Percent predicted value for the 6-minute walk test: using norm-referenced equations to characterize severity in persons with CHF

Accuracy of the 6-Minute Walk Test for Assessing Functional Capacity in Patients With Heart Failure With Preserved Ejection Fraction and Other Chronic Cardiac Pathologies: Results of the ExIC-FEp Trial and a Meta-Analysis

BACKGROUND

Heart diseases, particularly heart failure, significantly impact patient quality of life and mortality rates. Functional capacity assessment is vital for predicting prognosis and risk in these patients. While the cardiopulmonary exercise test is considered the gold standard, the 6-minute walk test has emerged as a more accessible alternative. However, the screening accuracy and optimal cut-off points of the 6-minute walk test for detecting severely reduced functional capacity in cardiac pathologies, including heart failure with preserved ejection fraction, are unclear. The study aimed to analyse the diagnostic accuracy of the 6-minute walk test for detecting reduced functional capacity, defined as VO2max < 14 ml/kg/min, compared with the cardiopulmonary exercise test in participants with heart failure with preserved ejection fraction using data from the "Ejercicio en Insuficiencia Cardiaca con Fracción de Eyección Preservada" (ExIC-FEp) trial; and to compare these results with previous studies investigating the screening accuracy for assessing functional capacity of the 6-minute walk test in participants with other chronic cardiac pathologies through a meta-analysis.

RESULTS

The ExIC-FEp trial involved 22 participants with heart failure with preserved ejection fraction, who were not treated with beta-blockers, using the cardiopulmonary exercise test, specifically VO2max, as the reference test. The 6-minute walk test had a sensitivity of 70%, a specificity of 80%, and an area under the curve of 76% in the ExIC-FEp trial. Five studies were included in the meta-analysis showing a sensitivity of 79%, a specificity of 78%, and an area under the curve of 85%.

CONCLUSION

In conclusion, the 6-minute walk test holds promise as a screening tool for assessing functional capacity in heart failure with preserved ejection fraction and chronic heart diseases, with a VO2max < 14 ml/kg/min as a reference point. It demonstrates moderate to good screening accuracy. However, the screening accuracy and optimal cut-off points of the 6-minute walk test for detecting severely reduced functional capacity, regardless of aetiology, are unclear.

TRIAL REGISTRATION

NCT05726474. Registered 16 February 2023, https://clinicaltrials.gov/study/NCT05726474 .

Usefulness of oxygen uptake efficiency slope in a 6 min walk test in chronic heart failure

AIMS

Frailty is an obstacle to performing cardiopulmonary exercise test (CPET) in patients with chronic heart failure (CHF). We evaluated the usefulness of oxygen uptake efficiency slope (OUES) using a 6 min walk test (6MWT) with portable gas analysis compared with CPET-derived parameters in patients with CHF.

METHODS AND RESULTS

Patients with CHF who underwent both the 6MWT with portable gas analysis and CPET between December 2016 and May 2020 were retrospectively investigated. The 6MWT-derived and echocardiographic parameters were compared with the OUES and peak oxygen consumption (VO2) from the CPET. Forty patients were analysed; 50% were male with a mean age of 55.45 ± 14.70 years. Twenty-six patients (65%) had New York Heart Association Functional Classification II or III dyspnoea. Twenty-five patients (62.5%) had heart failure (HF) with preserved ejection fraction (EF) (left ventricular EF > 50%), and nine patients (22.5%) had HF with reduced EF (EF < 40%). During the 6MWT, the peak VO2 was 14.97 ± 3.80 mL/kg/min, which was only 74% of the peak VO2 in the CPET, 20.18 ± 5.64 mL/kg/min. The OUES in the 6MWT was lower than that in the CPET (1528.87 ± 579.01 in the 6MWT vs. 1638.69 ± 601.31 in the CPET). The 6 min walk distance (6MWD) and OUES in the 6MWT were positively correlated with the OUES in the CPET (6MWD, r = 0.434, P = 0.005; OUES, r = 0.729, P < 0.001). The OUES in the 6MWT showed the strongest correlation with the OUES in the CPET. When we divided patients into two groups according to peak VO2 in the CPET, the correlation between OUES values of the 6MWT and that of the CPET was consistently confirmed (peak VO2 ≥ 20 mL/kg/min group, r = 0.661, P = 0.001; peak VO2 < 20 mL/kg/min group, r = 0.526, P = 0.021). In addition, the 6MWD, OUES, and peak VO2 in the 6MWT were associated with peak VO2 in the CPET (6MWD, r = 0.627, P < 0.001; OUES, r = 0.452, P = 0.003; and peak VO2, r = 0.492, P = 0.001).

