Effect of physical training on ventilatory patterns during exercise in patients with heart disease

Determinants of V̇+O2peak Changes After Aerobic Training in Coronary Heart Disease Patients

This study aimed to highlight the ventilatory and circulatory determinants of changes in ˙VO2peak after exercise-based cardiac rehabilitation (ECR) in patients with coronary heart disease (CHD). Eighty-two CHD patients performed, before and after a 3-month ECR, a cardiopulmonary exercise testing (CPET) on a bike with gas exchanges measurements (˙VO2peak, minute ventilation, i. e., ˙VE), and cardiac output (Q˙c). The arteriovenous difference in O2 (C(a-v¯)O2) and the alveolar capillary gradient in O2 (PAi-aO2) were calculated using Fick's laws. Oxygen uptake efficiency slope (OUES) was calculated. A 5.0% cut off was applied for differentiating non- (NR: ˙VO2<0.0%), low (LR: 0.0≤ ∆˙VO2<5.0%), moderate (MR: 5.0≤∆˙VO2 < 10.0%), and high responders (HR: ∆˙VO2≥10.0%) to ECR. A total of 44% of patients were HR (n=36), 20% MR (n=16), 23% LR (n=19), and 13% NR (n=11). For HR, the ˙VO2peak increase (p<0.01) was associated with increases in ˙VE (+12.8±13.0 L/min, p<0.01), (+1.0±0.9 L/min, p<0.01), and C(a-v¯)O2 (+2.3±2.5 mLO2/100 mL, p<0.01). MR patients were characterized by+6.7±19.7 L/min increase in ˙VE (p=0.04) and+0.7±1.0 L/min of Q˙c (p<0.01). ECR induced decreases in ˙VE (p=0.04) and C(a-v¯)O2 (p<0.01) and a Q˙c increase in LR and NR patients (p<0.01). Peripheral and ventilatory responses more than central adaptations could be responsible for the ˙VO2peak change with ECR in CHD patients.

Examination of the Relationship and Dissociation Between Minimum Minute Ventilation/Carbon Dioxide Production and Minute Ventilation vs. Carbon Dioxide Production Slope

BACKGROUND

Minute ventilation/carbon dioxide production (V̇E/V̇CO₂) is a variable of cardiopulmonary exercise testing (CPET), which is evaluated by arterial CO₂pressure and ventilation-perfusion mismatch via invasive methods. This study evaluated substitute non-invasively obtained variables for minimum V̇E/V̇CO₂(Min) and V̇E vs. V̇CO₂slope (Slope) and the relationship between Min and Slope.Methods and Results:This study enrolled 1,052 patients with heart disease who underwent CPET and impedance cardiography simultaneously. At first, the correlations between the end-tidal CO₂pressure (PETCO₂), tidal volume/respiratory rate (TV/RR) ratio, V̇E and V̇CO₂Y-intercept (Y-int), and cardiac index (CI) and the Min and Slope were investigated. Second, the correlation between Min and Slope was investigated. PETCO₂showed the largest correlation value among the 4 variables. These 4 variables could reveal 84.2% and 81.9% of Min and Slope, respectively. Although Slope correlated with Min (R=0.868) and predicted 78.9% of Min, considering these 4 variables, Slope+Y-int was more strongly correlated with Min (R=0.940); the Slope+Y-int revealed 90.6% of the Min relationship in the multiple regression analysis.

CONCLUSIONS

Over 80% of the Min and Slope values were revealed with the above-mentioned 4 variables collected non-invasively. The formula, Min∝Slope+Y-int, can reveal >90% of the Min/Slope relationships, and the Y-int may be a crucial factor to clarify the relationship between Min and Slope.

Exercise-based cardiac rehabilitation for coronary heart disease

BACKGROUND

Coronary heart disease (CHD) is the most common cause of death globally. However, with falling CHD mortality rates, an increasing number of people living with CHD may need support to manage their symptoms and prognosis. Exercise-based cardiac rehabilitation (CR) aims to improve the health and outcomes of people with CHD. This is an update of a Cochrane Review previously published in 2016.

OBJECTIVES

To assess the clinical effectiveness and cost-effectiveness of exercise-based CR (exercise training alone or in combination with psychosocial or educational interventions) compared with 'no exercise' control, on mortality, morbidity and health-related quality of life (HRQoL) in people with CHD.

