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Biomedical subjects

S Y Ho

Publications and source records attributed to S Y Ho.

At least 307 records · Page 17Linked to original sources
PubMed1983

Late sudden death after repair of tetralogy of Fallot: a clinicopathologic study.

Retrospective analysis was performed to determine the likely cause of death in six patients who died suddenly 1-9 years after repair of tetralogy of Fallot. The integrity of the atrioventricular conduction system and myocardium was examined in three hearts at necropsy. Two of three patients who complained of palpitation or syncope had frequent premature ventricular complexes on routine ECGs. All the patients had complete right bundle branch block and one had left-axis deviation after repair. Postoperative cardiac catheterization (four patients) showed no residual ventricular septal defects, but right ventricular pressure was elevated in all. At necropsy, the atrioventricular conduction tissue was related to the margin of perimembranous ventricular septal defect in two patients, but was well posterior in one patient with an infundibular muscular defect. Histologic examination showed that in all cases the atrioventricular node, atrioventricular bundle and left bundle branch were undamaged. There was, however, extensive fibrosis of the right ventricular myocardium in the ventriculotomy site (three patients), septum (one patient) and outflow tract (one patient). These clinical and necropsy findings suggest that ventricular arrhythmia rather than atrioventricular block was responsible for sudden death in these patients after repair of tetralogy of Fallot.

Adolescent↗
PubMed1982

Absent left atrioventricular connection with right atrium connected to morphologically left ventricular chamber, rudimentary right ventricular chamber, and ventriculoarterial discordance. Problem of mitral versus tricuspid atresia.

Four cases of absent left atrioventricular connection are reported. The observations from these cases have been used to emphasise problems concerning the use of the confusing terms "tricuspid" and "mitral" atresia to describe such hearts. One of the four cases represents a very uncommon condition since the rudimentary chamber was contralateral to the side of the absent emphasis given to the surgical implications of these anomalies.

Heart Atria↗
PubMed1982

Left-sided obstructive lesions in atrioventricular septal defects: an anatomic study.

Actual and potential factors that create an obstruction to the flow within the systemic side of the heart have been analyzed in 114 specimens with atrioventricular septal defects. Hearts with separate right and left atrioventricular orifices and with common atrioventricular orifice were included. Potential inlet obstruction was due to tethering of the "cleft" of the left atrioventricular valve to the septum in 17.5%, incomplete "cleft" in 8%, and deformed valve leaflets in 70% of cases. Potential factors predisposing to left ventricular outflow tract obstruction were seen in 70% of cases, 21% being due to abnormal position of the papillary muscle and the remainder due to intrinsic hypoplasia of the outflow tract. Anatomic factors producing unequivocal obstruction were seen in 29% of cases. Twenty-two percent had obstructions at the inlet level, of which 13% were due to malformations of the left atrioventricular valve or the left component of a common valve. The other 9% had overall inlet obstruction due to severe hypoplasia of the left ventricle itself. Unequivocal outlet obstruction was observed in 7% of cases, 5% due to abnormal disposition of papillary muscles in the outflow tract and 2% to aneurysm of the interventricular septal remnant. Although anatomic obstruction occurs in the minority of cases (29%), this report shows that potential obstruction must be taken into account when considering surgical repairs.

Heart Septal Defects↗
PubMed1981

The internodal atrial myocardium.

The anatomical substrates of internodal conduction have long been a contentious topic. Debated first by the German Pathological Society in 1910, the consensus of established opinion for over half a century was that conduction between sinus and atrioventricular nodes occurred through plain myocardium. This was a conclusion supported by Truex in 1961. Despite his restatement of this fact in 1976, it has become fashionable to describe internodal conduction as being mediated by specialized internodal pathways. To reinvestigate this problem we studied 22 human fetal and 32 human infant hearts. In each case it was possible to cut the atrial tissues as a single block of tissue and to examine serial sections through the internodal myocardium. The sinus node, atrioventricular node, and segments of atrioventricular ring specialized tissue were recognized as specialized tissue using the light microscope in each heart. In contrast, there was nothing "special" about the myocardium between the nodes, nor was it possible to recognize tracts on the basis of either histological appearance or cellular architecture. It is concluded that, from the standpoint of light microscopy, there is no evidence whatsoever to support the purported concept of specialized anatomical substrates for internodal conduction.

Atrioventricular Node↗
PubMed1981

Analysis of atrioventricular junction, ventricular mass, and ventriculoarterial junction in 43 specimens with atrial isomerism.

