Comparisons of Dyspnea, Fatigue, and Exercise Intolerance Between Individuals with Heart Failure with High Versus Low Knee Extensor Muscle Strength

Background: Maintaining muscle strength is problematic for patients with heart failure (HF) and may be related to increasing HF symptoms and exercise intolerance, leading to further decline in physical functioning. No recommendation for muscle strength assessment with HF patients is established in routine clinical practice. The purpose of this study was to compare differences in HF symptoms (dyspnea and fatigue) and exercise intolerance between patients with high versus low knee extensor strength. Method: Using a cross-sectional design, 102 patients with HF, New York Heart Association (NYHA) class II-IV were recruited at a HF clinic. Measures included: knee extensor muscle strength (hand-held dynamometer); dyspnea with activities of daily living (ADLs), instrumental activities of daily living (IADLs), and physical functioning (0-10 cm visual analogue scale); fatigue (Piper Fatigue Scale); and exercise tolerance (6-Minute Walk Test). Results: Patients were, on average, 59.6 years of age (SD 12.46). They had been diagnosed with HF for 3.34 years, and primarily had non-ischemic HF (60%) and NYHA Class II (80%). Patients were divided into groups of high vs. low knee extensor strength based on a median split (Mdn = 6.70 kg). Subjects with high knee extensor strength had significantly less dyspnea with ADLs, IADLs, and physical function (p < 0.05) and greater distances in the 6-minute walk test (t = -2.43, p<0.05). There was no significant difference in fatigue between groups. Conclusion: Findings indicate that symptoms of dyspnea and exercise intolerance were less in HF patients with greater knee extensor strength. Largerscale studies are needed to substantiate these results, and to determine if early interventions would improve strength and exercise tolerance in patients with HF.