Measurement of right ventricular outflow tract (RVOT) acceleration time, the time between the onset of flow and peak flow velocity. Acceleration time is usually greater than 100 ms, and values less than that (especially <80 ms) are suggestive of elevated pulmonary vascular resistance. Source: PULMONARY HYPERTENSION IN ADULTS WITH CONGENITAL HEART DISEASE, Color Atlas and Synopsis of Adult Congenital Heart Disease Citation: Daniels CJ, Zaidi AN. Color Atlas and Synopsis of Adult Congenital Heart Disease; 2016 Available at: http://accesscardiology.mhmedical.com/DownloadImage.aspx?image=/data/books/1829/danadult_ch9_f004.png&sec=127336308&BookID=1829&ChapterSecID=127336297&imagename= Accessed: October 23, 2017 Copyright © 2017 McGraw-Hill Education. All rights reserved