The relationship of symptoms to performance in paced patients with breathlessness

Objective assessment of functional capacity in patients with peripheral artery disease: a narrative review

INTRODUCTION

Peripheral artery disease (PAD) patients with claudication symptoms exhibit impaired functional capacity, which has been associated with disease severity, worse quality of life and higher risk of cardiovascular events. Different tests have been used to assess functional capacity in PAD patients. Therefore, understanding the characteristics, strengths and limitations of these tests are important to support the choice of tests to be used in clinical practice.

AREAS COVERED

This review summarizes the main methods to assess functional capacity in PAD patients, discussing their psychometric properties, applications, and limitations.

EXPERT OPINION

Robust evidence supports the use of treadmill and six-minute walk tests in PAD patients, as their results are associated with clinically meaningful outcomes, adequate psychometric properties and are sensitive to effects of interventions. On the other hand, other functional tests (Shuttle-walk test, outdoor walking capacity test, timed-up and go, four-meter walk test, heel-rise test, short physical performance battery and modified physical performance battery) are related to activities of daily living and do not require sophisticated equipment and can be easily used in clinical practice. However, these other tests still need evidence regarding their clinical relevance, reliability, and ability to detect long-term intervention changes, providing further investigation directions.

Machine Learning Confirms Nonlinear Relationship between Severity of Peripheral Arterial Disease, Functional Limitation and Symptom Severity

BACKGROUND

Peripheral arterial disease (PAD) involves arterial blockages in the body, except those serving the heart and brain. We explore the relationship of functional limitation and PAD symptoms obtained from a quality-of-life questionnaire about the severity of the disease. We used a supervised artificial intelligence-based method of data analyses known as machine learning (ML) to demonstrate a nonlinear relationship between symptoms and functional limitation amongst patients with and without PAD.

OBJECTIVES

This paper will demonstrate the use of machine learning to explore the relationship between functional limitation and symptom severity to PAD severity.

METHODS

We performed supervised machine learning and graphical analysis, analyzing 703 patients from an administrative database with data comprising the toe-brachial index (TBI), baseline demographics and symptom score(s) derived from a modified vascular quality-of-life questionnaire, calf circumference in centimeters and a six-minute walk (distance in meters).

RESULTS

Graphical analysis upon categorizing patients into critical limb ischemia (CLI), severe PAD, moderate PAD and no PAD demonstrated a decrease in walking distance as symptoms worsened and the relationship appeared nonlinear. A supervised ML ensemble (random forest, neural network, generalized linear model) found symptom score, calf circumference (cm), age in years, and six-minute walk (distance in meters) to be important variables to predict PAD. Graphical analysis of a six-minute walk distance against each of the other variables categorized by PAD status showed nonlinear relationships. For low symptom scores, a six-minute walk test (6MWT) demonstrated high specificity for PAD.

CONCLUSIONS

PAD patients with the greatest functional limitation may sometimes be asymptomatic. Patients without PAD show no relationship between functional limitation and symptoms. Machine learning allows exploration of nonlinear relationships. A simple linear model alone would have overlooked or considered such a nonlinear relationship unimportant.

Exercise performance, physical activity, and health-related quality of life in participants with stable angina

We compared exercise performance, daily physical activity, and health-related quality of life in 115 participants with stable angina and 441 controls without coronary artery disease or stable angina. Participants with stable angina had shorter 6-min walk distance (P = .003), and lower total leisure-time physical activity (P = .003) than the controls. Group differences in these measures remained (P < .05) after adjusting for age, race, current smoking, diabetes, hypertension, and obesity. Participants with stable angina also had lower health-related quality of life for physical function (P < .001), general health (P = .002), and vitality (P < .001), but group differences did not remain (P > .05) after adjustment for comorbid conditions. Participants with stable angina have impaired exercise performance and reduced daily physical activity. Thus, they are prime candidates for exercise interventions designed to improve daily physical activity and exercise performance.