SEARCH METHODS

We updated searches from the previous Cochrane Review, by searching CENTRAL, MEDLINE, Embase, and two other databases in September 2020. We also searched two clinical trials registers in June 2021.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of exercise-based interventions with at least six months' follow-up, compared with 'no exercise' control. The study population comprised adult men and women who have had a myocardial infarction (MI), coronary artery bypass graft (CABG) or percutaneous coronary intervention (PCI), or have angina pectoris, or coronary artery disease.

DATA COLLECTION AND ANALYSIS

We screened all identified references, extracted data and assessed risk of bias according to Cochrane methods. We stratified meta-analysis by duration of follow-up: short-term (6 to 12 months); medium-term (> 12 to 36 months); and long-term ( > 3 years), and used meta-regression to explore potential treatment effect modifiers. We used GRADE for primary outcomes at 6 to 12 months (the most common follow-up time point).  MAIN RESULTS: This review included 85 trials which randomised 23,430 people with CHD. This latest update identified 22 new trials (7795 participants). The population included predominantly post-MI and post-revascularisation patients, with a mean age ranging from 47 to 77 years. In the last decade, the median percentage of women with CHD has increased from 11% to 17%, but females still account for a similarly small percentage of participants recruited overall ( < 15%). Twenty-one of the included trials were performed in low- and middle-income countries (LMICs). Overall trial reporting was poor, although there was evidence of an improvement in quality over the last decade. The median longest follow-up time was 12 months (range 6 months to 19 years). At short-term follow-up (6 to 12 months), exercise-based CR likely results in a slight reduction in all-cause mortality (risk ratio (RR) 0.87, 95% confidence interval (CI) 0.73 to 1.04; 25 trials; moderate certainty evidence), a large reduction in MI (RR 0.72, 95% CI 0.55 to 0.93; 22 trials; number needed to treat for an additional beneficial outcome (NNTB) 75, 95% CI 47 to 298; high certainty evidence), and a large reduction in all-cause hospitalisation (RR 0.58, 95% CI 0.43 to 0.77; 14 trials;  NNTB 12, 95% CI 9 to 21; moderate certainty evidence). Exercise-based CR likely results in little to no difference in risk of cardiovascular mortality (RR 0.88, 95% CI 0.68 to 1.14; 15 trials; moderate certainty evidence), CABG (RR 0.99, 95% CI 0.78 to 1.27; 20 trials; high certainty evidence), and PCI (RR 0.86, 95% CI 0.63 to 1.19; 13 trials; moderate certainty evidence) up to 12 months' follow-up. We are uncertain about the effects of exercise-based CR on cardiovascular hospitalisation, with a wide confidence interval including considerable benefit as well as harm (RR 0.80, 95% CI 0.41 to 1.59; low certainty evidence). There was evidence of substantial heterogeneity across trials for cardiovascular hospitalisations (I2 = 53%), and of small study bias for all-cause hospitalisation, but not for all other outcomes. At medium-term follow-up, although there may be little to no difference in all-cause mortality (RR 0.90, 95% CI 0.80 to 1.02; 15 trials), MI (RR 1.07, 95% CI 0.91 to 1.27; 12 trials), PCI (RR 0.96, 95% CI 0.69 to 1.35; 6 trials), CABG (RR 0.97, 95% CI 0.77 to 1.23; 9 trials), and all-cause hospitalisation (RR 0.92, 95% CI 0.82 to 1.03; 9 trials), a large reduction in cardiovascular mortality was found (RR 0.77, 95% CI 0.63 to 0.93; 5 trials). Evidence is uncertain for difference in risk of cardiovascular hospitalisation (RR 0.92, 95% CI 0.76 to 1.12; 3 trials). At long-term follow-up, although there may be little to no difference in all-cause mortality (RR 0.91, 95% CI 0.75 to 1.10), exercise-based CR may result in a large reduction in cardiovascular mortality (RR 0.58, 95% CI 0.43 to 0.78; 8 trials) and MI (RR 0.67, 95% CI 0.50 to 0.90; 10 trials). Evidence is uncertain for CABG (RR 0.66, 95% CI 0.34 to 1.27; 4 trials), and PCI (RR 0.76, 95% CI 0.48 to 1.20; 3 trials). Meta-regression showed benefits in outcomes were independent of CHD case mix, type of CR, exercise dose, follow-up length, publication year, CR setting, study location, sample size or risk of bias. There was evidence that exercise-based CR may slightly increase HRQoL across several subscales (SF-36 mental component, physical functioning, physical performance, general health, vitality, social functioning and mental health scores) up to 12 months' follow-up; however, these may not be clinically important differences. The eight trial-based economic evaluation studies showed exercise-based CR to be a potentially cost-effective use of resources in terms of gain in quality-adjusted life years (QALYs).

