Book - Congenital Cardiac Disease 11
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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
Congenital Aortic Stenosis or Atresia
Subaortic Stenosis
This term has been applied to a curious annular thickening of the endocardium of the left ventricle, a few millimeters below the aortic valves, which involves the base of the aortic segment of the mitral valve, and encircles the ventricular wall at this point, and leads in most of the cases, to a localized narrowing of the cavity. The cases recorded are not numerous (seven in all), but the condition, when present, usually leads to serious results, and is therefore important. The thickened ring of tissue is often the seat of a chronic inflammatory process, probably of later incidence, but there can be little doubt that it is itself of congenital origin. Microscopic examination of the ring in a case reported by Moore showed it to be non-inflammatory in character. Keith explains it as an arrest of development, analogous to the conus stenosis of the right ventricle, the bulbus failing to atrophy about the root of the aorta.
1 Jour. Am. Med. Assn., 1913, Ix, 1150.
Endocarditis frequently develops both at the defect and at the aortic valves above it, and may lead to further contraction at these points. Shennan^ and Smart^ report two such cases under the term "double aortic stenosis," and a third is recently recorded by Thursfield and Scott.^ In the last, the aortic orifice was narrowed by a fibrous ring, situated on the interventricular septum, just below the undefended space and extending over the anterior mitral segment, and the aortic valves were thickened and fused; there was a thin line of fibrosis in the otherwise healthy aorta just above the margin of the valves, and slight coarctation at the isthmus. In Shennan's patient, and in that of Fletcher and Beattie, a thick calcareous ring lay below the thickened and ulcerated valves which were the seat of a malignant endocarditis.
Most of these patients reach adult life, and the clinical significance of the condition lies chiefly in the frequent incidence of acute endocarditis. The picture is that of an acquired aortic stenosis. Slight symptoms may exist from childhood, or no sign of the presence of the defect may be given until an acute endocarditis develops, or failing compensation sets in. The systolic murmur produced by the constriction may be very rough, and audible some distance from the chest wall. A precordial thrill existed in some cases.
Congenital Stenosis and Atresia of the Aortic Orifice
Aortic stenosis of antenatal origin is not common and the duration of life with it is very short. Two forms may be distinguished; those apparently inflammatory, with the stenosis limited to the valves and the ventricular septum entire, and those apparently due to an arrest in development. Unlike pulmonary stenosis, the inflammatory forms are here the commoner, fetal endocarditis, although rare in the left heart, usually involving the aortic orifice. Theremin collected 17 cases, in only 2 of which was there a defect of the septum. In our series there are 6 cases, 5 of which are inflammatory.
Monckeberg^ reports a case of inflammatory origin in an infant of
four days, and refers to 12 cases in the literature. He ascribes the
occurrence of the fetal inflammation to probably the fifth month of
gestation, for the left heart was very small, and the right side so hypertrophied that the apex of the right ventricle formed a recess-like cavity
below the left, a condition typical of a heart in which the right ventricle
had carried on the systemic circulation through the ductus arteriosus for a long time. In aortic atresia the left ventricle is aplastic, and when
a defect of the septum exists, may even be obliterated. The foramen
ovale and ductus, are nearly always widely patent, the latter supplying
the systemic circulation.
1 Lancet, 1905, vol. i, 21. ^ /f,^^,^ 1904, vol. u, 1417.
3 Brit. Jour. Child. Dis., 1913, x, 104. * Deut. path. Gesell, 1907, xi,'224.
Cyanosis is usually slight or absent in cases of aortic stenosis, but marked
in atresia. Physical signs may be absent, or there may be a loud systolic
or double murmur heard over the whole chest. In both conditions the
duration of life is very short. In aortic atresia the highest age attained
was twenty-seven weeks. Simmons^ described an interesting case in an
infant aged sixteen weeks, cyanotic from birth, with widely patent foramen
ovale and ductus arteriosus, the left ventricle aplasic, the right ventricle
greatly hypertrophied, and the aortic cusps fused to form a cone.