DIFFERENCES IN EXERCISE PERFORMANCE AND LEISURE-TIME PHYSICAL ACTIVITY IN OLDER CAUCASIANS AND AFRICAN-AMERICANS

PURPOSES: (a) To compare exercise performance and leisure-time physical activity (LTPA) between older Caucasians and African-Americans, (b) to assess the relationship between exercise performance and LTPA, and (c) to determine whether group differences in exercise performance persist after adjusting for differences in LTPA. METHODS: A total of 207 Caucasians and 160 African-Americans who were 65 years of age and older participated in this study. Subjects were characterized on exercise performance by a 6-minute walk test, and by a short physical performance battery (SPPB) score consisting of a repeated chair rise test, a standing balance test, and a 4-meter walk test. Additionally, LTPA was assessed using the Minnesota LTPA questionnaire. RESULTS: African-Americans had a 16% lower SPPB value (P < 0.001), a 14% shorter 6-minute walk distance (P < 0.001), and a 34% lower LTPA value (P < 0.011) than the Caucasians. LTPA was significantly related (P < 0.01) to both SPPB and 6-minute walk distance in both groups. Differences in SPPB and 6-minute walk distance between older Caucasians and African-Americans were no longer present (P > 0.05) after controlling for LTPA. CONCLUSIONS: Older African-Americans had impaired exercise performance and lower LTPA compared to older Caucasians. Racial differences in exercise performance were no longer present after adjusting for differences in LTPA.

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

BACKGROUND

We sought the value of the 6-min walk test (6MWT) in predicting morbidity and mortality in Asian patients with congestive heart failure (CHF).

METHODS

668 patients (Age 66+/-12 years, Ejection fraction 29+/-13%, NYHA I to IV) were prospectively followed up for 36+/-12 months. 386 patients (58%) took the 6MWT. Cardiac events, defined as the composite end-point of death or CHF readmission were documented.

RESULTS

188 patients (28%) reached the composite end-point (63 deaths, 125 readmissions). 6MWT distance was an independent predictor of cardiac events (quartile 1 vs quartile 4)(p=0.041), as were beta-blocker or spironolactone use (p=0.008 for both), diabetes (p=0.042), monthly income less than SGD$1000 (p=0.030), and NYHA class (class III vs class I)(p=0.003). A 6MWT distance <340 m predicted occurrence of cardiac events with a sensitivity of 69% and specificity of 48%.

CONCLUSIONS

The 6MWT is a safe and simple clinical tool, which could predict both morbidity and mortality in a large population of Asian patients with CHF of differing etiology and severity (169 words).

Preliminary report of the 6-minute walk test as a predictor of radiation-induced pulmonary toxicity

PURPOSE

To assess the 6-minute walk test (6MWT) as a predictor of radiation therapy-induced lung injury (RTLI).

METHODS AND MATERIALS

The 6MWT is a simple, economical, and reproducible test that measures both how far a person can walk in 6 min and any associated changes in vital signs. As part of a prospective trial to study RTLI, a pre-RT 6MWT was performed in 41 patients. The predictive capacities of pre-RT 6MWT, forced expiratory volume in 1 s (FEV1), and single-breath diffusing capacity for carbon monoxide (DLCO) for the development of RTLI were assessed with receiver operating curve (ROC) techniques. To evaluate the 6MWT, alone or with mean lung dose (MLD) of radiation, as a predictor of RTLI, the rates of RTLI in patient subgroups defined by 6MWT results were compared by using Fisher's exact test.

RESULTS

Thirty-one patients with > or =3 months' follow-up were evaluable. The median baseline 6MWT result was 1400 ft. Of 31 patients, 7 developed Grade > or =2 RTLI. Of 15 patients with an MLD >18 Gy (the median), 5 developed RTLI, compared with 2 of 16 with MLD < or =18 Gy (p = 0.22). Among those with an MLD < or =18 Gy, the RTLI rates were 0 of 8 and 2 of 8 for 6MWT results > or =1400 ft or <1400 ft, respectively, p = 0.46. The ROC area under the curve for individual metrics was as follows: FEV1 0.66, MLD 0.70, DLCO 0.61, and 6MWT 0.47. Combining FEV1 with 6MWT increased the ROC to 0.71, suggesting that the ratio might be a better predictor than the individual values. Patients with a high 6MWT/FEV1 ratio had a lower rate of RTLI than those with a relatively low ratio.

