OBJECTIVE The purpose of this study was to test the utility of measuring respiratory variation in pulmonary venous flow by transesophageal echocardiography. BACKGROUND Respiratory variation of atrioventricular and central venous flow velocities by Doppler echocardiography has been used to differentiate constrictive pericarditis from restrictive cardiomyopathy. METHODS We performed pulsed wave Doppler transesophageal echocardiography of the left or right pulmonary veins in 31 patients with diastolic dysfunction. Fourteen patients had constrictive pericarditis, and 17 had restrictive cardiomyopathy. We measured the pulmonary venous peak systolic and diastolic flow velocities and the systolic/diastolic flow ratio with transesophageal echocardiography during expiration and inspiration. The percent change in Doppler flow velocity from expiration to inspiration (%E) was calculated. RESULTS Pulmonary venous peak systolic flow in both inspiration and expiration was greater in constrictive pericarditis than in restrictive cardiomyopathy. The %E for peak systolic flow tended to be higher in constrictive pericarditis (19% vs. 10%, p = 0.09). In contrast, pulmonary venous peak diastolic flow during inspiration was lower in constrictive pericarditis than in restrictive cardiomyopathy. The %E for peak diastolic flow was larger in constrictive pericarditis (29% vs. 16%, p = 0.008). The pulmonary venous systolic/diastolic flow ratio was greater in constrictive pericarditis in both inspiration and expiration. The combination of pulmonary venous systolic/diastolic flow ratio > or = 0.65 in inspiration and a %E for peak diastolic flow > or = 40% correctly classified 86% of patients with constrictive pericarditis. CONCLUSIONS The relatively larger pulmonary venous systolic/diastolic flow ratio and greater respiratory variation in pulmonary venous systolic, and especially diastolic, flow velocities by transesophageal echocardiography can be useful signs in distinguishing constrictive pericarditis from restrictive cardiomyopathy.