The 6-min walk and peak oxygen consumption in advanced heart failure: aerobic capacity and survival

[Possibilities of Predicting Peak Oxygen Consumption in Patients With Chronic Heart Failure According to the 6‑Minute Walk Test]

AIM

To determine the correlation between the results of the 6-minute walk test (6MWT) and peak oxygen consumption (VO2peak) for populations of patients with chronic heart failure with pronounced clinical and demographic differences; to study a possibility of indirect measurement of VO2peak based on the results of 6MWT using the formulas available from the literature.

MATERIAL AND METHODS

Two databases were analyzed: 50 patients included in the AEROFIT study (group A), and 31 patients from the Almazov National Medical Research Center (group B). The inclusion criteria were the availability of data from the cardiopulmonary stress test and the 6MWT. The possibility of predicting VO2peak was calculated based on the results of 6MWT using the formulas reported in the literature (L. P. Cahalin et al., 1996; R. M. Ross et al., 2010; R. A. Adedoyin et al., 2010). The predictive accuracy of the models was assessed using the coefficient of determination (R2). The relationship between functional and clinical-demographic indicators was assessed using the Pearson or Spearman correlation analysis.

RESULTS

The study groups differed significantly in all parameters, except for the proportion of men and the mean VO2peak. Group B patients were 20 years younger than group A patients, had a lower left ventricular ejection fraction (24.06±7.75 and 41.52±10.48 %, respectively; p<0.001), and covered a 130 m shorter distance in the 6MWT. Despite the absence of a significant difference in VO2peak between groups A and B (13.6 and 13.1 ml / kg / min, respectively; p=0.6581), 61 % of group B patients and 20% of group A belonged to Weber functional class IV. In group A, the 6MWT distance correlated closely with VO2peak (R=0.78; p<0.01) and weakly with age (R=0.4) and body mass index (R=0.3). In group B, the 6MWT distance correlated only with VO2peak (R=0.77; p<0.01). For group A, the R.M. Ross et al. model demonstrated high accuracy in determining the mean VO2peak value with a 0.06% prediction error normalized to measured VO2peak. For group B, none of the models showed satisfactory predictive accuracy. The Ross and Cahalin models showed the best coefficients of determination for groups A and B: Group A, Ross et al. (R2=0.58) and Cahalin et al. (R2=0.59); Group B, Ross et al. (R2=0.59) and Cahalin et al. (R2=0.6).

CONCLUSION

In two groups of patients with a statistically insignificant difference in the mean values of VO2peak, the mean values of 6MWT distance were significantly different, although these indicators correlated closely. The VO2peak prediction models showed satisfactory accuracy for estimation of mean VO2, but poor accuracy for estimation of individual values. A better predictive accuracy is determined by similar clinical and demographic characteristics between the training and testing populations, and likely also by models based on larger, more diversified populations.

Progress in Cardiac Resynchronisation Therapy and Optimisation

Cardiac resynchronisation therapy (CRT) has become the cornerstone of heart failure (HF) treatment. Despite the obvious benefit from this therapy, an estimated 30% of CRT patients do not respond ("non-responders"). The cause of "non-response" is multi-factorial and includes suboptimal device settings. To optimise CRT settings, echocardiography has been considered the gold standard but has limitations: it is user dependent and consumes time and resources. CRT proprietary algorithms have been developed to perform device optimisation efficiently and with limited resources. In this review, we discuss CRT optimisation including the various adopted proprietary algorithms and conduction system pacing.

A Simple Equation to Estimate Maximal Oxygen Uptake in Older Adults Using the 6 min Walk Test, Sex, Age and Body Mass Index

PURPOSE

The 6 min walk test (6MWT) is used in clinical and epidemiological practice as a simple tool to evaluate the maximal aerobic exercise capacity (VO2max). To date, little evidence has been provided regarding regression equation models to predict VO2max in older adults. Therefore, the main purpose of the study was to develop a reference equation to estimate objectively measured VO2max, based on the 6MWT, sex, age and body mass index (BMI).

PATIENTS AND METHODS

In this observational prospective study, we collected the data from 233 asymptomatic participants aged 60-80 years (52.4% women). VO2max and the 6MWT were measured using standardized protocols. BMI was calculated as weight (kg) divided by height squared (m2). To be able to develop the predictive equation for VO2max, we used linear generalized estimating equations (GEE).

RESULTS

Older men performed better in VO2max (30.9 ± 8.8 vs. 26.3 ± 6.3 mL/kg/min, p < 0.001) and the 6MWT (673.9 ± 58.7 vs. 642.3 ± 48.0 m, p < 0.001), compared to women. VO2max was correlated with the 6MWT (r = 0.71, p < 0.001), sex (r = -0.29, p < 0.001), age (r = -0.62, p < 0.001) and BMI (r = -0.38, p < 0.001). The model to predict VO2max included: VO2max (mL/kg/min) = 59.44 - 3.83 *, sex (1-men; 2-women) - 0.56 *, age (years) - 0.48 *, BMI (kg/m2) + 0.04 *, and the 6MWT (m) (R = 0.85; R2 = 72.3%, SEE = 3.99 mL/kg/min, p < 0.001).

CONCLUSION

The newly developed regression equation can be a guideline in clinical and epidemiological practice to predict the VO2max in apparently healthy older adults.

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.

Does recovery from submaximal exercise predict response to cardiac resynchronisation therapy?

Background

Exercise parameters are not routinely incorporated in decision making for cardiac resynchronisation therapy (CRT). Submaximal exercise parameters better reflect daily functional capacity of heart failure patients than parameters measured at maximal exertion, and may therefore better predict response to CRT. We compared various exercise parameters, and sought to establish which best predict CRT response.

Methods

In 31 patients with chronic heart failure (61% male; age 68±7 years), submaximal and maximal cycling testing was performed before and 3 months after CRT. Submaximal oxygen onset (τVO₂ onset) and recovery kinetics (τVO₂ recovery), peak oxygen uptake (VO₂ peak) and oxygen uptake efficiency slope (OUES) where measured. Response was defined as ≥15% relative reduction in end-systolic volume.

Results

After controlling for age, New York Heart Association and VO₂ peak, fast submaximal VO₂ kinetics were significantly associated with response to CRT, measured either during onset or recovery of submaximal exercise (area under the curve, AUC=0.719 for both; p<0.05). By contrast, VO₂ peak (AUC=0.632; p=0.199) and OUES (AUC=0.577; p=0.469) were not associated with response. Among patients with fast onset and recovery kinetics, below 60 s, a significantly higher percentage of responders was observed (91% and 92% vs 43% and 40%, respectively).

Conclusions

Impaired VO₂ kinetics may serve as an objective marker of submaximal exercise capacity that is age-independently associated with non-response following CRT, whereas maximal exercise parameters are not. Assessment of VO₂ kinetics is feasible and easy to perform, but larger studies should confirm their clinical utility.