CONCLUSIONS

The 6MWT might provide prognostic information beyond pulmonary function tests and dosimetric parameters in predicting RTLI. Additional work is needed to better assess the utility of these functional metrics.

Utility of pedometers for assessing physical activity: construct validity

Valid assessment of physical activity is necessary to fully understand this important health-related behaviour for research, surveillance, intervention and evaluation purposes. This article is the second in a companion set exploring the validity of pedometer-assessed physical activity. The previous article published in Sports Medicine dealt with convergent validity (i.e. the extent to which an instrument's output is associated with that of other instruments intended to measure the same exposure of interest). The present focus is on construct validity. Construct validity is the extent to which the measurement corresponds with other measures of theoretically-related parameters. Construct validity is typically evaluated by correlational analysis, that is, the magnitude of concordance between two measures (e.g. pedometer-determined steps/day and a theoretically-related parameter such as age, anthropometric measures and fitness). A systematic literature review produced 29 articles published since > or =1980 directly relevant to construct validity of pedometers in relation to age, anthropometric measures and fitness. Reported correlations were combined and a median r-value was computed. Overall, there was a weak inverse relationship (median r = -0.21) between age and pedometer-determined physical activity. A weak inverse relationship was also apparent with both body mass index and percentage overweight (median r = -0.27 and r = -0.22, respectively). Positive relationships regarding indicators of fitness ranged from weak to moderate depending on the fitness measure utilised: 6-minute walk test (median r = 0.69), timed treadmill test (median r = 0.41) and estimated maximum oxygen uptake (median r = 0.22). Studies are warranted to assess the relationship of pedometer-determined physical activity with other important health-related outcomes including blood pressure and physiological parameters such as blood glucose and lipid profiles. The aggregated evidence of convergent validity (presented in the previous companion article) and construct validity herein provides support for considering simple and inexpensive pedometers in both research and practice.

A new device for the measurement of disease severity in patients with intermittent claudication

OBJECTIVES

To assess a new method of determining functional impairment in patients with intermittent claudication, the Double Physiological Walking Test (DPWT) using the PADHOC (Peripheral Arterial Disease Holter Control) device, against a standard treadmill test.

DESIGN

Patients with intermittent claudication presenting to the department were considered for both the DPWT and a standard treadmill test.

METHODS

initial claudicating distance, maximal walking distance and speed of walking were determined for both parts of the DPWT. Initial claudicating distance and maximal walking distance were determined from the treadmill test. Comparisons were made between the treadmill test and the DPWT.

RESULTS

The treadmill test was unable to be performed in 22% of patients due to defined contraindications. There were strong correlations in both walking distances and disease severity when comparing the DPWT and the treadmill test. Patients in whom the treadmill test was contraindicated had significantly shorter walking distances on the DPWT than those who were able to complete a treadmill walking test.

CONCLUSIONS

The DPWT correlates strongly with walking distances obtained from a standard treadmill test. However, the PADHOC can be used in a number of differing locations and settings as well as in patients in whom a treadmill test is contraindicated. It therefore has a role to play in the initial assessment of patients presenting with intermittent claudication.

A qualitative systematic overview of the measurement properties of functional walk tests used in the cardiorespiratory domain

OBJECTIVE

To perform a qualitative systematic overview of the measurement properties of the most commonly utilized walk tests in the cardiorespiratory domain: the 2-min walk test (2MWT), 6-min walk test (6MWT), 12-min walk test (12MWT), self-paced walk test (SPWT), and shuttle walk test (SWT).

DATA SOURCES

MEDLINE (1966 to January 2000) and CINAHL (1982 to December 1999) electronic databases were searched. Bibliographies of the retrieved articles were reviewed.

