Can anaerobic threshold be used as an end-point for therapeutic trials in heart failure? Lessons from a multicentre randomized placebo-controlled trial. The VO2 French Study Group

Cardiopulmonary Exercise Testing Distinguishes between Post-COVID-19 as a Dysfunctional Syndrome and Organ Pathologies

(1) Background: Dyspnea is one of the most frequent symptoms among post-COVID-19 patients. Cardiopulmonary exercise testing (CPET) is key to a differential diagnosis of dyspnea. This study aimed to describe and classify patterns of cardiopulmonary dysfunction in post-COVID-19 patients, using CPET. (2) Methods: A total of 143 symptomatic post-COVID-19 patients were included in the study. All patients underwent CPET, including oxygen consumption, slope of minute ventilation to CO₂ production, and capillary blood gas testing, and were evaluated for signs of limitation by two experienced examiners. In total, 120 patients reached a satisfactory level of exertion and were included in further analyses. (3) Results: Using CPET, cardiovascular diseases such as venous thromboembolism or ischemic and nonischemic heart disease were identified as either cardiac (4.2%) or pulmonary vascular (5.8%) limitations. Some patients also exhibited dysfunctional states, such as deconditioning (15.8%) or pulmonary mechanical limitation (9.2%), mostly resulting from dysfunctional breathing patterns. Most (65%) patients showed no signs of limitation. (4) Conclusions: CPET can identify patients with distinct limitation patterns, and potentially guide further therapy and rehabilitation. Dysfunctional breathing and deconditioning are crucial factors for the evaluation of post-COVID-19 patients, as they can differentiate these dysfunctional syndromes from organic diseases. This highlights the importance of dynamic (as opposed to static) investigations in the post-COVID-19 context.

Interobserver variability of ventilatory anaerobic threshold in asymptomatic volunteers

Background

The ventilatory anaerobic threshold (VO₂@AT) has been used in preoperative risk assessment and rehabilitation for many years. Our aim was to determine the interobserver variability of AT using cardiopulmonary exercise (CPET) data from a large epidemiological study (SHIP, Study of Health in Pomerania).

Methods

VO₂@AT was determined from CPET of 1,079 cross-sectional volunteers, according to American Heart Association guidelines. VO₂@AT determinations were compared between two experienced physicians, between physicians and qualified medical assistants, and between physicians or medical assistants and software-based algorithms. For the first 522 data sets, the two physicians discussed discrepant readings to reach consensus; the remaining data sets were analyzed without consensus discussion.

Results

VO₂@AT was detectable in 1,056 data sets. The physicians recorded identical VO₂@AT values in 319 out of 522 cases before consensus discussion (61.1%; intraclass correlation coefficient [ICC]: 0.90; 95% confidence interval [CI]: 0.88-0.92) and in 700 out of 1,056 cases overall (66.3%; ICC: 0.95; 95% CI: 0.95-0.96), with an interobserver difference of 0 ± 8% (95% limits of agreement [LOA]: ±161 mL/min). The interobserver difference was - 2 ± 18% (95% LOA: ±418 mL/min) between a physician and medical assistants, and - 19 ± 24% to - 22 ± 26% (95% LOAs: ±719-806 mL/min) between physicians or medical assistants and software-based algorithms.

Conclusions

Experienced physicians show high agreement when determining AT in asymptomatic volunteers. However, agreement between physicians and qualified medical assistants is lower, and there is substantial deviation in AT determination between physicians or medical assistants and software-based algorithms. This must be considered when using AT as a decision tool.

Relationship between peak cardiac pumping capability and indices of cardio-respiratory fitness in healthy individuals

