Determinants of maximal oxygen uptake in patients with heart failure

Accelerometer-measured physical activity in patients with heart failure and reduced ejection fraction: Determinants and relationship with patient-reported health status

BACKGROUND

Accelerometer-measured physical activity is an increasingly used endpoint in heart failure (HF) trials. We investigated the determinants of accelerometer-measured physical activity and the relationship with patient-reported health status.

METHODS

Post-hoc analysis of the Empire HF trial, including outpatients with HF with reduced ejection fraction (HFrEF). Physical activity was quantified as average accelerometer counts per minute (CPM) with higher values representing higher activity. We investigated associations between activity level and clinical variables, including age, sex, and body mass index, as well as patient-reported health status assessed by Kansas City Cardiomyopathy Questionnaire (KCCQ).

RESULTS

Complete data were available in 180 (95%) patients (86% male, mean age 65 year). Baseline median physical activity level was 1,318 CPM (Q1-Q3 1,111-1,585). Age and anemia were independently associated with activity level (β-coefficients: -10 CPM per year age increase [95% CI -16 to -5.1], P = .00015, and -126 CPM for anemia [95% CI -9.1 to -244], P = .035). Significant independent associations were observed between activity level and all KCCQ summary scores (β-coefficient point estimates of 3.7, 4.6, and 4.9 CPM, all P < .02). For 12-week changes in KCCQ-summary scores, only the KCCQ-CSS was associated with activity level; mean increase of 17.5 CPM [95% CI 1.5 to 34.0], P = 0.032, per 5-point increase in KCCQ-CSS. Associations were not modified by treatment allocation (interaction P-values > .05).

CONCLUSIONS

In patients with HFrEF, older age and anemia were independently associated with lower activity. Moreover, physical activity only weakly increased with better health status, suggesting that changes in physical activity reflect improvements in patients' health status to a limited degree. This highlights the need to better understand the endpoint with regards to all other health parameters to ease interpretation in future HF trials.

CA125 outperforms NT-proBNP in the prediction of maximum aerobic capacity in heart failure with preserved ejection fraction and kidney dysfunction

Background

Heart failure with preserved ejection fraction (HFpEF) often coexists with chronic kidney disease (CKD). Exercise intolerance is a major determinant of quality of life and morbidity in both scenarios. We aimed to evaluate the associations between N-terminal pro-B-type natriuretic peptide (NT-proBNP) and carbohydrate antigen 125 (CA125) with maximal aerobic capacity (peak VO2) in ambulatory HFpEF and whether these associations were influenced by kidney function.

Methods

This single-centre study prospectively enrolled 133 patients with HFpEF who performed maximal cardiopulmonary exercise testing. Patients were stratified across estimated glomerular filtration rate (eGFR) categories (<60 ml/min/1.73 m2 versus ≥60 ml/min/1.73 m2).

Results

The mean age of the sample was 73.2 ± 10.5 years and 56.4% were female. The median of peak VO2 was 11.0 ml/kg/min (interquartile range 9.0-13.0). A total of 67 (50.4%) patients had an eGFR <60 ml/min/1.73 m2. Those patients had higher levels of NT-proBNP and lower peak VO2, without differences in CA125. In the whole sample, NT-proBNP and CA125 were inversely correlated with peak VO2 (r = -0.43, P < .001 and r = -0.22, P = .010, respectively). After multivariate analysis, we found a differential association between NT-proBNP and peak VO2 across eGFR strata (P for interaction = .045). In patients with an eGFR ≥60 ml/min/1.73 m2, higher NT-proBNP identified patients with poorer maximal functional capacity. In individuals with eGFR <60 ml/min/1.73 m2, NT-proBNP was not significantly associated with peak VO2 [β = 0.02 (95% confidence interval -0.19-0.23), P = .834]. Higher CA125 was linear and significantly associated with worse functional capacity without evidence of heterogeneity across eGFR strata (P for interaction = .620).

Conclusions

In patients with stable HFpEF, NT-proBNP was not associated with maximal functional capacity when CKD was present. CA125 emerged as a useful biomarker for estimating effort intolerance in HFpEF irrespective of the presence of CKD.

The effects of rate pressure product at admission on cardiopulmonary function during hospitalization in patients with acute myocardial infarction

OBJECTIVE

This study aimed to analyze the correlation between the rate pressure product (RPP) and cardiopulmonary function during hospitalization in patients with acute myocardial infarction (AMI).

METHODS

A total of 362 patients with AMI were selected for the study, and the median admission RPP was used as the cutoff point to divide the patients into a low-RPP group (n = 181) and a high-RPP group (n = 181). The relationship between the RPP at admission and the cardiopulmonary function during hospitalization was analyzed.

