Patient-prosthesis mismatch /PPM/ is present when the effective orifice area (EAO) of the implanted valve is too small in relation to body surface area of the patient. Haemodynamically significant PPM is defined as an EOA indexed for body surface area less than 0.85 cm2/m2.
PPM results in higher transprosthetic gradient and slower and worse left ventricular mass regression. Early mortality of aortic valve replacement is twice higher in case of haemodynamically significant PPM, and even four times higher in patients with left ventricular dysfunction.
A prosthesis with the best-possible EOA and a correct technique of implantation is required in a narrow aortic annulus in order to avoid PPM.