Phase angle as a marker of frailty and prognosis in heart failure: Evidence from a prospective cohort study

BACKGROUND: Although frailty often coexists with heart failure (HF) and can have a significant impact on prognosis, its assessment in clinical practice is challenging. Therefore, it is pertinent to study new objective methods that can help identify frailty. OBJECTIVE: To evaluate the diagnostic and prognostic implications of phase angle (PhA) as a marker of frailty and prognosis in HF. METHODS: Prospective cohort study, with a sample composed of adults HF outpatients. Frailty was assessed using the Fried Frailty Phenotype. To obtain PhA, bioelectrical impedance analysis (Tetrapolar Biodynamics©, model 450) was used, according to the standard protocol. The prognosis (all-cause and cardiovascular (CV) mortality, hospitalization for all causes, CV and HF, and composite endpoint (CV mortality or HF hospitalization)) was also assessed. RESULTS: A total of 340 individuals were included, the majority of whom were male (67.6%), with a mean age of 60.39 ± 12.69 years, with a mean left ventricular ejection fraction of 33.79 ± 12.49. The PhA demonstrated accuracy in identifying frailty (AUC = 0.714 (0.647-0.781) p = 0.001). From the coordinates of the ROC curve, the cutoff point of 5.8° was identified, which demonstrated an independent association with frailty (Prevalence Ratio = 1.84, p = 0.001), hospitalization for HF (Hazard Ratio (HR) = 2.68, p = 0.001 and composite endpoint (HR = 2.18, p = 0.005). When analyzed continuously, PhA was associated with all outcomes, with risk decreasing for 1° increase (ranging from 22.8 to 45.2%). CONCLUSION: PhA demonstrated accuracy in identifying frailty and predicted prognosis in individuals with HF. Thus, the assessment of PhA in this population may represent a useful complementary marker in the identification of frailty and assessment of prognosis in clinical practice.