trial. The patients were 50 men and 31 women with a mean ejection fraction of 30.1% and a mean age of 69 years. From test 1 to 2, the exercise time increased from 419 +/- 140 to 462 +/- 130 seconds before it reached a plateau over the next three tests. Metabolic measurements at test 1 and test 3 revealed no change in peak oxygen consumption ( 1119 +/- 376 to 1105 +/- 346 ml/min). Maximum heart rate, systolic blood pressure, ventilation, and respiratory exchange ratio also were unchanged. The onset of the anaerobic threshold was delayed from 211 +/- 81 to 238 +/- 93 seconds, but there was no change in oxygen consumption at the anaerobic threshold (810 +/- 222 to 795 +/- 220 ml/min). At a predetermined submaximal level, oxygen consumption, ventilation, and respiratory exchange ratio all decreased to a statistically significant degree. These results indicate that a rapid increase in the mechanical efficiency of walking contributes to the placebo effect among patients with heart failure during serial exercise testing and is independent of changes in conditioning or motivation.

Short-term reproducibility of cardiopulmonary measurements during exercise testing in patients with severe chronic heart failure

Eleven men with severe chronic heart failure (peak cardiac index 4.0 +/- 0.2 L/m2/min), six on a heart transplantation waiting list, were prospectively assessed. To determine reproducibility of cardiopulmonary and hemodynamic variables for clinical purposes during ramp bicycle ergometry, the patients underwent two ramp bicycle ergometer tests (3 minutes unloaded, work rate increments of 12.5 W/min) with a 1-week interval between tests. Oxygen uptake (VO2) carbon dioxide production (VCO2), and ventilation were measured breath by breath, and calculations were performed to determine gas exchange ratio, oxygen pulse, ventilatory equivalents of oxygen and carbon dioxide, and end-tidal partial pressure for oxygen and carbon dioxide. Additionally, heart rate, blood pressure, and lactate levels were assessed. Measurements were performed at submaximum work rate levels of 25 W, 50 W, and 75 W at ventilatory threshold and at peak work rate. At all measurement points, the coefficient of variation for cardiopulmonary variables was between 1.4% and 7.1% for submaximum work rate levels, between 1.2% and 4.4% at ventilatory threshold, and between 2.4% and 7.1% at peak work rate. For heart rate, blood pressure, and lactate levels, coefficient of variation was between 2.7% and 5.7% for submaximum work rate levels, between 1.4% and 6.1% at ventilatory threshold, and between 1.2% and 5.5% at peak work rate. The data suggest high reproducibility for duplicate measurements of cardiopulmonary and hemodynamic variables during ramp bicycle ergometry in patients with severe chronic heart failure. The results may be used to determine whether any variable in a single patient is significantly different from that obtained in a previous exercise test or if the change is within experimental error.

Exercise testing and training of patients with heart failure due to left ventricular systolic dysfunction

Reducing the exercise intolerance and symptoms experienced by patients with chronic heart failure remains an important focus in their clinical care. A clear shortcoming exists; however, with respect to an appreciation that in addition to standard medical therapy, selected patients with stable heart failure also can benefit from a moderate exercise training program. Improvements in central transport, regional blood flow, and skeletal muscle histology and biochemistry all likely account for the increase in exercise capacity and delay in fatigue that these patients experience. Additionally, the autonomic imbalance that is characteristic of these patients is improved. Although the number of patients with heart failure participating in an exercise program is increasing, much work still exists relative to incorporating this treatment method into the care plans established by physicians and physician extenders.

Skeletal muscle metabolism during exercise in patients with chronic heart failure

OBJECTIVE

To investigate the metabolic response of skeletal muscle to exercise in patients with chronic heart failure and determine its relation to central haemodynamic variables.

SETTING

University hospital in Sweden.

PARTICIPANTS

16 patients in New York Heart Association class II-III and 10 healthy controls.

MAIN OUTCOME MEASURES

Skeletal muscle biopsies were obtained from the quadriceps muscle at rest and at submaximal and maximal exercise. Right sided heart catheterisation was performed in eight patients.

RESULTS

The patients had lower maximal oxygen consumption than the control group (13.2 (2.9) v 26.8 (4.4) ml/kg/min, P < 0.001). They had reduced activities of citrate synthetase (P < 0.05) and 3-hydroxyacyl-CoA dehydrogenase (P < 0.05) compared with the controls. At maximal exercise adenosine triphosphate (P < 0.05), creatine phosphate (P < 0.01), and glycogen (P < 0.01) were higher whereas glucose (P < 0.001) and lactate (P < 0.06) were lower in the patients than in the controls. Citrate synthetase correlated inversely with skeletal muscle lactate at submaximal exercise (r = -0.90, P < 0.003). No correlations between haemodynamic variables and skeletal muscle glycogen, glycolytic intermediates, and adenosine nucleotides during exercise were found.

CONCLUSION

Neither skeletal muscle energy compounds nor lactate accumulation were limiting factors for exercise capacity in patients with chronic heart failure. The decreased activity of oxidative enzymes may have contributed to the earlier onset of anaerobic metabolism, but haemodynamic variables seemed to be of lesser importance for skeletal muscle metabolism during exercise.