We have analysed the atrioventricular junction, ventricular mass, and ventriculoarterial junction in 43 hearts with isomeric atrial chambers. Of the hearts, 32 had atrial chambers of bilateral right morphology while 11 had atrial chambers with bilateral left atrial characteristics. Among the hearts with right atrial isomerism, there were 13 biventricular hearts, all with ambiguous atrioventricular connection. Eight had a common valve and five had two atrioventricular valves. In the other 19 hearts, the atrial chambers were connected to only one ventricular chamber, 18 having double inlet ventricle through a common valve and the other having absence of the left atrioventricular connection. In these univentricular hearts, all possible types of ventricular morphology were found. The ventriculoarterial junction among these hearts with right isomerism showed great variation. In the hearts with left atrial isomerism, nine hearts had two ventricles and two were univentricular. The biventricular hearts all had ambiguous atrioventricular connection, six via a common valve and three via two valves. The two univentricular hearts both had double inlet via a common valve, one to a chamber of right ventricular type and the other to a chamber of left ventricular type. Both had rudimentary chambers of complementary pattern. The ventriculoarterial junction again showed much variation. Statistical analysis showed that pulmonary obstruction and a univentricular heart were both significantly more frequent in association with right compared with left isomerism. Significant differences were also noted in the two groups in terms of ventriculoarterial connections and infundibular morphology.

Aorta↗
PubMed1981

Left ventricular fibre architecture in man.

In order to investigate the possibility of regional variation of ventricular structure, 25 normal postmortem human hearts were studied by inspection of cavity shape and subepicardial fibre orientation, by dissection, and by the histology of sections in two orthogonal planes. Ventricular architecture was complex. Inlet and outlet long axes were separated by 30 degrees in the left ventricle. In the right the corresponding figure was 90 degrees. The thickest part of the left ventricular wall was at the base. At the apex there was potential endo- and epicardial continuity. Left ventricular cavity shape departed significantly from any simple geometric figure, there being, consistently, regions of both positive and negative curvature on the diaphragmatic aspect. The presence of trabeculae caused considerable variation in wall thickness. Striking variation was found in the arrangement of subepicardial muscle fibres. Most pronounced was the contrast between the longitudinal arrangement of fibres observed on the oblique margin and the circumferential arrangement of those on the acute. On the diaphragmatic surface of the left ventricle, fibres near the crux and apex ran circumferentially while those between ran obliquely; those on the diaphragmatic surface of the right ventricle also ran circumferentially. Deeper in the myocardium the arrangement was simpler. In the mid-wall of the left ventricle fibres were circumferential, best developed towards the base and in the upper part of the septum. Near the apex of the left ventricle and in the mid-wall of the right ventricle such fibres were sparse. The subendocardial region consisted of longitudinally directed fibres forming the trabeculae and papillary muscles, while fibres deep to and between the trabeculae coursed more obliquely. These findings were confirmed by histology. Models based on uniform myocardial fibre structure cannot explain wall movement in normal subjects, and are likely to have significant limitations if used to investigated left ventricular function in disease.

Dissection↗
PubMed1981

Conduction tissue changes associated with enlarged membranous septum--a cause of sudden death?

We have studied four hearts in which enlargement of the ventricular membranous septum was associated with histological abnormalities of the atrioventricular conduction tissues. Two of the cases showed unusually formed penetrating and non-branching main atrioventricular bundles. These two cases plus one other also showed right-sided penetrating and main atrioventricular bundles. In addition these three cases all showed extensive fibre loss affecting the origin of the left bundle, which in one heart was further accompanied by fibre loss in the main bundle. The conduction tissue damage in the fourth case, though more extensive, was not as clearly related to the enlarged membranous septum since the heart in this case was also enlarged and dilated (congestive cardiomyopathy). Our findings, while obviously not conclusive, suggest that conduction changes in the presence of an enlarged membranous septum could be added to the list of causes of sudden cardiac death. They certainly indicate that when an enlarged membranous septum is found in cases of sudden death, histological study of the conduction system is desirable.

Adult↗
PubMed1981

Surgical anatomy of tetralogy of Fallot.

On the basis of previous experience, we have analyzed the anatomy of a series of 53 hearts catalogued as having tetralogy of Fallot in the museum of the Children's Hospital of Pittsburgh. All hearts had a ventricular septal defect, aortic overriding, infundibular pulmonary obstruction, and right ventricular hypertrophy. None of the hearts had been operated upon during life. We paid particular attention to features of surgical importance. Thus the ventricular septal defect was found to be of variable form. It was perimembranous in 42 hearts. In 11 hearts it had entirely muscular rims and in the remaining heart it was roofed by the conjoined aortic and pulmonary valve rings (subarterial). From our previous histologic experience, it was evident that this varying morphology significantly affected the surgical anatomy of the atrioventricular conduction tissues. We endeavored to display this disposition as might be viewed by the surgeon. The degree of aortic override was variable, the aortic valve being connected by 15% to 95% to the right ventricle. In 17 hearts more than half the aortic valve was attached to right ventricular musculature. The nature of the infundibular obstruction also varied markedly. In all cases (except the one with absent infundibular septum) the infundibular septum was deviated in cephalad and anterior direction so as to produce obstruction. In the majority of hearts further anatomic structures also contributed to the obstruction. In some hearts there was hypertrophy of the infundibular septum, particularly at its junction with the trabecular septum. In others there was hypertrophy of the trabecula septomarginalis, and in many hearts there was hypertrophy of additional anterior infundibular trabeculations. The pulmonary valve was the narrowest point of the outflow tract in only six hearts, but in many of the others, it was abnormal. The results emphasize that while hearts may exhibit the classical features of tetralogy of Fallot, there is usually considerable individual variation in each of these features which is of major surgical significance.