AUTHORS' CONCLUSIONS

This updated Cochrane Review supports the conclusions of the previous version, that exercise-based CR provides important benefits to people with CHD, including reduced risk of MI, a likely small reduction in all-cause mortality, and a large reduction in all-cause hospitalisation, along with associated healthcare costs, and improved HRQoL up to 12 months' follow-up. Over longer-term follow-up, benefits may include reductions in cardiovascular mortality and MI. In the last decade, trials were more likely to include females, and be undertaken in LMICs, increasing the generalisability of findings. Well-designed, adequately-reported RCTs of CR in people with CHD more representative of usual clinical practice are still needed. Trials should explicitly report clinical outcomes, including mortality and hospital admissions, and include validated HRQoL outcome measures, especially over longer-term follow-up, and assess costs and cost-effectiveness.

Changes and prognostic value of cardiopulmonary exercise testing parameters in elderly patients undergoing cardiac rehabilitation: The EU-CaRE observational study

Objective

We aimed 1) to test the applicability of the previously suggested prognostic value of CPET to elderly cardiac rehabilitation patients and 2) to explore the underlying mechanism of the greater improvement in exercise capacity (peak oxygen consumption, VO₂) after CR in surgical compared to non-surgical cardiac patients.

Methods

Elderly patients (≥65 years) commencing CR after coronary artery bypass grafting, surgical valve replacement (surgery-group), percutaneous coronary intervention, percutaneous valve replacement or without revascularisation (non-surgery group) were included in the prospective multi-center EU-CaRE study. CPETs were performed at start of CR, end of CR and 1-year-follow-up. Logistic models and receiver operating characteristics were used to determine prognostic values of CPET parameters for major adverse cardiac events (MACE). Linear models were performed for change in peak VO₂ (start to follow-up) and parameters accounting for the difference between surgery and non-surgery patients were sought.

Results

1421 out of 1633 EU-CaRE patients performed a valid CPET at start of CR (age 73±5.4, 81% male). No CPET parameter further improved the receiver operation characteristics significantly beyond the model with only clinical parameters. The higher improvement in peak VO₂ (25% vs. 7%) in the surgical group disappeared when adjusted for changes in peak tidal volume and haemoglobin.

Conclusion

CPET did not improve the prediction of MACE in elderly CR patients. The higher improvement of exercise capacity in surgery patients was mainly driven by restoration of haemoglobin levels and improvement in respiratory function after sternotomy.

Trial registration

Netherlands Trial Register, Trial NL5166.

Relationship between ventilatory pattern and peak VO2 and area M regulates the respiratory system during exercise

BACKGROUND

Exertional dyspnea is a major symptom of heart failure. We investigated the tidal volume (TV)-the respiratory rate (RR) regulation according to the peak O₂ uptake (VO₂) during cardiopulmonary exercise testing (CPET) for clarifying exercise ventilatory pattern.

METHODS

We enrolled 1111 patients (66±13 years old, 68% men) who had undergone CPET at our hospital. We investigated the relationship between TV and RR and drew the TV/height-RR figure according to the %peak VO₂.

RESULTS

During exercise, TV was greater, illustrated as higher %peak VO₂. However, RR was weakly correlated with %peak VO₂. Adjusted with age, height, sex, each point of RR, and %peak VO₂, TV during exercise highly correlated with age, height, each point of RR, and % peak VO₂ (R=0.726 to 0.821, p<0.01). In the figure, regardless of the %peak VO₂, TV/height and RR values were linearly related at rest, as well as at the point of anaerobic threshold, respiratory compensation, and peak exercise point, with each of these lines converging onto a single area (area M). The TV-RR slope values at early phase were also lower at lower %peak VO₂.

CONCLUSIONS

We identified three ventilatory regularities during exercise. First, TV increases as greater %peak VO₂. Second, the line relating TV/height and RR at each reference point during the incremental exercise test converged onto area M. Finally, the TV-RR slope at the early exercise phase was lower in patients with a lower %peak VO₂. These ventilatory regularities may assist in elucidating the excise ventilatory pattern and help the diagnosis of exertional dyspnea.

