Doppler echocardiographic assessment of hemodynamic progression of valvular aortic stenosis over time: comparison between aortic valve resistance and valve area

Abstract

Background: Doppler-derived aortic valve resistance (AVR), i.e. the ratio between pressure gradient and flow rate, has been proposed as an alternative parameter to valve area (AVA) for assessing the hemodynamic severity of aortic stenosis (AS). There are no data on the evaluation of hemodynamic progression of AS using AVR.

Methods: Forty-five adult patients (24 women and 21 men, mean age 72 +/- 10 years) with AS were followed up for 18 months (range 6 to 45 months) with serial Doppler-derived AVR (Isaaz, JACC 1991; 18: 1661) and AVA (continuity equation). Rates of change of AVR and AVA over time were indexed for year of follow-up; furthermore, variations of these parameters during follow-up were expressed as percent change from baseline.

Results: During the follow-up period, AVA decreased from 0.74 +/- 0.28 to 0.6 +/- 0.17 cm2 (p < 0.05), with a rate of change of -0.1 +/- 0.13 cm2/year; AVR increased from 349 +/- 187 to 462 +/- 180 dyne/s/cm-5 (p < 0.05), with a rate of change of 79 +/- 69 dyne/s/cm-5/year. Variations observed in AVR, expressed as percent change from baseline, were larger than those observed in AVA (51 +/- 62% versus -16.5 +/- 15%). AVR percent change from baseline significantly correlated with AVA percent change from baseline (r = 0.83, p < 0.05). During follow-up, 6 patients showed no change in AVA: AVR was unchanged in 3 and increased in the remaining 3 patients (6, 11 and 58%, respectively), indicating a progression of AS severity that could not be appreciated from AVA alone.

Conclusions: Serial changes in AVR, as assessed by Doppler echocardiography, significantly correlate with changes in AVA. Thus, the noninvasive assessment of AVR may be utilized in the evaluation of hemodynamic progression of AS and, in conjunction with AVA, may also provide complementary information for the management of these patients.