Prognostic value of 6-min walk test compared to cardiopulmonary exercise test in patients with severe heart failure

AIMS

The 6-min walk test (6MWT) and cardiopulmonary exercise test (CPET) are both predictive in heart failure (HFrEF). Although 6MWT substitutes for CPET in HFrEF patients, as submaximal testing may be preferable, its prognostic superiority still needs to be verified, particularly in regard to beta blockers (BBs). We aimed to compare the prognostic role of CPET and 6MWT and investigate whether BB therapy influences the predictive value.

METHODS

This is a single-center, retrospective study. Advanced HFrEF patients were followed up for 3 years: events were cardiovascular death or urgent heart transplantation. We analyzed the predictive capacity of CPET and 6MWT in patients, and subdivided according to use of BBs.

RESULTS

In a group of 251 HFrEF patients, we found a correlation between meters and peak VO2 (r2 = 0.94). Over the 3-year follow-up, 74 events were recorded. Both CPET and 6MWT variables were correlated with outcome at univariate analysis (meter and VE/VCO2 slope, peak VO2, VO2 at ventilatory anaerobic threshold, percentage predicted of peak VO2), but only percentage predicted of peak VO2 (pppVO2) was an independent predictor. In 103 HFrEF patients on BBs (23 nonsurvivors), neither pppVO2 nor meter were predictive, while in 148 patients not treated with BB (51 with events) pppVO2 was selected as an independent prognostic parameter (P = 0.001).

CONCLUSIONS

6MWT is a valid alternative to CPET, although the percentage of predicted of peak VO2 emerged as the strongest predictor. Nonetheless, our results suggest that both functional derived parameters are not predictive among those patients treated with BBs. Further studies are necessary to confirm these findings.

Validity of the 6-Minute Walk Test and YMCA Submaximal Cycle Test During Midpregnancy

Tinius, RA, Blankenship, M, Maples, JM, Pitts, BC, Furgal, K, Norris, ES, Hoover, DL, Olenick, A, Lambert, J, and Cade, WT. Validity of the 6-minute walk test and Young Men's Christian Association (YMCA) submaximal cycle test during midpregnancy. J Strength Cond Res 35(11): 3236-3242, 2021-Submaximal exercise testing can be a feasible alternative to maximal testing within special populations to safely predict fitness levels; however, submaximal exercise testing has not been well-validated for use during pregnancy. The purpose of this study was to determine the concurrent validity of the 6-minute walk test (6MWT) and the YMCA submaximal cycle test (YMCAT) to predict V̇o2max in physically active women during midpregnancy. Thirty-seven (n = 37) pregnant women (22.1 ± 1.4 weeks' gestation) and 10 (n = 10) nonpregnant women participated in the study. Subjects completed a graded maximal treadmill test at 1 visit to measure maximal oxygen consumption (V̇o2max), and then subjects completed the 6MWT and YMCAT in randomized order during a separate visit. The predicted V̇o2max from each submaximal test were compared with the measured V̇o2max from the treadmill test to assess the validity of these tests during pregnancy. Among pregnant women, predicted V̇o2max from the YMCAT was not correlated to the measured V̇o2max (r = 0.14, p = 0.42), and the predicted V̇o2max from the 6MWT was only moderately correlated (r = 0.40, p = 0.016) to the measured V̇o2max. Among nonpregnant women, the predicted V̇o2max values from both the YMCAT and the 6MWT had strong correlations with the measured V̇o2max values (YMCAT: r = 0.71, p = 0.02; 6MWT: r = 0.80, p = 0.006). Neither test demonstrated concurrent validity among the pregnant sample. The main finding is that the YMCAT is not a valid method to estimate V̇o2max during midpregnancy (likely due to physiological changes in heart rate [HR] during pregnancy). The 6MWT has potential to be used clinically for estimating fitness as actual and predicted values did positively correlate, and it is not dependent on HR responses to exercise. However, if a precise measure of fitness is needed, then neither test appears to have strong validity for use during midpregnancy.

Prognostic value of 6-minute walk test and cardiopulmonary exercise test in acute heart failure (from the ESCAPE trial)

Introduction

We aim to study the utility of 6-minute walk distance (6MWD) and cardiopulmonary exercise testing (CPET) in patients with acute systolic heart failure (HF) in predicting post-discharge outcomes.

Methods

The ESCAPE trial data was utilized to examine the prognostic role of 6MWD and CPET in predicting 6-month all-cause mortality and rehospitalization in acute HF.

Results

The average 6MWD recorded in 271 and 292 patients on admission and discharge was 597 and 765 ft., respectively. Compared with non-survivors, survivors had significantly higher 6MWD on admission (624 vs. 463 ft., P = 0.006) and discharge (789 vs. 636 ft., P = 0.006). Admission and discharge 6MWD had an AUC of 0.629 (P = 0.0047) and 0.628 (P = 0.0093) in predicting mortality. The combination of optimal 6MWD cutoff values of >288 ft. on admission and > 320 ft. on discharge was associated with significantly lower mortality (11.1% vs. 28.3%, OR 0.316, P = 0.002). When dividing the sample into quartiles of increasing walking distance, patients in the 1st quartile had significantly higher mortality on admission (OR 3.59, 95% CI 1.396-9.282, P = 0.008) and discharge (OR 3.66, 95% CI 1.357-9.839, P = 0.01) compared with 4th quartile. P-value for the trend in mortality across quartiles of 6MWD on admission and discharge was 0.016 and 0.047, respectively. Cox proportional hazard analysis revealed that admission (HR 0.632, 95% CI 0.449-0.890, P = 0.009) and discharge 6MWD (HR 0.657, 95% CI 0.467-0.926, P = 0.016) were independent mortality determinants after adjustment for age, creatinine, sodium, systolic blood pressure and NYHA class, all on admission. CPET-derived variables did not predict either outcomes.

Conclusion

6MWD is an independent mortality determinant in advanced systolic HF.

Six-minute walk test: prognostic value and effects of nebivolol versus placebo in elderly patients with heart failure from the SENIORS trial

BACKGROUND

There is limited information about the 6-min walk test (6MWT) in elderly patients with heart failure. We evaluated 6MWT and the effect of nebivolol on 6MWT from the SENIORS trial.

METHODS AND RESULTS

The SENIORS trial evaluated nebivolol versus placebo on death and hospitalisation in patients aged ≥ 70 years with heart failure. A total of 1982 patients undertook a 6MWT at baseline and 1716 patients at 6 months. Patients were divided into tertiles (≤ 200 m, 201 to ≤ 300 m and > 300 m) and to change in distance walked between baseline and 6 months (< 0 m, 0 to < 30 m and ≥ 30 m). The primary outcome was all-cause mortality and cardiovascular hospital admission. Secondary endpoint was all-cause mortality. Baseline walk distance of ≤ 200 m incurred a greater risk of the primary and secondary outcomes (HR 1.41, CI 95% 1.17-1.69, p < 0.001) and (HR 1.37, CI 95% 1.05-1.78, p = 0.019). A decline in walk distance over 6 months was associated with increased risk of clinical events. Nebivolol had no influence on change in walk distance over 6 months.

CONCLUSIONS

The 6MWT has prognostic utility in elderly patients. Those who walked less than 200 m were at highest risk. Nebivolol had no effect on 6MWT.

