Is severe valve prosthesis-patient mismatch (VP-PM) associated with a higher mortality?

Two papers in the current issue of the journal questioned whether valve prosthesis-patient mismatch (VP-PM) [1] is associated with an increased mortality and have come to different conclusions. Howell et al. [2] have classified severe VP-PM as prosthetic aortic valve area (PHVA) <0.6 cm2/m2, which was determined at the time of valve implantation from the manufacturer's in vitro data. The survival (‘all-cause mortality’) was not significantly different at 3 and 5 years from the ‘reference group’ (PHVA ≥ 0.6 cm2/m2). Walther et al. [3] have also classified PHVA from the manufacturer's effective office area. They have classified severe VP-PM as PHVA < 0.65 cm2/m2and moderate VP-PM as PHVA 0.65–0.85 cm2/m2. In their study, moderate VP-PM was ‘independently predictive for short-term and long-term mortality’. Three recent studies have documented an increased mortality with VP-PM: Moon et al. [4] have calculated VP-PM (PHVA < 0.75 cm2/m2) on the basis ‘published normal values’ of PHV and concluded that VP-PM had a negative impact on survival for young patients, patients of average-size and for large patients with mechanical valves. In a preliminary report, Mohan et al. [5] have shown that severe VP-PM (PHVA < 0.65 cm2/m2) was associated with a poorer survival. Mohty-Echahidi et al. [6] showed that severe VP-PM (PHVA ≤ 0.60 cm2/m2) was associated with lower survival (from all-cause mortality) than those with moderate or ‘mild’ VP-PM. VP-PM was calculated from ‘prosthesis internal orifice diameter, as provided by the manufacturer’. The problem with these studies as with other similar studies is the use of the manufacturer stated orifice size, using different criteria for grading severity of VP-PM and not determining the causes of death. To be able to address correctly the issue of mortality in patients with VP-PM the following data should be obtained: PHVA should be calculated from echocardiographic/Doppler studies obtained at 6 and/or 12 months after PHV implantation [7]; Severe VP-PM should be defined as PHVA ≤ 0.6 cm2/m2 (it is not possible to measure PHVA with any degree of precision to a hundredth of a centimeter) [7]; and Determine the cause of death by a ‘blinded’ committee, or in an adjudicative manner, whether the death is due to cardiac cause related to PHV, cardiac not related to PHV or non-cardiac.