[Measurement of tricuspid transvalvular flow by M-mode echocardiography and its application in the calculation of the A-V shunt in interatrial communication].

Previous studies have demonstrated that it is possible to measure the cardiac output by M-mode echocardiography (M-echo), using the echogram of the mitral (MV) or aortic valves. In this communication we pretend to demonstrate the possibility of calculating the right cardiac output by the echocardiographic image of the tricuspid valve (TV). We studied patients with atrial septal defects (ASD) because the anatomic and physiologic conditions allowed us to obtain a complete record of the TV. The study was done in a prospective form with 12 patients with isolated ASD, without pulmonary hypertension, cases with ostiumprimum were excluded. The measure of stroke volume of the MV and TV was made using Rasmussen's formula and mechanic planimetric measure of the diastolic opening area of both valves. For the TV area calculation it was considered that the area of the posterior valve was similar to the septal valve and the area of the last one was multiplicated by 2, in this form we obtained the value of the whole TV. For confirmation of the reliability of this method, we studied 8 healthy subjects for the comparison of the mitral and tricuspid flows. The velocity of the transvalvular flow was obtained by measuring the D-E slope. The correlation between MV and TV flows was good in healthy subjects (r = 0.957). Similar results were obtained with the areas of MV and TV in the same group (r = 0.971). In patients with ASD, the comparison between Rasmussen's method and the planimetric method showed that the value of TV increased higher than the MV values. The difference is most important between the areas. The correlation of the cardiac output calculated by the Fick method and M-echo was not significative. The defective output determined by catheterization and M-echo showed a significative correlation (r = 0.793). It is possible the quantitation of the right ventricle output by M-echo, this technic is useful because it shows the hemodynamic conditions of patients with ASD, and it is possible the measure the TV flow, and probably it will be useful in patients with other congenital heart disease with left right shunts.