Left-sided Conus Stenosis
Schmincke^ describes two cases in adults of a peculiar muscular stenosis of the conus of the left ventricle, with healthy aortic valves, and no apparent cause, which he thought must be of congenital origin, due to a primary asymmetry in the formation of the left ventricle.
Anomalies of the Semilunar Cusps
These cusps may be increased or diminished in number and defective, fenestrated, or otherwise malformed. A row of supplementary cusps may exist or they may be the seat of attachment of anomalous bands.
Increase in Number
Supernumerary cusps sometimes occur in the pulmonary artery and, less frequently in the aorta. A more or less perfectly formed fourth cusp of varying size, but frequently smaller than normal, may be inserted between two of the others. Or the usual number of segments may exist, and the sinus behind one of these be divided by a raphe which runs from the back of the cusp to the aorta, indicating fusion of the additional segment or imperfect division from its fellows. In rare instances five cusps occur. Peacock figures a case of five aortic cusps, and Dilg enumerates from the literature 4 cases, in 2 of which the five cusps were in the aorta, and in the pulmonary artery.
The supernumerary cusps have sometimes been explained as an effort
at repair of some inflammatory process of long standing, but when the
fourth segment is perfectly formed, or the raphe indicating it shows no
sign of thickening (as in a case in the McGill Museum), a true malformation must be concluded, which is usually explained as a formation
by excess. As this condition is of congenital origin, the cusps are generally
so adapted to each other as to be competent to close the orifice, no
insufficiency resulting; they occur usually in a heart free from other
malformations, and are of very infrequent occurrence. Their clinical
significance is slight, and lies chiefly in their tendency, like all valvular
anomalies, to become the seat of endocarditis.
1 Intercol. Jour, of Austral., February 20, 1906.
2 Deutsch. med. Wchnschr., 1907, xxxiii, 2082.
Diminution in Number
A bicuspid pulmonary valve is not uncommon with other cardiac anomalies, especially transposition and septal defects. A bicuspid aortic valve usually occurs in an otherwise normal heart or associated with coarctation or hypoplasia of the aorta. In some instances both pulmonary and aortic valves may be bicuspid. The anomalous segments may be large, with smooth surfaces, showing no sign of further division, a true reduction in number existing; or one or both may present on the arterial aspect a ridge or raphe imperfectly dividing the sinus behind it into two parts, and indicating either a fusion of two formerly independent segments or a beginning separation of a single cusp into two elements ; in other instances a single membranous ring or diaphragm may exist with two such raphes on its aortic surface, indicating the union with each other of all three cusps. Where such a raphe is absent, the condition is undoubtedly a true malformation, but where this exists, the origin of the bicuspid state of the valve admits of much discussion. Peacock arrived at the conclusion that the majority of cases were congenital, due either to an original malformation or to fusion in a fetal endocarditis.
A series of cases illustrating the same line of thought was published by
Osier. ^ As pointing to a fusion originating in fetal life, he enumerates
(1) the presence of a low, sometimes half obliterated, raphe behind one of the cusps; (2) compensatory changes in the fused cusps, so that their
free edge becomes equal to or even shorter than the single segment; and (3) the fusion of the coronary or right and left segments of the valve.
That the lateral (right and left) segments are the seat of the congenital fusion, the posterior cusp remaining always single, is stated also by Birch-Hirschfeld .
Thickening of cusp and raphe does not prove that the fusion is not of "congenital origin, for endocarditis is likely to supervene on any valvular
anomaly. On the other hand, it is admitted that many cases are of postnatal inflammatory origin. Such postnatal fusion may be reasonably
deduced when (1) the two sections of the cusp are approximately equal;
(2) when the raphe dividing them has its superior origin on a level with the superior origin of the unaffected cusp (instead of at the lower
level, as described by Osier); and (3) when in addition the only thickening observable is in the angle betiveen the fused cusys. This latter point
has been called to the attention of the T\Titer by Dr. Adami, who points
out that the free part of the cusps, being in constant motion, is but little
liable to undergo inflammatory adhesion, and that this will be prone to
occur at the point of their insertion into the orifice wall, which is the
only portion of their edge that is fixed and relatively motionless. Therefore, inflammation originating at the angle of junction of contiguous
cusps may lead to localized obliteration of the prinaary angle, or to fusion
of the cusps with a new immovable angle of junction further removed
from the aortic wall, a progressive fusion occurring.
