Physical capacity determines physical and mental health in patients with chronic heart failure - a case control study

Abstract Background Chronic heart failure (CHF) is associated with reduced quality of life (QoL), but underlying mechanisms are incompletely understood. In this study we aimed to assess determinants of both physical and mental functioning in patients with and without chronic heart failure and investigated the impact of physical capacity (PC). Methods This is a cross-sectional analysis conducted in two cohorts using a case-control design. Both, the case cohort (RoC-HF, n=205) and the control cohort (BioPersMed, n=1022) were prospective, single center cohort studies. The case cohort included patients with diagnosed CHF with a current left ventricular ejection fraction (LVEF) <50%, while the control cohort included apparently healthy individuals with at least one cardiovascular risk factor. Laboratory parameters, transthoracic echocardiography, PC (Biopersmed: 6-minute walking distance [6MWD]; RoC-HF: 4-meter gait speed [4MGS]), and SF-36 health survey parameters as the main read-out of this study, were available in all participants. Results Cases and controls were matched by age, sex and body mass index yielding a study sample of 188 vs. 188 individuals. Medians with interquartile range of NT-proBNP and LVEF were 985 (325 – 2183) pg/dl and 37 (30 – 44) % in cases, and 72 (33 - 118) pg/dl and 64 (60 – 68) % in controls. Cases had lower levels than controls regarding all eight QoL aspects of the SF-36 HS (Figure 1). Both within the case and the control cohort, measures of heart failure severity (LVEF, NT-proBNP, TAPSE) were not or only marginally associated with SF-36 HS scales. PC parameters correlated significantly with physical component summary score (PCS) both within cases and controls, and with mental component summary score (MCS) only in cases (Figure 2). Multivariate linear regression analyses with adjustment for age, sex, eGFR, LVEF, NT-proBNP and TAPSE were conducted in each cohort, respectively. Within cases, 4MGS, but not LVEF, NT-proBNP and TAPSE, was significantly associated with MCS (adjusted beta 0.228, P=0.011) and PCS (beta = 0.318, P<0.001). Within controls, 6MWD was significantly associated with PCS (beta = 0.332, P<0.001), but not with MCS (beta = -0.62, P=0.472). Conclusion In patients with CHF, impairment of both physical and mental functioning is determined by physical capacity, but not by measures of cardiac function and congestion. By contrast, only physical functioning, but not mental functioning, can be explained by PC in healthy controls. Given the increasing relevance of QoL as a patient-oriented outcome in CHF, assessment and improvement of PC should be considered essential aspects in CHF care, besides biomarker-guided improvements in cardiac function and congestion. Whether targeting PC, for instance by medical and device therapies, translates into better physical and mental well-being in CHF should be specifically addressed in randomized controlled trials.