We would like to apologize for an error that appeared in our article published in the Journal of the American Society of Echocardiography in May 2009 (Haddad F, Zamanian R, Beraud A-S, Schnittger I, Feinstein J, Peterson T, et al. A Novel Non-Invasive Method of Estimating Pulmonary Vascular Resistance in Patients with Pulmonary Arterial Hypertension. J Am Soc Echocardiogr 2009;22:523-529). Pulmonary vascular resistance index is calculated as the ratio of transpulmonary pressure gradient divided by cardiac index. Hence, the correct units for the pulmonary vascular resistance index (PVRI) are Wood units ^∗ m ² . In the published article, the PVRI units were reported as Wood units/m ² .

We would also like to correct another typographical error that appeared in the second row of table 4. The second row should read inferior vena cava (IVC) size > 2.0 cm and collapse index > 50% (instead of collapse index < 50%.