When a thin delicate raphe exists behind one of the segments of a bicuspid valve vdthout any trace of thickening. Babes insists that it cannot be ascribed to a fusion in fetal endocarditis, but must be regarded as a true malformation dependent perhaps on incomplete division of an originally single cusp. The semilunar cusps originate from the four distal bulbar endocardial ridges, two of which are divided by the descent of the aortic septum, so that a third segment is placed in each artery. The four cusps of the undivided truncus are sometimes seen in the cases of common arterial trunk.
1 Montreal General Hasp. Reports, 1880. YOL. IV — 26
The results upon the heart and circulation of a reduction in the number
of the aortic cusps may be summed up as follows:
1. The segments may approximate and be perfectly competent, no pathological effects ensuing. This is proved by the occasional finding of a bicuspid valve in healthy adults even of advanced age.
2. The gradual bulging of the cusps, their greater length, the free space that sometimes exists between them, perhaps a yielding of the aortic ring, lead frequently to a valvular insufficiency or to a narrowing of the orifice.
3. Endocarditis commonly supervenes, either as the acute, often malignant form, or as a chronic inflammatory process, leading to thickening and deformity of the cusps and to subsequent valvular disease.
4. Atheromatous changes at the base of the aorta have been frequently noted, and in 6 of the 11 cases described by Babes and Deteindre there was an aneurismal bulging of the right posterior wall of the aorta, which formed in 5 instances a definite aneurism, from the rupture of which, in 2 cases, death ensued. This is seen also in two cases in the McGill Museum.
This remarkable combination of an aneurism of the base of the aorta with a bicuspid valve is believed by Babes to be directly connected with the bicuspid character of the aortic cusp below it, and is ascribed by him (a) to an extension of the same thinning or trophic process that led to the anomalous condition of the cusp, (b) to the lack of support given to the aorta at this its weakest point, and (c) to the frequent insufficiency of the cusps and the yielding of the aortic ring.
Miscellaneous Anomalies
Dilg reports a remarkable case, in a child aged two years, of an endocardial fold divided roughly into two cusps with their convexity toward the ventricle, just below the base of a bicuspid aortic valve, both coronaries being behind one cusp. Banks^ reported a woman, aged thirty-four years, with physical signs of aortic insufficiency and a loud, musical murmur at the base, audible at some distance from the chest, whose heart was hypertrophied and presented a cribriform condition of the aortic valve, and one-quarter inch below it in the left ventricle three other rudimentary cusps. These may be of compensatory, postnatal origin, as in a number of other cases recorded of long-standing aortic insufficiency.
In a case in the McGill Museum, reported by Campbell and Hepburn,^ of pulmonary conus stenosis with septal defect, two well-formed valves are situated 1.8 cm. behind the pulmonary semilunar cusps, at the point which marks the lower bulbar orifice, and the site of the proximal bulbar swelling in the embryo. This is an entirely unique finding and suggests an atavistic reversion to the cusps seen at this point in the dipnoan heart.
In one of Babes' cases of bicuspid aortic valves, a peculiar band, like a papillary muscle of the mitral valve, traversed the sinus of Valsalva.
Hektoen^ quotes from the literature several other instances of anomalous
cords at the level of the valves, and a case observed by himself of a large
defect at the base of one of the segments, all of which he ascribed to
defects in the development of the aortic septum.
1 Dublin Hosp. Gazette, 1857, p. 330.
2 Can. Med. Assn. Jour., 1913, iii, 871.
Defective Development of the Semilunar Cusps
In a few instances of bicuspid valve a gap may be left on the wall of the vessel between the segments where evidently no third cusp has formed. This occurred in two of Deteindre's series. A remarkable instance of such a defect in the pulmonary valve is recorded by Stinzing. Here there are only two pulmonary cusps, and a large free space occupying the position of the third was traversed by two low ridges, evidently its rudiments. The heart was from a woman, aged sixty-four years, presenting signs and symptoms of pulmonary insufficiency, a history of pneumonia eight months before death, and failing compensation since.
