A turbulence in-vitro assessment of ON-X and St. Jude Medical prostheses

Abstract

Objective:

The objective of this study is to investigate and compare the hemodynamic and turbulence characteristics upon implantation of St. Jude Medical (SJM) and ON-X bileaflet mechanical valves (BMHV). Both valves are considered highly successful BMHVs characterized by good clinical outcomes despite their numerous design differences. While thromboembolism remains the main disadvantage of BMHVs, ON-X has been shown to need less anti-coagulation therapy.

Methods:

Hemodynamic assessment of a 23mm ON-X bileaflet mechanical valve and a 23mm bileaflet St. Jude Mechanical valve (SJM) implanted in an aortic root was performed under pulsatile physiological conditions. Time-resolved and phase-locked Particle-Image-Velocimetry images and high-speed imaging data were acquired. Pressure gradients (PG), effective orifice areas (EOA), dimensionless area index (AI), leaflet position tracking, velocity and Principal Reynolds shear stress (RSS) were calculated.

Results:

(a) PG across ON-X was 4.15±0.099mmHg versus 4.75±0.048mmHg for SJM(p<0.001). EOA across ON-X was 2.61±0.045cm ² versus 2.36±0.022cm ² for SJM(p<0.001); (b) AI was higher with SJM (0.87±0.008) than with ON-X (0.73±0.013)(p<0.001); (c)ON-X showed a fluctuating leaflet behavior during systole while SJM leaflets were stable; (d) at peak systole, the maximal velocity with ON-X was 1.86m/s versus 2.33m/s with SJM; (d) RSS was higher with ON-X compared with SJM at peak systole (95 versus 72Pa); (e) Higher velocity fluctuations was noted with ON-X.

Conclusions:

This study shows that despite the design differences that characterize ON-X, the hemodynamic and turbulence parameters were not necessarily improved compared with SJM.