Utility of 6-Minute Walk Test to Predict Response to Cardiac Resynchronization Therapy in Patients With Mild Heart Failure

Clinical studies of heart failure (HF) generally utilize the 6-minute walk test (6MWT) for functional capacity (FC) assessment. However, data on the impact of cardiac resynchronization therapy (CRT) on 6MWT and its role to predict long-term outcomes in mild HF patients with CRT are lacking. We studied 1,381 subjects with mild HF enrolled in Multicenter Automatic Defibrillator Implantation Trial - Cardiac Resynchronization Therapy with 6MWT data at baseline and 1 year. We assessed the effects of CRT-D on percent change in 6MWT at 1 year by left bundle branch block (LBBB) status, identified independent predictors of 6MWT at 1 year, and evaluated the association between changes in 6MWT and risk for HF or death. Treatment with CRT-D versus implantable cardiac defibrillator (ICD) was not associated with a significant improvement in 6MWT at 1-year in LBBB subjects (2.2 % vs 0.0%, p = 0.428, but it was associated with a deterioration in 6MWT in non-LBBB subjects (4.1% vs 0.0%, p = 0.308). Multivariate analysis showed that each 5% reduction in 6MWT was independently associated with a corresponding 3% increase in the risk of subsequent HF or death (p = 0.014). In conclusion, our findings suggest that 6MWT has limited utility to identify CRT response in mild HF subjects with LBBB. However, 6MWT showed a signal toward deterioration in mild HF subjects with non-LBBB, and this was predictive of subsequent increased risk of HF or death.

6 min walk test is a strong independent predictor of death in outpatients with heart failure

AIMS

The aim of this study was to examine the prognostic value of the 6 min walk test (6MWT) in a large cohort of outpatients with heart failure.

METHODS AND RESULTS

A total of 5519 outpatients with heart failure from the National Norwegian Heart Failure Registry (NNHFR), which is part of the Norwegian Cardiovascular Disease Registry, were included in this analysis. The NNHFR recommended the use of the 6MWT for prognostic assessment of all patients included in the registry. Patients were categorized according to the 6MWT: Category 1 walked the longest and Category 3 the shortest. During a median (25th-75th percentiles) follow-up of 24 (14-36), 12.9% of the patients died. Patients in Category 3 had the overall worst outcome than had patients in Categories 1 and 2. 6MWT used as a continuous variable was a highly significant independent predictor for mortality in a multivariate Cox regression model adjusted for 16 other variables with a hazard ratio of 0.979 [(95% confidence interval 0.972-0.986), P < 0.001]. The four most important predictors for mortality were active cancer in the last 5 years, age, 6MWT, and natriuretic peptides (all P < 0.001).

CONCLUSIONS

6MWT is a strong independent predictor of mortality in outpatients with HF. The findings support the use of the 6MWT in the prognostic assessment of patients with HF irrespective of HF aetiology.

Associação entre consumo de oxigênio de pico e teste de caminhada de seis minutos em pacientes após cirurgia cardíaca

RESUMO Pacientes submetidos a cirurgia de revascularização do miocárdio (CRM) apresentam redução da capacidade funcional cardiorrespiratória após o procedimento. Uma avaliação adequada no período pós-operatório desses indivíduos se faz fundamental, tendo em vista uma melhor prescrição para a reabilitação cardiopulmonar fase II e retorno às atividades de vida diária. Nosso objetivo foi verificar a associação entre a distância percorrida no teste de caminhada de 6 minutos (TC6) e o consumo de oxigênio de pico (VO2 pico) obtido no teste cardiopulmonar de exercício (TCPE) em pacientes 40 dias após a CRM. Nesse estudo observacional transversal, foram incluídos pacientes submetidos a CRM. A avaliação ocorreu 40 dias após a realização da cirurgia em ambiente hospitalar. Os testes realizados foram o TCPE, o protocolo em esteira rolante e o TC6, de acordo com as normas da American Thoracic Society. Para a análise dos resultados, utilizamos o teste de correlação de Pearson. A amostra contém 39 pacientes, dos quais 28 (71,8%) são do sexo masculino, com idade média de 58 anos. Foi possível observar predominância de sedentarismo (74,4%), uso de tabaco (74,4%) e alta prevalência de hipertensão arterial sistêmica (82,1%). Nos testes realizados, a distância média percorrida no TC6 foi de 494m±70m, e no TCPE o VO2 pico médio foi de 19,5±3,6ml/kg/min. A correlação linear observada entre eles foi r=0,48; p=0,02. Concluindo, houve correlação moderada e estatisticamente significativa entre distância percorrida no TC6 e o VO2 pico em pacientes 40 dias após CRM.

6-minute walking test: a useful tool in the management of heart failure patients

Reduced functional ability and exercise tolerance in patients with heart failure (HF) are associated with poor quality of life and a worse prognosis. The 6-minute walking test (6MWT) is a widely available and well-tolerated test for the assessment of the functional capacity of patients with HF. Although the cardiopulmonary exercise test (a maximal exercise test) remains the gold standard for the evaluation of exercise capacity in patients with HF, the 6MWT (submaximal exercise test) may provide reliable information about the patient’s daily activity. The current review summarizes the value of 6MWT in patients with HF and identifies its usefulness and limitations in everyday clinical practice in populations of HF. We aimed to investigate potential associations of 6MWD with other measures of functional status and determinants of 6MWD in patients with HF as well as to review its prognostic role and changes to various interventions in these patients.

Amino Acid-Based Metabolic Profile Provides Functional Assessment and Prognostic Value for Heart Failure Outpatients

Functional capacity is a crucial parameter correlated with outcomes. The currently used New York Heart Association functional classification (NYHA Fc) system has substantial limitations, leading to inaccurate classification. This study investigated whether amino acid-based assessment on metabolic status provides an objective way to assess functional capacity and prognosis in heart failure (HF) outpatients. Plasma concentrations of histidine, ornithine, and phenylalanine (HOP) were measured on 890 HF outpatients to assess metabolic status by calculating the HOP score. Cardiopulmonary exercise testing (CPET) was performed in 387 patients to measure metabolic equivalents (MET) in order to define the functional class based on MET (MET Fc). Patients were followed for composite events (death/HF-related rehospitalization) up to one year. We found only 47% concordance between the MET Fc and NYHA Fc. HOP scores worked better than NYHA Fc for discriminating patients with MET Fc II and III from those with MET Fc I, with the optimal cutoff value set at 8.8. HOP scores ≥ 8.8 were associated with risk factors for composite events in different kinds of HF populations and were a powerful predictor of composite events in univariate analysis. In multivariable analysis, HOP scores ≥ 8.8 remained a powerful event predictor, independent of other risk factors. Kaplan-Meier curves revealed that HOP scores of ≥8.8 stratified patients at higher risk of composite events in a variety of HF populations. In conclusion, amino acid-based assessment of metabolic status correlates with functional capacity in HF outpatients and provides prognostic value for a variety of HF populations.

Efficacy of heart failure reversal treatment in patients with low ejection fraction

BACKGROUND

Heart failure reversal therapy (HFRT) is designed to enhance cardiorespiratory fitness of chronic heart failure (CHF) patients.

