Discordance and Pseudo-Discordance in the Hemodynamic Assessment of Aortic Stenosis

Conflicting echocardiographic parameters of aortic stenosis (AS) severity pose a serious clinical challenge, most notably the combination of a small aortic valve area valve area (AVA) and a low mean gradient (MG). While this discordance is frequently labeled ‘low-flow low-gradient AS’, there are two additional potential causes: underestimation of MG and underestimation of AVA.

We studied 67 symptomatic patients with AS considered for transcatheter valve replacement (TAVR) to investigate prevalence and root causes of discordant echocardiographic findings by comparing Doppler data to invasive hemodynamic data and CT findings.

Thirty patients (45%) had discordant echocardiographic findings (MG²). Of those, 11 had also discordant findings by invasive measurements, compatible with low-gradient severe AS. However, in 19, catheterization data were concordant and hence discrepant to the echocardiographic findings: In 13, the MG was >40 mmHg, in 6 the AVA was >1cm². Among the 13 patients in whom the invasive MG had been underestimated, only 2 had a MG <30 mm Hg. In 6 of the 13 patients with underestimated MG, no right parasternal Doppler examination had been performed; in an additional 4, the study was technically difficult. Based on calcium score thresholds for severe AS, an echocardiographic AVA ≤1.0 cm² had a predictive value of 95% for patients with concordant findings (MG>40 mmHg), but only 80% for patients with discordant findings (MG

Conclusion: 1. The vast majority of symptomatic patients with an echocardiographic AVA ≤1.0 cm² considered for TAVR have severe AS by calcium score. 2. Discrepant echocardiographic findings in symptomatic patients with AS are more frequently the result of technical factors leading to (moderate) underestimation of gradients than due to true low-flow AS, which should not be diagnosed without a careful Doppler interrogation from the right parasternal window.