The 6-minute walk test predicts clinical outcome in Asian patients with chronic congestive heart failure on contemporary medical therapy: a study of the multiracial population in Singapore

Prognostic Role of Metabolic Exercise Testing in Heart Failure

Heart failure is a clinical syndrome with significant heterogeneity in presentation and severity. Serial risk-stratification and prognostication can guide management decisions, particularly in advanced heart failure, when progression toward advanced therapies or end-of-life care is warranted. Each currently utilized prognostic marker carries its own set of challenges in acquisition, reproducibility, accuracy, and significance. Left ventricular ejection fraction is foundational for heart failure syndrome classification after clinical diagnosis and remains the primary parameter for inclusion in most clinical trials; however, it does not consistently correlate with symptoms and functional capacity, which are also independently prognostic in this patient population. Utilizing the left ventricular ejection fraction as the sole basis of prognostication provides an incomplete characterization of this condition and is prone to misguide medical decision-making when used in isolation. In this review article, we survey and exposit the important role of metabolic exercise testing across the heart failure spectrum, as a complementary diagnostic and prognostic modality. Metabolic exercise testing, also known as cardiopulmonary exercise testing, provides a comprehensive evaluation of the multisystem (i.e., neurological, respiratory, circulatory, and musculoskeletal) response to exercise performance. These differential responses can help identify the predominant contributors to exercise intolerance and exercise symptoms. Additionally, the aerobic exercise capacity (i.e., oxygen consumption during exercise) is directly correlated with overall life expectancy and prognosis in many disease states. Specifically in heart failure patients, metabolic exercise testing provides an accurate, objective, and reproducible assessment of the overall circulatory sufficiency and circulatory reserve during physical stress, being able to isolate the concurrent chronotropic and stroke volume responses for a reliable depiction of the circulatory flow rate in real time.

Normative reference values and regression equations to predict the 6-minute walk distance in the Asian adult population aged 21-80 years

SUMMARY AT A GLANCE

The 6-min walk test (6MWT) is a widely used field walking test. This study reports the normative reference values (NRV) of distance walked during 6MWT (6MWD) in healthy Singaporeans (aged 21-80) and updates the 6MWD reference equations. This information may facilitate the interpretation of the 6MWD in clinical populations.

ETHICS APPROVAL

The Singapore Institute of Technology-Institutional Review Board (SIT-IRB Project Number: 2019099) approved this study to be carried out from June 2019 to January 2021. All participants gave written informed consent before data collection began.

BACKGROUND

The six-minute walk test (6MWT) is a widely adopted submaximal field-walking test to evaluate functional exercise capacity. This validated test is a reliable, safe, inexpensive, and straightforward assessment tool commonly used as an outcome measure, using the distance walked (6MWD) as the primary outcome. An earlier study has established the normative reference values (NRV) and equation in healthy Singaporeans - however, the small sample size and narrow age range curb adequate representation of the adult population profile.

OBJECTIVES

This study aims to update the NRV and reference equations to predict the distance walked during 6MWT (6MWD) for healthy Singaporeans aged 21-80.

METHODS

This cross-sectional study recruited community-dwelling healthy subjects aged 21-80 via convenience sampling. Each subject completed two trials of 6MWT according to the standard protocol. Primary outcome measures included 6MWD, pre-and post-test heart rate (HR), oxygen saturation, and blood pressure (BP).

RESULTS

172 healthy Singaporeans (females = 90 , males = 82 ) participated. The overall mean 6MWD was 578 . 00 ± 75 . 38 metres. The age-stratified mean 6MWD ranged from 601 . 3 ± 71 . 79 metres (aged 21-39) to 519 . 02 ± 55 . 42 metres (aged 60-80). Age, gender, and percentage maximum HR predicted (%PredHRmax) were the most significant variables (p < 0 . 001 ). 6MWD reference equation = 288 . 282 ( height , m )+ 27 . 463 × Gender ( male = 1 ; female = 0 )+ 4 . 349 ( % predHRmax )+ 1 . 191 (HR reserve, bpm) - 185 . 431 - 1 . 343 ( age , years )- 1 . 614 (weight, kg), R 2 = 58 % . Applying equations from other studies to the Singaporean population resulted in an overestimation of the 6MWD.