OBJECTIVE(S)

The present study was designed to evaluate efficacy of HFRT that uses herbal procedure (panchakarma) and allied therapies, in CHF patients with low ejection fraction.

METHODS

This efficacy study was conducted in CHF patients (aged: 25-65 years, ejection fraction (EF) 10-30%) wherein HFRT (60-75 min) consisting of snehana (external oleation), swedana (passive heat therapy), hrudaydhara (concoction dripping treatment) and basti (enema) was administered twice daily for 7 days. During this therapy and next 30 days, patients followed the study dinarcharya and were prescribed ARJ kadha in addition to their conventional treatment. The primary endpoint of this study was evaluation of maximum aerobic capacity uptake (MAC) as assessed by 6 min walk distance (6MWD) using Cahalins equation from baseline, at the end of 7 day treatment, follow-up after 30 days and 90 days. EF was assessed by 2D Echo at baseline and after 30 days of follow-up.

RESULTS

Fifty-two CHF patients with 10-30% EF (mean [SD] age: 58.8 [10.8], 85% men) were enrolled in the study. There was a 100% compliance to study therapy. A significant improvement was observed in MAC levels (7.11%, p = 0.029), at the end of 7 day therapy as compared to baseline. This improvement was maintained at two follow-up visits. Moreover ejection fraction was observed to be increased by 6.38%, p = 0.012 as compared to baseline at day 7 of the therapy.

CONCLUSION

This 90 day follow up study highlights the benefit of HFRT, as a part of maintenance treatment for CHF patients with reduced ejection fraction.

Variations in subclinical left ventricular dysfunction, functional capacity, and clinical outcomes in different heart failure aetiologies

Aims

Patients with heart failure (HF) risk factors are described as being in Stage A of this condition (SAHF). Management is directed towards prevention of HF progression, but to date, no evidence has been described to align the intensity of this intervention to HF risk. We sought to what extent SAHF of Type 2 diabetes mellitus (T2DM) and other HF risks showed differences in subclinical left ventricular function, exercise capacity, and prognosis.

Methods and results

We recruited 551 elder asymptomatic SAHF patients (age 71 ± 5 years, 49% men, 290 T2DM) with at least one risk factor from a community‐based population with preserved ejection fraction. All underwent a comprehensive echocardiogram including global longitudinal strain (GLS) and a 6 min walk test and were followed for 2 years. The primary endpoints were new‐onset HF and all‐cause mortality. The T2DM group was associated with reduced 6 min walk test distance (451 ± 111 vs. 493 ± 87 m, P < 0.001), worse diastolic function (E/e′ 9.2 ± 2.7 vs. 8.7 ± 2.4, P = 0.028), and impaired GLS (−17.7 ± 2.6% vs. −19.0 ± 2.6%, P < 0.001). Over a median follow‐up of 1.6 years, 49 T2DM‐SAHF and 27 other‐SAHF met the primary endpoint. T2DM‐SAHF had significantly worse outcome than other‐SAHF (P = 0.021). In Cox models, obesity [hazard ratio (HR) = 2.46; P = 0.007], atrial fibrillation (HR = 2.39; P = 0.028), 6 min walk distance (HR = 0.99; P = 0.034), and GLS (HR = 1.14; P = 0.033) were independently associated with the primary endpoint in T2DM‐SAHF, independent of age and glycaemic control.

Conclusions

The T2DM‐SAHF has worse subclinical left ventricular function, exercise capacity, and prognosis than other‐SAHF. Impaired GLS, atrial fibrillation, exercise capacity, and obesity are associated with a worse prognosis in T2DM‐SAHF but not in other‐SAHF.

Correlation of 6-min walk test with left ventricular function and quality of life in heart failure due to Chagas disease

OBJECTIVES

To evaluate the correlation of the total distance walked during the six-minute walk test (6MWT) with left ventricular function and quality of life in patients with Chagas Disease (ChD) complicated by heart failure.

METHODS

This is a cross-sectional study of adult patients with ChD and heart failure diagnosed based on Framingham criteria. 6MWT was performed following international guidelines. New York Heart Association functional class, brain natriuretic peptide (BNP) serum levels, echocardiographic parameters and quality of life (SF-36 and MLHFQ questionnaires) were determined and their correlation with the distance covered at the 6MWT was tested.

RESULTS

Forty adult patients (19 male; 60 ± 12 years old) with ChD and heart failure were included in this study. The mean left ventricular ejection fraction was 35 ± 12%. Only two patients (5%) ceased walking before 6 min had elapsed. There were no cardiac events during the test. The average distance covered was 337 ± 105 metres. The distance covered presented a negative correlation with BNP (r = -0.37; P = 0.02), MLHFQ quality-of-life score (r = -0.54; P = 0.002), pulmonary artery systolic pressure (r = -0.42; P = 0.02) and the degree of diastolic dysfunction (r = -0.36; P = 0.03) and mitral regurgitation (r = -0.53; P = 0.0006) and positive correlation with several domains of the SF-36 questionnaire.

CONCLUSIONS

The distance walked during the 6MWT correlates with BNP, quality of life and parameters of left ventricular diastolic function in ChD patients with heart failure. We propose this test to be adopted in endemic areas with limited resources to aid in the identification of patients who need referral for tertiary centres for further evaluation and treatment.

Comparison of Supervised Hospital-based versus Educated Home-based Exercise Training in Korean Heart Failure Patients

Background and Objectives

Although many clinical trials have shown that exercise training (ET) improves functional capacity and clinical outcomes in heart failure (HF) patients, data comparing supervised hospital-based and educated home-based ET in HF patients is lacking.

Subjects and Methods

This was a single-center, non-randomized, prospective study of 82 HF patients with reduced ejection fraction (≤40%) who completed ET. The hospital-based group (n=30) underwent supervised ET at 60% of peak oxygen consumption (VO₂), while a physiotherapist-educated group (n=52) exercised at home without monitoring. The 2 groups were compared before and after the 3-month ET program with respect to functional capacity, quality of life (QOL), and cardiac events (all-cause mortality or hospitalization with worsening HF).

Results

After ET, peak VO₂ increased in the hospital-based group (19.4±4.4 to 21.4±4.3 mL/min/kg, p=0.006) and remained unchanged in the home-based group (18.9±4.6 to 18.4±4.6 mL/min/kg, p=0.660). The change in peak VO₂ after ET was greater in the hospital-based group compared to the home-based group by 2.5 mL/min/kg (p=0.014). QOL improved in the hospital-based group (43.1±18.0 to 28.1±21.6, p=0.003). During one year of follow-up, a comparison of the 2 groups did not reveal a statistical difference in cardiac events (hazard ratio, 0.66; 95% confidence interval, 0.2–2.8; p=0.570).

Conclusion

Hospital-based ET was beneficial for HF patients, improving functional capacity and QOL. However, no significant advantages were observed in terms of a composite endpoint compared to home-based ET. Further investigations are required to address the effects and roles of the 2 ET programs for HF patients.