CONCLUSIONS

In frail patients with CHF who have difficulty performing maximal exercises, the OUES through the 6MWT may be applied instead of the OUES and peak VO2 from the CPET.

Physical performance and glycemic control under SGLT-2-inhibitors in patients with type 2 diabetes and established atherosclerotic cardiovascular diseases or high cardiovascular risk (PUSH): Design of a 4-week prospective observational study

Background

Type 2 diabetes (T2D) is associated with limitation in physical performance. Results from animal studies report enhancement of physical performance in T2D rodents treated with sodium glucose cotransporter 2 inhibitors (SGLT2is). However, in human patients with T2D and established atherosclerotic cardiovascular disease (ASCVD) or high cardiovascular risk, the impact of guideline directed SGLT2i medication on physical performance has not been sufficiently examined.

Objectives

The main objectives of this study are thus firstly, to assess the changes in physical performance after 4 weeks of exercise therapy in patients with established ASCVD or high cardiovascular risk categorized into three groups according to their glycemic control at baseline. Secondly, to investigate the association of glycemic control at baseline and new guideline directed antidiabetic treatment (inadequate glycemic control and diabetes + new SGLT2i vs. adequate glycemic control and diabetes vs. no diabetes) with change in physical performance.

Methods and design

This is a 4-week prospective observational study of 450 participants with established ASCVD or high cardiovascular risk with or without T2D and without previous SGLT2i medication undergoing exercise therapy during inpatient rehabilitation in a single center in Switzerland. Upon admission, participants are categorized into 3 groups of 150 participants each according to their glycemic control. Group I consisting of participants with inadequately controlled T2D defined as mean fasting plasma glucose (FPG) of ≥7 mmol/L, who are consequently administered new treatment with an SGLT2i. Group II comprises of participants with adequately controlled T2D with mean FPG of <7 mmol/L requiring no antidiabetic medication change. Group III consists of participants with no diabetes and mean FPG of ≤ 5.5 mmol/L. Primary outcomes are 6-min walk distance and rate of perceived exertion. Secondary outcomes are echocardiographic parameters (left ventricular mass index; global longitudinal strain average; end-diastolic volume), fatigue, muscle, metabolic, and anthropometric measures.

Ethics and dissemination

This study is conducted in accordance with the Declaration of Helsinki with ethical approval from the Cantonal Ethical Commission of Bern, Switzerland. The results will be published in a peer-reviewed journal. The implementation and reporting will be according to the SPIRIT guidelines.

Study protocol registration

https://www.clinicaltrials.gov/, identifier: NCT03422263.

Role of frailty on cardiac rehabilitation in hospitalized older patients

BACKGROUND

Cardiovascular diseases are the leading cause of mortality, morbidity, and disability in the world, especially in the older adults. A relevant proportion of patients admitted to Cardiac Rehabilitation (CR) may suffer from frailty, a complex geriatric syndrome with multifactorial aetiology.

AIMS

The hypothesis underlying the study is that frailty complicates the management of older patients undergoing CR. The main objective is, therefore, to determine the relationship between frailty and CR outcomes in hospitalized older adults.

METHODS

The participants have been recruited among patients aged ≥ 65 years admitted at the hospital for CR. A Comprehensive Geriatric Assessment (CGA)-based Frailty Index (FI) was created following a standard procedure. The outcome was measured as the ratio between 6-min walk test (6MWT) distance at the end of CR and normal predicted values for a healthy adult of same age and gender, according to reference equations.

