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.

Prognostic implications of six-minute walking distance in patients with heart failure with preserved ejection fraction

BACKGROUND

The incremental prognostic value of the six-minute walking test over conventional risk factors has not been evaluated in an adequate number of patients with heart failure with preserved ejection fraction (HFpEF). Therefore, we aimed to examine its prognostic significance using data from the FRAGILE-HF study.

METHODS AND RESULTS

A total of 513 older patients who were hospitalized for worsening heart failure were examined. Patients were classified according to the tertiles of six-minute walking distance (6MWD): T1 (<166 m), T2 (166-285 m), and T3 (≥285 m). During the 2-year follow-up period after discharge, 90 all-cause deaths occurred. Kaplan-Meier curves showed that the T1 group had significantly higher event rates than the other groups (log-rank p = 0.007). Cox proportional hazard analysis revealed that the T1 group was independently associated with lower survival, even after adjusting for conventional risk factors (T3: hazard ratio 1.79, 95% confidence interval 1.02-3.14, p = 0.042). The addition of the 6MWD to the conventional prognostic model showed a statistically significant incremental prognostic value (net reclassification improvement 0.27, 95% confidence interval 0.04-0.49; p = 0.019).

CONCLUSIONS

The 6MWD is associated with survival in patients with HFpEF and has an incremental prognostic value over conventional well-validated risk factors.

Reference equations for the six-minute walking distance in obese Chinese subjects more than 40 years old

BACKGROUND

Studies have shown that the reference equations for the six-minute walking distance (6MWD), which were mainly derived from healthy, normal-weight people, are not suitable for individuals with obesity. The main purpose of this study was to establish reference equations for the 6MWD in obese Chinese subjects.

METHODS

In our study, a total of 214 individuals with obesity performed the six-minute walking tests (6MWTs) according to the American thoracic society (ATS) guidelines, and the longer 6MWD was used for further analysis. The reference equations for the 6MWD were developed using stepwise multiple regression analysis. The newly established equations for the 6MWD were compared to the existing prediction equations.

RESULTS

The mean 6MWD for the cohort was 523 ± 56 m. We found that the reliability of two 6MWTs was good. Age and BMI were identified as independent factors, and explained 31% and 27% of the variance in the 6MWD for the male and female participants, respectively. Thus, the reference equations reported in the previous studies did not accurately predict the 6MWD in our subjects.

CONCLUSION

Our study was the first to describe the 6MWD in obese Chinese subjects and to propose new predictive equations. These established equations can improve the assessment of the health of obese Chinese patients whose exercise capacity is affected by the disease.

LEVEL OF EVIDENCE

III, Cohort study.

Reply to "Six-minute walking test performance is associated with survival in cirrhotic patients" to the editor

Use of the six-minute walk test has been proposed as a prognostic marker in liver cirrhosis. In the Letter to the Editor presented here, the authors highlight some important points, which were raised after the article was published in the November issue of the World Journal of Hepatology.

Six-minute walking test performance is associated with survival in cirrhotic patients

BACKGROUND

Patients with cirrhosis are at risk of cirrhotic cardiomyopathy, with resulting cardiac dysfunction and exercise limitations. Six minute walking test (6MWT) assesses functional status and predicts morbidity and mortality in cardiopulmonary diseases.

AIM

To determine if it associates with mortality by analyzing 6MWT performance in patients with liver cirrhosis.

METHODS

A cohort of 106 cirrhotic patients was evaluated in the outpatient setting with echocardiogram and 6MWT and follow up for one year to document hepatic decompensation and mortality. The distance in meters was recorded at the end of 6 min (6MWD).

RESULTS

This cohort had a mean age of 51 years and 56% male; patients were staged as Child A in 21.7%, B 66% and C 12.3%. Walk distance inversely correlated with Child scores, and was significantly reduced as Child stages progresses. Patients who died (10.4%) showed shorter mean 6MWD (P = 0.006). Low 6MWD was an independent predictor of mortality (P = 0.01).

CONCLUSION

6MWT is a noninvasive inexpensive test whose result is related to Child scores and mortality. It is useful to identify patients with liver cirrhosis at high risk of mortality for closer monitoring and potential early intervention.

Validity of a novel respiratory rate monitor comprising stretchable strain sensors during a 6-min walking test in patients with chronic pulmonary obstructive disease

BACKGROUND

Breathing frequency is rarely measured during a field walking test since the current monitoring system using a face mask is cumbersome for older adults. For effective clinical application, we aimed to validate the new respiratory monitor using wearable strain sensors during a 6-min walk test (6MWT) in young adults and patients with chronic obstructive pulmonary disease (COPD).

METHODS

The study included young adults and patients with stable COPD voluntarily recruited from three hospitals. Breathing frequency during 6MWT were measured by the strain sensor and a nasal capnometer. Total breathing frequencies were measured by the capnometer. The Bland-Altman method was used to estimate the mean limit of agreement for breathing frequency.

