Second, Brown et al1 reported that the absolute transverse shortening was larger in the PAH group compared with the control group. Although not mentioned by the authors, different studies exist that do not support these findings. An echocardiography study demonstrated a significant reduction in centerline excursions, of which transverse wall motion is the main component, in patients with acute pulmonary embolism and idiopathic PAH compared with normal subjects.6 We reported a similar observation in an MRI study, although it should be noted that septal movements were incorporated into the transverse measures in this study.4 All studies used the same four-chamber image plane, and, therefore, the choice of image plane cannot explain the difference in results. Possibly, the computational method used by Brown et al1 explains some of the difference. They computed transverse movements as the transverse area between the end-diastolic and end-systolic free wall, thereby neglecting the rigid body motion of the whole heart. Therefore, the computed area may not be solely determined by free-wall movements. We would appreciate the authors’ view regarding the difference in results.