RESULTS

The patients in the high-RPP group had a higher body mass index (BMI) (p = 0.014), a higher prevalence of combined hypertension and diabetes mellitus (p < 0.001), a lower incidence of smoking (p = 0.044), and a higher incidence of oscillatory ventilation (6.1% vs. 1.7%, p = 0.029). The differences in RPP at rest, during warm-up, and within 1 and 4 minutes of recovery were statistically significant between the two groups (p < 0.01 on each occasion), while the differences in anaerobic threshold (AT) and watt max (Max) were not statistically significant (p > 0.05 for both). The patients in the low-RPP group had higher oxygen uptake (VO2 [AT]: 14.9 ± 3.4 vs. 14.2 ± 3.6, p = 0.048) and (VO2peak [Max]:18.2 ± 3.8 vs. 17.3 ± 3.8, p = 0.020). The RPP at admission was negatively correlated with VO2 (AT) and VO2peak (p < 0.05) using the regression Equation VO2peak = 33.682 + (-0.012 * RPP at admission/100) + (-0.105 * Age) + (-0.350 * BMI), while there was no correlation between the RPP at admission and VO2 (AT) (p = 0.149).

CONCLUSION

The RPP at admission was negatively correlated with cardiopulmonary function during hospitalization in patients with AMI. Patients with a high RPP were more likely to have a combination of obesity, hypertension, diabetes mellitus, and reduced oxygen uptake during exercise, while a high RPP at admission appeared to affect their cardiovascular response indicators during exercise.

Locomotor and respiratory muscle abnormalities in HFrEF and HFpEF

Heart failure (HF) is a chronic and progressive syndrome affecting worldwide billions of patients. Exercise intolerance and early fatigue are hallmarks of HF patients either with a reduced (HFrEF) or a preserved (HFpEF) ejection fraction. Alterations of the skeletal muscle contribute to exercise intolerance in HF. This review will provide a contemporary summary of the clinical and molecular alterations currently known to occur in the skeletal muscles of both HFrEF and HFpEF, and thereby differentiate the effects on locomotor and respiratory muscles, in particular the diaphragm. Moreover, current and future therapeutic options to address skeletal muscle weakness will be discussed focusing mainly on the effects of exercise training.

Left atrial dysfunction can independently predict exercise capacity in patients with chronic heart failure who use beta-blockers

BACKGROUND

Beta-blockers are first-line clinical drugs for the treatment of chronic heart failure (CHF). In the guidelines for cardiac rehabilitation, patients with heart failure who do or do not receive beta-blocker therapy have different reference thresholds for maximal oxygen uptake (VO_2max). It has been reported that left atrial (LA) strain can be used to predict VO_2max in patients with heart failure, which can be used to assess exercise capacity. However, most existing studies included patients who did not receive beta-blocker therapy, which could have a heterogeneous influence on the conclusions. For the vast majority of CHF patients receiving beta-blockers, the exact relationship between LA strain parameters and exercise capacity is unclear.

METHODS

This cross-sectional study enrolled 73 patients with CHF who received beta-blockers. All patients underwent a thorough resting echocardiogram and a cardiopulmonary exercise test to obtain VO_2max, which was used to reflect exercise capacity.

RESULTS

LA reservoir strain, LA maximum volume index (LAVI_max), LA minimum volume index (LAVI_min) (P < 0.0001) and LA booster strain (P < 0.01) were all significantly correlated with VO_2max, and LA conduit strain was significantly correlated with VO_2max (P < 0.05) after adjusting for sex, age, and body mass index. LA reservoir strain, LAVI_max, LAVI_min (P < 0.001), and LA booster strain (P < 0.05) were significantly correlated with VO_2max after adjusting for left ventricular ejection fraction, the ratio of transmitral E velocity to tissue Doppler mitral annulus e' velocity (E/e'), and tricuspid annular plane systolic excursion. LA reservoir strain with a cutoff value of 24.9% had a sensitivity of 74% and specificity of 63% for the identification of patients with VO_2max < 16 mL/kg/min.

CONCLUSION

Among CHF patients receiving beta-blocker therapy, resting LA strain is linearly correlated with exercise capacity. LA reservoir strain is a robust independent predictor of reduced exercise capacity among all resting echocardiography parameters.

CLINICAL TRIAL REGISTRATION

This study is a part of the Baduanjin-Eight-Silken-Movement with Self-efficacy Building for Patients with Chronic Heart Failure (BESMILE-HF) trial NCT03180320 (ClinicalTrials.gov, registration date: 08/06/2017).