RESULTS

The study population consisted of 559 elderly patients, 387 males (69.2%), with age of 72 (69-76) years. The most frequent diagnosis at admission was ischaemic heart disease (231, 41.5%) and overall 6MWT ratio was 0.62 ± 0.21. At the multivariable regression analysis, gender, diagnosis and FI were significantly and independently associated with 6MWT ratio (p ≤ 0.0001, p ≤ 0.001 and p ≤ 0.0001, respectively), while no significant association emerged for age.

CONCLUSION

FI resulted independently correlated to 6MWT ratio in a population of older patients undergoing in-hospital CR programs. Frailty is a multifactorial geriatric syndrome whose assessment is essential for prognostic evaluation of older patients, also in CR clinical setting.

Predictors of treatment benefits after enhanced external counterpulsation in patients with refractory angina pectoris

Background

Enhanced external counterpulsation (EECP) is a noninvasive treatment that can decrease limiting symptoms in patients with refractory angina pectoris (RAP). Identifying responders to EECP is important as EECP is not widely available and relatively time intensive.

Hypothesis

The effect of EECP treatment on physical capacity in patients with RAP can be predicted from baseline patient characteristics and clinical factors.

Methods

This explorative study includes all patients from a cardiology clinic who had finished one EECP treatment and a 6 min walk test pre and post EECP. Clinical data, including Canadian Cardiovascular Society (CCS) classification and left ventricular ejection fraction (LVEF), were assessed before treatment. If patients increased their 6 min walking distance (6MWD) by 10% post EECP, they were considered responders.

Results

Of the 119 patients (men = 97, 40–91 years), 49 (41.2%) were responders. Multinomial regression analysis showed that functional status (i.e., CCS class ≥3) (OR 3.10, 95% CI 1.12–8.57), LVEF <50% (OR 2.82, 95% CI 1.02–7.80), and prior performed revascularization (i.e., ≤ 1 type of intervention) (OR 2.77, 95% CI 1.06–7.20) were predictors of response to EECP (p < .05, Accuracy 63.6%). Traditional risk factors (e.g., gender, smoking, and comorbidities) did not predict response.

Conclusions

EECP treatment should be considered preferentially for patients that have a greater functional impairment, evidence of systolic left ventricular dysfunction, and exposure to fewer types of revascularization, either PCI or CABG. Improvement in 6MWD post EECP could imply improvement in physical capacity, which is a likely contributor to improved well‐being among patients with RAP.

Feasibility and safety of high-intensity interval training for the rehabilitation of geriatric inpatients (HIITERGY) a pilot randomized study

BACKGROUND

High-intensity interval training (HIIT) has been shown to be more effective than moderate-intensity continuous training (MICT) for the physical rehabilitation. However, data on its suitability for older hospitalized patients is scarce.

METHODS

Randomized controlled trial in a hospital setting. Inclusion of 100 patients, ≥65 years old, hospitalized for rehabilitation after an acute medical condition, in a two-week rehabilitation program of either four HIIT or three MICT sessions per week. Completion was defined as participation in all but two planned sessions accomplishing ≥50% of each session. We assessed: upper-limb muscle strength (handgrip isometric strength test), lower-limb muscle strength (quadriceps and ankle flexion and extension tests); gait speed and spatio-temporal parameters (instrumented walkway), and exercise capacity (6-min walk test). All adverse events were recorded as safety endpoints.

RESULTS

An intention-to-treat analysis showed a 44% completion rate for the HIIT group (95% CI, 30-59) and 77% for MICT (95% CI, 55-82). A modified intention-to-treat analysis restricted to patients who participated in ≥1 session showed an 88% completion rate in the HIIT group (95%CI, 69-97) and an 80% completion rate in MICT (95%CI, 65-90). The exercises most frequently undertaken were the pedal exerciser (54%) and the NuStep (32%). There were no significant differences in the various measures. No serious adverse events occurred.

CONCLUSION

A HIIT rehabilitation program for this population was feasible, safe and had a high adherence rate.

