Measurement of turbulent kinetic energy with colour Doppler echocardiography and particle tracing velocimetry in an ex-vivo aortic stenosis model.

Introduction: Grading of aortic stenosis (AS) is paramount to determine the ideal timing for aortic valve replacement. However, echocardiographic assessment of AS is challenging and subject to inaccuracy. Increased turbulent kinetic energy (TKE) in the aorta, created by a restricted opening stenotic aortic valve, could serve as a new marker for assessing AS severity. However, in this contest, TKE evaluated with ultrasound colour Doppler have not yet been clinically validated. Methods and results: Porcine aortic valves were tested ex-vivo in a left heart mock loop under various flowrates (1, 2.5, and 4 L/min) and three stiffness grades (SGa, SGb, SGc as native, stiffer, and stiffest stiffness grade, respectively). Reference TKE values were obtained using backlight particle tracking velocimetry. In parallel, TKE was estimated from ultrasound colour Doppler measurements by computing the local spatial fluctuations of blood flow velocities. Transvalvular pressure gradients were evaluated both with continuous wave Doppler and pressure sensors (PGaolv). At 4 L/min, pressure gradients with continuous wave Doppler for SGc reached severe AS levels (41 mmHg ± 14). Both TKE measurement methods, adjusted for flow rates, increased significantly across all stiffness grades and distinguished between severe (SGc) and non-severe (SGa and SGb) AS. Conclusion: In this ex-vivo AS model, both TKE measurement methods successfully differentiated severe from non-severe AS. These findings underscore the potential importance of ultrasound colour Doppler echocardiography in estimating energy loss through turbulence, paving the way for the development of a new diagnostic tool for grading AS severity.