CONCLUSION

This study updated the NRV and reference equations of 6MWD for healthy Singaporeans aged between 21-80 years. This update revises the local benchmarks of 6MWD in Singapore, a widely adopted outcome measure.

Prognostic impact of 6 min walk test distance in patients with systolic heart failure: insights from the WARCEF trial

AIMS

This study aimed to investigate the impact of baseline 6 min walk test distance (6MWTD) on time to major cardiovascular (CV) events in heart failure with reduced ejection fraction (HFrEF) and its impact in clinically relevant subgroups.

METHODS AND RESULTS

In the WARCEF (Warfarin versus Aspirin in Reduced Cardiac Ejection Fraction) trial, 6MWTD at baseline was available in 2102 HFrEF patients. Median follow-up was 3.4 years. All-cause death and heart failure hospitalization (HFH) exhibited a significant non-linear relationship with 6MWTD (P = 0.023 and 0.032, respectively), whereas a significant association between 6MWTD and CV death was shown in a linear model [hazard ratio (HR) per 10 m increase, 0.989; P = 0.011]. In linear splines with the best cut-off point at 200 m, the positive effect of a longer 6MWTD on all-cause death and HFH was only observed for 6MWTD > 200 m (HR per 10 m increase, 0.987; P = 0.0036 and 0.986; P = 0.0022, respectively). The associations between 6MWTD and CV outcomes were consistent across clinical subgroups; for age, a significant relationship between 6MWTD and HFH was observed in patients ≥60 years (HR per 10 m increase, 0.98; P < 0.001), but not in patients <60 years (HR per 10 m increase, 1.00; P = 0.98; P = 0.02 for the interaction).

CONCLUSIONS

In HFrEF, 6MWTD is independently associated with all-cause death, CV death, and HFH. 6MWTD of 200 m is the best cut-off point for predicting these adverse events. The prognostic impact of 6MWTD for HFH was only observed in older patients.

Physical functional performance and prognosis in patients with heart failure: a systematic review and meta-analysis

Background

Patients with Heart Failure (HF) show impaired functional capacities which have been related to their prognosis. Moreover, physical functional performance in functional tests has also been related to the prognosis in patients with HF. Thus, it would be useful to investigate how physical functional performance in functional tests could determine the prognosis in patients with HF, because HF is the leading cause of hospital admissions for people older than 65 years old. This systematic review and meta-analysis aims to summarise and synthesise the evidence published about the relationship between physical functional performance and prognosis in patients with HF, as well as assess the risk of bias of included studies and the level of evidence per outcome.

Methods

Major electronic databases, such as PubMed, AMED, CINAHL, EMBASE, PEDro, Web of Science, were searched from inception to March 2020 for observational longitudinal cohort studies (prospective or retrospective) examining the relationship between physical functional performance and prognosis in patients with HF.

Results

44 observational longitudinal cohort studies with a total of 22,598 patients with HF were included. 26 included studies reported a low risk of bias, and 17 included studies showed a moderate risk of bias. Patients with poor physical functional performance in the Six Minute Walking Test (6MWT), in the Short Physical Performance Battery (SPPB) and in the Gait Speed Test showed worse prognosis in terms of larger risk of hospitalisation or mortality than patients with good physical functional performance. However, there was a lack of homogeneity regarding which cut-off points should be used to stratify patients with poor physical functional performance from patients with good physical functional performance.

Conclusion

The review includes a large number of studies which show a strong relationship between physical functional performance and prognosis in patients with HF. Most of the included studies reported a low risk of bias, and GRADE criteria showed a low and a moderate level of evidence per outcome.

