Robust Quantification of Intraventricular Flow Using Ultrafast Vector Doppler Imaging in a Murine Model of Dilated Cardiomyopathy.

Accurate assessment of cardiac mechanics and hemodynamics is important for understanding cardiac dysfunction and disease progression. However, conventional echocardiographic metrics primarily reflect global mechanical performance and provide limited insight into intraventricular flow dynamics. Ultrafast vector Doppler imaging (VDI) enables contrast-agent-free quantification of intracardiac flow, but acquisition-related reproducibility is difficult to isolate clinically because physiological conditions, acoustic windows, and probe orientation may vary simultaneously. Murine imaging permits repeated acquisitions under standardized conditions, enabling controlled assessment of cycle-to-cycle and imaging-plane variability, and providing a platform for systematic evaluation of VDI in the heart. We established a standardized framework for intraventricular flow quantification using ultrafast VDI and evaluated its reproducibility in a cardiomyocyte-specific Tafazzin knockout (Taz-cKO) murine model of dilated cardiomyopathy (DCM). Nine male mice (n = 3 Taz-cKO and n = 6 controls), aged 12-13 months, were studied. Cycle-to-cycle variability (beat-to-beat variation) averaged ~17.5%, whereas between-acquisition variability was higher (~25.5%), reflecting differences in imaging-plane orientation. Despite this variability, VDI-derived parameters differentiated control and DCM mice, with reduced kinetic energy and vector concentration, increased flow angle difference, and reduced vorticity magnitude during systole. Correlations with conventional echocardiographic indices ranged from weak to strong and varied by parameter, region, and cardiac phase, reflecting heterogeneous associations across metrics. These findings indicate that VDI-derived parameters capture complementary aspects of intraventricular flow not fully reflected by conventional measures of cardiac function. Overall, these results establish the reproducibility and physiological relevance of ultrafast VDI and support its potential for longitudinal and translational studies of cardiac flow dynamics.