TRIAL REGISTRATION NUMBER

Clinicatrials.gov ID: NCT02318459. Trial registration date: November 7th, 2014. Retrospectively registered. This study adheres to the CONSORT guidelines.

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.

Reliability and Validity of Self-Report Questionnaires as Indicators of Fatigue in RYR1-Related Disorders

BACKGROUND

RYR1-related disorders (RYR1-RD), are a spectrum of genetic neuromuscular disorders. Affected individuals frequently experience fatigue yet appropriate tools to assess RYR1-RD-associated fatigue remain underdeveloped.

OBJECTIVE

This study assessed the reliability and validity of two self-report questionnaires, the multidimensional fatigue inventory (MFI-20) and adult/pediatric functional assessment of chronic illness-fatigue (FACIT-F/Peds-FACIT-F) as potential fatigue measures in RYR1-RD affected individuals.

METHODS

Participants (n = 37) were enrolled in an RYR1-RD combined natural history study and clinical trial. At baseline, participants completed fatigue questionnaires, six-minute walk test (6MWT), cardiopulmonary exercise test (CPET) and saliva collection for fatigue biomarker index (FBI) quantification.

RESULTS

All questionnaires exhibited good test-retest reliability (n = 18, ICC > 0.80). MFI-20 (n = 37), and FACIT-F (n = 28) also showed good internal consistency (Cronbach's α> 0.80). All MFI-20 subscales, except mental fatigue, and FACIT-F demonstrated evidence of criterion validity when correlated against percent predicted 6MWT distance (MFI-20 n = 37; r = -0.34 to -0.47, all p < 0.05, mental fatigue, r = -0.16, p = 0.35; FACIT-F n = 28, r = 0.41, p = 0.03). This was not the case for percent predicted VO2 peak (all p > 0.05). FBI correlated with MFI-20 general fatigue dimension only (r = -0.35, p = 0.03). Comparison of standardized questionnaire scores revealed that RYR1-RD affected individuals experience significantly greater fatigue than the general population.

CONCLUSIONS

MFI-20 and FACIT-F are valid and reliable tools for assessing RYR1-RD-associated fatigue, a symptom centrally implicated in this rare disorder.

Measuring quality of life in advanced heart failure

PURPOSE OF REVIEW

Patients with Stage D heart failure can benefit from palliative care consultation to help them manage unpleasant symptoms and improve quality of life. Although guidelines describe how to manage symptoms, very little direction is provided on how to evaluate the effectiveness of those interventions.

RECENT FINDINGS

Numerous studies have used the measurement of symptoms, emotional distress, functional capacity and quality of life to evaluate the effectiveness of interventions in heart failure. There is limited evidence on the use of these instruments in heart failure palliative care. Four studies were identified that evaluate the effectiveness of palliative care consultation for patients with advanced heart failure. All four studies measured symptom severity, emotional distress, and quality of life. The application of appropriate instruments is discussed. Suggestions for scores that should trigger palliative care consultation are identified.

SUMMARY

The routine administration of standardized instruments to measure symptom severity and quality of life may improve the assessment and management of patients with Stage D heart failure. Ongoing discussion and research is needed to determine if these instruments are the best tools to use with heart failure palliative care patients.

Early decline in six-minute walk distance from the time of diagnosis predicts clinical worsening in pulmonary arterial hypertension

BACKGROUND

The six-minute walk distance (6MWD) is commonly used to assess pulmonary arterial hypertension (PAH). However, the role of 6MWD in predicting outcomes in PAH is controversial. Clinical worsening is being increasingly considered as a clinically meaningful end point in PAH.

OBJECTIVES

We aimed to investigate whether early longitudinal changes in 6MWD (Δ6MWD) in meters and percent predicted (%pred) from the time of diagnosis predict clinical worsening of PAH.

METHODS

One hundred patients with group I PAH were retrospectively assessed. 6MWD was calculated using American (%pred US) or Canadian (%pred CAN) reference equations. Δ6MWD at 6 months were recorded. Clinical worsening was defined as either: development of right heart failure, hospital admission for PAH, referral for lung transplantation or initiation of prostanoids after oral therapy failed. Optimal 6-month differences in 6MWD to detect worsening were defined with receiver operating characteristics (ROC) analysis.