STUDY SELECTION

Clinical trials and observational studies were included if they reported data on the validity, reliability, interpretability, or responsiveness of the 2MWT, 6MWT, 12MWT, SPWT, or SWT. Only studies conducted on patients with cardiac and/or respiratory involvement were included.

RESULTS

Fifty-two studies examining measurement properties of the various walk tests were found: 5 studies on the 2MWT, 29 studies on the 6MWT, 13 studies on the 12MWT, 6 studies on the SPWT, and 4 studies on the SWT. Measurement properties were most strongly demonstrated for the 6MWT. Correlations of 6MWT distance and maximal oxygen consumption ranged from 0.51 to 0.90. A change in distance walked of at least 54 m was found to be clinically significant for the 6MWT. Reliability was shown to be optimized when the administration of walk tests was standardized and at least two practice walks were performed. Patients with increased likelihood of postoperative complications, hospitalization, and death were identified by analysis of distance walked.

CONCLUSIONS

Measurement properties of the 6MWT have been the most extensively researched and established. In addition, the 6MWT is easy to administer, better tolerated, and more reflective of activities of daily living than the other walk tests. Therefore, the 6MWT is currently the test of choice when using a functional walk test for clinical or research purposes.

Accuracy of recall of dyspnea after exercise training sessions

BACKGROUND

Although clinicians often rely on patients' retrospective reporting of dyspnea, it is not known if dyspnea scores recalled after exercise are equivalent to dyspnea scores during exercise. The objective of this study was to determine whether patients could accurately recall after exercise the maximum ratings of the intensity of dyspnea and the anxiety associated with it that they experienced during exercise.

METHODS

Forty-nine patients with chronic obstructive pulmonary disease (COPD) (forced expiratory volume in 1 second 0.92 +/- 0.23 L) participating in a randomized clinical trial of the impact of coached versus monitored exercise training on dyspnea rated dyspnea intensity (shortness of breath [SOB]) and dyspnea-related anxiety (DA) on a visual analog scale every 2 minutes during treadmill exercise. After each of 12 training sessions each subject was asked to rate the worst level of the two sensations that they recalled having experienced during exercise.

RESULTS

For the groups as a whole, actual maximum scores for SOB and DA during exercise were highly correlated with recalled maximum values after exercise (r > or = 0.85, P < 0.0001) and the average differences were small (0-10.9 mm on a 200-mm scale). However, individual variation was substantial, limiting predictability for individual ratings.

CONCLUSIONS

After exercise, patients with COPD as a group can accurately recall the worst SOB and DA that they experienced during exercise. This finding supports the further study and use of retrospective symptom ratings as a method for dyspnea assessment during exercise training in pulmonary rehabilitation.

The clinical utility of a six-minute walk test in peripheral arterial occlusive disease patients

OBJECTIVES

To determine the test-retest reliability of the distance covered and the steps taken to complete a 6-minute walk test by peripheral arterial occlusive disease (PAOD) patients with intermittent claudication. To determine the relationship between the total distance and steps covered during the 6-minute walk test and clinical measures of PAOD severity.

DESIGN

Cross-sectional design.

SETTING

The Claude Pepper Older Americans Independence Center at the University of Maryland at Baltimore.

PARTICIPANTS

Sixty-four PAOD patients between the ages of 45 and 88 years (age = 68 +/- 7 years, ankle/brachial index (ABI) = .61 +/- .19) were recruited from the Vascular Clinic at the Baltimore Veterans Affairs Medical Center and from radio and newspaper advertisements.

MEASUREMENTS

Patients were assessed on a 6-minute walk test and a treadmill graded exercise test. A second 6-minute walk test was administered approximately 1 week later. Patients also were characterized in regard to blood pressure in the arms and legs, ABI, anthropometry, body composition, and physical activity.

RESULTS

The distances walked during the two 6-minute walk tests were similar (350 +/- 78 m vs 360 +/- 73 m), resulting in a high reliability coefficient (R = .94) and a low coefficient of variation (10.4%). The total steps taken during the 6-minute walk test also were similar (562 +/- 113 steps vs 587 +/- 107 steps), resulting in a high reliability coefficient (R = .90) and a low coefficient of variation (11.7%). Furthermore, the 6-minute walking distance correlated with the distances to onset (r = .346, P = .007) and with maximal claudication pain (r = .525, P < .001) during the treadmill test as well as with ABI (r = .552, P < .001).