Cardiac power output (CPO) is a unique and direct measure of overall cardiac function (i.e. cardiac pumping capability) that integrates both flow- and pressure-generating capacities of the heart. The present study assessed the relationship between peak exercise CPO and selected indices of cardio-respiratory fitness. Thirty-seven healthy adults (23 men and 14 women) performed an incremental exercise test to volitional fatigue using the Bruce protocol with gas exchange and ventilatory measurements. Following a 40-min recovery, the subjects performed a constant maximum workload exercise test at or above 95% of maximal oxygen consumption. Cardiac output was measured using the exponential CO(2) rebreathing method. The CPO, expressed in W, was calculated as the product of the mean arterial blood pressure and cardiac output. At peak exercise, CPO was well correlated with cardiac output (r = 0·92, P<0·01), stroke volume (r = 0·90, P<0·01) and peak oxygen consumption (r = 0·77, P<0·01). The coefficient of correlation was moderate between CPO and anaerobic threshold (r = 0·47, P<0·01), oxygen pulse (r = 0·57, P<0·01), minute ventilation (r = 0·53, P<0·01) and carbon dioxide production (r = 0·56, P<0·01). Small but significant relationship was found between peak CPO and peak heart rate (r = 0·23, P<0·05). These findings suggest that only peak cardiac output and stroke volume truly reflect CPO. Other indices of cardio-respiratory fitness such as oxygen consumption, anaerobic threshold, oxygen pulse, minute ventilation, carbon dioxide production and heart rate should not be used as surrogates for overall cardiac function and pumping capability of the heart.

Evaluation of cardiorespiratory functional reserve from arm exercise in the elderly

BACKGROUND

When the subject is not able to satisfy traditional testing procedures, alternative exercises or indices such as arm cranking or the oxygen uptake efficiency slope (OUES) have been proposed. However, the OUES has not yet been used on elderly subjects from an exercise performed with the arms.

OBJECTIVE

The aim of our study was to evaluate the possibility of using the OUES as an index of the cardiorespiratory functional reserve in the elderly when the exercise evaluation test is performed with the arms and when this parameter is estimated from submaximal responses.

METHODS

Seventeen adults (62-82 years) undergoing total joint arthroplasty of the hip took part in this study. Maximal incremental exercise tests were performed on an arm crank ergometer 1 month before (T₁) and 2 months after (T₂) surgery. Gas exchanges were measured continuously to determine oxygen consumption at peak exercise (V˙O₂ peak) and were used to calculate the OUES. The correlation coefficient was calculated between V˙O₂ peak and OUES, and their relative changes between T₁ and T₂.

RESULTS

V˙O₂ peak was not significantly different between T₁ and T₂: 10.3 ± 0.7 and 9.8 ± 0.5 mL/min per kilogramme respectively. The OUES estimated from submaximal responses did not show a significant difference between T₁ and T₂. Significant correlations were observed between individual V˙O₂ peak and OUES, as well as at T₁ and T₂.

CONCLUSION

The use of arm cranking exercises and the calculation of the OUES from the submaximal respiratory response can be used for the objective quantification of cardiorespiratory functional reserve in the elderly.

Standards for the use of cardiopulmonary exercise testing for the functional evaluation of cardiac patients: a report from the Exercise Physiology Section of the European Association for Cardiovascular Prevention and Rehabilitation

Cardiopulmonary exercise testing (CPET) is a methodology that has profoundly affected the approach to patients' functional evaluation, linking performance and physiological parameters to the underlying metabolic substratum and providing highly reproducible exercise capacity descriptors. This study provides professionals with an up-to-date review of the rationale sustaining the use of CPET for functional evaluation of cardiac patients in both the clinical and research settings, describing parameters obtainable either from ramp incremental or step constant-power CPET and illustrating the wealth of information obtainable through an experienced use of this powerful tool. The choice of parameters to be measured will depend on the specific goals of functional evaluation in the individual patient, namely, exercise tolerance assessment, training prescription, treatment efficacy evaluation, and/or investigation of exercise-induced adaptations of the oxygen transport/utilization system. The full potentialities of CPET in the clinical and research setting still remain largely underused and strong efforts are recommended to promote a more widespread use of CPET in the functional evaluation of cardiac patients.

Exercise based rehabilitation for heart failure

BACKGROUND

The prevalence of chronic heart failure is increasing, and increases with increasing age. Major symptoms include breathlessness and restricted activities of daily living due to reduced functional capacity, which in turn affects quality of life. Exercise training has been shown to be effective in patients with coronary heart disease and has been proposed as an intervention to improve exercise tolerance in patients with heart failure.

OBJECTIVES

To determine the effectiveness of exercise based interventions compared with usual medical care on the mortality, morbidity, exercise capacity and health related quality of life, of patients with heart failure.