RESULTS

Progressors, i.e. patients with clinical worsening, and nonprogressors showed significant differences in Δ6MWD. The most clinically significant declines in 6MWD at 6 months were ≥35 m, ≥8%pred US and ≥6%pred CAN. ROC and Cox proportional hazard analyses showed equivalent results for 6MWD %pred and meters. Six-month declines in 6MWD predicted worsening with a high specificity (94%) but a low sensitivity (33%).

CONCLUSIONS

Early declines in 6MWD (within the first 6 months) predict future clinical worsening of PAH with high specificity. Δ6MWD may still be part of a comprehensive assessment of a patient's clinical status. However, given the poor sensitivity, a decline in 6MWD should be used with other clinical tools to make an appropriate assessment of the progression of PAH.

Physiological and perceived health effects from daily changes in air pollution and weather among persons with heart failure: a panel study

We carried out this daily diary panel study in Montreal, Quebec, to determine whether oxygen saturation, pulse rate, blood pressure, self-rated health, and shortness of breath at night were associated with concentrations of indoor carbon monoxide (CO), and indoor and outdoor fine particles (PM2.5), temperature, and relative humidity. Over a 2-month consecutive period between 2008 and 2010, we measured daily indoor and outdoor levels of the air pollutants and weather variables and 55 subjects measured their daily health and other variables. To estimate the associations between the health outcomes and the environmental exposures, we used a mixed effects regression model using an autoregressive model of order-one and we adjusted for month and day and personal variables. The general pattern of associations can be summarized as follows: oxygen saturation was reduced for increases in indoor- and outdoor-PM2.5 and temperature. Pulse rate increased on the concurrent day for increases in indoor CO and PM2.5. Diastolic blood pressure increased with increasing indoor and outdoor PM2.5 and relative humidity. Systolic blood pressure increased with indoor PM2.5 and decreased with increasing indoor and outdoor temperature. Self-rated health diminished with increases in outdoor PM2.5 and indoor and outdoor temperature. Self-reported shortness of breath at night increased with increasing indoor and outdoor temperatures. Health in heart failure is affected in the short term by personal and environmental conditions that are manifest in intermediate physiological parameters.

An Internet-Based Counseling Intervention With Email Reminders that Promotes Self-Care in Adults With Chronic Heart Failure: Randomized Controlled Trial Protocol

Background

Chronic heart failure (CHF) is a public health priority. Its age-standardized prevalence has increased over the past decade. A major challenge for the management of CHF is to promote long-term adherence to self-care behaviors without overtaxing available health care resources. Counseling by multidisciplinary health care teams helps to improve adherence to self-care behaviors and to reduce the rate of death and hospitalization. In the absence of intervention, adherence to self-care is below recommended standards.

Objective

This trial aims to establish and evaluate a Canadian e-platform that will provide a core, standardized protocol of behavioral counseling and education to facilitate long-term adherence to self-care among patients with CHF.

Methods

Canadian e-Platform to Promote Behavioral Self-Management in Chronic Heart Failure (CHF-CePPORT) is a multi-site, double blind, randomized controlled trial with a 2 parallel-group (e-Counseling + Usual Care vs e-Info Control + Usual Care) by 3 assessments (baseline, 4-, and 12-month) design. We will identify subjects with New York Heart Association Class II or III systolic heart failure from collaborating CHF clinics and then recruit them (n=278) by phone. Subjects will be randomized in blocks within each site (Toronto, Montreal, and Vancouver). The primary outcome will be improved quality of life, defined as an increased number of subjects with an improvement of ≥5 points on the summary score of the Kansas City Cardiomyopathy Questionnaire. We will also assess the following secondary outcomes: (1) diet habits, depression, anxiety, smoking history, stress level, and readiness for change using self-report questionnaires, (2) physical activity level, current smoking status, and vagal-heart rate modulation by physiological tests, and (3) exercise capacity, prognostic indicators of cardiovascular functioning, and medication adherence through medical chart review. The primary outcome will be analyzed using generalized estimation equations with repeated measures on an intention-to-treat basis. Secondary outcomes will be analyzed using repeated-measures linear mixed models with a random effects intercept. All significant main effects or interactions in the statistical models will be followed up with post hoc contrasts using a Bonferroni correction with a 2-sided statistical significance criterion of P<.05.

