Brisk walking can be a maximal effort in heart failure patients: a comparison of cardiopulmonary exercise and 6 min walking test cardiorespiratory data

Feasibility of a Novel Augmented 6-Minute Incremental Step Test: A Simplified Cardiorespiratory Fitness Assessment Tool

Background

The cardiopulmonary exercise test (CPET) is considered a gold standard in assessing cardiorespiratory fitness (CRF) but has limited accessibility due to competency requirements and cost. Incorporating portable sensor devices into a simple bedside test of CRF could improve diagnostic and prognostic value.

Objectives

The authors sought to evaluate the association of an augmented 6-minute incremental step test (6MIST) with standard CPET.

Methods

We enrolled patients undergoing clinically indicated supine cycle ergometry CPET with invasive hemodynamics (iCPET) for the same-day 6MIST. CRF-related variables were simultaneously recorded using a signal morphology-based impedance cardiograph (PhysioFlow Enduro) and a portable metabolic analyzer (VO2 Master Pro) during incremental pace stationary stepping. The correlation between CPET and hemodynamic parameters from both tests was assessed using the intraclass correlation coefficient (ICC).

Results

Fifteen patients (mean age 60 ± 14 years, 40% female, 27% Black) were included. All patients who agreed to undergo 6MIST completed the study without any test-related adverse events. We observed good to excellent correlation between iCPET- and 6MIST-measured CPET parameters: peak heart rate (ICC = 0.60; 95% CI: 0.15-0.85), absolute peak O2 consumption (VO2) (ICC = 0.77; 95% CI: 0.44-0.92), relative peak VO2 (ICC = 0.64; 95% CI: 0.20-0.86), maximum ventilation (ICC = 0.59; 95% CI: 0.13-0.84), O2 pulse (ICC = 0.71; 95% CI: 0.33-0.89), and cardiorespiratory optimal point (ICC = 0.82; 95% CI: 0.52-0.94). No significant correlation was determined between iCPET and 6MIST in measuring cardiac index at rest (ICC = 0.19; 95% CI: -0.34 to 0.63) or at peak exercise (ICC = 0.36; 95% CI: -0.17 to 0.73).

Conclusions

We demonstrate the feasibility of a novel augmented 6MIST with wearable devices for simultaneous CPET and hemodynamic assessment. 6MIST-measured CPET parameters were strongly correlated with the iCPET-derived measurements. Additional studies are needed to confirm the validity of the 6MIST compared to standard upright CPET.

Estimating maximum work rate during cardiopulmonary exercise testing from the six-minute walk distance in patients with heart failure

Background

Exercise is recommended for patients with chronic heart failure (CHF) and its intensity is usually set as a percentage of the maximal work rate (MWR) during cardiopulmonary exercise testing (CPX) or a symptom-limited incremental test (SLIT). As these tests are not always available in cardiac rehabilitation due to logistic/cost constraints, we aimed to develop a predictive model to estimate MWR at CPX (estMWR@CPX) in CHF patients using anthropometric and clinical measures and the 6-min walk test (6 MWT), the most widely used exercise field test.

Methods

This is a multicentre cross-sectional retrospective study in a cardiac rehabilitation setting. Six hundred patients with HF in New York Heart Association (NYHA) functional class I-III underwent both CPX and 6 MWT and, through multivariable linear regression analysis, we defined several predictive models to define estMWR@CPX.

Results

The best model included 6 MWT, sex, age, weight, NYHA class, left ventricular ejection fraction (LVEF), smoking status and chronic obstructive pulmonary disease COPD (adjusted R2 = 0.55; 95% LoA -39 to 33 W). When LVEF was excluded as a predictor, the resulting model performed only slightly worse (adjusted R2 = 0.54; 95% LoA -42 to 34 W). Only in 34% of cases was the percentage difference between estMWR@CPX and real MWR@CPX <10% in absolute value. EstMWR@CPX tended to overestimate low values and underestimate high values of true MWR@CPX.

