Book - Congenital Cardiac Disease 7
Embryology - 26 Apr 2024    Expand to Translate
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Abbott ME. Congenital Cardiac Disease (1915) Osler & Mccrae's Modern Medicine 6, 2nd Edition.
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- 1915 Congenital Cardiac: Congenital Cardiac Disease | Heart Development | Literature | Etiology | Cyanosis | Classification | Pericardium | Heart Displacement | Whole Heart | Anomalous Septa | Interauricular Septum | Interventricular Septum | Absence of Cardiac Septa | Aortic Septum | Pulmonary Stenosis and Atresia | Pulmonary Artery Dilatation | Aortic Stenosis or Atresia | Primary Patency and Ductus Arteriosus | Aorta Coarctation | Aorta Hypoplasia | Diagnosis Prognosis and Treatment | Figures | Embryology History | Historic Disclaimer
Defects of the Interventricular Septum
The interventricular septum may be completely absent (cor biatriatrum triloculare), or it may be rudimentary, represented by a falciform process growing up from the lower and anterior wall of the ventricle, or localized defects may occur. These usually lie at its base, and are relatively common in association with other anomalies, but are not frequent alone. Defects elsewhere than at the base, whether alone or in combination, are among the rarest of cardiac anomalies.
1 Trans. Path. Soc, London, 1881, viii, 142.
2 Zeit.f. klin. Med., 1907, Ixii, 374. 3 Archiv. gen. de. med., 1880.
- XIII Verh. Deut. Path. Gesell, 1909, p. 215.
Defects at the Base
The cases of congenital cardiac disease here studied have been drawn only from reliable sources, and all have postmortem reports attached, which should make them a fair index of relative frequency. It is therefore of interest to note that among them, while defects elsewhere in the septum are exceedingly rare, "pure" defects at the base are commoner than is usually supposed, and, in combination with other defects they rank as the most frequent cardiac anomaly.
Among the 631 cases, a defect at the base occurred 177 times, elsewhere than at the base, 12 times, making 189 cases, or 30 per cent. Of
the 177 defects at the base, 34 were classed as the primary defect and
143 complicated other conditions. Of the 34 "primary" defects at the
base, 8 were combined with rechtslage of the aorta, and in 1 of these
there was also pulmonary hypoplasia; in another there was pulmonary
hypoplasia without rechtslage; in 3 there was a patent ductus arteriosus,
leaving 22 "pure" defects at the base unassociated with rechtslage or
other anomaly except (in 5 cases) bicuspid or defective aortic or pulmonary valves
Of the 143 defects at the base complicating other anomalies, 75 were
in cases of pulmonary stenosis or atresia, in 53 of which there was also
rechtslage of the aorta. Of the remainder, 26 were in transposition of the
great trunks, 3 in other defects complicated by rechtslage, and 13 in persistent truncus arteriosus. That is to say, in 42 other cases the defect
was associated with an irregularity of development of the great trunks.
In the remaining 26 of these 143 cases, the septal defect was associated
with tricuspid atresia in 9 cases, with mitral atresia in 1, with aortic
stenosis or dextrocardia in 2, and with partial defect of the aortic septum
in two.
Pathogenesis
The combination of a defect of the interventricular septum vvith pulmonary stenosis and rechtslage of the aorta constitutes one of the commonest forms of congenital cardiac disease. So frequent is the combination that a causal connection between the three conditions has been sought, and rival theories as to which is the primary lesion have been suggested.
Much light was thrown upon this subject by Rokitansky, who concluded that non-inflammatory pulmonary stenosis, displacement to
the right of the aorta, transposition of the great arterial trunks, and
defects at the base Jf the interventricular septum were alike dependent
upon a common cause, a deviation of the aortic, so that it failed to unite
with the interventricular septum. He divided the latter into a part
anterior, and one posterior to the undefended space, and classified defects
at the base according as they lay in the anterior part of the anterior
septum, in the posterior part of the anterior septum, or in the posterior
septum. He pointed out that their usual situation was in the "posterior
part of the anterior septum," that is, just anterior to the pars membranacea, in which case he believed they were practically invariably
associated with a malposition of the arterial trunks. Keith has suggested
that in the large number of cases in which a septal defect is associated
with stenosis of the conus of the right ventricle the defect is a direct result of the inadequate expansion of the bulbus cordis to form the infundibuhim of the right ventricle.
