Residual congestion at discharge assessed by bioelectrical impedance and its prognostic value in acute heart failure: a multicenter, prospective registry study

Aims Residual congestion at discharge is an important risk factor for early readmission and mortality in acute heart failure (AHF); however, it is often underestimated. This study aimed to evaluate the clinical value of edema index (EI) and phase angle (PA) from bioelectrical impedance analysis (BIA) in assessing residual congestion and predicting short-term outcomes in patients with AHF. Methods A multicenter registry database from the Steady Movement with Innovating Leadership for Heart Failure between 2019 and 2023 was analyzed. EI and PA were measured using direct segmental multifrequency BIA device. The worsening heart failure events (WHF) were defined as a composite of heart failure readmission and all-cause mortality at 90- and 180-days. Receiver operating characteristic analysis determined the EI and PA cutoff values. Logistic regression and Cox proportional hazards analyses were used to assess the associations between BIA parameters and clinical outcomes. Results A total of 600 patients were included, of whom 360 (60%) were male, with a median age of 72.1 years. Within 180 days, 63 patients (11%) experienced WHFs. EI (odds ratio [OR] 1.83; 95% confidence interval [CI] 1.43–2.35 at 90 days, OR 1.76; CI 1.44–2.14 at 180 days, all p<0.01) and PA (OR 0.93; CI 0.90–0.96 at 90 days, OR 0.94; CI 0.91–0.96 at 180 days, all p<0.01) showed correlation in univariate analysis. EI≥0.4 and PA<4.5° were identified as prognostic thresholds for unfavorable outcomes, with predictive values of 75% (p<0.01, sensitivity 83%, specificity 56%), and 71% (p<0.01, sensitivity 81%, specificity 54%), respectively. Increased EI (adjusted hazards ratio [aHR] 1.71; CI 1.26–2.31 at 90 days, aHR 1.64; CI 1.30–2.07 at 180 days, all p<0.01) and decreased PA (aHR 0.91; CI 0.86–0.96 at 90 days, aHR 0.92; CI 0.89–0.97 at 180 days, all p<0.01) were independently associated with WHFs. Based on the estimated cutoffs, when EI and PA were considered together to classify the high-risk BIA group (EI≥0.4 & PA<4.5°), the risk was apparently increased (aHR 6.79; CI 1.71–26.93 at 90 days, aHR 3.43; CI 1.41–8.32 at 180 days, all p < 0.05) compared to normal BIA (EI<0.4 & PA≥4.5°) group. Conclusions The EI and PA measured at discharge independently predicted short-term WHFs in patients with AHF. The suggested thresholds for identifying patients at high-risk of residual congestion were EI≥0.4 and PA<4.5°. As a noninvasive and accessible modality, BIA holds promise as a complementary tool to established biomarkers for evaluating congestion at discharge.