Primary Defects of the Auriculoventricular Orifices
Congenital disease of the auriculoventricular valves differs from that of postnatal life chiefly in its infrequency, in the more extreme character of the process, atresia being more common than stenosis, and in the fact that the right side of the heart is usually affected rather than the left. Owing to the rarity of the cases, to the short duration of life, and to the fact that in the infant heart the picture presented is hard to distinguish from that of the more frequent lesions at the arterial ostia, this subject is not of great clinical importance, and its chief interest lies in the contribution which it brings to our information upon the question of the pathogenesis of cardiac defects.
Tricuspid Stenosis
Although this lesion is not very uncommon in adults the cases which can be proved to have originated in intrauterine life are very rare. Vierordt knew of only three instances, unassociated with disease of the pulmonary valves, in the literature. In combination with pulmonary stenosis or atresia it is more frequent. A good illustration of the latter combination is seen in a specimen in the McGill Museum, presented by Sir William Osier. In the heart of a cyanotic infant aged four months, both pulmonary and tricuspid valves are thickened, shortened, and fused, and their orifices markedly reduced; the ventricular septum is entire, the foramen ovale widely patent, the right auricle hugely dilated, and the tricuspid surmounted by recent vegetations. Such cases are undoubtedly of inflammatory origin, and are of value as proving that fetal endocarditis, although it has been overrated as. a cause, certainly has its place as an etiological factor in congenital cardiac disease.
Tricuspid Atresia
Although in itself rare, tricuspid atresia is the commonest of all congenital lesions of the auriculoventricular cusps. Rauchfuss collected 16 cases from the literature of which 5 were due to a defect in development, 5 were apparently inflammatory, and the remainder were of "doubtful" origin. Since then additionalcases have been reported by Chapotot (quoted by Vierordt), Sieveking, Kiihiie^ (two cases) Bernstein^ and Wieland.^
1 Chicago Path. Soc, 1905.
Pathological Anatomy and Pathogenesis
Cases of inflammaton' origin must be distinguished from those due to a defect in development, for the latter present several points of special interest. Those of inflammatory origin have usually progressed tlirough a stenosis and show distinct evidence of an antenatal valvuhtis in the form of an extensive cicatricial contraction of the endocardium adjacent to the obliterated tricuspid orifice, and often of the pulmonary valves. The developmental cases, on the other hand, may present no sign of inflammation, but the tricuspid orifice is absent, and either shows no trace of its presence, or this is marked by a shallow groove, the tricuspid segments are lacking, and the right auricle is divided from the right ventricle by a thick muscular septum. Kiihne, and subsequently Wieland, subdivided these developmental cases into a group of (a) "isolated" primary atresias in which certain pathological changes of a secondary nature are constant so that a definite type is set up, and (6) tricuspid atresia complicated by other grave cardiac anomalies of independent origin, such as transposition of the arterial trunks, pulmonary atresia, etc. Eight cases of the "isolated" form that constitutes the first group were separated by Kiihne, and later by Wieland, from the others. To these may be added one by Bernstein from our series. The changes in all of these are practically identical and clearly indicate the sequence of events. There is an entire absence of the tricuspid orifice, and the body of the right ventricle is an aplastic structiu-e, while the left is highly hypertrophied and dilated, appearing at first sight to form the whole heart, with the right chamber as an appendage to it; the right auricle is also hugely dilated and the foramen ovale is widely patent, or a defect of the interventricular septum exists; in addition there is always a defect in the muscular interventricular septum leading from the cavity of the left ventricle into the dilated conus of the right ventricle and thence into the pulmonary artery. The course of the circulation is necessarily from right to left auricle through the foramen ovale, and thence to the left ventricle, from which the blood is distributed in part to the aorta and in part through the septal defect to the pulmonary artery. The aorta is usually dilated, and the pulmonary is normal or somewhat reduced in size owing to the smallness of the chamber from which it springs.