CONCLUSION

The 6-minute walk test yields highly reliable measurements, which are related to the functional and hemodynamic severity of PAOD, in patients with intermittent claudication.

Relationship between free-living daily physical activity and ambulatory measures in older claudicants

The purpose of this study was to determine the relationship between free-living daily physical activity and ambulatory measurements in peripheral arterial occlusive disease (PAOD) patients with intermittent claudication. Thirty-four older, nonsmoking PAOD patients with intermittent claudication (age=69.0 +/- 6.0 years, ankle/brachial index [ABI] =0.63 +/- 0.18) were recruited from the Vascular Clinic at the Baltimore Veterans Affairs Medical Center and from radio and newspaper advertisements. Energy expenditure of physical activity (EEPA) was determined by using doubly labeled water and indirect calorimetry techniques. Patients were also characterized on claudication distances and peak oxygen uptake during a graded treadmill test, 6-minute walking distance, weight, body mass index, and percent body fat. The claudication patients were sedentary, as EEPA was 362 +/- 266 kcal/day. EEPA was related to the 6-minute walk distance (369 +/- 68 meters; r=0.629, P<0.001), to the number of steps taken during 6 minutes (605 +/- 99 steps; r=0.485, P=0.008), to the treadmill distance to maximal claudication (313 +/- 131 meters; r=0.470, P=0.010), and to the time to relief of pain (6:21 +/- 3:57 min:sec; r=-0.417, P=0.017). None of the other ambulatory and body composition measurements were correlated with EEPA. In conclusion, a reduction in free-living daily physical activity was associated with a decrease in ambulatory ability and with more severe intermittent claudication in older PAOD patients.

The six-minute walk test predicts peak oxygen uptake and survival in patients with advanced heart failure

BACKGROUND

The 6-min walk test (6'WT) is a simple measure of functional capacity and predicts survival in patients with moderate heart failure (HF).

METHODS

To assess the role of the 6'WT in the evaluation of patients with advanced HF, 45 patients (age 49 +/- 8 years, mean +/- SD; New York Heart Association class 3.3 +/- 0.6; left ventricular ejection fraction 0.20 +/- 0.06; right ventricular ejection fraction 0.31 +/- 0.11) underwent symptom-limited cardiopulmonary exercise testing and the 6'WT during cardiac transplant evaluation.

RESULTS

Mean 6'WT distance ambulated was 310 +/- 100 m and peak oxygen uptake (peak Vo2) was 12.2 +/- 4.5 mL/kg/min. There was a significant correlation between 6'WT distance ambulated and peak Vo2 (r = 0.64, p < 0.001). Multivariate analysis of patient characteristics, resting hemodynamics, and 6'WT results identified the distance ambulated during the 6'WT as the strongest predictor of peak Vo2 (p < 0.001). 6'WT distance ambulated less than 300 m predicted an increased likelihood of death or pretransplant hospital admission for continuous inotropic or mechanical support within 6 months (p = 0.04), but did not predict long-term overall or event-free survival with a mean follow-up of 62 weeks. Peak Vo2 was the best predictor of long-term overall and event-free survival.

CONCLUSIONS

In patients with advanced HF evaluated for cardiac transplantation, distance ambulated during the 6'WT predicts (1) peak Vo2 and (2) short-term event-free survival.

