Aortic Acceleration Time and the Intraoperative Assessment of Aortic Stenosis

Abstract

Aortic acceleration time (AAT) and the ratio of AAT to ejection time (AAT/ET) are relatively new echocardiographic measures of the severity of aortic stenosis (AS). This study investigated the utility of transesophageal echocardiography (TEE) measurements of AAT and AAT/ET to predict the severity of AS under intraoperative conditions. Retrospective diagnostic accuracy study. St. Vincent's Hospital, Melbourne, Australia, from July 2007 to February 2017. The study comprised 199 patients who underwent aortic valve replacement (AVR) and whose aortic valves were evaluated with spectral Doppler analysis in both preoperative transthoracic echocardiography (TTE) and intraoperative TEE studies fewer than three months apart. Exclusion criteria included AVR for only aortic regurgitation, AVR of prosthetic aortic valves, and known left ventricular outflow tract obstruction. Standard echocardiography assessment of AS and the AAT and AAT/ET measurements was performed using preoperative TTE and intraoperative TEE. The intraoperative AAT and AAT/ET were increased significantly in patients with both high- and low-gradient severe AS compared with patients without severe AS (p < 0.01). Comparing preoperative TTE and intraoperative TEE measurements showed that the AAT was significantly prolonged during general anesthesia (mean difference 9.67 msec [95% confidence interval -13.54 to -5.81]), whereas the AAT/ET was preserved (mean difference -0.0018 [95% confidence interval -0.013 to 0.0091]). An intraoperative TEE cutoff of 109 msec for AAT and 0.35 for AAT/ET had a 74% and 67% sensitivity and 72% and 78% specificity, respectively, to differentiate severe from non-severe AS. The AAT and AAT/ET may be useful adjuncts for the intraoperative measurement of AS. The agreement between intraoperative TEE and preoperative TTE was better with AAT/ET compared with AAT alone.