These cases of "isolated primary tricuspid atresia" are of interest
from the standpoint of the pathogenesis of ventricular septal defects,
for they show that the old mechanical or congestive theory of septal
defects in pulmonary stenosis, in which the defect was thought to be
secondary to the raised pressure in the right ventricle, which has long
been justly discarded in this connection, at least in regard to the developmental forms of pulmonary stenosis, must be accredited here. That is
to say, the septal defect in tricuspid atresia is here evidently secondary
to the congestion in the left ventricle which forces an outlet in the conus of the pulmonary artery and this allows the circulation to be maintained.
Wieland points out and insists on the importance of Kiihne's separation
of this group, with its constant secondary complex, on this account.
1 Jahrb. f. Kinderh., 1906, Ixiii, 235.
- New York Path. Soc. Reports, February, 1906.
3 Jahrb. f. Kinderh., 1914, Ixxix, .320.
It should be remembered that cases of developmental tricuspid atresia with or without complicating cardiac anomalie, constitute one well recognized form of the cor biatriatrum triloculare. The subject is discussed under that head.
Etiology
The causation of the cases of inflammatory origin is that of fetal endocarditis elsewhere. In tricuspid atresia the secondary ventricular septal defect is bound to occur, for the proper maintenance of the circulation as well here as in the developmental forms.
Much interest attaches to the causation of the developmental forms
of tricuspid atresia. In the embryo the auricular canal opens at first
by a common orifice into the left side of the common ventricle, and later
by a process of shifting to the right comes to lie more in the median line.
The theory had been advanced that either a lack or an exaggeration of
this shifting to the right would lead to a wrong adjustment of the parts,
and to a mitral or tricuspid atresia. Again, the auriculo ventricular
orifice is divided into the mitral and tricuspid ostia b}^ the growth of
endocardial cushions in its centre, and by a union of these with the interauricular and interventricular septa. Should these cushions become
deviated to the right or to the left in their formation they may become
adherent to the corresponding wall of the common ostium and thus lead
to tricuspid or mitral atresia. Rokitansky thus explains his case of
mitral atresia. In that by Robertson the tricuspid atresia present was
ascribed to a fusion of the endocardial cushions with the malposed
auricular secondary septum, in consequence of a persistence of the
valvulae venosse which formed a coarse network across the cavity of
the right auricle. The suggestion has also been made that a premature
obliteration of the ductus arteriosus during early fetal life, might lead
to aplasia of the right ventricle and tricuspid orifice by cutting this
part of the heart out of the fetal circulation. This possibility is disproved,
however, by the fact that in several of the cases this passage is freely
patent. The conclusion remains that the probable causation of mitral
and tricuspid atresia lies in the mal-position and irregular union of
those parts of the cardiac septa dividing the mitral from the tricuspid
ostium.
Symptoms and Signs of Tricuspid Stenosis not Atresia
Cyanosis may be present from birth, or may develop after a few days or weeks. In the classical developmental type described above it is usually extreme in the end, though its onset may be delayed for some time. In Bernstein's case, aged two years and eight months, it did not appear until the sixteenth month, but then became marked with clubbing, and a polycythemia of 10,000,000 developed. This late appearance was possibly explained by the absence in this case of the auricular septum, a condition which must have facilitated the circulation. On the other hand, Ivelley's patient, a delicate, unhealthy child, showed only slight lividity on crying or wdien he had a cold, and in Sieveking's case, dying at nine weeks, cyanosis was absent throughout, but dyspnoea was a prominent symptom.
Dyspnceic attacks are a prominent feature, are often of daily occurrence
and are frequently the direct cause of death.
Physical signs are not very characteristic, being obscured by those of
the septal defect that in tricuspid atresia is always present, and by the
fact that a systolic murmur with maximum intensity over the right
ventricle, such as is usually produced in these cases, may with difficulty,
be distinguished from one generated at the pulmonary area. The marked
hypertrophy of the left combined with the smallness of the right ventricle
is of assistance in the differential diagnosis from pulmonary valve
disease, although allowance must be made for the increased cardiac area
produced by dilatation of the right auricle. This feature was indicated
in Wieland's patient by a zone of dulness to the right of the vertebral
column behind. His case was characterized also by a strong systolic
murmur and precordial thrill of maximum intensity at the apex, both
of which were of a curiously intermittent character.
