970-7 In Vivo Comparison of Simultaneous Doppler and Hemodynamic Transvalvular Pressure Gradients Across Bileaflet Mechanical Valves in the Mitral Position

Abstract

Continuous wave Doppler (CW) is routinely used clinically to measure pressure gradients across bileaflet mechanical mitral valves; however discrepancies with catheter (CATH) gradients have been recognized. Recently it has been hypothesized that inertial and viscous forces, which are partially affected by valve size and orifice geometry. may control pressure recovery and thus playa role in these discrepancies. Therefore, in this study we examined the accuracy of CW derived pressure gradients us a function of valve size and orifice position in an attempt to determine the clinical utility of this technique. In 10 sheep with chronically implanted (anatomic orientation) St. Jude mitral valves (23, 25, 27 mm), 76 hemodynamic states (3 to 14 per sheep) were studied using Millar catheters in the LA and LV. Peak gradient (PG) range = 2.0–23.0 mmHg ® mean gradient (MG) range = 1.9–18.7 mmHg. Simultaneously, a Vingmed 775 with a port for transfer of digital data was used to obtain CW velocities across the three valve orifices: central (C), LV septal (S). and LV free watll (FW). Regression analysis for the 25 mm valve, for which the largest number of studies was available (n = 40), showed CW PG and MG correlated with CATH (PG: y = 1.28x - 0.16, r = 0.89, SEE = 2.9; MG: y = 1.05x + 0.03, r = 0.88, SEE = 2.1) but with consistent overestimation. In addition, considerable CW scatter was seen in the moderate range of CATH gradients. Analysis of the 25 mm valve orifices revealed the following % overestimation: PG(S) PG(C) PG(FW) MG(S) MG(C) MG(FW) 27% 32% 19% 4% 8% 0% The 23 mm (n = 21) valves demonstrated significantly greater overestimation than either the 25 or 27 mm (n = 15) valves for both PG (p < 0.02) and MG (p < 0.05). There is good correlation of CVV derived and CATH measured pressure gradients across bileaflet mechanical mitral valves. For a given CATH gradient, the CVV derived pressure gradients vary for different valve sizes and their individual orifices. CVV overestimated CATH gradients particularly in the smallest valve tested. For all valve sizes and individual orifice CVV scatter was noted particularly in the mid range of gradients tested. Therefore, simplified Bernoulli calculations using CVV velocities from any specific valve/orifice, although useful, are limited as accurate clinical predictors of CATH gradients.