RVOT VTI identifies a low flow-congestion phenotype in severe VExUS grade patients
V Kozluca, G C Yilmaz, S Kilic, N B Ozbeyaz, A OngunAbstract
Background
Systemic venous congestion is a major determinant of organ dysfunction and outcomes in heart failure (HF). The Venous Excess Ultrasound Score (VExUS) grades venous congestion, with grade 3 indicating severe congestion. However, congestion severity alone does not explain variability in diuretic response. Renal perfusion depends on both venous pressure and forward flow. Reduced forward flow may impair effective arterial filling with severe congestion, contributing to diuretic resistance. Right ventricular outflow tract velocity–time integral (RVOT VTI) is a noninvasive marker of forward flow. We hypothesized that in VExUS grade 3 patients, reduced forward flow (RVOT VTI <10 cm) identifies a more severe congestion phenotype with impaired natriuresis.
Methods
This prospective observational study included 42 patients admitted with acute decompensated HF, all with VExUS grade 3 congestion on echocardiography. RVOT VTI was measured to assess forward flow, and two-hour spot urinary sodium was obtained after the first IV loop diuretic dose to evaluate natriuretic response. RVOT VTI was analyzed as a continuous variable and using a clinically relevant threshold (<10 vs ≥10 cm). Group comparisons, correlation analyses, and regression models were performed. A two-sided p value <0.05 was considered significant.
Results
Baseline demographic, renal, biochemical, and echocardiographic congestion parameters were similar between groups. Patients with RVOT VTI <10 cm showed significantly impaired natriuretic response compared with those with preserved forward flow. Two-hour spot urinary sodium was markedly lower (63.5 ± 35.4 vs 95.2 ± 28.9 mEq/L; p = 0.004) despite similar congestion severity and diuretic exposure. RVOT VTI correlated positively with urinary sodium (ρ = 0.25, p = 0.04)(Table 1). In univariable analysis, RVOT VTI <10 cm was associated with reduced sodium excretion (p = 0.004), and this association remained independent after adjustment for eGFR, EF, MELD-Na, and RAP (p = 0.015)(Table 2). ROC analysis showed moderate discrimination for impaired natriuresis (UNa <50 mEq/L) (AUC = 0.66), with an optimal threshold near 10 cm.
Discussion
Forward flow modifies the clinical impact of severe venous congestion. Venous congestion elevates renal interstitial pressure, and when low forward flow coexists, effective arterial filling and renal perfusion decline further, limiting sodium delivery and blunting natriuretic response. Clinically, VExUS grade 3 combined with low RVOT VTI may define a low flow-congestion phenotype requiring intensified decongestion. Integrating forward flow with congestion staging may improve hemodynamic phenotyping.
Conclusion
In VExUS grade 3 heart failure, reduced forward flow (RVOT VTI <10 cm) identifies a more severe congestion phenotype characterized by impaired natriuretic response. Integrating forward flow assessment with congestion staging may support personalized decongestion strategies.