Sex-dependent changes in physical, mental, and quality of life outcomes in metoprolol-treated Chinese chronic heart failure patients

This study assessed sex differences in cardiac and motor functions, quality of life (QoL), and mental status in Chinese chronic heart failure (CHF) patients after metoprolol treatment.This single-center prospective study, conducted from February 2013 to April 2016, included CHF patients (men and women) with resting heart rate (HR) >80 beats/min using metoprolol continuous release tablets. Metoprolol-induced changes in cardiac and motor functions, QoL, and mental status at 1, 3, 6, 9, and 12 months from baseline, within and between the sexes, were analyzed. Descriptive data were represented as counts, percentages, and mean ± standard deviation. Differences at various follow-up periods were compared using repeated measures one-way analysis of variance, followed by post hoc Dunnett's multiple comparison test. Statistical significance was considered at P < .05.Compared with men, women reported significantly higher systolic blood pressure (SBP) (122.28 ± 6.76 vs 125.47 ± 6.67 mm Hg, P < .05) and Veterans Specific Activity Questionnaire score (8.16 ± 0.98 vs 8.47 ± 0.89, P = .05) at 12 months. Men reported higher Hospital Anxiety and Depression Scale scores for depression than women at 1 month (10.27 vs 8.83, P < .05) and for anxiety at 12 months (8.4 vs 7.72, P < .05). Metoprolol significantly decreased HR and Minnesota Living with Heart Failure Questionnaire score in men (64.5 ± 3.13 and 53.7 ± 8.00) and women (65.38 ± 3.32 and 53.85 ± 8.42, respectively). Ejection fraction (%, men: 50.00 ± 4.45, women: 50.72 ± 4.09), cardiac index (L/min/m, men: 2.70 ± 0.25, women: 2.78 ± 0.23), 6-minute walk test distance (m, men: 414.41 ± 20.84, women: 420.34 ± 20.35), and short form-8 questionnaire scores (men: 52.05 ± 1.94, women: 52.19 ± 2.58) increased significantly in both the sexes (P < .001 for all) at 12 months. Copenhagen Burnout Inventory score significantly increased in men (mean score 62.43, P < .05).Metoprolol treatment improves cardiac and motor functions, QoL, and anxiety scores but causes greater depression and burnout in men and women. Sex was seen to affect mental status of CHF patients the most.

Using Physical Function to Predict Hospital Readmission within 1 Year in Patients with Heart Failure

OBJECTIVE

The aim of this study was to investigate which method of evaluating physical function could predict 1-year readmission due to worsening of heart failure (HF) in newly diagnosed HF patients.

METHODS

One hundred sixteen consecutive patients with HF who underwent cardiac rehabilitation at our hospital between May 2012 and September 2015 were retrospectively enrolled. Participants were divided into two groups based on whether they were readmitted for worsening HF within 1 year. Logistic regression analysis was used to evaluate whether physical function at the time of discharge was related to HF readmission within 1 year.

RESULTS

After a mean follow-up period of 327 days, 22 patients were readmitted because of worsening HF. In the readmission group, the results of the 6-Minute Walk Test (6MWT), One-Leg Standing Test, and 30-Second Chair-Stand Test at initial discharge were significantly worse than those in the non-readmission group. In a multivariable logistic regression model, after adjusting for age and sex, a lower 6MWT distance was independently associated with increased risk of readmission within 1 year (odds ratio: 0.990, 95% confidence interval: 0.985-0.996). The 6MWT showed better prognostic value (area under the receiver operating characteristic curve: 0.696) than other evaluation methods of physical function. The 1-year non-readmission rates were 90% for 6MWT ≥382.5 m, 68% for 6MWT <382.5 m, and 53% for those unable to walk 200 m independently (P <0.001).

CONCLUSION

Physical function, particularly the 6MWT distance at time of discharge, can be used to predict the likelihood of readmission within 1 year for patients with HF.

Exercise and Cognitive Training as a Strategy to Improve Neurocognitive Outcomes in Heart Failure: A Pilot Study

OBJECTIVE

Mild cognitive impairment, especially memory loss, is prevalent in patients with heart failure (HF) and contributes to poor clinical outcomes and higher mortality.