RESULTS

A total of 23 young adults (age = 23.1 ± 3.7, mean ± SD) and 50 patients with COPD (age = 75.2 ± 7.2, %FEV1 = 59.1 ± 19.7) were analyzed. During the entire test period, the total breathing frequencies were measured based on an average of 252 ± 46 breaths, and the total breathing frequency was higher in patients with COPD than in young adults (mean difference = -3.349, p < 0.0013). The mean difference in breathing frequency between the strain sensors and capnometer was -0.28 (95%CI: 0.75 to 0.20), and the limit of agreement ranged from -4.1 to 3.6. The CI of the limit of agreement included the limit of equivalence (4 counts/min).

CONCLUSIONS

The novel respiratory monitor with wearable sensors achieved the target accuracy in both young adults and patients with COPD in the 6MWT.

Portable High-Flow Nasal Oxygen during Walking in Patients with Severe Chronic Obstructive Pulmonary Disease: A Randomized Controlled Trial

BACKGROUND

High-flow nasal oxygen (HFNO) improves exercise capacity, oxygen saturation, and symptoms in patients with chronic obstructive pulmonary disease (COPD). Due to the need of electricity supply, HFNO has not been applied during free ambulation.

OBJECTIVE

We evaluated whether HFNO delivered during walking by a battery-supplied portable device was more effective than usual portable oxygen in improving exercise capacity in patients with COPD and severe exercise limitation. The effects on 6-min walking tests (6MWTs) were the primary outcome.

METHODS

After a baseline 6MWT, 20 stable patients requiring an oxygen inspiratory fraction (FiO2) <0.60 during exercise, randomly underwent 2 6MWT carrying a rollator, under either HFNO with a portable device (HFNO test) or oxygen supplementation by a Venturi mask (Control) at isoFiO2. Walked distance, perceived dyspnea, pulse oximetry, and inspiratory capacity at end of the tests as well as patients' comfort were compared between the tests.

RESULTS

As compared to baseline, walked distance improved significantly more in HFNO than in the control test (by 61.1 ± 37.8 and 39.7 ± 43.8 m, respectively, p = 0.01). There were no significant differences between the tests in dyspnea, peripheral oxygen saturation, or inspiratory capacity, but HFNO test was appreciated as more comfortable.

CONCLUSION

In patients with COPD and severe exercise limitation, HFNO delivered by a battery-supplied portable device was more effective in improving walking distance than usual oxygen supplementation.

Six-minute walking distance in healthy Chinese people older than 60 years

Background

The six-minute walking test (6MWT) is a tool that plays a key role in evaluating the functional exercise capacity, prognosis and evaluation of treatment response of patients with various cardiopulmonary diseases. However, standard reference equations are currently unavailable for the six-minute walking distance (6MWD) for people aged 60–85 years in China. The purpose of this study was to 1) measure the 6MWD of healthy Chinese people aged 60–85 years, 2) establish reference equations for predicting the 6MWD, and 3) compare our reference equations with equations reported in previously published studies.

Method

We obtained informed consent from each participant prior to the test, and the research design was approved by the Ethics Committee of Wenzhou People’s Hospital. The demographic and anthropometric data and the 6MWD of healthy Chinese subjects aged 60–85 years old were measured using a standardized protocol. Every subject completed two 6MWTs, and the longest 6MWD further analyzed.

Results

Two hundred sixty-six subjects (128 males and 138 females) completed the 6MWT, and the mean walking distance was 518 ± 72 m. Males achieved a longer walking distance than females (518 ± 72 m vs. 487 ± 70 m; p < 0.0001), and active subjects achieved a longer walking distance than nonactive subjects (512 ± 76 m vs. 485 ± 63 m; p < 0.0001). According to the univariate analysis, the 6MWD was significantly associated with age, height, body mass index (BMI), heart rate and blood pressure after exercise and changes in heart rate before and after exercise. The stepwise multivariate regression analysis identified age, height and BMI as independent predictors of the 6MWD. The reference equations for Caucasians and South Americans tended to overestimate the 6MWD of our subjects, while the equations for Asian and African populations tended to underestimate the 6MWD.

Conclusions

This study is the first to describe the 6MWD of healthy Chinese people aged 60–85 years, and reference prediction equations were proposed. These findings will help to improve the evaluation of Chinese patients with diseases that affect exercise capacity.

Sacubitril-valsartan in heart failure and multimorbidity patients

Aims

The poor control of symptoms in patients with advanced heart failure with reduced ejection function (HFrEF) can limit the functionality of patients. Sacubitril–valsartan, compared with enalapril, has been shown to reduce mortality and hospitalization, and nowadays, there is still little evidence about the improvement on functionality. The aim of our study is to analyse the improvement of the functional class and the 6 min walking test (6MWT) in patients with multiple pathologies and advanced heart failure.

