Abstract 4130072: Prognostic Impact of Renal Microcirculatory Dysfunction in Heart Failure Assessed by the Advanced Doppler technique, Superb Microvascular Imaging

Aims: The significance of cardio-renal interactions in heart failure (HF) prognosis has become increasingly evident, yet there are no established methods to assess them. To address this issue, we propose a novel approach using Superb Microvascular Imaging (SMI), an ultrasound method that that enables detailed visualization of microvascular flow, to assess renal microcirculation. Methods: We retrospectively analyzed 78 patients who underwent renal ultrasonography using SMI from October 2020 to May 2023. We measured changes over time of Vascular Index (VI), which quantifies the blood flow signal area in the region of interest on the SMI image (Figure 1). Key measurements included Maximum VI (Max.VI), Minimum VI (Min.VI), and the cyclic variation of VI, calculated as the intrarenal perfusion index (IRPI) = (Max.VI - Min.VI) / Max.VI within one cardiac cycle. The primary endpoint of this study was a composite event (CE), defined as a composite of all-cause death and unplanned hospitalization for worsening HF. Results: During a mean follow-up period of 1.6±0.8 years, 13 of 78 patients (17%) experienced a CE. Compared with patients without CE, those with CE had significantly lower Max.VI (0.28±0.15 vs 0.46±0.18, p=0.002) and Min.VI (0.10±0.12 vs 0.22±0.14, p=0.007), and IRPI was significantly higher in the event group (0.68±0.19 vs 0.55±0.17, p=0.018). In univariable Cox regression analyses, Max.VI (HR 0.35, 95%CI 0.17-0.71, p=0.004), Min.VI (HR 0.28, 95%CI 0.10-0.75, p=0.012), IRPI (HR 1.97, 95%CI 1.11-3.51, p=0.021), creatinine (Cr) (HR 1.67, 95%CI 1.26-2.21, p<0.001) and estimated right atrial pressure by echocardiography (eRAP) (HR 4.22, 95%CI 1.42-12.5, p<0.001) were significantly associated with CE. In multivariable Cox regression analyses, Min.VI remained significantly associated with CE in the model adjusted for Cr (HR 0.35, 95%CI: 0.13-0.92, p=0.033), and in the model adjusted for eRAP (HR 0.11, 95%CI: 0.11-0.82, p=0.019). ROC curve analysis showed that, although not statistically significant, the predictive power of Min.VI was superior to that of Cr and eRAP (Figure 2). Stratifying patients by a Min.VI cut-off value of 0.08, determined through ROC analysis, showed that those with Min.VI < 0.08 had a significantly poorer prognosis (log-rank p<0.001) (Figure 3). Conclusion: The use of Superb Microvascular Imaging to assess renal circulation provides new insights into the prognosis of HF and allows risk stratification beyond conventional markers.