Duration of Life
Very few of the developmental cases of tricuspid atresia live more than one year. Bernstein's patient reached two years and eight months, a relatively high age that is perhaps explained by the almost complete absence of the interauricular septum that was present. In the inflammatory cases, in which the atresia has probably progressed through a stenosis, adult life is frequently attained. Such was Bierdach's case dying at twenty-eight years.
Congenital Mitral Stenosis
This is even rarer than the same lesion at the tricuspid orifice. A typical case evidently due to an antenatal valvulitis, in a child of ten months, with cyanosis and dyspnoea from birth, is reported by Simmons. A curious combination of dwarfism and mitral stenosis in patients who have attained adult life has been observed. L'Abbe reports a case in a woman, aged twenty-seven years, of extremely small stature (1 meter high, 43 kilos weight), puerile intelligence, and marked infantilism. There was a clear history as well as physical evidence of congenital syphilis, and a pure mitral stenosis.
Mitral Atresia
A complete obliteration of the mitral orifice is still rarer than stenosis. The same remarks apply in regard to etiology as in tricuspid atresia, but here a primarj'^ defect in development may be almost constantly assumed. Grave associated anomalies are also nearly always present, and give additional proof of a teratological origin. In Theremin's observation of an infant aged two days, the left auricle and ventricle were aplastic without any trace in the latter of a mitral orifice, its walls being formed throughout of finely reticulated muscle fibres; the foramen ovale was closed, the interventricular septum defective, the pulmonary valve bicuspid, and the aorta appeared to arise from the right ventricle; there was a horseshoe kidney and double ureter. Lawrence and Nabarro give a similar case of mitral atresia, defect of the septum, aplastic left ventricle, the aorta arising behind the pulmonary artery from the right ventricle, with coarctation of the aorta, transposition of the stomach, absence of spleen and hepatic section of inferior vena cava; anomalies in form of liver and lungs. In Rokitansky's case of aortic and mitral atresia with defect of the septum, patent foramen ovale, and dilated pulmonary artery, in a child aged twelve days, there was an accessory right bronchus.
Congenital Mitral and Tricuspid Insufficiency
These lesions may result from a primary malformation of the cusps or from secondary deformity in the arrest of development of neighboring structures, as in persistent ostium primum. Or they may be due to thickening and shortening of the valve in a fetal endocarditis; thus Barth and Roger describe a case in which, on auscultation before birth, a long, loud, rough murmur was heard accompanying the heart sounds. The child was stillborn three days later, and the right ventricle was found dilated, the tricuspid orifice enlarged, and its cusps shrunken and insufficient, and evidently the seat of an endocarditis. In the case of Steffen, of a child aged ten and a half months, there were no tricuspid segments, but the valve formed a low ridge which was thickened, reddened, and slightly jagged. The mitral cusps were similarly thickened and reddened, and one of them was reduced likewise to a narrow ridge.
Congenital Mitral Insufficiency
Steffen's case is the only instance of congenital mitral insufiiciency found in the literature. True congenital tricuspid insufiiciency is also rare, probably there are not a dozen cases.
Anomalies of the Auriculoventricular Cusps
Double Auriculoventricular Orifice
A second valvular opening supplied with its own cusps, chordae tendinese and papillary muscles, may lie within the segments of an otherwise normal auriculoventricular valve. Seven such cases are recorded, six of double mitral orifice by Greenfield,^ Cohn,^ Degen,^ Stuhlenweisenberg,* and Camisa,^ and one of double tricuspid by Pisenti.*' In Stuhlenweisenberg's case, and in one of Camisa's, the two orifices were of equal size, and were separated by a bridge of valve tissue which supplied a cusp to either opening; in all the other cases the second opening was much smaller, and lay in one of the segments of the primary orifice.