Methods and results

From September 2016 to March 2018, 65 multimorbidity patients with severe symptomatic HFrEF were initiated to receive sacubitril–valsartan. Mean age was 78.6 ± 7.4 years, and 68% were male. The Charlson co‐morbidity index was 8 points. Seventy‐four per cent had New York Heart Association (NYHA) Functional Class IV. After the treatment, patients were able to achieve 55.68 m or more on 6MWT, and 91% presented an improvement in the NYHA functional class.

Conclusions

Sacubitril–valsartan relieves symptoms and improves functional class prognostic risk of patients with advanced HFrEF and co‐morbidity.

Physical performance in newly diagnosed hypothyroidism: a pilot study

OBJECTIVE

Hypothyroidism is complicated by neuromuscular symptoms (myalgias, slowness of movements, and tiredness) and signs (easy fatigability and cramps), which may have a negative impact on general well-being and quality of life. In a pilot, prospective, controlled study, we investigated the features of muscle dysfunction in hypothyroidism by disease questionnaire, biochemical measures, and physical performance tests.

MATERIALS AND METHODS

Fifty-seven consecutive patients with newly diagnosed hypothyroidism were enrolled, 27 subclinical (S-Hypo) and 30 overt (O-Hypo). A series of 30 euthyroid subjects, with similar demographic characteristics, served as controls. Patients were administered a short disease questionnaire and underwent laboratory exams and standardized physical tests, both at baseline and after restoration of biochemical euthyroidism.

RESULTS

Compared to euthyroid controls, the O-Hypo group showed significantly higher prevalence of neuromuscular symptoms and significantly higher serum creatine phosphokinase (CPK) levels (p value < 0.0001). S-Hypo had slightly higher CPK levels and prevalence of neuromuscular symptoms than controls. Both S-Hypo and O-Hypo patients performed worse than controls in the six-minute walking test. Differences between patients and controls in handgrip strength test and timed chair standing test failed to reach statistical significance (although a trend was noticeable), possibly due to the small sample size. In O-Hypo, an inverse correlation was found between CPK levels and the handgrip strength test (p value < 0.001). Restoration of euthyroidism was associated with normalization of questionnaire responses, six-minute walking test, as well as serum CPK levels.

CONCLUSION

In addition to neuromuscular symptoms, hypothyroidism is associated with abnormalities of physical performance. The six-minute walking test is the most valuable test to assess this aspect. In the pilot study, levothyroxine therapy could reverse muscle functional abnormalities.

Design of wearable and wireless multi-parameter monitoring system for evaluating cardiopulmonary function

The 6-minute walking test (6MWT) is the test most commonly used to evaluate cardiopulmonary function in patients with respiratory or heart disease. However, there was previously no integrated monitoring system available to simultaneously record both the real-time cardiopulmonary physiological parameters and the walking information (i.e., walking distance, speed, and acceleration) during the 6MWT. In this study, then, a wearable and wireless multi-parameter monitoring system was proposed to simultaneously monitor oxygen saturation (SpO₂), heart rhythm, and the walking information during the 6MWT. A multi-parameter detection algorithm was also designed to estimate the heart rate effectively. The results of the study indicate that this system was able to reveal the dynamic changes and differences in walking speed and acceleration during the 6MWT. As such, the system has the potential to provide a more integrated approach to monitoring cardiopulmonary parameters and walking information simultaneously during the 6MWT. The proposed system warrants further investigation as an assistive assessment tool in evaluating cardiopulmonary function and may be widely applied in cardiopulmonary-related and sports medicine applications in the future.

Does telomere length predict decline in physical functioning in older twin sisters during an 11-year follow-up?

Leukocyte telomere length (LTL) is known to be associated with mortality, but its association with age-related decline in physical functioning and the development of disability is less clear. This study examined the associations between LTL and physical functioning, and investigated whether LTL predicts level of physical functioning over an 11-year follow-up. Older mono- (MZ) and dizygotic (DZ) twin sisters (n = 386) participated in the study. Relative LTL was measured by qPCR at baseline. Physical functioning was measured by 6-min walking distance and level of physical activity (PA). Walking distance was measured at baseline and at 3-year follow-up. PA was assessed by questionnaire at baseline and at 3- and 11-year follow-ups. The baseline analysis was performed with path models, adjusted with age and within-pair dependence of twin pairs. The longitudinal analysis was performed with a repeated measures linear model adjusted for age and longitudinal within-pair dependence. A nonrandom missing data analysis was utilized. At baseline, in all individuals, LTL was associated with PA (est. 0.14, SE 0.06, p = 0.011), but not with walking distance. Over the follow-up, a borderline significant association was observed between LTL and walking distance (est. 0.14, SE 0.07, p = 0.060) and a significant association between LTL and PA (est. 0.19, SE 0.06, p = 0.001). The results suggest that LTL is associated with PA and may, therefore, serve as a biomarker predicting the development of disability. Longitudinal associations between LTL and PA were observed only when nonrandom data missingness was taken into account in the analysis.