Discrepancies between catheter and Doppler estimates of valve effective orifice area can be predicted from the pressure recovery phenomenon: practical implications with regard to quantification of aortic stenosis severity☆
We sought to obtain more coherent evaluations of aortic stenosis severity.
Background
The valve effective orifice area (EOA) is routinely used to assess aortic stenosis severity. However, there are often discrepancies between measurements of EOA by Doppler echocardiography (EOADop) and those by a catheter (EOAcath). We hypothesized that these discrepancies might be due to the influence of pressure recovery.
Methods
The relationship between EOAcathand EOADopwas studied as follows: 1) in an in vitro model measuring the effects of different flow rates and aortic diameters on two fixed stenoses and seven bioprostheses; 2) in an animal model of supravalvular aortic stenosis (14 pigs); and 3) based on catheterization data from 37 patients studied by Schöbel et al.
Results
Pooling of in vitro, animal, and patient data showed a good correlation (r = 0.97) between EOAcath(range 0.3 to 2.3 cm2) and EOADop(range 0.2 to 1.7 cm2), but EOAcathsystematically overestimated EOADop(24 ± 17% [mean ± SD]). However, when the energy loss coefficient (ELCo) was calculated from EOADopand aortic cross-sectional area (AA) to account for pressure recovery, a similar correlation (r = 0.97) with EOAcathwas observed, but the previously noted overestimation was no longer present.
Conclusions
Discrepancies between EOAcathand EOADopare largely due to the pressure recovery phenomenon and can be reconciled by calculating ELCo from the echocardiogram. Thus, ELCo and EOAcathare equivalent indexes representing the net energy loss due to stenosis and probably are the most appropriate for quantifying aortic stenosis severity.
Abbreviations
AA
cross-sectional area of the aorta
EL
energy loss
ELCo
energy loss coefficient
EOA
effective orifice area
EOAcath
effective orifice area measured by catheter
EOAcath/max
effective orifice area measured by catheter with use of maximal transvalvular pressure gradient
EOADop
effective orifice area measured by Doppler echocardiography
This work was supported by the Canadian Institutes of Health Research (MA-10929), Ottawa, and the Canadian Foundation for Innovation, Ottawa, Ontario, Canada. Dr. Pibarot is the recipient of a research scholarship from the Heart and Stroke Foundation of Canada, Ottawa, Ontario, Canada.
