Congenital Intracardiac Fistulas

The abnormal development of the heart that occurs in the presence of congenital anomalies has not been well understood and, consequently, not adequately explained. The following excerpt from a recent standard textbook 1 illustrates the difficulties of explanation presented by the patent septum: In an uncomplicated patent interventricular septum the blood seeks its way through the patency, flowing back and forth between the two ventricles , and if the opening is small the pressure between the right and left ventricles may remain equal, giving rise to no symptoms. In the majority of cases, however, the pressure in the two chambers is unequal. Thus part of the blood is left over during the diastole, first in one side, then in the other. This in turn causes dilatation and finally hypertrophy . Usually, enlargment of the right ventricle precedes that of the left, and complications may result from the accumulation of the blood in the