SPECIAL PATHOLOGY OF CONGENITAL HEART ANOMALIES 1. The Defects of the Cardiac Septa (a) Defects of the Interventricular Septum A defective septum, permitting communications between the two ventricles, as well as a foramen ovale which remains open, is a very fre quent congenital heart affection. It may occur as an isolated malfor mation, but is more often combined with stenosis of the ostia, especially with pulmonary stenosis.
Rauchfuss brought fonvard the idea, formerly generally believed but denied by Rokitansky-, that septum defects are primarily due to arrested development of the membranous portion of the septum. The openings may be found either in the posterior septum or the anterior part of the anterior septum, which is formed before the membranous portion; or, finally, in the posterior part of the anterior septum, which is in place before the septum membranaceum. The openings may be so placed that they form an oblique canal in the cardiac septum or they may lead from one ventricle obliquely into the opposite auricle, or may put all four cardiac cavities into communication.
Endocarditis is very often associated with defects of the ventricles in extra-uterine life, about these apertures as well as on the valvular apparatus, with which the general symptoms of poly-arthritis may be found. Anatomically the differentiation as to whether the changes at the ostium (affecting the mitral and tricuspid valves) occurred congeni tally or only later is then impossible.
Only rarely is the interventricular septum totally absent (cor uniloculare). Iffore frequently disturbances of development or the for mation of perforations are found; sometimes the septum is reduced to a single membranous fold or a short projection, rising from the apex of the heart. Finally, there are also cases in which the septum has appar ently- developed completely, but S11011.6 perforations in one or more places.
Symptoms and IS79 Roger described a symptom complex in which a systolic murmur with its point of maximum inten sity in the centre of the cardiac region (third intercostal space to the left) played the chief part, and he considered this murmur due to the presence of a defect formed in the interventricular septum. This mur mur is harsh, decidedly high in pitch, heard over the entire anterior surface of the chest and also over the back, without being accompanied by a palpable thrill.
According to Roger the children affected suffer neitber from dysp ncea, cyanosis, palpitation or especial acceleration of the pulse. The cause of this so-called Roger's disease is very frequently perforation of the interventricular septum. But many children with rnitral insuffi ciency show the same symptoms, which makes the differential diagnosis between this and defective septum very difficult.
Defects of the interventricular septum may run their course with out producing heart murmurs. The size of the defect has no effect on the absence or presence of murmurs. Small perforations may occur with murmurs and large defects without, or vice versa. The murmurs, in defective septum, arise as the result of the blood whirling about when both blood currents meet at the communicating opening in the septum, under the pressure of the contractions of the ventricles with each systole. The following conditions are necessary for the appear ance of murmurs: 1. Difference in pressure between both ventricles.
2. That the perforation remain open during contraction of the ventricles.
Small and medium-sized perforations within the muscular septum can be closed by the contraction of the septum iu systole. Condition 2 is wanting. With complete defect of the interventricular septum mur murs may be absent, because condition 1 is not fulfilled.
Incomplete closure of the interventricular septum is often com bined with other cardiac anomalies, by which the symptom-complex established by Roger may be greatly toodified.
Accentuation of the second sound at the pulmonary, area is im portant, a result of overloading the right side of the heart, to which blood is forced through the defective septum by the left ventricle, where the pressure is greater. With defect of the membranous (upper) portion of the septum, this accentuation is most distinctly heard. Murmurs are never absent in this form of defect, so that we may correctly say, if septum defects produce murmurs, accentuation of the second sound at the pulmonary area is also present. The latter symptom almost always prevents mistaking the murmur due to septum defect for that of pul monary stenosis.