Prosthesis-patient mismatch following aortic and mitral valves replacement - A comprehensive review

Prothesis-patient mismatch (PPM) occurs when there is a mismatch between the effective orifice area (EOA) of the prosthetic valve and the required cardiac output to meet the need of the patient's body surface area (BSA). The clinical threshold for PPM occurs when the indexed effective orifice area (iEOA) is ≤0.65 cm²/m² for the aortic valve prosthesis, and ≤ 1.20 cm²/m² for the mitral valve prosthesis. The wide variation of reported incidence of PPM is most likely attributed to the variation in the methods of calculating iEOA [(for e.g., using continuity equation across the prosthesis versus using projected EOA (generated by the industry)]. Newer generation mechanical valves have shown less PPM than older generation, and stentless bioprosthesis have less PPM than stented prosthesis. Long-term clinical outcome of PPM is associated with adverse cardiovascular events especially in the presence of pre-existing left ventricle dysfunction or with concomitant procedure such as coronary artery bypass graft surgery. Strategies to mitigate the risk of PPM such as aortic root replacement in patients with the small aortic annulus should be utilized. Accurate assessment of the patient's annular size and indexing the effective orifice area (EOA) of the prosthesis to patient's BSA at the time of prosthesis implantation are important steps to preventing future PPM.