Ultrafast power Doppler imaging for RV myocardial perfusion assessment: histopathologic correlation and in vivo comparison – a pilot study

Abstract Background Myocardial vascular remodeling is a key feature in various diseases associated with right ventricular (RV) pressure overload but its non-invasive assessment remains challenging. The new technique attenuation-compensated fractional moving blood volume (acFMBV) based on ultrafast power Doppler (UPD) was developed for myocardial blood volume quantification, linked to RV remodeling and capillary density, but not validated in vivo. Objectives To quantify RV myocardial blood volume across the cardiac cycle using UPD in rodent models, with histopathological validation, and assess its feasibility in human patients. Methods Twelve rats (sex ratio 1/1) were randomized to pulmonary artery banding (PAB) (n=6) or sham controls (n=6). After six weeks, UPD-derived acFMBV was measured in the RV lateral wall, representing myocardial blood volume. Capillary density was quantified via CD31 immunostaining, and its correlation with mid-diastolic acFMBV was evaluated. UPD was also applied in 7 healthy human volunteers and 7 age-matched patients with RV pressure overload. Results Mid-diastolic acFMBV in PAB rats was significantly lower than in controls (5.3% ± 0.9% vs. 7.8% ± 1.2%, p0.05), correlating with reduced capillary density (r=0.78, p0.01). In humans, mid-diastolic acFMBV was also lower in RV pressure overload patients compared to healthy volunteers (4.8% ±0.7% vs. 3.1% ±2.3%, respectively, p = 0.03). Conclusion In this pilot study, UPD-based acFMBV correlates with histological capillary density, supporting its potential as a reliable, non-invasive tool for quantifying RV myocardial blood volume in clinical settings. These observations will need to be confirmed in studies with larger sample sizes.