Fig. 28 Defect of the interventricular septum at undefended space. Heart of infant. No other anomaly. (From a specimen in the McGill Pathological Museum.)
Later advances in embryological knowledge show that the aortic septum is prolonged downward to assist in closing the interventricular septum at the undefended space, instead of the interventricular septum growing upward to form part of the aortic wall, as Rokitansky supposed. Moreover, independent defects of the interventricular septum in this situation, unassociated with any alterations in the relations of the great arterial trunks, and evidently not of inflammatory origin, may and do occur. This is so in the specimen seen in Fig. 28, and in cases reported by Orth,^ Arnold, Preisz,^ and Hart.^
Such conditions cannot be explained on Rokitansky's theory as due to deviation of the septum, or, a deficient expansion of the infundibuhim, but
are due, as Keith himself points
out, to a primary arrest of growth
of unknown origin. In Hart's case
an interesting associated anomaly,
which may have had some bearing
on the defect, was an anomalous cord
which extended from the lower border
of the conus of the right ventricle
through the septal opening, to the
anterior segment of the mitral valve.
Pathology
The commonest situation for the defect is directly beneath the aortic cusps and just anterior to the undefended space (Rokitansky's posterior part of the anterior septum) (Fig. 28). Here it lies with the fleshy muscular septum before it and the thin pars membranacea behind, and opens in the right heart beneath the septal cusp of the tricuspid, sometimes perforating this or bulging the (adherent) tricuspid leaflet before it, or opening into the right auricle directly above the base of the tricuspid, thus establishing a communication between this cavity and the two ventricles. IMore rarely the defect is placed farther forward in the septum in its anterior fleshy part, just behind the front wall of the heart, and is separated behind from the undefended space by a muscular column, opening into the conus of the right ventricle below the pulmonary valves. (Rokitansky's anterior part of the anterior septum). Examples are the cases by Coupland^ and Rolleston.^ Keith points out that in these cases, the defect is evidently in the musculature of the interbulbar septum, i. e., it is in that part of the interventricular septum which in the embryo formed the proximal part of the bulbus cordis before its division into the conus of the pulmonary artery and the vestibule of the aorta.
Defect of the interventricular septum at undefended space. Heart of infant. No other anomaly. (From a specimen in the McGill Pathological Museum.)
1 Virchoivs Archiv, 1880, Bd. 82, 529. 3 Virchows Archiv, 1905, Bd. 181, p. 7.3.
- Trans. Path. Soc. London, 1879, xxx, 226.
= lUd., 1891, xlii, 65.
2 Ziegler's Beitrage, 1890, Bd. 7, 245.
^j66 diseases of the circulatory system
The defect varies in form and size from a pinhead perforation with tendinous edges, a round or oval hole admitting a goose-quill, knitting needle, index finger, etc., to a large triangular, semilunar, or crescentic space with thick-walled lower muscular border. Aneurismal pouching of the pars membranacea into the right ventricle may occur, with multiple sacculations perforated at their apices at one or more points (vide infra).
Quite frequently the margins of the defect with the adjacent valves are the seat of an acute inflammatory process which apparently originates at this point, because, as the seat of greatest strain,' it affords a site of lowered resistance. Such a case is reported by Gordon.^ In a boy aged five years who died of malignant endocarditis, a marked precordial thrill, and loud, harsh systolic murmur over the whole chest, with maximum intensity at the third and fourth left cartilages, indicated the septal defect. The autopsy showed a congenital opening, admitting a lead pencil, between the ventricles. The pulmonary valves and adjacent wall of the right ventricle were the seat of a number of large grayishgreen vegetations which extended below the level of the interventricular opening.
