Submitted on April 25, 2008
Revised on July 21, 2008
Accepted on August 18, 2008
Hemodynamic impact of mitral prosthesis-patient mismatch on pulmonary hypertension: an in-silico study
David Tanne1, Lyes Kadem2, Regis Rieu1, and Philippe Pibarot3*
1 IRPHE
2 Concordia Univesity
3 Laval University
* To whom correspondence should be addressed. E-mail: Philippe.Pibarot{at}med.ulaval.ca.
Recent clinical studies reported that prosthesis-patient mismatch (PPM) becomes clinically relevant when the effective orifice area (EOA) indexed by the body surface area (BSA) is {less than} 1.2-1.25 cm2/m2. To examine the effect of PPM on transmitral pressure gradient, left atrial (LA) and pulmonary arterial (PA) pressures and to validate the PPM cut-off values, we used a lumped model to compute instantaneous pressures, volumes and flows into the left-sided heart, the pulmonary and systemic circulations. We simulated hemodynamic conditions at low cardiac output, at rest and at three levels of exercise. The indexed effective orifice area (iEOA) was varied from 0.44 to 1.67 cm2/m2. We normalized the mean mitral pressure gradient by the square of mean mitral flow indexed by the BSA to determine at which cut-off values of iEOA the impact of PPM becomes hemodynamically significant. In vivo data were used to validate the numerical model that shows that small values of iEOA (severe PPM) induce high PA pressure (residual PA hypertension) and contribute to its non-normalization following a valve replacement, providing a justification to the prevention of PPM. Furthermore, we emphasize the major impact of both pulmonary resistance and compliance on the PA pressure. The model suggests also that the cut-off iEOA value that should be used to define PPM at rest in the mitral position is around 1.16 cm2/m2. At higher levels of exercise, the threshold value is rather close to 1.5 cm2/m2. Severe PPM should be considered when the iEOA is < 0.94 cm2/m2 at rest.