Conclusions

Our results showed a lack of accuracy in the predictive model evaluated; therefore, for an accurate prescription of cycle-ergometer exercise training, it is necessary to assess MWR by CPX or SLIT.

Taking a walk on the heart failure side: comparison of metabolic variables during walking and maximal exertion

AIMS

Although cardiopulmonary exercise testing (CPET) is the gold standard to assess exercise capacity, simpler tests (i.e., 6-min walk test, 6MWT) are also commonly used. The aim of this study was to evaluate the relationship between cardiorespiratory parameters during CPET and 6MWT in a large, multicentre, heterogeneous population.

METHODS

We included athletes, healthy subjects, and heart failure (HF) patients of different severity, including left ventricular assist device (LVAD) carriers, who underwent both CPET and 6MWT with oxygen consumption measurement.

RESULTS

We enrolled 186 subjects (16 athletes, 40 healthy, 115 non-LVAD HF patients, and 15 LVAD carriers). CPET-peakV̇O2 was 41.0 [35.0-45.8], 26.2 [23.1-31.0], 12.8 [11.1-15.3], and 15.2 [13.6-15.6] ml/Kg/min in athletes, healthy, HF patients, and LVAD carriers, respectively (P < 0.001). During 6MWT they used 63.5 [56.3-76.8], 72.0 [57.8-81.0], 95.5 [80.3-109], and 95.0 [92.0-99.0] % of their peakV̇O2, respectively. None of the athletes, 1 healthy (2.5%), 30 HF patients (26.1%), and 1 LVAD carrier (6.7%), reached a 6MWT-V̇O2 higher than their CPET-peakV̇O2. Both 6MWT-V̇O2 and walked distance were significantly associated with CPET-peakV̇O2 in the whole population (R2 = 0.637 and R2 = 0.533, P ≤ 0.001) but not in the sub-groups. This was confirmed after adjustment for groups.

CONCLUSIONS

The 6MWT can be a maximal effort especially in most severe HF patients and suggest that, in absence of prognostic studies related to 6MWT metabolic values, CPET should remain the first method of choice in the functional assessment of patients with HF as well as in sport medicine.

Incremental prognostic value of functional impairment assessed by 6-min walking test for the prediction of mortality in heart failure

Natriuretic peptides (NP) are recognized as the most powerful predictors of adverse outcomes in heart failure (HF). We hypothesized that a measure of functional limitation, as assessed by 6-min walking test (6MWT), would improve the accuracy of a prognostic model incorporating a NP. This was a multicenter observational retrospective study. We studied the prognostic value of severe functional impairment (SFI), defined as the inability to perform a 6MWT or a distance walked during a 6MWT < 300 m, in 1696 patients with HF admitted to cardiac rehabilitation. The primary outcome was 1-year all-cause mortality. After adjusting for the baseline multivariable risk model-including age, sex, systolic blood pressure, anemia, renal dysfunction, sodium level, and NT-proBNP-or for the MAGGIC score, SFI had an odds ratio of 2.58 (95% CI 1.72-3.88; p < 0.001) and 3.12 (95% CI 2.16-4.52; p < 0.001), respectively. Adding SFI to the baseline risk model or the MAGGIC score yielded a significant improvement in discrimination and risk classification. Our data suggest that a simple, 6MWT-derived measure of SFI is a strong predictor of death and provide incremental prognostic information over well-established risk markers in HF, including NP, and the MAGGIC score.