Reliability and Validity of a Twelve-Minute Walking Test for Coronary Heart Disease Patients

This study examined the reliability and validity of a 12-min. walking test for coronary heart disease patients. CHD patients (28 men, 18 women) were recruited out of 86 CHD patients of the Martini Hospital Groningen, The Netherlands. 46 CHD patients (age M = 66.0 yr., SD = 6.8) participated in the reliability study and 24 (age M = 62.0 yr., SD = 9.2) in the validity study. A test-retest analysis showed a satisfactory Bland-Altman plot and an intraclass coefficient of .98. The Pearson correlation between the score on the test and the VO2 peak was .77. This test gives a reliable and valid assessment of cardiorespiratory fitness of CHD patients.

Effect of Tinospora cordifolia on physical and cardiovascular performance induced by physical stress in healthy human volunteers

INTRODUCTION

In Ayurveda Tinospora cordifolia (Willd.) Miers., has been used for its Rasayana, Deepana, Jwaranashana, Tridosha Shamaka properties. It is an immunomodulator, useful in stress, hyperlipidemia, pyrexia. T. cordifolia was evaluated for adaptogenic activity in healthy volunteers during exercise.

AIMS

The primary objective of this study was to evaluate the effect of T. cordifolia on physical performance, and secondary objectives were to evaluate muscle power, maximal oxygen consumption, and sympathetic activity in comparison with placebo when subjected to physical stress.

MATERIALS AND METHODS

A total of thirty participants were randomly assigned into three groups (n = 10 each) namely placebo, TC 150 and TC 300. Placebo group received maize starch capsule, TC 150 and TC 300 received 150 mg and 300 mg, respectively of T. cordifolia aqueous extract in capsule form once daily in the morning for 28 days. The assessment was performed at baseline visit, day 14 and 28. Physical stressors were cycle ergometer exercise, Jammer's hand-held dynamometer, and cold pressor tests. Physical performance evaluated was maximum distance and speed, oxygen consumption (VO2 max), and hand grip strength. Cardiovascular response was assessed by multiple heart rate (HR) and blood pressure (BP) measurements during each test.

RESULTS

On day 28, TC 150 mg group showed a significant increase in mean maximum speed compared to placebo. On day 14 and 28, TC 300 mg group showed a significant decrease in mean systolic BP (SBP) and HR on fixed workload exercise compared to placebo. There was significant increasing dose effect of both TC groups on SBP on day 14 and 28 and on HR on day 28 only. On day 14 and 28, TC 300 mg showed a significant decrease in mean HR on the cold pressor test, compared to placebo.

CONCLUSION

T. cordifolia improved physical performance and suppressed over activation of the sympathetic nervous system showing its adaptogenic property.

Effects of a Structured Exercise Program on Physical Activity and Fitness in Colon Cancer Survivors: One Year Feasibility Results from the CHALLENGE Trial

BACKGROUND

There is strong interest in testing lifestyle interventions to improve cancer outcomes; however, the optimal methods for achieving behavior change in large-scale pragmatic trials are unknown. Here, we report the 1-year feasibility results for exercise behavior change in the Canadian Cancer Trials Group CO.21 (CHALLENGE) Trial.

METHODS

Between 2009 and 2014, 273 high-risk stage II and III colon cancer survivors from 42 centers in Canada and Australia were randomized to a structured exercise program (SEP; n = 136) or health education materials (HEM; n = 137). The primary feasibility outcome in a prespecified interim analysis was a difference between randomized groups of ≥5 metabolic equivalent task (MET)-hours/week in self-reported recreational physical activity (PA) after at least 250 participants reached the 1-year follow-up. Secondary outcomes included health-related fitness.

RESULTS

The SEP group reported an increase in recreational PA of 15.6 MET-hours/week compared with 5.1 MET-hours/week in the HEM group [mean difference = +10.5; 95% confidence interval (CI) = +3.1-+17.9; P = 0.002]. The SEP group also improved relative to the HEM group in predicted VO2max (P = 0.068), 6-minute walk (P < 0.001), 30-second chair stand (P < 0.001), 8-foot up-and-go (P = 0.004), and sit-and-reach (P = 0.08).

CONCLUSIONS

The behavior change intervention in the CHALLENGE Trial produced a substantial increase in self-reported recreational PA that met the feasibility criterion for trial continuation, resulted in objective fitness improvements, and is consistent with the amount of PA associated with improved colon cancer outcomes in observational studies.

IMPACT

The CHALLENGE Trial is poised to determine the causal effects of PA on colon cancer outcomes. Cancer Epidemiol Biomarkers Prev; 25(6); 969-77. ©2016 AACR.

The long-term prognostic significance of 6-minute walk test distance in patients with chronic heart failure

Background. The 6-minute walk test (6-MWT) is used to assess patients with chronic heart failure (CHF). The prognostic significance of the 6-MWT distance during long-term followup (>5 years) is unclear. Methods. 1,667 patients (median [inter-quartile range, IQR]) (age 72 [65–77]; 75% males) with heart failure due to left ventricular systolic impairment undertook a 6-MWT as part of their baseline assessment and were followed up for 5 years. Results. At 5 years' followup, those patients who died (n = 959) were older at baseline and had a higher log NT pro-BNP than those who survived to 5 years (n = 708). 6-MWT distance was lower in those who died [163 (153) m versus 269 (160) m; P < 0.0001]. Median 6-MWT distance was 300 (150–376) m, and quartile ranges were <46 m, 46–240 m, 241–360 m, and >360 m. 6-MWT distance was a predictor of all-cause mortality (HR 0.97; 95% CI 0.96-0.97; Chi-square = 184.1; P < 0.0001). Independent predictors of all-cause mortality were decreasing 6-MWT distance, increasing age, increasing NYHA classification, increasing log NT pro-BNP, decreasing diastolic blood pressure, decreasing sodium, and increasing urea. Conclusion. The 6-MWT is an important independent predictor of all-cause mortality following long-term followup in patients with CHF.

Walking tests during the exercise training: specific use for the cardiac rehabilitation

Walk tests, principally the six-minute walk test (6mWT), constitute a safe, useful submaximal tool for exercise tolerance testing in cardiac rehabilitation (CR). The 6mWT result reflects functional status, walking autonomy and efficacy of CR on walking endurance, which is more pronounced in patients with low functional capacity (heart failure - cardiac surgery). The 6mWT result is a strong predictor of mortality. However, clinically significant changes and reliability are still subject to debate - probably because of the ambiguity in terms of the target speed (either comfortable or brisk walking). Of the other time-based walk tests, the 2-minute-walk test is the only one applicable during CR, reserved for patients with severe disabilities by its psychometric properties. Fixed-distance tests (principally the 200m fast walk test) and incremental shuttle walking, tests explore higher levels of effort and may represent a safe and inexpensive alternative to laboratory-based tests during CR. These walking tests may be useful for personalizing prescription of training programs. However, the minimum clinically significant difference has not yet been determined. Lastly, walking tests appear to be potential useful tools in promoting physical activity and behavioural changes at home. Thus, validation of other walk tests with better psychometric properties will be necessary.