Two hitherto unpublished cases of the latter description, are in the
collections of the Harvard and the McGill Medical Museums. In the
Harvard case, an opening 2 cm. long lies in the aortic cusp of the main
mitral orifice, and leads into an aneurismal pouch formed by the apex
of this segment, which communicates with the cavity of the ventricle
by numerous fenestrations. The McGill heart (Fig. 37) is of bizarre
external form owing to its bifid apex, deep auriculoventricular groove,
and hypertrophied right chambers. The inter auricular septum presents
a small valvular patent foramen ovale above, and is absent in its lower
two-thirds, a large crescentic defect {persisient ostium jprimum) existing.
The mitral valve is replaced by a single large segment which is cleft
in its anterior portion, passing forward from either side to be inserted into the middle of the base of the interventricular septum where this
bounds the interauricular defect below. The secondary mitral ostium
lies in the posterior half of this large primary segment, 7 mm. back from
its free margin. It is a perfect valvular opening admitting a lead-pencil
with two well-formed cusps attached to slender chordae, arising from_ two
short papillary muscles which lie behind and independent of the single
group from which the chordae of the primary segment spring. The right
auriculo ventricular valve is malformed and an irregular excavation in
its septal cusp suggests an unsuccessful attempt at a double tricuspid
ostium. The aortic valve is bicuspid. The endocardium is healthy.
1 Trans. Path. Soc, 1876, xxvii, 128 (with plate).
2 Inaug. Dissertation, Konigsberg, 1896 (with plate).
3 Inaug. Dissertation, Greifswald, 1903.
4 Centralb. f. Pathol, 1912, xxiii, 1027. _ ^ /^^(^^ p. 342 ^ Di una rarissima Anomalia della tricuspide, Perugia, 1888.
Fig. 37 Heart of a child, aged five years, showing; A, defect of lower part of interauricular septum; B, patent foramen ovale; C, double mitral orifice; D, cleavage of mitral segment. (From a specimen in the Pathological Museum, MoGill University.)
Etiology
Camisa believed a fetal endocarditis had led to a fusion of segments at their apices and to the formation of secondary orifices. Cohn and Stuhlenweisenberg suggest a malformation by excess, a view supported in the latter's case by the equal size of the two orifices. Pisenti supposed a fenestration of the endocardial cushions, which had transmitted the blood stream in early embryonic life and had become transformed into a second valvular orifice by a natural adaptation of growth, the papillary muscles and chordae growing up to its borders.
In the two specimens seen by us, Pisenti's explanation seems to
apply, the marked irregularities in both auriculoventricular valves due
to the auricular septal defect in the McGill specunen, and the multiple
fenestrations in the Harvard case, alike arguing for such accidental
origin at an early embryonic period. Camisa's theory of a fetal endocarditis is not tenable in the case of the McGill specimen and others in
which the endocardium is free from every trace of sclerotic change.
Symptoms
The double orifice is in itself of no clinical significance, the secondary segments functioning as normal valves. In the majority of the cases, including Cohn's patient, who died at seventy-one years, both sets of valves were thin, healthy and competent. Chronic endocarditis had supervened in both Camisa's cases and in Stuhlenweisenberg's. In the latter a loud systolic murmur over the precordium was associated with insufficiency and sclerosis of the segments of the anterior mitral ostium, the posterior remaining free.
Displaced Orifice
A double mitral orifice is described by Andrewes,^ in which two orifices separated by a fibrous septum lay one behind the other in the left ventricle. The right ventricle was rudimentary, the interventricular septum defective and the tricuspid valve absent. A deflection of the septum to the right so that both orifices are placed in the same ventricle was assumed.
Miscellaneous Anomalies
Various minor defects, as irregularly formed or accessory leaflets and anomalous arrangement of the chordae tendinese or papillary muscles occasionally occur, and may in some instances contribute to an insufficiency of the valves.
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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
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Cite this page: Hill, M.A. (2024, April 16) Embryology Book - Congenital Cardiac Disease 11. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Book_-_Congenital_Cardiac_Disease_11
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
