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Biomedical subjects

S Y Ho

Publications and source records attributed to S Y Ho.

At least 163 records · Page 9Linked to original sources
PubMed1995

Left ventricular structures in atrioventricular septal defect associated with isomerism of atrial appendages compared with similar features with usual atrial arrangement.

In patients with isomeric atrial appendages, regurgitation of atrioventricular valves is recognized clinically as one of the risk factors that militate against successful achievement of definitive repairs. To determine whether this reflected anatomic features, we investigated 91 specimens with atrioventricular septal defect that had a common atrioventricular valve and biventricular atrioventricular connections. Of these specimens, 35 had isomeric right appendages, 23 showed isomeric left appendages, and 33 had usual atrial arrangement. We measured either the size or location of the supporting papillary muscles and the circumference of the mural leaflet within the morphologically systemic ventricle, as well as the length of outlet, inlet, and so-called scooped dimensions of the muscular ventricular septum. Presence of a solitary papillary muscle, or deviation of the attachments of the papillary muscles, was more frequent in hearts with isomeric right appendages. Values for the diameter and lengths of the papillary muscles were significantly smaller in hearts with isomeric right appendages compared with those with usual atrial arrangement (p < 0.001), as were the distances between the papillary muscles (p < 0.002) and the circumference of the mural leaflet (p < 0.001). The proportional length of ventricular outlet was longer in the setting of isomeric right appendages than in the other groups (p < 0.001), whereas the extent of septal scooping showed no differences among these three groups. We conclude that these structural features could be factors in the known insufficiency of the common atrioventricular valve and the ventricular dysfunction in patients with isomeric right appendages.

Heart Atria↗
PubMed1995

The architecture of the atrioventricular conduction axis in dog compared to man: its significance to ablation of the atrioventricular nodal approaches.

UNLABELLED: AV Node in Dog and Man. INTRODUCTION: Advances in treating patients with dual atrioventricular nodal pathways have called for a better understanding of the morphology of the approaches to the atrioventricular node. In this respect, it has recently been suggested that, in dog, anatomically discrete muscle bundles originating from the sinus node represent the substrate of the dual pathways recognized electrophysiologically in patients with atrioventricular nodal reentrant tachycardia. This concept is at odds with most anatomic studies of the human specialized atrioventricular junctional area. In this study, therefore, we studied histologically the junctional area in dog hearts, comparing them with our own findings in human heart and the descriptions of the earliest investigators. METHODS AND RESULTS: Five dog and six human hearts were prepared for histology and sectioned serially in different planes. Reconstructions were then made from each of three dog and two human hearts sectioned in orthogonal planes. Gross differences in the anatomy of the atrioventricular junctional area and in the structure of the conduction system were obvious between dog and human hearts. The penetrating portion of the conduction axis was longer in the dog, being much more extensively embedded in the central fibrous body. The atrioventricular node, in both dog and man, was composed of a zone of transitional cells overlying a compact region. The zone of transitional cells in the dog was more extensive posteriorly than anteriorly. No bundles insulated anatomically by fibrous tissue were found either in the internodal atrial myocardium or in the approaches to the atrioventricular node. Our findings in both dog and man are comparable with the initial descriptions of the atrioventricular junctional area. CONCLUSION: Although the disposition of the conduction system in dog and man is basically similar, there are important differences which relate to the gross anatomy. The anatomic substrate for functional duality of the inputs to the atrioventricular node remains unclear, since our study confirms that the concept of insulated atrionodal tract has no morphologic basis.

Animals↗
PubMed1995

Assessment of congenital heart defects by dynamic three-dimensional echocardiography: methods of data acquisition and clinical potential.

