On the Significance of Systolic Flow Waveform on Aortic Valve Energy Loss

Abstract

This study aims to quantitatively and qualitatively assess energy dissipation in the aortic valve as a function of systolic aortic flow waveform representing pathologies where flow time-to-peak is delayed. A bioprosthetic valve was tested in the aortic position of a left-heart simulator under physiological pressure and flow conditions. The flow loop piston pump was programmed to generate three different flow waveforms each with a different peak time annotated as early peak (EP) with a rapid acceleration, mid peak (MP) and late peak (LP) with a rapid deceleration. Energy dissipation was calculated from flow and pressure measurements while sinus vorticity dynamics were evaluated using time-resolved planar particle image velocimetry. Average pressure gradients during systole are found 30.2 ± 0.19, 30.7 ± 0.25 and 32.9 ± 0.29 mmHg and average dissipation over systole is found 0.95 ± 0.026, 1.05 ± 0.034 and 1.25 ± 0.043 W for EP, MP and LP respectively. As systole's acceleration phase is slower, sinus vortices are more likely to form, necessitating more energy exchange from shear layers inducing more viscous dissipation. EP found in healthy individuals is superior in terms of reducing energy dissipation and increasing aortic valve efficiency. In the context of possible left ventricular dysfunction and aortic stenosis, this means that delayed time-to-peak in the aortic flow waveform seen is not compensatory.

Spatiotemporal Complexity of the Aortic Sinus Vortex as a Function of Leaflet Calcification

“…Post processing was executed using adaptive median filtering. Further details of PIV measurements can be found in our previous publications [7,8,14,[27][28][29].…”

“…Talukder et al [5] demonstrated that valve closure can be achieved primarily by the adverse pressure gradient and does not necessitate a trapped sinus vortex. Given all these studies, it is now acknowledged that the aortic sinus vortex plays a role not only in the opening and closing mechanisms of the leaflets, but also has a crucial role in the context of sinus washout and overall energy efficiency of the aortic valve system [6][7][8][9][10]. Recent studies by Hatoum et al demonstrated how the evolution of the aortic sinus mechanism can correlate with aortic valve efficiency and energy dissipation [8].…”

“…Given all these studies, it is now acknowledged that the aortic sinus vortex plays a role not only in the opening and closing mechanisms of the leaflets, but also has a crucial role in the context of sinus washout and overall energy efficiency of the aortic valve system [6][7][8][9][10]. Recent studies by Hatoum et al demonstrated how the evolution of the aortic sinus mechanism can correlate with aortic valve efficiency and energy dissipation [8]. In addition, it was demonstrated that aortic sinus vortices initiation, entrapment and evolution play an important role in sinus stasis and washout [7,[11][12][13][14].…”

Sinus Hemodynamics Variation with Tilted Transcatheter Aortic Valve Deployments

“…Velocity vectors were calculated using adaptive cross-correlation algorithms. Further details of PIV measurements can be found in Hatoum et al 12, 13, 16–20 .…”

Sinus Hemodynamics in Representative Stenotic Native Bicuspid and Tricuspid Aortic Valves: An In-Vitro Study

“…Velocity vectors were calculated using adaptive cross-correlation algorithms. Further details of PIV measurements can be found in Hatoum et al [6][7][8][19][20][21][22].…”