Reverse area and gradient mismatch: The discordance of a large valve area and high gradients

In previous chapters, we have defined Area gradient match or concordance as present when criteria for AS severity is met by both gradient (ΔP) and area variables. Clinical decision making in these cases is rather straightforward and referral for aortic valve replacement, in the appropriate clinical circumstance, is the rule. Area gradient mismatch was discussed in detail in the previous chapter and refers to the situations where AS is severe by area but not by gradient criteria. Less commonly, and conversely, an elevated gradient may be present across the aortic valve (AV) in the absence of severe decrease in aortic valve area (AVA); and this has been referred to as reverse area gradient mismatch or discordance. This later form of area/gradient severity discordance has not received as much emphasis in the literature as the former and yet maybe present in both native and prosthetic valves (AV_prosthesis). In these patients, Doppler-derived gradients and areas may not correspond to those obtained invasively, hence creating a Doppler catheter mismatch which may add further challenges in the appropriate determination of the AS severity. Errors of measurements and assumption, alterations in trans aortic valve flow (Q) and pressure recovery (P_rec), and paravalvular obstructions may account for a significant portion of this mismatch phenomenon. P_rec may also account for the discrepancy between Doppler- and catheter-derived estimations of AS severity.