Background and aims of the study: Previous studies have shown that the effective orifice area of an aortic prosthetic valve may be too small in relation to the patient's body surface area, resulting in abnormally high gradients. The consequences of this condition, termed prosthesis-patient mismatch, have not been fully studied. The study objective was to determine if the condition has a detrimental effect on symptomatic and hemodynamic status, morbidity and mortality of patients undergoing aortic valve replacement.

Methods: A cohort of 392 patients was prospectively followed for up to seven years after implantation of a Medtronic Intact bioprosthesis. Doppler echocardiography was performed annually in 72 patients. Based on previous studies, presence of mismatch was defined as an indexed valve area < or = 0.85 cm2/m2.

Results: Mismatch was associated with less postoperative improvement of NYHA functional class (p < 0.009) independently of other predictors, such as age and preoperative functional class, but had no significant impact on patient survival (mismatch: 75 +/- 4%, no mismatch: 79 +/- 3%; p = 0.59) and valve-related morbidity up to seven years. Cardiac index was similar in patients with and without mismatch up to three years after operation but decreased significantly thereafter only in patients with mismatch (-0.54 +/- 0.32 versus -0.17 +/- 0.49 l/min/m2; p = 0.04). Likewise, the mean transprosthetic gradient, which was higher at one year after operation in patients with mismatch (22 +/- 8 versus 15 +/- 7 mmHg), increased significantly (+6 +/- 6 versus +1 +/- 1 mmHg; p = 0.008) only in this group during follow up.

Conclusions: Patients with mismatch have less symptomatic improvement and worse hemodynamics that continue to deteriorate with time. However, medium-term prognosis (up to seven years) is relatively good. Further studies are necessary to determine the longer-term effects of mismatch on morbidity and mortality.