METHODS

This study evaluated a combined aerobic exercise and cognitive training (EX/CT) program on memory, executive function, attention, processing speed and reaction time compared to exercise only or a usual care attention control (UCAC) stretching and flexibility program. Participants completed a standardized neurocognitive battery at baseline, 3 months, and 6 months along with demographic, clinical, and functional capacity (6-minute walk test). A linear mixed model analysis was used with comorbidity as a covariate.

RESULTS

Sixty-nine participants were enrolled, the mean age was 61 ± 10 years, 54% were women, 55% were African American, and the mean left ventricular ejection fraction percentage was 35 ± 15. A significant group by time interaction for verbal memory was found at 3 months (F [2, 53] = 4.3, p = 0.018) but was not sustained at 6 months in the EX/CT group. Processing speed/attention differed across treatment groups between baseline and 6 months, but improvement occurred among UCAC participants. There were also significant group differences in the 6MWT distance occurring at 3 months (F [2, 52] = 3.5, p = 0.036); however, significant improvement was observed within the EX/CT group only. There were no significant differences in 6MWT in the other groups at 3 or 6 months.

CONCLUSION

An EX/CT intervention was associated with improved memory in persons with HF and warrants further investigation in a larger trial. The relationship between functional capacity and cognitive function also needs further study.

Single-dose intravenous iron in Southeast Asian heart failure patients: A pilot randomized placebo-controlled study (PRACTICE-ASIA-HF)

AIMS

Iron deficiency is highly prevalent in Southeast Asians with heart failure (HF) and associated with worse outcomes. This trial aimed to assess the effect of intravenous iron in Southeast Asians hospitalized with decompensated HF.

METHODS AND RESULTS

Fifty patients hospitalized for acute decompensated HF, regardless of ejection fraction, with iron deficiency (defined as serum ferritin <300 ng/mL if transferrin saturation is <20%) were randomized to receive either one dose of intravenous ferric carboxymaltose (FCM) 1000 mg or placebo (0.9% saline) following HF stabilization and before discharge in two Singapore tertiary centres. The primary endpoint was difference in 6-min walk test (6MWT) distance over 12 weeks, while secondary endpoints were quality of life assessed using validated Kansas City Cardiomyopathy Questionnaire (KCCQ) and Visual Analogue Scale (VAS). Improvement in 6MWT distance at Week 12 was observed in both FCM and placebo groups (from 252 ± 123 to 334 ± 128 m and from 243 ± 67 to 301 ± 83 m, respectively). Unadjusted analysis showed 6MWT distance for FCM exceeded that for placebo, but adjustment for baseline covariates and time attenuated this effect {adjusted mean difference between groups: 0.88 m [95% confidence interval (CI) -30.2 to 32.0, P = 0.956]}. KCCQ overall summary and VAS were similar in both groups [adjusted mean difference: KCCQ -1.48 (95% CI -8.27 to 5.31, P = 0.670) and VAS 0.26 (95% CI -0.33 to 0.86, P = 0.386)]. FCM was well tolerated with no serious treatment-related adverse events.

CONCLUSIONS

Intravenous FCM administered pre-discharge in Southeast Asians hospitalized with decompensated HF is clinically feasible. Changes in 6MWT distance should be measured beyond Week 12 to account for background therapy effects.

Correlation of the New York Heart Association Classification and the 6-Minute Walk Distance: A Systematic Review

BACKGROUND

Functional status assessment is the cornerstone of heart failure management and trials. The New York Heart Association (NYHA) classification and 6-minute walk distance (6MWD) are commonly used tools; however, the correlation between them is not well understood.

HYPOTHESIS

We hypothesised that the relationship between the NYHA classification and 6MWD might vary across studies.

METHODS

A systematic literature search was performed to identify all studies reporting both NYHA class and 6MWD. Two reviewers independently assessed study eligibility and extracted data. Thirty-seven studies involving 5678 patients were included.