Moschcowitz^ related a very similar finding in a woman of twenty-nine years, who had had cardiac symptoms, palpitation, dyspnoea and occasional oedema of the legs since her fifteenth year, with exacerbation during the last four months, and symptoms of acute infection with chills and septic fever for one week. The blood cultures on one occasion showed Streptococcus viridans. At the autopsy both ventricles were hypertrophied, and the right also dilated, and there was a defect in the membranous septum admitting a lead-pencil. The pulmonary valves were replaced by large gray pedunculated vegetations, which extended up the wall of the pulmonary artery to its bifurcation, and had led to multiple emboli in either lung. The prolonged history of cardiac symptoms without adequate cause suggested a congenital lesion upon which the malignant endocarditis had been engrafted.
Dr. W. Thalhimer has sent me photographs of a heart from a cyanotic boy of nine years, with a huge septal defect and pulmonary stenosis in which a vegetative process had developed along the line of closure of the mitral and tricuspid valves. As there was no clinical history of an infective process, no Aschoff bodies in the myocardium, and no evidences of bacteria in the vegetations on microscopic examination, he is inclined to explain the vegetations on the ground of mechanical strain by the unnatural whirls in the blood stream, which have caused microscopic injuries of the valves and have thus given rise to an aseptic thrombosis. From a statistical study of the literature one is led to conclude that, at least in a large proportion of cases, the infective nature of the inflammatory process, so common in the neighborhood of cardiac defects, has been demonstrated.
1 Brit. Med. Journ., 1897, ii, 1174. ^ pj-^c. New York Path. Soc, 1914, xiv, 18.
In a case reported by Hebb[1] of a girl, aged eighteen years, whose heart showed a funnel-shaped defect at the base of the septum admitting a goose-quill, there were large vegetations bn the aortic, mitral, and pulmonary valves, and a 'patch of vegetations ivas also situated on the wall of the right ventricle opposite the defect. This observation, which is repeated in several other cases, as well as the frequent localization of the vegetations in the right ventricle affords an interesting proof of the fact that under normal conditions the current of blood flows from the left ventricle to the right through the defect. It is natural to suppose that this would be so, for the pressure in the systemic circulation is normally higher than it is in the pulmonary. Further anatomical confirmation of this direction of the stream is afforded by the oblique direction and funnelshape, with its larger end toward the left ventricle which the opening often assumes, and also by the not infrequent occurrence of patches of fibrosis on the opposite wall of the right ventricle.
Septal defects may exist without producing any change in the heart chambers, but they lead, still more frequently than do defects of the interauricular septum, to hypertrophy and dilatation of both ventricles. Where the defect is combined with rechtslage of the aorta, marked hypertrophy of the right ventricle is a constant feature. The pulmonary artery may be markedly dilated, as in 9 cases of the 34 "primary" defects at the base.
The distribution of the auriculoventricular junctional bundle in septal defects is of much interest, and has been investigated by Keith, Monckeberg, Morison,[2] and others. As is well known this bundle emerges from the auriculoventricular node close to the interauricular septum behind the medial cusp of the tricuspid valve, and divides into two branches, the left of which pierces the interventricular septum just in front of the pars membranacea, and passes downward superficially beneath the endocardium of the septum to be distributed to the papillary muscles and columnee carnese of this chamber, while the right branch runs, more deeply imbedded in the musculature of the right side of the septum, to the apex of the right ventricle. In most of the cases of septal defect examined there was surprisingly little change in this normal arrangement, the fibres streaming over the free border of the septum that formed the base of the defect toward the apices of their respective ventricles. In Morison's case the left branch was abortive. Keith described an abnormal band of "subaortic musculature," which may develop in the pars membranacea and overlie the bundle as it courses down the surface of the septum in the left ventricle, and in one of Monckeberg's cases of septal defect the bundle lay deeply in the musculature of the left septum instead of sub-endocardially as normally occurs. Recent investigations by Flack and Mall have shown that the interventricular septum is formed, not by a process growing upward from below, as Rokitansky supposed, but by a hollowing out of the spongy musculature of the embryonic ventricle to form the right and left chambers; the tip of the inferior septum, therefore, represents the wall of the lumen of the original cardiac tube, and this may account for the persistence of the bundle at this point in septal defects.
