The distinction between right ventricular (RV) dysfunction due to an acute etiology (pulmonary embolism [PE]) or chronic afterload (pulmonary arterial hypertension [PAH]) has important therapeutic implications. The aim of this study was to test the hypothesis that RV remodeling would alter RV free wall strain (RVFWS) and differentiate chronic from acute RV afterload.In this retrospective study, patients with PE (n = 45) who underwent echocardiography within 48 hours of computed tomographic pulmonary angiography were matched 1:1 for age, gender, and pulmonary artery systolic pressure with patients with PAH (n = 45) and a larger unmatched PAH control group (n = 116). RV function was evaluated with end-diastolic area, fractional area change (FAC), and RVFWS by two-dimensional speckle-tracking. The ability of RVFWS to distinguish acute from chronic RV dysfunction was assessed using receiver operating characteristic curves, and its incremental value was sought with stepwise models.RV end-diastolic area, FAC, and RVFWS were significantly impaired in patients with PE (P < .001), with no significant differences in other clinical variables. In matched patients, receiver operating characteristic curve analysis revealed that RVFWS had significantly better discriminative power than the McConnell sign (P = .02), with a cutoff of -17.9%, sensitivity of 87.5%, specificity of 62.5%, and an area under the curve of 0.76. Sequential logistic regression demonstrated an incremental and independent benefit of using RVFWS to predict acute PE versus chronic PAH (P = .01). Observer concordance was superior for RVFWS compared with FAC (P < .01).RVFWS is more predictive than RV end-diastolic area and less variable than FAC in distinguishing acute from chronic RV pressure overload. RVFWS adds incremental and independent information to standard measures of RV function in assessing the acuity of pulmonary hypertension.