Results

This 3.5-year, proof-of-principle trial will establish the e-infrastructure for a pan-Canadian e-platform for CHF that is comprised of a standardized, evidence-based protocol of e-Counseling.

Conclusions

CHF-CePPORT is designed to improve long-term adherence to self-care behaviors and quality of life among patients with CHF. It will demonstrate a distinct Canadian initiative to build capacity for preventive eHealth services for patients with CHF.

Trial Registration

ClinicalTrials.gov NCT01864369; http://clinicaltrials.gov/ct2/show/NCT01864369 (Archived by WebCite at http://www.webcitation.org/6Iiv6so7E).

Validity of activity monitors in health and chronic disease: a systematic review

The assessment of physical activity in healthy populations and in those with chronic diseases is challenging. The aim of this systematic review was to identify whether available activity monitors (AM) have been appropriately validated for use in assessing physical activity in these groups. Following a systematic literature search we found 134 papers meeting the inclusion criteria; 40 conducted in a field setting (validation against doubly labelled water), 86 in a laboratory setting (validation against a metabolic cart, metabolic chamber) and 8 in a field and laboratory setting. Correlation coefficients between AM outcomes and energy expenditure (EE) by the criterion method (doubly labelled water and metabolic cart/chamber) and percentage mean differences between EE estimation from the monitor and EE measurement by the criterion method were extracted. Random-effects meta-analyses were performed to pool the results across studies where possible. Types of devices were compared using meta-regression analyses. Most validation studies had been performed in healthy adults (n = 118), with few carried out in patients with chronic diseases (n = 16). For total EE, correlation coefficients were statistically significantly lower in uniaxial compared to multisensor devices. For active EE, correlations were slightly but not significantly lower in uniaxial compared to triaxial and multisensor devices. Uniaxial devices tended to underestimate TEE (−12.07 (95%CI; -18.28 to −5.85) %) compared to triaxial (−6.85 (95%CI; -18.20 to 4.49) %, p = 0.37) and were statistically significantly less accurate than multisensor devices (−3.64 (95%CI; -8.97 to 1.70) %, p<0.001). TEE was underestimated during slow walking speeds in 69% of the lab validation studies compared to 37%, 30% and 37% of the studies during intermediate, fast walking speed and running, respectively. The high level of heterogeneity in the validation studies is only partly explained by the type of activity monitor and the activity monitor outcome. Triaxial and multisensor devices tend to be more valid monitors. Since activity monitors are less accurate at slow walking speeds and information about validated activity monitors in chronic disease populations is lacking, proper validation studies in these populations are needed prior to their inclusion in clinical trials.

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.

Severity at entry to specialized heart failure clinics: discrepancies between health-related quality of life and function in men and women

BACKGROUND

We compared severity of heart failure (HF) between men and women at entry to the multidisciplinary HF clinic based on 3 measures: New York Heart Association functional class, norm-referenced 6-minute walk distance, and health-related quality of life.

METHODS

Newly admitted patients to 1 of 6 HF clinics were enrolled. Data were collected from a clinical database, questionnaires were administered to patients, and tests were administered by clinic nurses. We compared men and women with respect to the 3 severity indicators at entry to the clinic.

RESULTS

In adjusted analyses, women had a lower health-related quality of life (P = 0.04) but did not have lower norm-referenced 6-minute walk distance or lower New York Heart Association functional class on entry to the clinic. Having more comorbid conditions, being on medication, and having visited the emergency department or been admitted to hospital in the past 6 months were associated with higher severity at entry according to all 3 indicators.

CONCLUSIONS

Women report a lower health-related quality of life at entry to the clinic, although functional capacity does not seem to differ between women and men. Reasons for these discrepancies will need to be elucidated to better address women's health needs.