SEARCH STRATEGY

We searched the Cochrane Controlled Trials Register (The Cochrane Library Issue 2, 2001), MEDLINE (2000 to March 2001), EMBASE (1998 to March 2001), CINAHL (1984 to March 2001) and reference lists of articles. We also sought advice from experts.

SELECTION CRITERIA

RCTs of exercise based interventions. The comparison group was usual medical care as defined by the study, or placebo. Adults of all ages with chronic heart failure. Only those studies with criteria for diagnosis of heart failure (based on clinical findings or objective indices) have been included.

DATA COLLECTION AND ANALYSIS

Studies were selected, and data were abstracted, independently by two reviewers. Authors were contacted where possible to obtain missing information.

MAIN RESULTS

Twenty-nine studies met the inclusion criteria, with 1126 patients randomised. The majority of studies included both patients with primary and secondary heart failure, NYHA class II or III. None of the studies specifically examined the effect of exercise training on mortality and morbidity as most were of short duration. Exercise training significantly increased VO(2) max by (WMD random effects model) 2.16 ml/kg/min (95% CI 2.82 to 1.49), exercise duration increased by 2.38 minutes (95% CI 2.85 to 1.9), work capacity by 15.1 Watts (95% CI 17.7 to 12.6) and distance on the six minute walk by 40.9 metres (95% CI 64.7 to 17.1). Improvements in VO(2) max were greater for training programmes of greater intensity and duration. HRQoL improved in the seven of nine trials that measured this outcome.

REVIEWERS' CONCLUSIONS

Exercise training improves exercise capacity and quality of life in patients mild to moderate heart failure in the short term. There is currently no information regarding the effect of exercise training on clinical outcomes. The findings are based on small-scale trials in patients who are unrepresentative of the total population of patients with heart failure. Other groups (more severe patients, the elderly, women) may also benefit. Large-scale pragmatic trials of exercise training of longer duration, recruiting a wider spectrum of patients are needed to address these issues.

Exercise responses of elderly patients with diastolic versus systolic heart failure

PURPOSE

Little information is available regarding peak and submaximal exercise performance in elderly heart failure (HF) patients, particularly in those with diastolic dysfunction (DD). Therefore, the purpose of this investigation was to compare exercise responses of elderly patients with HF due to either systolic dysfunction (SD) or DD, to age-matched healthy volunteers (HV).

METHODS

Patients with chronic HF > or = 60 yr (N = 119) due to SD (N = 60) or primary DD (N = 59) underwent a maximal cycle ergometry test with expired gas analysis and venous lactate measurement. Twenty-eight HV > or = 60 yr served as a control group. Anaerobic threshold was determined by gas analysis (ATVEN) and by plasma lactate rise (ATLAC).

RESULTS

Peak oxygen consumption (VO(2peak)) was significantly (P < 0.001) reduced in both SD and DD patients (13 +/- 0.4 vs 14 +/- 0.4 ml x kg(-1) x min(-1), respectively) versus HV (20 +/- 0.6 ml x kg(-1) x min(-1)). Peak heart rate was reduced in patients versus HV (131 +/- 3 bpm vs 145 +/- 4, respectively; P < or = 0.01), but heart rate at a given submaximal work rate was significantly lower (P < or = 0.01) in HV than in SD and DD patients. ATVEN of 11.8 +/- 0.3 ml x kg(-1) x min(-1) for HV was significantly higher than SD (8.9 +/- 0.2) and DD (9.2 +/- 0.3). Peak lactate concentration was 6.6 +/- 0.6 mmol x kg(-1) x l(-1) in HV and was significantly reduced in both SD and DD HF patients. ATVEN correlated well with ATLAC in HV and in DD patients, but not in SD patients.

CONCLUSIONS

Submaximal and peak exercise performance are markedly altered in elderly HF patients compared with age-matched HV but do not appear to be different between SD and DD patients.

Individual assessment of intensity-level for exercise training in patients with coronary artery disease is necessary

BACKGROUND

Target intensity-level of exercise training in patients with coronary artery disease is adjusted usually by a target heart rate (THR). This THR is aimed to be at or nearby the anaerobic threshold (AT) and is calculated commonly from parameters of regular exercise training, instead of an actual measurement of AT and its related heart rate. Therefore, this study evaluated whether a calculation is reliable.