Right Ventricular Contractile Reserve: A Key Metric to Identifying when Cardiorespiratory Fitness will Improve with Pulmonary Vasodilators

Cardiorespiratory fitness (CRF) has been proposed as a vital sign for the past several years, supported by a wealth of evidence demonstrating its significance as a predictor of health trajectory, exercise/functional capacity, and quality of life. According to the Fick equation, oxygen consumption (VO₂) is the product of cardiac output (CO) and arterial-venous oxygen difference, with the former being a primary driver of one's aerobic capacity. In terms of the dependence of aerobic capacity on a robust augmentation of CO from rest to maximal exercise, left ventricular (LV) CO has been the historic focal point. Patients with pulmonary arterial hypertension (PAH) or secondary pulmonary hypertension (PH) present with a significantly compromised CRF; as pathophysiology worsens, so too does CRF. Interventions to improve pulmonary hemodynamics continue to emerge and are now a standard of clinical care in several patient populations with increased pulmonary pressures; new pharmacologic options continue to be explored. Improvement in CRF/aerobic capacity has been and continues to be a primary or leading secondary endpoint in clinical trials examining the effectiveness of pulmonary vasodilators. A central premise for including CRF/aerobic capacity as an endpoint is that pulmonary vasodilation will lead to a significant downstream increase in LV CO and therefore peak VO₂. However, the importance of right ventricular (RV) CO to the peak VO₂ response continues to be overlooked. The current review provides an overview of relevant principles of exercise physiology, approaches to assessing RV contractile reserve and proposals for clinical trial design and subject phenotyping.

Determinants of Peak Oxygen Uptake at Each Stage of Renal Dysfunction in Patients with Heart Disease

Background

Identifying the causes of low peak oxygen uptake (peak V̇ O 2 ) in heart disease patients with renal dysfunction is necessary for prognostic improvement strategies. The purpose of this study was to verify the determinants of peak V̇ O 2 for each stage of renal function in heart disease patients, focusing on end-tidal oxygen partial pressure ( PETO 2 ).

Methods

Two hundred fifty heart disease patients who underwent cardiopulmonary exercise testing (CPET) in our institution were consecutively enrolled. Patients were divided into three groups by their estimated glomerular filtration rate (eGFR): < 45, 45-59 and ≥ 60 mL/min/1.73 m 2 . Patient characteristics and CPET parameters including Δ 2 (rest-anaerobic threshold) were compared between the groups. The relationship between Δ PETO PETO 2 and peak V̇ O 2 was also investigated for each group.

Results

In total, 201 patients were analyzed. Δ PETO 2 decreased with the deterioration of renal function (eGFR < 45, 0.1 mmHg vs. eGFR 45-59, 2.4 mmHg vs. eGFR ≥ 60, 5.2 mmHg, p < 0.001). In the eGFR < 45 group, left ventricular ejection fraction (LVEF) and hemoglobin (Hb) were significantly associated with peak V̇ O 2 β = 0.518, p < 0.001 and β = 0.567, p < 0.001, respectively), whereas Δ PETO 2 was not. In the eGFR 45-59 group, age, Hb, and Δ PETO 2 showed a significant association with peak V̇ O 2 ( β = -0.354, p = 0.006; β = 0.258, p = 0.007; β = 0.501, p < 0.001; respectively). In the univariate analysis, eGFR 45-59 group showed the highest coefficient of determination of Δ PETO 2 to peak V̇ O 2 ( R 2 = 0.247, p < 0.001).

Conclusions

The determinants of peak V̇ O 2 in heart disease patients depended on the stage of renal function. The determinants of peak V̇ O 2 in patients with eGFR < 45 were LVEF and Hb, while Δ PETO 2 was the strongest predictor of peak V̇ O 2 in patients with eGFR 45-59.

Determinants of maximal oxygen uptake in patients with heart failure

Aims

Maximum oxygen uptake (VO_2max) is an essential parameter to assess functional capacity of patients with heart failure (HF). We aimed to identify clinical factors that determine its value, as they have not been well characterized yet.

Methods

We conducted a retrospective, observational, single‐centre study of 362 consecutive patients with HF who underwent cardiopulmonary exercise testing (CPET) as part of standard clinical assessment since 2009–2019. CPET was performed on treadmill, according to Bruce's protocol (n = 360) or Naughton's protocol (n = 2). We performed multivariable linear regression analyses in order to identify independent clinical predictors associated with peak VO_2max.

Results

Mean age of study patients was 57.3 ± 10.9 years, mean left ventricular ejection fraction was 32.8 ± 14.2%, and mean VO_2max was 19.8 ± 5.2 mL/kg/min. Eighty‐nine (24.6%) patients were women, and 114 (31.5%) had ischaemic heart disease. Multivariable linear regression analysis identified six independent clinical predictors of VO_2max, including NYHA class (B coefficient = −2.585; P < 0.001), age (B coefficient per 1 year = −0.104; P < 0.001), tricuspid annulus plane systolic excursion (B coefficient per 1 mm = +0.209; P < 0.001), body mass index (B coefficient per 1 kg/m² = −0.172; P = 0.002), haemoglobin (B coefficient per 1 g/dL = +0.418; P = 0.007) and NT‐proBNP (B coefficient per 1000 pg/mL = −0.142; P = 0.019).

Conclusions

The severity of HF (NYHA class, NT‐proBNP) as well as age, body composition and haemoglobin levels influence significantly exercise capacity. In patients with HF, the right ventricular systolic function is of greater importance for the physical capacity than the left ventricular systolic function.