With the purpose of studying the right ventricular infundibulum response to the obstruction of the pulmonary blood flow, the authors inform the results of the right ventricular volumes, and function changes before and after pulmonary intraluminal valvuloplasty performed in six adult patients with congenital stenosis of the pulmonary valve. After the valvuloplasty, all right ventricular volumes increased but only slightly, except for the end systolic volume at the right infundibulum, which decreased after valvuloplasty (for alpha = 0.10, p less than 0.10). The ejection fraction of this infundibulum increased after valvuloplasty (for alpha = 0.05 p less than 0.03), while the ejection fraction of the inflow chamber remained unaltered. In the same way decreased the work and power of the inflow tract of the right ventricle, regardless the decreased in the ventricular overload post-valvuloplasty; however, the ratio work vs. end diastolic volume of the right ventricle decreased (for alpha = 0.05, p less than 0.03). The authors discuss these results in relation with the changes produced by the obstruction, acute or chronic, of the pulmonary blood flow on the infundibular wall tension and contractility, whose structure and behavior allow to propose that the function of the infundibulum by means of contraction protects the pulmonary vasculature, against right ventricle hypertension.