Exercise intolerance in patients with chronic heart failure

Patients with chronic heart failure (CHF) experience significant morbidity because of dyspnea and fatigue with activities of daily living. Although central hemodynamic abnormalities are the hallmark of this disorder, investigators have not shown a relationship between left ventricular ejection fraction or exercise pulmonary capillary wedge pressure and exercise intolerance in this disorder. Recent studies have focused on the contributions of pulmonary abnormalities and alterations in peripheral vasomotor control and skeletal muscle in exercise intolerance in this disorder. Early anaerobic metabolism occurs in patients with CHF and appears to be caused by a combination of reduced skeletal muscle blood flow and decreased aerobic enzyme content in skeletal muscle. Atrophy in skeletal muscle and alterations in skeletal muscle fiber typing are accompanied by alterations in contractile function in skeletal muscle. These results suggest that exercise intolerance in patients with CHF is multifactorial, and that research efforts must consider central hemodynamic abnormalities, pulmonary abnormalities, and alterations in peripheral blood flow and skeletal muscle biochemistry and histology. The present review will explore current research in this area and develop a model for understanding exercise intolerance in CHF.

Effects of chronotropic responsive cardiac pacing on ventilatory response to exercise in patients with complete AV block

To identify the effect of chronotropic responsive cardiac pacing on the ventilatory response to exercise, ten selected patients with complete atrioventricular block underwent paired cardiopulmonary exercise tests in fixed rate ventricular (VVI) and dual chamber (DDD) or rate responsive ventricular (VVIR) pacing modes. Compared to VVI pacing, DDD or VVIR pacing increased peak oxygen uptake (P < 0.005) and augmented anaerobic threshold (P < 0.001). In eight patients, dyspnea was the major symptom limiting exercise with VVI pacing and this was markedly attenuated with DDD or VVIR pacing. In all patients, ventilation (VE) and the ratio of ventilation to CO2 production (VE/VCO2) were consistently higher with VVI pacing during exercise. To compare the response of the two pacing modes at the same workloads in an aerobic condition, we measured ventilatory variables 1 minute prior to the anaerobic threshold obtained with VVI pacing. When DDD or VVIR pacing was compared with VVI pacing, VE and VE/VCO2 significantly decreased from 20.5 +/- 5.3 L/min to 18.3 +/- 5.0 L/min (P < 0.005) and from 35.9 +/- 5.8 to 31.9 +/- 5.0 (P < 0.001), respectively. Respiratory frequency rose significantly more with VVI pacing (P < 0.001) despite an unchanged tidal volume. Although peak VE did not differ between the two pacing modes, VE/VCO2 at the peak exercise increased significantly more with VVI pacing (P < 0.005). Respiratory frequency also rose more with VVI pacing (P < 0.005) and tidal volume did not change. This study suggests that chronotropic responsive cardiac pacing attenuates the exertional dyspnea by improving the ventilatory response to exercise as well as increasing the cardiac output in patients with complete atrioventricular block.

Use of limb movement sensors as indicators of the level of everyday physical activity in chronic congestive heart failure

The level of everyday physical activity of patients with chronic congestive heart failure (CHF) may be an important reflection of their quality of life. Everyday physical activity is difficult to measure objectively, and may not relate to exercise capacity determined by laboratory exercise testing. A light-weight sensor worn on the wrist or ankle, which provides a cumulative record of limb movement, was evaluated. The sensor counted reliably when tested in a laboratory rig and during treadmill exercise. In 20 young normal subjects, hourly movement scores showed the expected diurnal rhythm. Twenty-four-hour movement scores in 30 patients with stable CHF were lower than in 20 age-matched control subjects (p less than 0.005). Movement scores in CHF correlated with a standard questionnaire scale assessing everyday physical activity (R = +0.72, p less than 0.001). Consecutive daily scores varied widely, but wrist and ankle scores were correlated (R greater than +0.7, p less than 0.05 in each subject), suggesting true day-to-day differences in activity rather than variability in the recording method. Recording for 5 to 6 consecutive days provides a reliable estimate of mean 24-hour movement score for a subject, and mean 24-hour scores were reproducible when subjects were retested after 8 weeks. There was a weak correlation between movement scores and exercise capacity as measured by peak oxygen consumption during maximal treadmill exercise (R = +0.42, p = 0.01). Quality-of-life score correlated with movement scores (R = +0.53, p less than 0.002) but not with peak oxygen consumption (R = +0.36; p = not significant).(ABSTRACT TRUNCATED AT 250 WORDS)