METHODS

In 91 male patients (age 52+/-9 years) exercise capacity was measured after a recent (>4 weeks) coronary event. AT was compared with peak exercise capacity and heart rate at AT was compared with THR, using the Karvonen method.

RESULTS

Mean AT (18.2 ml/min/kg, range 9.2-32.2) and mean peak V(O2) (24.5, range 10.9-43.9) were slightly decreased (respectively 0.83 and 0.79 of predicted). When related to peak exercise capacity, AT showed a large inter-individual variation. For example, heart rate at AT ranged from 0.55 to 0.96 of peak heart rate. As a result heart rate at AT varied considerably with THR. The mean THR, although significantly higher, correlated well with mean heart rate at AT (respectively, 109 and 105/min, P<0.01; r=0.86, P<0.001). However, in an important number of patients heart rate at AT was more than 10% below or above THR (respectively, 30 and 7%).

CONCLUSION

In individual exercise prescription for cardiac rehabilitation the training level should be determined directly, and not indirectly by calculation from heart rate parameters of exercise testing.

The role of exercise testing in the evaluation and management of heart failure

The clinical syndrome of heart failure has been investigated so extensively that it may now almost be regarded as a metabolic disorder. Although an initial insult reduces cardiac pump efficacy, the resultant physiological response culminates in complex neurohormonal dysfunction. This has created confusion and prevented the acceptance of a universal definition of cardiac failure. With much current research concentrating on the pharmacological modification of neuroendocrine imbalance, it is easy to lose sight of the fundamental principles behind heart failure management, namely, to improve cardiac function. In attempting to achieve this, the issues of morbidity and mortality must be addressed jointly; they are not mutually exclusive entities. Discrepant results between mortality studies and changes in exercise capacity have undermined the value of exercise testing. Because a treatment enhances longevity we should not ignore its effect on symptomatic status, and likewise we should not discard a therapy, which improves function because adverse events result in occasional premature deaths. Informed patient choice must exist. Historically, exercise testing has been quintessential in our understanding and evaluation of heart failure. Peak oxygen consumption remains the best overall indicator of symptomatic status, exercise capacity, prognosis and hospitalisation. Unfortunately, muddling of surrogate and true end-points has confused many of these issues. Improved comprehension may be gained by applying the concept of cardiac reserve which has been described in a variety of heart conditions and used in cardiac failure patients to provide an indication of prognosis and functional capacity.

Objective effects of a 6 months' endurance and strength training program in outpatients with congestive heart failure

PURPOSE

The aim of this study was to assess the feasibility and the effects of a long-term training program with endurance and strength elements for patients with advanced congestive heart failure (CHF).

METHODS

We studied 14 patients, mean age 57 yr, mean NYHA class 2.7, mean LVEF 29%, and mean VO2max 17.2 mL x kg(-1) x min(-1). They underwent a 6 months' outpatient "in-hospital" training program (80 sessions). After an introduction period the program was subdivided into four cycles in which endurance and strength were revalued and progressively increased. Endurance was measured by spiro-ergometric exercise testing with concomitant lactate determination, while strength was measured on an isokinetic dynamometer.

RESULTS

The compliance ratio was 89% and there were no major problems during training. NYHA class improved from a mean of 2.7 to 1.5 (P = 0.0001), working capacity from 83 to 100 W (P = 0.001), VO2 from 16.7 to 18.4 mL x kg(-1) x min(-1) (P = 0.02), and maximal exercise lactate from 4.1 to 5.2 mmol x L(-1) (P = 0.01). At isokinetic testing we found a significant 18% increase in muscular endurance of knee flexors (P = 0.008) and 25% increase of knee extensors (P = 0.007). The increase of peak torque, total work, and average power reached statistical significance only for the knee extensors.

CONCLUSION

This pilot study showed that progressively adapted global strength training in association with traditional endurance training is feasible for selected patients with CHF. Additional larger studies should be done to test the effects, the safety, and the composition of such supervised "in-hospital" training programs.

Reproducibility of cardiopulmonary exercise parameters in patients with valvular heart disease

STUDY OBJECTIVES

To determine the degree of reproducibility of exercise parameters in patients with chronic heart failure. Parameters such as treadmill walking time (TWT), oxygen uptake (Vo2), heart rate, oxygen pulse, minute ventilation (VE) ventilatory equivalents for oxygen uptake (VE/Vo2) and carbon dioxide output (Vco2), and respiratory quotient at both anaerobic threshold (AT) and peak exercise (PE) each were assessed.