Symptoms and Physical Signs of Septal Defects
These may be absent and the defect discovered at autopsy. When cyanosis is present it may be slight or transient, appearing only on exertion, or terminal at the end of a long life, or, more rarely, and usually in those cases associated with rechtslage of the aorta, it may be well marked. Among the 34 "primary" defects at the base there was an entire absence of cyanosis in 17; it was slight in 5, moderate in 2, marked in 3, and terminal in 4 cases.
Physical signs may also be absent, as in two otherwise normal hearts with defects admitting a goose-quill, in the McGill Museum. On the other hand, physical signs atypical of acquired valvular disease are often present, even in the absence of symptoms, and are frequently sufficiently characteristic to permit of a diagnosis being made. In pronounced cases there may be visible pulsation and precordial bulging, and a thrill, usually systolic in time and diffuse over the precordium, or most marked over the middle of the cardia, is common and is more frequent than in auricular septal defects. A thrill was present in no less than 11 of the 34 cases of primary defects at the base; in 10 being systolic and in 1 a "continuous vibration." In 7 it was diffused over the whole cardia; in 3 it was most marked over its upper half; in 2 others it was localized at the apex.
A harsh, systolic murmur localized in the third or fourth left space is the most frequent evidence of the defect. Sometimes a very small hole may be accompanied by a very loud murmur. Roger described as characteristic a " single long, constant murmur beginning with systole and continuing through both heart sounds, localized in the upper third of the precordial region." Reiss mentions as typical a loud systolic murmur in the middle of the precordium, localized over the inner part of the third left space and the fourth rib.
A murmur apparently due to the defect was present in 26 of the 34 cases. In those in which its character was specified it was loud in 18, rough in 3, whistling, grating, harsh, sawing, each in 1, rasping in 3; in 3 instances it was blowing. It was systolic in rhythm in all 26 cases, and in 3 of these a diastolic murmur was present as well. The point of maximum intensity was 12 times in the upper third of the precordium near the left sternal border; of these, in 4 it was stated to be at the third left space, in 2 others also at the fourth left space, in 2 at the third costal cartilage (in 1 of which it was heard with equal intensity at the apex),
in 2 at the pulmonary cartilage and second left space, and in 1 " over the middle of the sternum opposite the third left interspace." Besides these, in 2 other cases it was "along the left sternal border," "just to the left of the xiphoid cartilage," and "at the aortic cartilage;" in 2 (in 1 of which it was associated with rechtslage) it was "loudest at the apex," and in 4 it was diffuse over the precordium.
The murmur is usually transmitted downward along the left sternal border, and is frequently heard behind in the left infrascapular region. It may be diffused over the whole precordium, but is usually not heard in the axilla nor below the clavicle. In 6 cases in this series it was so loud as to be heard over the whole chest, and in 2 cases it could be traced into the vessels of the neck.
Eisenmenger^ claimed that a systolic murmur produced by the defect may be transmitted along the aorta, and thus be heard in the vessels of the neck, when pulmonary hypoplasia is also present, in which case the blood is diverted by the obstruction from its usual course into this vessel, and so passes from right to left into the aorta. In his own case, diagnosed by Schrotter before death, there was a defect admitting the thumb in the posterior part of the anterior septum, with rechtslage of the aorta and a dilated pulmonary artery. The patient, a man aged thirty-two years, had had cyanosis and dyspnoea from birth. There
was visible precordial pulsation and bulging, and a systolic murmur over the middle of the heart transmitted everjn^v'here over its surface, but chiefly to the right and inferiorly, not heard above its base, along the course of the aorta nor in the pulmonary artery, the latter vessel being too far below the surface to transmit the sound.
