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CLINICAL STUDY: CARDIAC ULTRASOUND

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

Damien Garcia, Eng^*, Jean G. Dumesnil, MD, FACC, Louis-Gilles Durand, Eng, PhD^*, Lyes Kadem, Eng and Philippe Pibarot, DVM, PhD, FACC^*,*

^* Laboratoire de Génie Biomédical, Institut de Recherches Cliniques de Montréal, Montreal, Canada
Quebec Heart Institute/Laval Hospital, Laval University, Sainte-Foy, Quebec, Canada

Manuscript received May 6, 2002; revised manuscript received August 2, 2002, accepted August 19, 2002.

^* Reprint requests and correspondence: Dr. Philippe Pibarot, Quebec Heart Institute/Laval Hospital, Laval University, 2725 Chemin Sainte-Foy, Sainte-Foy, Quebec, Canada, G1V-4G5.
philippe.pibarot{at}med.ulaval.ca

OBJECTIVES: 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 (EOA_Dop) and those by a catheter (EOA_cath). We hypothesized that these discrepancies might be due to the influence of pressure recovery.

METHODS: The relationship between EOA_cath and EOA_Dop was 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 EOA_cath (range 0.3 to 2.3 cm²) and EOA_Dop (range 0.2 to 1.7 cm²), but EOA_cath systematically overestimated EOA_Dop (24 ± 17% [mean ± SD]). However, when the energy loss coefficient (ELCo) was calculated from EOA_Dop and aortic cross-sectional area (A_A) to account for pressure recovery, a similar correlation (r = 0.97) with EOA_cath was observed, but the previously noted overestimation was no longer present.

CONCLUSIONS: Discrepancies between EOA_cath and EOA_Dop are largely due to the pressure recovery phenomenon and can be reconciled by calculating ELCo from the echocardiogram. Thus, ELCo and EOA_cath are equivalent indexes representing the net energy loss due to stenosis and probably are the most appropriate for quantifying aortic stenosis severity.

Abbreviations and Acronyms   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   TPGnet   net transvalvular pressure gradient   TPGmax   maximal transvalvular pressure gradient

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