Activities of daily living in heart failure patients and healthy subjects: when the cardiopulmonary assessment goes beyond traditional exercise test protocols

Heart failure (HF) patients traditionally report dyspnoea as their main symptom. Although the cardiopulmonary exercise test (CPET) and 6 min walking test are the standardized tools in assessing functional capacity, neither cycle ergometers nor treadmill maximal efforts do fully represent the actual HF patients' everyday activities [activities of daily living (ADLs)] (i.e. climbing the stairs). New-generation portable metabolimeters allow the clinician to measure task-related oxygen intake (VO2) in different scenarios and exercise protocols. In the last years, we have made considerable progress in understanding the ventilatory and metabolic behaviours of HF patients and healthy subjects during tasks aimed to reproduce ADLs. In this paper, we describe the most recent findings in the field, with special attention to the relationship between the metabolic variables obtained during ADLs and CPET parameters (i.e. peak VO2), demonstrating, for example, how exercises traditionally thought to be undemanding, such as a walk, instead represent supramaximal efforts, particularly for subjects with advanced HF and/or artificial heart (left ventricular assist devices) wearers.

Tolerability and beneficial effects of sacubitril/valsartan on systemic right ventricular failure

OBJECTIVE

Patients with a systemic right ventricle (sRV) in the context of transposition of the great arteries (TGA) after atrial switch or congenitally corrected TGA (ccTGA) are prone to sRV dysfunction. Pharmacological options for sRV failure remain poorly defined. This study aims to investigate the tolerability and effects of sacubitril/valsartan on sRV failure in adult patients with sRV.

METHODS

In this two-centre, prospective cohort study, all consecutive adult patients with symptomatic heart failure and at least moderately reduced sRV systolic function were initiated on sacubitril/valsartan and underwent structured follow-up.

RESULTS

Data of 40 patients were included (40% female, 30% ccTGA, median age 48 (44-53) years). Five patients discontinued therapy during titration. Median follow-up was 24 (12-36) months. The maximal dose was tolerated by 49% of patients. No episodes of hyperkalaemia or renal function decline occurred. Six-minute walking distance increased significantly after 6 months of treatment (569±16 to 597±16 m, p=0.016). Serum N-terminal-prohormone brain natriuretic peptide (NT-proBNP) levels decreased significantly after 3 months (567 (374-1134) to 404 (226-633) ng/L, p<0.001). Small, yet consistent echocardiographic improvements in sRV function were observed after 6 months (sRV global longitudinal strain: -11.1±0.5% to -12.6±0.7%, p<0.001, and fractional area change: 20% (16%-24%) to 26% (19%-30%), p<0.001). The linear mixed-effects model illustrated that after first follow-up moment, no time effect was present for the parameters.

CONCLUSIONS

Treatment with sacubitril/valsartan was associated with a low rate of adverse effects in this adult sRV cohort. Persisting improvement in 6-minute walking test distance, NT-proBNP levels and echocardiographic parameters of sRV function was observed in an on-treatment analysis and showed no differential response based on sex or anatomy.

Prognostic Value of 6-Minute Walk Test in Advanced Heart Failure With Reduced Ejection Fraction

There is limited evidence regarding the prognostic value of the 6-minute walk test for patients with advanced heart failure (HF). Accordingly, we studied 260 patients presenting to inpatient cardiac rehabilitation (CR) with advanced HF. The primary outcome was 3-year all-cause mortality after discharge from CR. The association between 6-minute walk distance (6MWD) and the primary outcome was determined using the multivariable Cox regression analysis. To avoid collinearity, 6MWD at admission (6MWDadm) to CR and 6MWD at discharge (6MWDdisch) from CR were analyzed separately. At multivariable analysis, 4 baseline characteristics (age, ejection fraction, systolic blood pressure, and blood urea nitrogen) were identified as prognostic of the primary outcome (baseline risk model). After adjusting for the baseline risk model, the hazard ratios of 6MWDadm and 6MWDdisch modeled as per 50-m increase for the primary outcome were 0.92 (95% confidence interval [CI] 0.85 to 0.99, p = 0.035) and 0.93 (95% CI 0.88 to 0.99, p = -017), respectively. After adjusting for the Meta-analysis Global Group in Chronic Heart Failure (MAGGIC) score, the corresponding hazard ratios were 0.91 (95% CI 0.84 to 0.98, p = 0.017) and 0.93 (95% CI 0.88 to 0.99, p = 0.016). The addition of either 6MWDadm or 6MWDdisch to the baseline risk model or the MAGGIC score yielded a statistically significant increase in global chi-square and in the net proportion of survivors reclassified downward. In conclusion, our data suggest that the distance covered during a 6-minute walk test predicts survival and provides incremental prognostic information on the top of well-established prognostic factors and the MAGGIC risk score in advanced HF.