RESULTS

There was significant heterogeneity across studies in 6MWD within all NYHA classes: I (n = 16, Q = 934.2; P < 0.001), II (n = 25, Q = 1658.3; P < 0.001), III (n = 30, Q = 1020.1; P < 0.001), and IV (n = 6, Q = 335.5; P < 0.001). There was no significant difference in average 6MWD between NYHA I and II (420 m vs 393 m; P = 0.416). There was a significant difference in average 6MWD between NYHA II and III (393 m vs 321 m; P = 0.014) and III and IV (321 m vs 224 m; P = 0.027). This remained significant after adjusting for region of study, age, and sex.

CONCLUSIONS

Although there is an inverse correlation between NYHA II-IV and 6MWD, there is significant heterogeneity across studies in 6MWD within each NYHA class and overlap in 6MWD between NYHA I and II. The NYHA classification performs well in more symptomatic patients (NYHA III/IV) but less so in asymptomatic/mildly symptomatic patients (NYHA I/II). Nonetheless, the NYHA classification is an easily applied first-line tool in everyday clinical practice, but its potential subjectivity should be considered when performing comparisons across studies.

Test-retest reliability and developmental evolution of the 6-min walk test in Caucasian boys aged 5-12 years

The 6-min walk test (6MWT) assesses functional capacity and has been used as outcome measure in therapeutic studies in childhood neuromuscular disorders. The objectives were to evaluate test-retest reliability of the 6MWT and to generate normative data for healthy boys aged 5-12 years. Ninety boys (mean age 8 years 10 months) were recruited over four age subcategories (5-6, 7-8, 9-10, 11-12 years). Mean 6MWT distance and velocity (±standard deviation) for the total group were 555.5±93 m and 92.6±16.6 m/min. The 6MWT distance increased significantly with age. Test-retest reliability (mean interval 12 days) was very high for the total group (ICC>0.95) and for all age subcategories (ICC>0.80) a moderately high reliability (ICC>0.75) was found from 3 min onwards for each age subcategory. There was a mean difference of 5.2 m between test and retest without systematic bias. The standard error of measurement and smallest detectable difference were 20.7 and 57.4 m, respectively. These findings demonstrate the reliability of the 6MWT in young children, underscore its evolution with age, and indicate that a shorter version of the test is also reliable.

Impact of race on morbidity and mortality in patients with congestive heart failure: a study of the multiracial population in Singapore

AIM

We assessed the impact of race on clinical outcome in the multiracial Singapore congestive heart failure (CHF) population.

METHODS

668 CHF patients (Age 66+/-12 years, Ejection fraction 29+/-13%), consisting of Chinese (72%), Malays (17.1%) and Indians (10.9%) were prospectively followed up for 24+/-12 months. Primary outcome measure was the composite end-point of all-cause mortality or CHF readmission.

RESULTS

Composite end-points occurred in 198 (29.6%) patients (133 deaths, 112 CHF readmissions). Diabetes mellitus (DM), peripheral vascular disease and hyperlipidemia were more prevalent in Indians compared to Malays or Chinese (all p<0.05). Indians and Malays had higher composite end-point rates compared to the Chinese (p=0.01). Although Indians and Malays had higher CHF readmission rates compared to the Chinese (p<0.01), a trend towards a higher all-cause mortality rate was seen in Malays (p=0.12). Malay race was an independent predictor of the composite end-point (OR=1.65, 95% CI=1.04-2.63, p=0.034), as were age, diabetes mellitus, ischemic cardiomyopathy, beta-blocker use, and NYHA class (all p<0.05).

CONCLUSIONS

In the multiracial Singapore CHF population, Indians and Malays had a worse outcome compared to the Chinese, due to higher CHF readmission rates in Indians and higher mortality and CHF readmission rates in Malays. While the worse outcome in Indians may be due to the greater prevalence of diabetes mellitus and atherosclerotic vascular disease, the cause of the poorer prognosis in Malays is unclear.