987-102 Proximal Flow Convergence Calculation of Forward Flow and Valve Area of Normal Mitral Prostheses: An Intraoperative Validation

Abstract

We have previously shown in vitro that the proximal flow convergence method (FC) can be used to calculate flow through larger orifices such as normal prosthetic heart valves. To validate FC clinically, we performed intraoperative transesophageal echocardiography on 22 patients (mean age 63 ± 8 yrs, 64% female) undergoing mitral valve replacement with St Jude valve (n = 17) or Carpentier-Edwards valve (n = 5). For St Jude prostheses, peak velocities and velocity integrals through the center (V c and TVI c , respectively) and side (V s and TVI s ) orifices were interrogated separately with CW Doppler. As our in vitro model suggested about 80% of flow occurred through the side orifices, the corrected peak Velocity (V o ) is given by V o = 0.8V s + 0.2V c and the corrected velocity integral (TVI o ) by TVI o = 0.8TVI s + 0.2 TVI c . The flow rate (Q) was calculated by Q = 2 π r 2 V a where Va is the aliasing velocity. Q was multiplied by V o /(V o -V a ), a previously validated factor, to account for flattening of isotachs near the prosthetic orifice. Cardiac output (CO) calculated by (Q c * TVIo/V o ) * HR showed good correlation with thermodilution CO (Range 3.3–8.1 I/min, y = 0.87x + 0.67, r = 0.9, p < 0.001, ΔCO = -0.02 ± 0.5 I/min). Effective prosthetic orifice area (EOA) of St Jude valves, given by Q c /V o , correlated well with geometric orifice area (GOA) from the manufacturers (r = 0.7, p = 0.002, y = 1.42x + 1.47). However, calculated EOA is significantly smaller than the GOA (ΔMVA = -2.23 ± 0.49 cm 2 , p < 0.01) The proximal flow convergence method can give reliable in vivo estimates of 1) forward flow through normal mitral prostheses and 2) EOA of St Jude valves. The EOA of St Jude valve in vivo is significantly smaller than its GOA.