Underestimation of Aortic Stenosis Severity by Doppler Mean Gradient during Atrial Fibrillation: Insights from Aortic Valve Weight

Abstract

Doppler mean gradient (MG) can underestimate aortic stenosis (AS) severity when obtained during atrial fibrillation (AF) compared with sinus rhythm (SR). Aortic valve weight (AVW) is a flow-independent measure of AS severity. The objective of this study was to determine whether AVW or AVW/MG ratio was increased in AF versus SR in patients with AS. Excised native aortic valves from 495 consecutive patients (median age, 77years; interquartile range [IQR], 71-82years; 40% women), with left ventricular ejection fractions ≥50% who underwent surgical aortic valve replacement for native valve severe AS (aortic valve area ≤ 1cm2 or indexed aortic valve area ≤ 0.6cm2/m2) were weighed. Excised AVW/MG ratios were compared in AF versus SR in patients with high-gradient AS (aortic peak velocity ≥ 4m/sec or MG≥40mm Hg) and low-gradient AS (aortic peak velocity < 4m/sec and MG<40mm Hg) in sex-specific analyses. AF was present in 51 patients (10%; 11 of 51 [22%] had low-gradient AS) and SR in 444 (90%; 23 of 444 [5%] had low-gradient AS). There was no difference in sex distribution between AF and SR. Aortic valve area was not different, but forward stroke volume index and transaortic valve flow rate were lower in AF (P≤.002 for all); MG was lower in AF versus SR (median, 46mm Hg [IQR, 37-50mm Hg] vs 50mm Hg [IQR, 44-61mm Hg]; P<.0001). Overall AVW was not different (median, 2,290mg [IQR, 1,830-3,063mg] vs 2,140mg [IQR, 1,530-2,958mg]; P=.31), but overall AVW/MG ratio was higher in AF (median, 55 [IQR, 41-67] vs 42 [IQR, 30-55]; P=.001). In sex- and MG-specific analyses, the AVW/MG ratio was higher in AF compared with SR in men with high-gradient AS (median, 58 [IQR, 41-75] vs 51 [IQR, 39-61]; P=.03), but the differences were not statistically significant between AF and SR in other groups. AVW was discordant to Doppler MG in AF compared with SR in men with high-gradient AS. Additional studies of the relationship of MG to other measures of AS severity, such as leaflet fibrosis, are needed.