Aneurisms of the Undefended Space
Cases have been recorded by Rokitansky, Zahn,[3] Hart,[4] IMacCallum,[5] and others, in which, in the absence of any evidence of endocarditis, sacculations, single or multilocular, of the membranous portion of the septum project into the right auricle above the medial cusp of the tricuspid, and in some cases extend also into the musculature of the interventricular septum. Malignant endocarditis of the bulging area is not infrequent and rupture into the right auricle may occur. On this ground it has been argued^ that these aneurisms are not of congenital origin, but are due to the action of the inflammatory process upon this delicate part of the septum. As was pointed out by Rokitansky, however, the reverse is probably true, the aneurism supplying a nidus of lowered resistance upon which an infective process has been secondarily engrafted. This point has been made the subject of an interesting communication by Mall,[6] who pronounces definitely upon the congenital and non-inflammatory origin of these aneurisms, and shows the cause to be a malposition of the inferior septum (inferior septum proper) so that "the membranous septum develops improperly and becomes placed in a horizontal position, and is thus weakened in every way, and predisposed to the formation of aneurisms." In his own case the membranous septum was cribriform, and the hole communicated with numerous sacs in the medial segment of the tricuspid, and also bulged into the right atrium.
Such aneurisms may give rise to marked and characteristic physical signs. This was true of two remarkable cases, one a heart which is in the McGill Museum, the other reported by Tate,[7] in which a trumpetshaped tube, which formed the apex of a saccular pouching of the pars membranacea, projected behind and perforated the medial cusp of the tricuspid valve ; in the McGill specimen there was malignant endocarditis of the immediately adjacent tricuspid segment.
The relative frequency of aneurisms of the right aortic sinus of Valsalva and the probable dependence of these upon the juxtaposition of the pars membranacea of the right aortic cusp, has been discussed by Hart.^ The insertion of the medial cusp of the tricuspid just behind this point may further weaken this region by making it a seat of traction. It is not necessary to presuppose a congenital defect, although this may occur. In a case reported by Hale White^ an oval defect admitting a No. 10 catheter lay just below the right half of the anterior aortic cusp: its edges were thickened, but the septum around it for three-quarters of an
inch was thin and translucent, and the sinus of Valsalva above it was expanded into an aneurismal pouch, which protruded and burst into the right ventricle. The author thought that the whole septum between the lower part of the aorta and the base of the ventricles was abnormally thin.
Defects in the Septum Elsewhere than at the Base
These are usually multiple, and irregular or slit-like in form. They are of the greatest rarity. This is especially true of those low down in the septum.
- ↑ Trans. Path. Soc. London, 1897, xlviii, 41.
- ↑ Jour. Anat. and Physiol., 1913, xlvii, 459.
- ↑ Zeitschr. f. klin. Med., 1897, xxxii, Supp. Heft, 1.
- ↑ Virchows Arch., 1878, Ixxii, 206. » j^j^Z., 1905, clxxxi, 51.
- ↑ Johns Hopkins Hosp. Bull, 1900, xi, 69. 6 B^hl, Zeits.f. Biol, 1880, xvi.
- ↑ Anat. Record, June, 1912, p. 2921.
- ↑ Trans. Path. Soc. London, 1892, xliii, 36. VOL. IV - 24
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| Embryology - 26 Apr 2024 Expand to Translate
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العربية | català | 中文 | 中國傳統的 | français | Deutsche | עִברִית | हिंदी | bahasa Indonesia | italiano | 日本語 | 한국어 | မြန်မာ | Pilipino | Polskie | português | ਪੰਜਾਬੀ ਦੇ | Română | русский | Español | Swahili | Svensk | ไทย | Türkçe | اردو | ייִדיש | Tiếng Việt These external translations are automated and may not be accurate. (More? About Translations) |
Abbott ME. Congenital Cardiac Disease (1915) Osler & Mccrae's Modern Medicine 6, 2nd Edition.
| Historic Disclaimer - information about historic embryology pages |
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- 1915 Congenital Cardiac: Congenital Cardiac Disease | Heart Development | Literature | Etiology | Cyanosis | Classification | Pericardium | Heart Displacement | Whole Heart | Anomalous Septa | Interauricular Septum | Interventricular Septum | Absence of Cardiac Septa | Aortic Septum | Pulmonary Stenosis and Atresia | Pulmonary Artery Dilatation | Aortic Stenosis or Atresia | Primary Patency and Ductus Arteriosus | Aorta Coarctation | Aorta Hypoplasia | Diagnosis Prognosis and Treatment | Figures | Embryology History | Historic Disclaimer
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