Clinically meaningful change estimates for the six-minute walk test and daily activity in individuals with chronic heart failure

PURPOSE

The purpose of the present pilot study was to provide a preliminary estimate of the minimum detectable difference (MDD) and minimum clinically important difference (MCID) of the six-minute walk test (6MWT) and daily activity in outpatients with chronic heart failure (CHF).

METHODS

A convenience sample of 22 adults with stable New York Heart Association Functional Class II and III CHF performed two baseline 6MWTs separated by 30 minutes of rest. Subjects then wore a triaxial accelerometer for 7 days to monitor daily activity. After 7 weeks of usual care, subjects again wore the accelerometer for 7 days and then returned to the clinic to complete the Global Rating of Change Scale (GRS) with regard to their heart disease and perform another set of 6MWTs. For the 6MWT, the MDD was calculated using the two baseline 6MWT distances. For daily activity, the MDD was calculated using two methods: (1) day-to-day test-retest reliability during baseline monitoring, and (2) baseline to follow-up test-retest reliability in those who reported no change on the GRS. The MCID for the 6MWT and daily activity was calculated using the mean and 95% confidence interval (CI95%) for those subjects who reported 'improvement' on the GRS.

RESULTS

The MDD at the CI95% for the 6MWT was 32.4 meters. The MCID for the 6MWT was 30.1 (CI95% 20.8, 39.4) meters. The MDD for daily activity was 5,909 vector magnitude units (VMU·hr.(-1)) The MCID for daily activity was 1,337 VMU·hr.(-1) There was good alignment of the MDD and MCID for the 6MWT, suggesting that clinically meaningful change is approximately 32 meters. However, the calculated MCID was substantially less than measurement error as represented by the MDD, indicating that the MCID was underestimated in this sample or that daily activity may be robust to change in overall disease status.

Association of the veterans aging cohort study index with exercise capacity in HIV-infected adults

Physical disability is a major priority in aging, affecting morbidity, mortality, and quality of life. Despite the large number of adults aging with HIV, our understanding of the physiologic and clinical risk factors for disability is limited. Our goal is to determine whether the Veterans Aging Cohort Study (VACS) Index, based on routine clinical blood tests, could serve as a point of care screening tool to identify HIV-infected adults at high risk for physical disability. HIV-infected adults enrolled in the VACS participated in a cross-sectional exercise study with established measures of strength and endurance. The VACS Index was calculated using recent clinical laboratory values and age; a higher score reflects greater mortality risk. Statistical analyses included correlation and linear regression models adjusted for muscle mass. Fifty-five HIV-infected adults, predominantly African-American men, were included with age mean±SD of 52±7 years. Median (IQR) CD4 cell count was 356 cells/mm(3) (212-527). The VACS Index was inversely correlated with quadriceps strength (r=-0.45, p<0.01), grip strength (r=-0.28, p=0.04), and 6-min walk distance (r=-0.27, p=0.05). A 20-point increase in VACS Index score was associated with a 10% lower leg strength (p<0.01), which remained significant after adjustment for muscle cross-sectional area (p=0.02). The VACS Index explained 31% of the variance in specific leg strength. In this group of middle-aged adults with well-controlled HIV infection the VACS Index was significantly associated with upper and lower extremity strength. The VACS Index may be valuable for identification of patients at high risk for disability due to muscle weakness.

Poorer physical fitness is associated with reduced structural brain integrity in heart failure

OBJECTIVE

Physical fitness is an important correlate of structural and functional integrity of the brain in healthy adults. In heart failure (HF) patients, poor physical fitness may contribute to cognitive dysfunction and we examined the unique contribution of physical fitness to brain structural integrity among patients with HF.

METHODS

Sixty-nine HF patients performed the Modified Mini Mental State examination (3MS) and underwent brain magnetic resonance imaging. All participants completed the 2-minute step test (2MST), a brief measure of physical fitness. We examined the associations between cognitive performance, physical fitness, and three indices of global brain integrity: total cortical gray matter volume, total white matter volume, and whole brain cortical thickness.

RESULTS

Regression analyses adjusting for demographic characteristics, medical variables (e.g., left ventricular ejection fraction), and intracranial volume revealed reduced performance on the 2MST were associated with decreased gray matter volume and thinner cortex (p<.05). Follow up analyses showed that reduced gray matter volume and decreased cortical thickness were associated with poorer 3MS scores (p<.05).

CONCLUSIONS

Poor physical fitness is common in HF and associated with reduced structural brain integrity. Prospective studies are needed to elucidate underlying mechanisms for the influence of physical fitness on brain health in HF.

6-min walk test provides prognostic utility comparable to cardiopulmonary exercise testing in ambulatory outpatients with systolic heart failure

OBJECTIVES

The goal of this study was to compare the prognostic efficacy of the 6-min walk (6MW) and cardiopulmonary exercise (CPX) tests in stable outpatients with chronic heart failure (HF).

BACKGROUND

CPX and 6MW tests are commonly applied as prognostic gauges for systolic HF patients, but few direct comparisons have been conducted.

METHODS

Stable New York Heart Association (NYHA) functional class II and III systolic HF patients (ejection fraction ≤ 35%) from the HF-ACTION (Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training) trial were studied. 6MW distance (6MWD) and CPX indices (peak oxygen consumption [VO(2)] and ventilatory equivalents for exhaled carbon dioxide [VE/VCO(2)] slope) were compared as predictors of all-cause mortality/hospitalization and all-cause mortality over 2.5 years of mean follow-up.

RESULTS

A total of 2,054 HF-ACTION participants underwent both CPX and 6MW tests at baseline (median age 59 years; 71% male; 64% NYHA functional class II and 36% NYHA functional class III/IV). In unadjusted models and in models that included key clinical and demographic covariates, C-indices of 6MWD were 0.58 and 0.65 (unadjusted) and 0.62 and 0.72 (adjusted) in predicting all-cause mortality/hospitalization and all-cause mortality, respectively. C-indices for peak VO(2) were 0.61 and 0.68 (unadjusted) and 0.63 and 0.73 (adjusted). C-indices for VE/VCO(2) slope were 0.56 and 0.65 (unadjusted) and 0.61 and 0.71 (adjusted); combining peak VO(2) and VE/VCO(2) slope did not improve the C-indices. Overlapping 95% confidence intervals and modest integrated discrimination improvement values confirmed similar prognostic discrimination by 6MWD and CPX indices within adjusted models.

CONCLUSIONS

In systolic HF outpatients, 6MWD and CPX indices demonstrated similar utility as univariate predictors for all-cause hospitalization/mortality and all-cause mortality. However, 6MWD or CPX indices added only modest prognostic discrimination to models that included important demographic and clinical covariates.

Responsiveness and validity of the six-minute walk test in individuals with traumatic brain injury

BACKGROUND

A simple test of aerobic fitness for patients with traumatic brain injury (TBI) that is valid, reliable, and responsive to change is needed to provide clinicians a functional measure of cardiorespiratory capacity.

OBJECTIVE

The purpose of this study was to examine the validity and responsiveness to change of the Six-Minute Walk Test (6MWT) in individuals with TBI.