Cardiomyopathy, Hypertrophic↗
PubMed1981

Surgical anatomy of double-outlet right ventricle with situs solitus and atrioventricular concordance.

Sixty-three hearts with situs solitus, concordant atrioventricular connection, and more than half of both great arteries connected to the right ventricle have been studied to delineate their surgically important features. Specifically noted were the relationship of the arterial valves to each other and the type and position of the ventricular septal defect with special reference to the conduction tissue location. Infundibular morphology was ascertained and other congenital abnormalities were recorded. An estimate was made of the surgical options available given the various anatomic abnormalities present. The aorta was most commonly in the right posterior position but could be found anywhere in the arc extending to left anterior position. The septal defects were most frequently in subaortic position (34/65) and were usually of perimembranous type (45/65). Three hearts had two defects each and one heart had an intact ventricular septum. Identifying the type of defect was helpful in locating the conduction tissues. In addition, there were numerous associated anomalies, including 19 hearts with coronary artery malformations. Retrospective analysis of the surgical options suggested that 36% of the hearts would not have been operable during life. Approximately another third could have been corrected by use of an intraventricular tunnel from the ventricular septal defect to the aorta, and the remaining third would have needed more complex procedures. In the final analysis it was concluded that hearts with the ventriculoarterial connection of double-outlet right ventricle, though so varied as to preclude "standardization," did permit anatomic analysis and description in clear and consistent terms.

Coronary Vessels↗
PubMed1981

Aortic atresia associated with the right atrial isomeric form of situs ambiguus.

A case is described which had the right isomeric form of situs ambiguus. A common atrial chamber was found with bilateral appendages of right morphology and bilateral superior venae cavae entered the chamber. It communicated through a common atrioventricular valve with a sole ventricular chamber of morphologically right ventricular type which gave rise anteriorly to the pulmonary trunk. There was aortic atresia, the coronary arteries and head and arm arteries being fed in retrograde fashion by a ductus arteriosus. It is emphasized that while aortic atresia is exceedingly rare in situs ambiguus of right isomeric type, it can exist. The case also exhibits the advantages to be gained from categorizing atrial situs on the basis of atrial morphology.

Abnormalities, Multiple↗
PubMed1980

Cervical aortic arch with aortic obstruction: report of two cases.

The occurrence of aortic obstruction in patients with cervical arch is very rare. The clinical and angiocardiographic findings of two patients with this combination of defects are presented. One of these patients, in whom tricuspid atresia with reduced pulmonary blood flow was also present, had a successful resection of the obstruction together with construction of a Waterston shunt.

Aorta, Thoracic↗
PubMed1980

Atrioventricular conduction system in univentricular heart of right ventricular type with right-sided rudimentary chamber.

The conduction tissue in a univentricular heart of the right ventricular type with a right-sided rudimentary chamber was studied. Both an anterior and conventional node were found, the anterior node being positioned in the atrial septum very close to the conventional node. Between the two nodes, a sling of conduction tissue passed through the annulus fibrosus but was not related to the trabecular septum. A non-branching bundle descended on to a free-running trabecula in the main ventricular chamber, the trabecular septum itself being devoid of conduction tissue. We believe it is likely that this trabecula represents the trabecula septomarginalis of the normal right ventricle. It has recently been suggested that during development the primordium of the trabecula septomarginalis is the structure which carries the conduction tissue from the atrioventricular node (whatever its position) to the trabecular septum. The present findings seem to support this.

Atrioventricular Node↗
PubMed1980

Straddling right atrioventricular valves in atrioventricular discordance.

Four hearts are described in which the right atrioventricular valve, draining a morphologically right atrium, straddled and overrode a septum between a right-sided chamber of left ventricular morphology and a left-sided chamber of right ventricular morphology. The degree of override varied between the straddling valve and was committed by 20-45% to the morphologically right ventricle. The ventriculoarterial connections in the hearts were discordant in one, double outlet from the morphologically right ventricle in two and single outlet via an aorta from the morphologically right ventricle with pulmonary atresia in the other. The straddling valve in one of the cases with double outlet had a dual orifice. Pulmonary stenosis was present in three cases, and pulmonary atresia in the fourth. Study of the conduction system in three of the hearts revealed subtle but important differences from the pattern expected in atrioventricular discordance. Each case had an anterior atrioventricular node and penetrating bundle, but the connection thus formed was more lateral than usual, and in the case with ventriculoarterial discordance, the nonbranching bundle was unrelated to the pulmonary outflow tract. A sling of conduction tissue between the anterior node and the regular node was found in the case with single outlet and pulmonary atresia.

Adult↗