Two-dimensional echocardiography (2D echo) and Doppler were performed in a group of patients who had a high probability of having right ventricular (RV) dysplasia (left bundle branch block arrhythmias, no signs of cardiopulmonary diseases) and in a group of age-matched normals. 2D echo showed RV morphofunctional abnormalities (free wall and apical irregularities, wall motion abnormalities) in 25% of patients with suspected RV dysplasia but in none of the normals. Concordance with angiography was good (75% of cases with positive 2D echo study had a positive angiography, while only 33% of the patients with suspected RV dysplasia and negative 2D echo had a positive angiography). In patients with high probability of RV dysplasia (positive 2D echo and angiography) left ventricular filling was similar to that of normal subjects whereas RV filling was markedly rearranged, as demonstrated by the significant decrease in RV early-to-atrial peak flow velocities.