Clinical Investigation
Association of Functional and Health Status Measures in Heart Failure

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Abstract

Background

A wide variety of instruments have been used to assess the functional capabilities and health status of patients with chronic heart failure (HF), but it is not known how well these tests are correlated with one another, nor which one has the best association with measured exercise capacity.

Methods and Results

Forty-one patients with HF were assessed with commonly used functional, health status, and quality of life measures, including maximal cardiopulmonary exercise testing, the Duke Activity Status Index (DASI), the Veterans Specific Activity Questionnaire (VSAQ), the Kansas City Cardiomyopathy Questionnaire (KCCQ), and 6-minute walk distance. Pretest clinical variables, including age, resting pulmonary function tests (forced expiratory volume in 1 s and forced vital capacity), and ejection fraction (EF) were also considered. The association between performance on these functional tools, clinical variables, and exercise test responses including peak VO2 and the VO2 at the ventilatory threshold, was determined. Peak oxygen uptake (VO2) was significantly related to VO2 at the ventilatory threshold (r = 0.76, P < .001) and estimated METs from treadmill speed and grade (r = 0.72, P < .001), but had only a modest association with 6-minute walk performance (r = 0.49, P < .01). The functional questionnaires had modest associations with peak VO2 (r = 0.37, P < .05 and r = 0.26, NS for the VSAQ and DASI, respectively). Of the components of the KCCQ, peak VO2 was significantly related only to quality of life score (r = 0.46, P < .05). Six-minute walk performance was significantly related to KCCQ physical limitation (r = 0.53, P < .01) and clinical summary (r = 0.44, P < .05) scores. Among pretest variables, only age and EF were significantly related to peak VO2 (r = −0.58, and 0.46, respectively, P < .01). Multivariately, age and KCCQ quality of life score were the only significant predictors of peak VO2, accounting for 72% of the variance in peak VO2.

Conclusion

Commonly used functional measures, symptom tools, and quality of life assessments for patients with HF are poorly correlated with one another and are only modestly associated with exercise test responses. These findings suggest that exercise test responses, non-exercise test estimates of physical function, and quality of life indices reflect different facets of health status in HF and one should not be considered a surrogate for another.

Section snippets

Patients

Forty-one male patients with stable HF (mean age 68 ± 12 years) participated in the study. HF was documented by clinical history and diagnosis in outpatient medical records, and an ejection fraction (EF) <40%. Ischemic HF (n = 22) was defined by having a history of myocardial infarction, coronary bypass surgery, or documented angiographic coronary disease. Only patients with stable, compensated HF >30 years of age were included in the study. Written informed consent was obtained from all

Exercise Test Responses

Exercise test results are listed in Table 3. The mean maximal perceived exertion was 17.6 ± 2.0, and the mean peak respiratory exchange ratio was 1.14 ± 0.23, suggesting that maximal effort was achieved by most patients. The mean maximal heart rate of 124 ± 28 beats/min was lower than that expected for age (82% of predicted), reflecting that many patients were limited by symptoms associated with HF, that heart rate was limited by the effects of β-blockade, or both. Mean maximal oxygen uptake

Discussion

The present results suggest that commonly-used functional measures, estimates of quality of life, and symptom tools in patients with HF generally have only modest associations with peak VO2 and with one another. The clinical implications of these findings are that: (1) each test or instrument targets a specific aspect of clinical status and they should not be considered interchangeable and (2) none of these measures alone is a reliable surrogate for peak VO2.

Peak VO2 was used as the dependent

Summary

Health status, including functional capabilities, symptoms associated with daily activities, and physical or psychologic well-being are important indices that are widely used in the assessment of interventions for HF. Accurate and reliable tools that quantify health status are important to appropriately assess responsiveness to therapy in this population. We observed that tools commonly used to assess health and functional status in HF had only modest associations with peak VO2 and with

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