FLOW DIFFUSER CHARACTERISTICS OF ST. JUDE HEART VALVE PROSTHESIS: DOPPLER AND CATHETER TRANSVALVULAR GRADIENT MEASUREMENTS

摘要

The flow diffuser characteristics of the St. Jude heart valve were investigated and compared to theoretical calculations based on the two dimensional geometry of the valve. Pressure recovery (C{sub}p) and loss (K) coefficients were calculated for varying sized prostheses in both mitral and aortic valve configurations over a range of steady flow rates. In vitro experiments demonstrated that the pressure recovery (C{sub}p=0.36±0.04) and loss (K=0.64±0.04) coefficients for flow through the central orifice were independent of the valve sizes and configurations examined. Comparison of ideal and experimentally determined pressure recovery coefficients yielded diffuser effectiveness (TV=0.62). We applied these flow diffuser characteristics to investigate the discrepancies between Doppler and catheter gradients across prosthetic St. Jude bileaflet valves. Transvalvular Doppler gradients can be reconciled with catheter measurements by multiplying the Doppler gradient by the pressure loss coefficient (K=0.64) (r=0.99, y=1.11×-0.19).