Physiologic Differentiation of Pulmonic Stenosis with and without an Intact Ventricular Septum

Since May 1957 cardiac catheterization has been carried out in 46 patients with pulmonic stenosis and an intact ventricular septum (pulmonic stenosis) and 42 patients with pulmonic stenosis and a right-to-left shunt through a septal defect (tetralogy of Fallot). Right atrial pressures were usually higher in pulmonic stenosis. Average pulmonary arterial and left atrial mean pressures were similar in the 2 groups, as were the pulmonary blood flows. Although significant differences between right ventricular and systemic arterial systolic pressures may be demonstrated in tetralogy of Fallot, simultaneous right ventricular and left ventricular or aortic systolic pressures were always within a few mm. Hg of each other. The postectopic right ventricular systolic pressure was always at least 10 mm. Hg above its previous level in pulmonic stenosis, whereas in tetralogy of Fallot it almost never exceeded its previous level by more than 10 mm. Hg. All patients with tetralogy of Fallot had flat-topped right ventricular pressure curves, whereas 31 of 46 patients with pulmonic stenosis had triangular right ventricular pressure curves. The phonocardiogram was found to be among the most useful tools in differentiating the 2 groups. Auscultatory phenomena of severe pulmonic stenosis with a widely split second heart sound, late crescendic diamond-shaped systolic murmur, and persistence of this murmur beyond the sound of aortic closure differed strongly from tetralogy of Fallot of equal severity. At cardiac catheterization proof of the presence of a ventricular septal defect may be gained by passing the catheter through it. If this is not done, the presence of a ventricular septal defect may be strongly inferred if the right ventricular pressure curve has almost parallel sides and a flat or rounded top, if the right ventricular systolic pressure is near that in the systemic circulation, and if it does not rise after ectopic beats more than 10 mm. Hg above its previous level. For greater certainty in diagnosis indicator-dilution curves or angiocardiography should be done. The accurate preoperative diagnosis of the presence or absence of a ventricular septal defect is extremely important, for at open-heart operation it is essential not to miss the ventricular septal defect after completely relieving the obstruction to right ventricular outflow; it is just as important not to do unnecessary right ventriculotomies.