Diastolic Bulging of the Interventricular Septum Toward the Left Ventricle

Diastolic bulging of the interventricular septum (IVS) toward the left ventricle was observed by real-time cross-sectional echocardiography in three patients with primary pulmonary hypertension and one patient with secondary pulmonary hypertension after closure of an atrial septal defect. M-mode echocardiography showed a characteristic abnormal pattern of septal motion in diastole and in systole. In two patients, we attempted to correlate M-mode motion to the interventricular pressure gradient. During diastole, the interventricular pressure gradient between the left and right ventricles was negative and the pressure gradient