Identifying relative cut-off scores with neural networks for interpretation of the Minnesota Living with Heart Failure questionnaire

BACKGROUND

Quality of life (QoL) is an important end point in heart failure (HF) studies. The Minnesota Living with Heart Failure questionnaire (MLHFQ) is the instrument most widely used to evaluate QoL in Heart Failure (HF) patients. It is a questionnaire containing 21 questions with scores ranging from 0 to 105. A best cut-off value for MLHFQ scores to identify those patients with good, moderate or poor QoL has not been determined.

OBJECTIVE

To determine a cut-off score for the MLHFQ based on the neural network (NN) approach. These cut-off scores will help discriminate between HF patients having good, moderate or poor QoL.

METHODS

This research was carried out in the context of a longitudinal cohort study of new patients attending specialized HF clinics in six participating centers in Quebec, Canada. Patients completed a questionnaire that included the MLHFQ. In addition to this scale, self-perceived health status and clinical information related to the severity of HF were obtained including: the New York Heart Association (NYHA) functional class, 6 minute walk test and survival status. We analyzed the database using NN and conventional statistical tools. The NN is a statistical program that recognizes clusters of MLHFQ and relates similar QoL measures to one another. Among the 531 eligible patients, 447 patients with complete questionnaires were used to build randomly two sets for training (learning set) and for testing (validation set) the NN.

RESULTS

Participants had a mean age of 65 years and 24% were women. The median MLHFQ score was 45 (inter-quartile range: 27 to 64). NN identified 3 distinct clusters of MLHFQ that represent the full spectrum of possible scores on the MLHFQ. We estimated that a score of < 24 on the MLHFQ represents a good QoL, a score between 24 and 45 represents a moderate QoL, and a score > 45 represents a poor QoL. Validation with the different severity measures confirmed these categories. These cut-offs allowed us to reach a good total accuracy (91%). These cutoffs were strongly correlated with survival status (p = 0.004), self-perceived health status (p = 0.0032), NYHA functional class (p<0.0001) and standardized 6 minutes walk test (p = 0.05)

CONCLUSION

The identification of three levels of MLHFQ should be useful in clinical decision making.

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.

Quality of life and functional status in patients surviving 12 months after left ventricular assist device implantation

BACKGROUND

As left ventricular assist device (LVAD) support duration increases, quality of life (QoL) becomes a concern. We reviewed the QoL in patients on LVAD support for >or=1 year.

METHODS

We retrospectively reviewed our prospective database for patients supported >or=1 year by HeartMate pulsatile- (HM1) or continuous-flow (HM2) LVADs from 2000 to 2009. Transplant or death before 1 year merited exclusion. Metabolic equivalents of tasks (METs), the Minnesota Living with Heart Failure Questionnaire (MLHFQ), the 6-minute walk distance (6MWD), and New York Heart Association (NYHA) class were reviewed. Complications and re-admissions were assessed.

RESULTS

Thirty patients were supported for >or=1 year (7 HM1s, 23 HM2s). Mean support duration was 594 +/- 173 days. Mean QoL metrics/functional status indicators at 12 months were: 6MWD, 393 +/- 290 m; MET tolerance, 3.3 +/- 1; MLHFQ, 35 +/- 31; and NYHA, 1.4 +/- 0.6. Mean re-admissions/year was 2.9 +/- 2, with a duration of 13.8 +/- 21 days. Three patients were never re-admitted. Mean out-of-hospital time was 471 +/- 172 days (87.3% of days). Infectious complications led to 43% of re-admissions and occurred in the: drive-line (47%) at 442 +/- 236 days; blood (37%) at 472 +/- 257 days; and LVAD pocket (20%) at 550 +/- 202 days. Twenty-three patients (77%) required additional operations (1.7 +/- 1.8/year). The most common indication was drive-line infection, but ranged from ischemic bowel to defibrillator exchange. Eight required LVAD exchanges for mechanical (n = 4), electrical (n = 3), and thrombotic (n = 1) issues.

CONCLUSIONS

Although LVAD support is not without complications, patients spend the majority of time outside the hospital enjoying a good quality of life.