Cognitive function in post-cardiac intensive care: patient characteristics and impact of multidisciplinary cardiac rehabilitation

New/worsening cognitive and physical impairments following critical care pose significant problems. Multidisciplinary cardiac rehabilitation (CR) can improve physical function after cardiac intensive care (CIC). This observational study aimed to evaluate cognitive function in patients participating in multidisciplinary CR and to identify correlates of impaired cognitive function after CIC. We analyzed 111 consecutive patients admitted to our comprehensive care ward at least 7 days after CIC and assessed factors associated with cognitive function using the Functional Independence Measure (FIM). Patients were stratified into two groups based on the median FIM-Cognitive scores: impaired (n = 56) and preserved cognition (n = 55) groups. Multiple logistic regression analysis identified age [odds ratio (OR) 1.06; 95% confidence interval (CI) 1.00-1.13; p = 0.042], Mini-Nutrition Assessment-Short Form (MNA-SF; OR 0.73; 95% CI 0.56-0.95; p = 0.017), and FIM-Physical scores (OR: 0.94; 95% CI 0.90-0.99; p = 0.012) as significant and independent factors associated with impaired cognition. The median length of hospital stay was 28 (interquartile range: 18, 43) days. The FIM-Cognitive and FIM-Physical scores significantly increased from admission to discharge [32.0 (27.0, 35.0) vs. 34.0 (29.0, 35.0) points; p < 0.001; 67.0 (53.0, 75.0) vs. 85.0 (73.5, 89.0) points; p < 0.001, respectively]. On subgroup analysis within the impaired cognition group, increased FIM-Cognitive scores positively and significantly correlated with increased FIM-Physical scores (ρ = 0.450; p = 0.001). Multiple linear regression analysis identified atrial fibrillation (AF; β = - 0.29; p = 0.016), ln(glycated hemoglobin; HbA1c) (β = 0.29; p = 0.018), and ln(high-sensitivity C-reactive protein; hs-CRP) (β = - 0.26; p = 0.034) as significant and independent factors correlated with increased FIM-Cognitive scores. In conclusion, advanced age, low MNA-SF score, and FIM-Physical score were independent factors associated with impaired cognition in post-CIC patients. Multidisciplinary CR improved both physical and cognitive functions, and AF, HbA1c, and hs-CRP were independent factors correlated with increased FIM-Cognitive score.

Cardiopulmonary Exercise Test

The cardiopulmonary exercise test (CPX) is an essential examination for detecting pathophysiological derangement and determining treatment policy because it clarifies not only the changes of hemodynamics but also abnormality in the whole body during exercise where heart disease patients often feel symptoms.To utilize CPX effectively, we must understand each parameter, such as peak oxygen uptake (peak VO₂), peak VO₂/HR, and VE/VCO₂. In addition, comparison of each parameter, for example, peak VO₂ and VE/VCO₂, and peak VO₂ and peak VO₂/HR, is useful to detect the pathophysiological abnormalities.In this article, I will describe how CPX should be used in clinical settings.

Importance of compensatory heart rate increase during myocardial ischemia to preserve appropriate oxygen kinetics

BACKGROUND

Myocardial ischemia induces cardiac dysfunction, resulting in insufficient oxygen supply to peripheral tissues and mismatched energy production during exercise. To relieve the insufficient oxygen supply, heart rate (HR) response is augmented; however, beta-adrenergic receptor blockers (BB) restrict HR response. Although BB are essential drugs for angina pectoris, the effect of BB on exercise tolerance in patients with angina has not been studied. The aim of this study was to clarify the importance of HR augmentation to preserve exercise tolerance in patients with angina pectoris.

METHODS

Forty-two subjects who underwent cardiopulmonary exercise testing (CPX) to detect myocardial ischemia were enrolled. CPX was performed until exhaustion or onset of significant myocardial ischemia using a ramp protocol. Subjects were assigned to three groups (Group A: with ST depression during CPX with significant coronary stenosis and taking BB; Group B: with ST depression and not taking BB; Group C: without ST depression and not taking BB). HR response to exercise was evaluated during the following two periods: below and above ischemic threshold (IT). In Group C, it was evaluated during the first 2min and the last 2min of a ramp exercise.

RESULTS

No significant differences were observed among the three groups with regard to patients' basic characteristics. Below IT, there were no differences in oxygen pulse/watt (O₂ pulse increasing rate), HR/watt (ΔHR/ΔWR), and ΔV˙O₂/ΔWR. Above IT, O₂ pulse increasing rate was greater in Group A than in Group B. ΔHR/ΔWR was smaller in Group A than in Group B. ΔV˙O₂/ΔWR became smaller in Group A than in Group B. There was no difference in anaerobic threshold, and peak V˙O₂ was smaller in Group A than in Group B.

