Background Noninvasive, physiology-based methods to monitor systemic venous congestion and guide volume management early after durable LVAD implantation are lacking. We investigated whether changes in portal, hepatic, and renal vein Doppler flow patterns correlate with net fluid balance and whether these changes are associated with renal function and right ventricular (RV) performance in this setting. Methods In this prospective, proof-of-concept observational study at a national referral center for mechanical circulatory support, we enrolled 20 adult patients undergoing durable LVAD implantation between June 2024 and May 2025. Each patient underwent splanchnic venous Doppler ultrasound (hepatic, portal, and renal veins) and focused echocardiography at two time points: early after ICU admission (T0) and within 7 days (T1), post-implantation. Clinical, biochemical, and device parameters were recorded at each time point. Doppler findings were available to treating physicians and could inform real-time decisions; however, no predefined Doppler-guided protocol was applied. Results Patients experienced a significant negative fluid balance (median=-6034 mL; IQR:8145 to 3476), which was accompanied by consistent improvement in venous Doppler profiles and a significant reduction in VExUS score (p < 0.001). Changes in portal and renal vein Doppler patterns correlated with net fluid balance (rho=0.45, p=0.046 and rho=0.68, p=0.001, respectively). A trend was also observed between VExUS change and fluid balance (rho=0.45, p=0.053). Renal function improved significantly, with an increase in eGFR (p=0.033), and right ventricular function showed parallel recovery: RV systolic velocity (S) increased (p=0.001), RV dilation regressed (p=0.008), and tricuspid regurgitation grade decreased (p=0.001). Conclusions Point-of-care Doppler assessment of splanchnic venous flow is feasible early after LVAD implantation and reflects dynamic changes in fluid balance, renal function, and RV performance. These findings suggest that venous Doppler ultrasound may provide a physiologic, bedside method to guide decongestive therapy in this complex population, warranting validation in larger, protocol-driven studies.

The authors have declared no competing interest.

Not applicable. This was a prospective observational study without randomization of participant or any interventional component, and therefore registration in a clinical trial registry was not required. The study protocol was approved by the Institutional Review Board of the Onassis Cardiac Surgery Center

This work received no funding

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The study was approved by the Institutional Review Board of the Onassis Cardiac Surgery Center (Approval No. 809/06.06.2024), and all participants or their legal surrogates provided written informed consent in accordance with the Declaration of Helsinki.

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The data that support the findings of this study are available from the corresponding author upon reasonable request.