DESIGN

A cohort, pretest-posttest, comparison study was conducted.

METHODS

Twenty-one patients performed the 6MWT upon admission to and prior to discharge from a postacute rehabilitation facility. Heart rate and distance traveled were recorded. A physiologic cost index (PCI) (beats per meter) was calculated based on steady-state heart rate. At discharge, all participants were able to perform a graded treadmill exercise test to exhaustion during which peak oxygen consumption (Vo(2)) was measured.

RESULTS

Between admission and discharge, mean total distance increased from 342.6 m (SD=127.0) to 408.9 m (SD=124.2), and work increased from 27,185 kg·m (SD=10,528) to 34,114 kg·m (SD=12,057). The effect size indexes were 1.10 and 1.12 for distance and work, respectively. Correlations (r) between the discharge peak Vo(2) and the discharge 6MWT distance, PCI, and work were .58, -.61, and .47, respectively.

LIMITATIONS

Stratification by gait speed may have improved responsiveness, especially for the slow ambulators.

CONCLUSIONS

All measures correlated well with peak Vo(2), establishing an acceptable level of criterion-related (concurrent) validity. The addition of heart rate and calculating the PCI was only slightly better at predicting peak Vo(2), albeit nonsignificant, than a simple measure of total distance. The 6MWT provides a good estimate of peak aerobic capacity, and some measures are more responsive to change than others in patients recovering from TBI.

Baseline functional capacity and the benefit of cardiac resynchronization therapy in patients with mildly symptomatic heart failure enrolled in MADIT-CRT

BACKGROUND

Mildly symptomatic heart failure (HF) patients were shown to derive substantial clinical benefit from cardiac resynchronization therapy with defibrillator (CRT-D) in Multicenter Automatic Defibrillator Implantation Trial in Cardiac Resynchronization Therapy. However, the relationship between functional capacity (FC) and CRT-D benefit in the trial was not assessed.

OBJECTIVE

To evaluate the association between FC and response to CRT-D in Multicenter Automatic Defibrillator Implantation Trial in Cardiac Resynchronization Therapy.

METHODS

We evaluated the association between preimplantation FC and the benefit of CRT-D in reducing the risk of HF or death in Multicenter Automatic Defibrillator Implantation Trial in Cardiac Resynchronization Therapy. Functional status was assessed by a 6-minute walk test (6MWT), dichotomized at the median value as poor (<350 m) or good (≥350 m).

RESULTS

Implantable cardioverter-defibrillator-only patients with a poor FC had an adjusted 73% increased risk for HF or death (P <.001) and a 2.4-fold (P = .001) increased risk for all-cause mortality. CRT-D therapy was associated with 63% (P <.001) and 44% (P <.001) reductions in the risk of HF or death among left bundle branch block patients with a poor FC and a good FC, respectively (P for interaction = .10). Among left bundle branch block patients with a poor FC, CRT-D was also associated with a significant reduction in the risk of all-cause mortality (hazard ratio 0.52; P = .015) whereas the survival benefit of CRT-D was not observed among those who had a higher FC at enrollment (hazard ratio 1.01; P = .98; P for interaction = .10).

CONCLUSIONS

Poor FC is a strong independent predictor for mortality and HF events in patients with mildly symptomatic HF. Left bundle branch block patients with poor baseline FC derive a pronounced benefit from CRT-D, manifest by a significant reduction in mortality.

Muscle function, physical performance and body composition changes in men with prostate cancer undergoing androgen deprivation therapy

Prostate cancer (PCa) is the most common visceral malignancy in men with androgen deprivation therapy (ADT) the preferred therapy to suppress testosterone production and hence tumor growth. Despite its effectiveness in lowering testosterone, ADT is associated with side effects including loss of muscle mass, diminished muscle strength, decrements in physical performance, earlier fatigue and declining quality of life. This review reports a survey of the literature with a focus on changes in muscle strength, physical function and body composition, due to short-term and long-term ADT. Studies in these areas are sparse, especially well-controlled, prospective randomized trials. Cross-sectional and longitudinal data (up to 2 years) for men with PCa treated with ADT as well as patients with PCa not receiving ADT and age-matched healthy men are presented when available. Based on limited longitudinal data, the adverse effects of ADT on muscle function, physical performance and body composition occur shortly after the onset of ADT and tend to persist and worsen over time. Exercise training is a safe and effective intervention for mitigating these changes and initial guidelines for exercise program design for men with PCa have been published by the American College of Sports Medicine. Disparities in study duration, types of studies and other patient-specific variables such as time since diagnosis, cancer stage and comorbidities may all affect an understanding of the influence of ADT on health, physical performance and mortality.

The 6-min walk test: is it an effective method for evaluating heart failure therapies?

The 6-min walk (6MW) is a self-paced test for measuring functional capacity. Lower 6MW distances have been associated with adverse outcomes in patients with heart failure. The purpose of this article is to describe the history of the 6MW test and to evaluate its reliability, validity, and predictive value as well as the responsiveness of the test to therapies. In the literature we reviewed, reliability was affected by several factors including learning effects and protocol deviations. The 6MW distance was moderately correlated with peak oxygen consumption derived from cardiopulmonary exercise stress testing. In some studies the 6MW distance was predictive of hospitalization and mortality. In pharmacological and cardiac resynchronization trials the 6MW distance did not consistently detect clinical improvements. Despite limitations, the 6MW test is a viable alternative to stress testing for objectively evaluating functional capacity in some settings. We provide recommendations for using the 6MW test in future studies.

The six minute walk test accurately estimates mean peak oxygen uptake

Background

Both Peak Oxygen Uptake (peak VO2), from cardiopulmonary exercise testing (CPET) and the distance walked during a Six-Minute Walk Test (6 MWD) are used for following the natural history of various diseases, timing of procedures such as transplantation and for assessing the response to therapeutic interventions. However, their relationship has not been clearly defined.

Methods

We determined the ability of 6 MWD to predict peak VO2 using data points from 1,083 patients with diverse cardiopulmonary disorders. The patient data came from a study we performed and 10 separate studies where we were able to electronically convert published scattergrams to bivariate points. Using Linear Mixed Model analysis (LMM), we determined what effect factors such as disease entity and different inter-site testing protocols contributed to the magnitude of the standard error of estimate (SEE).

Results

The LMM analysis found that only 0.16 ml/kg/min or about 4% of the SEE was due to all of the inter-site testing differences. The major source of error is the inherent variability related to the two tests. Therefore, we were able to create a generalized equation that can be used to predict peak VO2 among patients with different diseases, who have undergone various exercise protocols, with minimal loss of accuracy. Although 6 MWD and peak VO2 are significantly correlated, the SEE is unacceptably large for clinical usefulness in an individual patient. For the data as a whole it is 3.82 ml/kg/min or 26.7% of mean peak VO2. Conversely, the SEE for predicting the mean peak VO2 from mean 6 MWD for the 11 study groups is only 1.1 ml/kg/min.