Cardiopulmonary exercise testing and heart failure: a tale born from oxygen uptake

Since 50 years, cardiopulmonary exercise testing (CPET) plays a central role in heart failure (HF) assessment. Oxygen uptake (VO₂) is one of the main HF prognostic indicators, then paralleled by ventilation to carbon dioxide (VE/VCO₂) relationship slope. Also anaerobic threshold retains a strong prognostic power in severe HF, especially if expressed as a percent of maximal VO₂ predicted value. Moving beyond its absolute value, a modern approach is to consider the percentage of predicted value for peak VO₂ and VE/VCO₂ slope, thus allowing a better comparison between genders, ages, and races. Several VO₂ equations have been adopted to predict peak VO₂, built considering different populations. A step forward was made possible by the introduction of reliable non-invasive methods able to calculate cardiac output during exercise: the inert gas rebreathing method and the thoracic electrical bioimpedance. These techniques made possible to calculate the artero-venous oxygen content differences (ΔC(a-v)O₂), a value related to haemoglobin concentration, pO₂, muscle perfusion, and oxygen extraction. The role of haemoglobin, frequently neglected, is however essential being anaemia a frequent HF comorbidity. Finally, peak VO₂ is traditionally obtained in a laboratory setting while performing a standardized physical effort. Recently, different wearable ergo-spirometers have been developed to allow an accurate metabolic data collection during different activities that better reproduce HF patients' everyday life. The evaluation of exercise performance is now part of the holistic approach to the HF syndrome, with the inclusion of CPET data into multiparametric prognostic scores, such as the MECKI score.

Echocardiographic diagnosis of heart failure with preserved ejection fraction in elderly patients with hypertension

Objectives. The aim of this study is to evaluate the diagnostic performance of echocardiography for the diagnosis of heart failure with preserved ejection fraction (HFpEF) in the elderly and to validate the Heart Failure Association diagnostic algorithm (HFA-PEFF). Design. A case-control study was conducted in patients with hypertension with or without HFpEF who were matched for age (n = 33; 78.4 ± 5.3 years) and sex. Participants underwent echocardiography including assessment of left atrial (LA) volume index (LAVI), early mitral filling to early diastolic mitral annulus velocity ratio (E/e'), LA reservoir strain (LASr), tissue Doppler LA contraction (a'), right ventricular isovolumic relaxation time (RVIVRT), and a 6-minute walk test (6-MWT). The filling pressure algorithm from the European association of cardiovascular imaging (EACVI) 2021 was applied. The HFA-PEFF score was also applied, using echocardiography parameters and the value of NT pro-BNP, without considering symptomatic status. Results. Echocardiographic parameters identified patients with HFpEF with an area under the curve (AUC) >0.9 for E/e', RVIVRT, LASr, a', and the ratio of LAVI/a'. LASr correlated with 6-MWT (r = 0.59, p = .0003). The EACVI algorithm classified all controls with normal filling pressure and 94% of patients with HFpEF with increased filling pressure. When the HFA-PEFF diagnostic algorithm was validated, a high score (≥5 points) had 100% sensitivity for HFpEF, while 88% of controls had intermediate scores (2-4 points). Conclusion. The EACVI filling pressure algorithm, RVIVRT, LASr, and the ratio LAVI/a' were accurate for diagnosing HFpEF in elderly patients with hypertension. The HFA-PEFF score had high sensitivity but limited ability to exclude HFpEF.