DESIGN

Using the Naughton-Weber protocol, two repeated cardiopulmonary treadmill exercise tests were performed after detailed instructions prior to the first test and on strict adherence to standardized investigational conditions, viz, at the same time of day and at the same ambient temperature, receiving constant medication, and while in a 12-h fasting state.

PATIENTS

The studies were carried out in 17 patients with chronic heart failure due to valvular heart disease considered candidates for intervention because of symptoms. According to Weber's classification of functional capacity, 10 patients were in class A (Vo2 max > 20 mL O2/min/kg), 5 patients were in class B (16 to 20 mL O2/min/kg), and the remaining 2 were in class C (10 to 16 mL O2/min/kg).

MEASUREMENTS

Parameters assessed were TWT, Vo2, heart rate, oxygen pulse, VE and ventilatory equivalents for oxygen (VE/Vo2) and carbon dioxide (VE/Vco2) both at AT and at PE. To reflect reproducibility, correlation coefficients (r) were calculated.

RESULTS

An excellent reproducibility was found for TWT (r = 0.963, p < 0.0001), Vo2 at AT in percent of predicted Vo2max (r = 0.984, p < 0.0001), Vo2 at PE (r = 0.996, p < 0.0001), heart rate at AT (r = 0.943, p < 0.0001) and at PE (r = 0.928, p < 0.0001), oxygen pulse at AT (r = 0.980, p < 0.001) and at PE (r = 0.991, p < 0.0001), VE at AT (r = 0.949, p < 0.0001) and at PE (r = 0.912, p < 0.0001) as well as VE/Vo2 at AT (r = 0.942, p < 0.0001) and at PE (r = 0.781, p < 0.0002) and VE/Vco2 at AT (r = 0.995, p < 0.0001) and at PE (r = 0.943, p < 0.0001), respectively.

CONCLUSIONS

On adherence to standardized conditions, an excellent reproducibility existed for TWT, Vo2 (reflecting cardiac output), ventilation, and heart rate as well as derived parameters, rendering cardiopulmonary exercise testing a reliable means of quantification of heart failure as a prerequisite for enabling diagnostic or therapeutic decisions.

Improvement of exercise capacity with treatment of Cheyne-Stokes respiration in patients with congestive heart failure

OBJECTIVES

The aim of this study was to determine the impact of nasal nocturnal oxygen therapy on respiration, sleep, exercise capacity, cognitive function and daytime symptoms in patients with congestive heart failure and Cheyne-Stokes respiration.

BACKGROUND

Cheyne-Stokes respiration is common in patients with congestive heart failure and is associated with significant nocturnal oxygen desaturation and sleep disruption with arousals. Oxygen desaturations and arousals cause an increase in pulmonary artery pressure and sympathoneural activity and therefore may reduce exercise capacity. Oxygen is an effective treatment of Cheyne-Stokes respiration and should improve exercise capacity in these patients.

METHODS

The study was designed as a randomized crossover, double-blind, placebo-controlled trial: 22 patients were assigned to 1 week each of nocturnal oxygen and room air. After each week, polysomnography, maximal bicycle exercise with expiratory gas analysis and trail-making test were performed, and a health assessment chart was completed.

RESULTS

Nocturnal oxygen significantly reduced the duration of Cheyne-Stokes respiration (162 +/- 142 vs. 88 +/- 105 min [mean +/- SD]; p < 0.005). Sleep improved as evidenced by less stage 1 sleep and fewer arousals (20 +/- 13 vs. 15 +/- 9/h total sleep time; p < 0.05) as well as more stage 2 and slow-wave sleep; nocturnal oxygen saturation also improved. Peak oxygen consumption during exercise testing increased after oxygen treatment (835 +/- 395 vs. 960 +/- 389 ml/min; p < 0.05). Cognitive function evaluated by the trail-making test improved, but daytime symptoms in the health assessment chart did not improve significantly.

CONCLUSIONS

Successful treatment of Cheyne-Stokes respiration with nocturnal nasal oxygen improves not only sleep, but also exercise tolerance and cognitive function in patients with congestive heart failure.