CONCLUSIONS

Restriction of HR response by a BB is shown to be one of the important factors in diminished exercise tolerance.

Influence of stroke volume and exercise tolerance on peak oxygen pulse in patients with and without beta-adrenergic receptor blockers in patients with heart disease

BACKGROUND

In a given individual, a consistent relationship exists between oxygen uptake (V˙O₂) and heart rate (HR) during exercise. The quotient of V˙O₂ and HR (V˙O₂/HR) is called the oxygen pulse (O₂ pulse), and its value is dependent on stroke volume (SV). However, it is difficult to believe that the O₂ pulse would indicate the SV when HR has been modified as with the use of beta-adrenergic receptor blockers (BB). Until now, the effect of BB on peak O₂ pulse has not been precisely studied. We tried to clarify the effect of BB on the relationship between O₂ pulse and SV.

METHODS

Of 699 consecutive heart disease subjects who performed cardiopulmonary exercise tests (CPX) from 2012 to 2014, we enrolled 430 subjects who had sinus rhythm and could perform CPX until exhaustion. One hundred and fifty-seven subjects were taking BB. SV was evaluated during CPX using impedance cardiography, and we compared the peak O₂ pulse with peak SV between patients without BB (Group A) and with BB (Group B).

RESULTS

The HRs at rest and peak exercise in Group A were greater than those in Group B (74.4±13.0/min vs. 71.8±11.3/min, p<0.01, 134.9±21.7/min vs. 124.9±23.6/min, p<0.01, respectively). The regression line of the peak O₂ pulse against the peak SV was steeper in Group B than in Group A. When we divided the patients into two groups according to the average values of the peak SV and peak V˙O₂, O₂ pulse/SV ratio in Group B above the average was greater than that in Group A, whereas it was similar in the two groups that were below average.

CONCLUSION

We found that the increase in the O₂ pulse was disproportionately greater than the SV that was measured by impedance cardiography when a BB was used in patients with preserved SV and exercise tolerance.

Usefulness of anaerobic threshold to peak oxygen uptake ratio to determine the severity and pathophysiological condition of chronic heart failure

BACKGROUND

Anaerobic threshold (AT) and peak oxygen uptake (V˙O₂) are well known as indicators of severity and prognosis of heart failure. Since these parameters are regulated by many factors, multiple organ dysfunction may occur in chronic heart failure, and these two parameters would vary among patients. However, it is not clear whether AT and peak V˙O₂ deteriorate similarly. Therefore, we planned to compare the degree of deterioration of these two parameters using a ratio of AT and peak V˙O₂ (%AT/peak), and evaluated its significance in heart failure subjects.

METHODS

One hundred ninety-four stable heart failure patients who had optimal medical treatment for at least 3 months were enrolled. Cardiopulmonary exercise testing, echocardiography, and blood sampling were examined within one week. Since %AT/peak varied from 50.3% to 108.5%, we divided patients into tertiles of %AT/peak [Group A, 50.1-70.0 (n=112), Group B, 70.1-90.0 (n=64), Group C, 90.1-110.0 (n=18)], and compared factors relating with skeletal muscle and heart failure among these 3 groups.

RESULTS

In Group A, ratio of measured AT against predicted value (%AT) and measured peak V˙O₂ against predicted value (%peak V˙O₂) were similar (80.3±19.0% and 80.4±17.1%, respectively). Peak V˙O₂ became lower as %AT/peak increased (Group B; 65.6±14.8%, p<0.01 vs. Group A, Group C; 38.3±9.7%, p<0.01 vs. Group B). On the other hand, %AT in Group B (77.1±18.5%) was similar to Group A, and diminished in Group C (58.0±8.2%, p<0.05 vs. Group B). Peak work rate and lean body mass were smaller in Group B than those in Group A. Although, left ventricular ejection fraction and E/E' deteriorated in Group B compared with Group A, plasma B-type natriuretic peptide and estimated glomerular filtration rate stayed constant in Group B and deteriorated in Group C.

CONCLUSIONS

%AT/peak showed negative correlation with peak V˙O₂. In chronic heart failure, muscle weakness occurs at an early stage, and this can be evaluated using %AT/peak.