The Terminal Portion of the Pulmonary Arterial Tree in People Native to High Altitudes By JAVIER

RADIOGRAPHIC evidence of right ventricular enlargement with bulging of the main pulmonary artery13 and electroveetoreardiographic signs of right ventricular preponderance2' 4-6 are common findings in people born and living at high altitudes. Anatomically, the existence of right ventricular hypertrophy has been demonstrated both in adults7-9 and children.10 Recently, hemodynamic studies have disclosed that these people present, at rest, a mild degree of pulmonary hypertension and increased pulmonary vascular resistance."-'3 Children below 5 years of age show higher pulmonary pressure values than older children and adults.'3 Furthermore, different from what occurs in normal persons at sea level, the pulmonary pressure increases markedly during exercise.14 The small muscular branches of the pulmonary arterial tree are primarily concerned in determining pulmonary vascular resistance. Therefore, the study of their morphologic eharacteristics is of paramount importance for understanding the genesis and significance of high altitude pulmonary hypertension. This forms the subject of the present report.