Conclusions

A generalized equation can be used to predict peak VO2 from 6 MWD. Unfortunately, like other prediction equations, it is of limited usefulness for individual patients. However, the generalized equation can be used to accurately estimate mean peak VO2 from mean 6 MWD, among groups of patients with diverse diseases without the need for cardiopulmonary exercise testing. The equation is:

The six-minute walk test: a useful metric for the cardiopulmonary patient

Measurement of exercise capacity is an integral element in assessment of patients with cardiopulmonary disease. The 6-min walk test (6MWT) provides information regarding functional capacity, response to therapy and prognosis across a range of chronic cardiopulmonary conditions. A distance less than 350 m is associated with increased mortality in chronic obstructive pulmonary disease, chronic heart failure and pulmonary arterial hypertension. Desaturation during a 6MWT is an important prognostic indicator for patients with interstitial lung disease. The 6MWT is sensitive to commonly used therapies in chronic obstructive pulmonary disease such as pulmonary rehabilitation, oxygen, long-term use of inhaled corticosteroids and lung volume reduction surgery. However, it appears less reliable to detect changes in clinical status associated with medical therapies for heart failure. A change in walking distance of more than 50 m is clinically significant in most disease states. When interpreting the results of a 6MWT, consideration should be given to choice of predictive values and the methods by which the test was carried out.

Assessment of exercise capacity in African patients with chronic heart failure using six minutes walk test

BACKGROUND

The purpose of this study was to assess the functional capacity during a 6-minute corridor walk and a 6-minute bicycle ergometry exercise in patients with chronic heart failure (CHF).

METHOD

Thirty five patients with stable CHF were recruited for the study. Each subject performed six minutes corridor walk and 6-minute bicycle ergometry testing. The 6-minute walk required the subjects to walk at a self selected speed on a 20 meter marked level ground for 6-minute. All the subjects also performed a 6-minute exercise on a stationary bicycle ergometer with initial resistance of 20 watts and increased by 10 watts after 3-minutes. The perceived rate of exertion was assessed using a modified Borg Scale after each exercise mode. The maximum oxygen consumption was derived using American College of Sport Medicine equations.

RESULTS

Result showed high positive correlation between distance walked in the 6-minute and the maximum volume of oxygen (VO(2) max) (r = 0.65, P < 0.01). The average distance walked was 327 m +/- 12.03 m. The VO(2) max estimated during bicycle ergometry was higher (13.7 +/- 1.9 L) than during the six minutes walk (8.9 +/- 1.2 L).

CONCLUSION

Six minutes walk could be useful to evaluate exercise tolerance in patients with chronic heart failure, while the bicycle ergometer could be more appropriate in the assessment of maximum functional capacity in these patients.

Lower extremity performance measures predict long-term prognosis in older patients hospitalized for heart failure

BACKGROUND

In older heart failure (HF) patients, survival depends on the severity of their cardiac condition and on their functional status. Lower extremity performance, assessed with the Short Physical Performance Battery (SPPB), predicts survival in older persons, both in epidemiologic and clinical settings. We evaluated whether SPPB predicts long-term survival in older subjects hospitalized for HF, independent of traditional measures of HF severity.

METHODS AND RESULTS

Subjects aged 65+ years were enrolled on discharge after hospitalization for decompensated HF. Participants underwent echocardiography, comprehensive geriatric assessment, and SPPB. Cox proportional hazards regression models were used to predict survival over a 30-month follow-up. Of 157 participants (mean age 80 years, range 65-101; 50% men), 61 died. After adjustment for potential confounders, including demographics, ejection fraction, New York Heart Association classification, and comorbidity, we found a graded independent association between SBBP score and mortality risk: compared with an SPPB score of 9-12, scores of 0, 1-4, and 5-8 were associated with hazard ratios (HR) and 95% confidence interval (CI) of death of 6.06 (2.19-16.76), 4.78 (1.63-14.02), and 1.95 (0.67-5.70), respectively.

CONCLUSIONS

SPPB is an independent predictor of long-term survival of older subjects hospitalized for decompensated HF.

Six-Minute Walk Test and Cardiopulmonary Exercise Testing in Patients With Chronic Heart Failure

Background— The six-minute walk test (6MWT) and cardiopulmonary exercise testing (CPET) are the 2 testing modalities most broadly used for assessing functional limitation in patients with heart failure (HF). A comprehensive comparison on clinical and prognostic validity of the 2 techniques has not been performed and is the aim of the present investigation.

Methods and Results— Two hundred fifty-three patients diagnosed with systolic (n=211) or diastolic (n=42) HF (age: 61.9�10.1 years; New York Heart Association Class: 2.2�0.78) underwent a 6MWT and a symptom-limited CPET evaluation and were prospectively followed up. During the 4-year tracking period, there were 43 cardiac-related deaths with an annual cardiac mortality rate of 8.7%. The 6MWT distance correlated with CPET-derived variables (ie, peak V o 2 , V o 2 at anaerobic threshold, and V e /V co 2 slope) and was significantly reduced in proportion with lower peak V o 2 and higher V e /V co 2 slope classes and presence of an exercise oscillatory breathing (EOB) pattern ( P <0.01). However, no significant differences were observed in distance covered between survivors and nonsurvivors (353.2�95.8 m versus 338.5�76.4 m; P =NS). At univariate and multivariate Cox proportional analyses, the association of the 6MWT distance with survival was not significant either as a continuous or dicotomized variable (≤300 m). Conversely, CPET-derived variables emerged as prognostic with the strongest association found for EOB (systolic HF) and V e /V co 2 slope (entire population with HF and patients with a 6MWT≤300 m).

Conclusions— The 6MWT is confirmed to be a simple and reliable first-line test for quantification of exercise intolerance in patients with HF. However, there is no supportive evidence for its use as a prognostic marker in alternative to or in conjunction with CPET-derived variables.

Accelerometer-based quantification of 6-minute walk test performance in patients with chronic heart failure: applicability in telemedicine

BACKGROUND

Distance walked in the 6-minute walk test (6MWT) is an important prognostic parameter used clinically to assess functional status in patients with chronic heart failure (CHF). In this study, we investigated if alternative performance parameters with similar prognostic value can be gained from accelerometers.

METHODS AND RESULTS

Fifty CHF patients (age, 60.9 +/- 14.0 years) were asked to perform a 6MWT while wearing 2 accelerometers and 1 pedometer. Total 6MWT step frequency (SF) and activity counts (VMU) were correlated to 6MWT distance. The accelerometer was highly accurate at quantifying SF (detected vs. observed: r = 0.99; P < .001), whereas the pedometer was unreliable below 50 m/min. VMU increased linearly with walking speed (r = 0.99), and both SF and VMU correlated strongly with 6MWT distance (VMU: r = 0.91; SF: r = 0.87, respectively; P < .001) and each other (r = 0.80, P < .001).

CONCLUSIONS

Accelerometers are reliable in measuring physical performance during the 6MWT in CHF patients. Besides the simple acquisition of 6MWT distance currently used for patient assessment, accelerometers provide new data that might be useful to evaluate exercise performance during the 6MWT. This allows for routine assessment of exercise capacity in a home-based setting in the context of telemedicine.