To evaluate the use of three-dimensional (3D) echocardiography in the diagnosis of congenital heart defects, we studied 238 patients aged 3 days to 19 years (mean 4.3 years) with normal hearts (n=13) or a variety of congenital heart defects (n=225). Three different modalities of data acquisition suitable for 3D reconstruction were applied. For parallel scanning, the transducer is held in a 6-cm long scan frame and then moved over the thorax, or in the subcostal position, by a stepper motor using 0.5-mm steps with acquisition of perpendicular parallel images of the heart. For rotational scanning, the transducer is rotated at sectors of 2 degrees over a span of 180 degrees. For fan-like scanning, the transducer is moved in an arc 45 degrees each way from its vertical axis. Movement of the transducer is computer-controlled and performed with electrocardiographic and respiratory gating. Between 80 and 120 slices of the heart are thus obtained, which form the 3D dataset. This dataset can then be ¿sectioned¿ in any desired plane, thus permitting generation of views simulating intraoperative perspectives. Ventricular septal defects and atrioventricular valves can be displayed as viewed via the atrium. Muscular ventricular septal defects can be viewed as seen through a ventriculotomy. Obstruction in the left ventricular outflow tract can be viewed as via an aortotomy, and so on. We concluded that this new imaging modality has a vast potential and may facilitate planning of intracardiac surgery.

Adolescent↗
PubMed1995

Increasing cyanosis early after cavopulmonary connection caused by abnormal systemic venous channels.

OBJECTIVE: To show that abnormal systemic venous channels in patients who undergo cavopulmonary anastomoses can become manifest and haemodynamically important only after surgery despite detailed preoperative investigation. DESIGN: Descriptive study of patients fulfilling the above criteria selected from hospital records over the past three years. SETTING: A tertiary referral centre. PATIENTS: Of the three cases identified, two were isomeric, one with left atrial isomerism and hemiazygos continuation of the inferior vena cava who underwent bilateral bidirectional Glenn anastomoses and one with right isomerism who underwent total cavopulmonary anastomosis. Case 3 had absent left atrioventricular connection with a hypoplastic left lung and underwent a classic right Glenn procedure. All three cases presented with progressive cyanosis in the early postoperative period. INTERVENTIONS AND RESULTS: Postoperative angiography in case 1 showed a remnant of a left inferior vena cava draining to the atrium to have become grossly dilated causing cyanosis, which resolved after redirection of this vessel and of the hepatic veins into the right pulmonary artery with an intra-atrial baffle. Cyanosis in case 2 was caused by intra-hepatic shunting to a hepatic vein draining to the left of the intra-atrial baffle. The diagnosis was made at necropsy, being overlooked on postoperative angiography. Repeat angiography in case 3 showed progressive dilatation of a small left superior vena cava to coronary sinus. Test occlusion with a view to embolisation revealed hitherto an undemonstrated hemiazygos continuation of inferior caval to brachiocephalic vein. The patient underwent surgical ligation of these two venous channels. CONCLUSIONS: Despite appropriate investigation some "abnormal" venous pathways manifest themselves, dilate, and become haemodynamically important only after surgical cavopulmonary anastomoses. In the presence of early postoperative cyanosis "new" systemic venous collateral channels should be considered as a possible cause, which may require reintervention.

Child↗
PubMed1995

Architecture of atrial musculature in humans.

OBJECTIVE: To investigate the gross arrangement of the principal muscular bundles of the two atria, and to suggest how it may contribute to contraction and spread of atrial excitation. DESIGN: A prospective analysis based on anatomical examination of adult human hearts. SETTING: A national heart and lung institute and a tertiary referral centre for cardiac disease. MATERIAL: 9 normal postmortem human hearts. METHODS: Dissection of atrial muscles with macrophotography. RESUltS--The atrial walls consist of circumferential and longitudinal muscular bundles, the former being arranged at the base of the atria with the latter predominating in the parietal walls. The muscular bundles in the right atrium are larger than those in the left. The main muscles forming the right atrial wall are the terminal crest and terminal pectinate muscles. The terminal crest, the most obvious muscle, is arranged longitudinally with its pectinate muscles connecting to the musculature of the atrioventricular vestibule. No structure resembling the terminal crest is seen in the left atrium. Instead the left atrial wall is composed of intermingled series of muscles, chief of these being the interatrial band and the septoatrial bundle. The former is arranged circumferentially at the atrial base, while the latter is mainly longitudinal. The wall of the right atrium is not of uniform thickness because of the presence of the terminal crest and its pectinate muscles on its internal surface. By contrast, the left atrial wall is much more uniform and its average thickness is greater than that of the right atrium. The rim of the oval fossa is the most important muscular structure on the septal surface and is formed by the infolded atrial walls. The other principal muscles of the atria attach to it, so that the rim provides mechanical support for overall movement of the atrial walls. Comparison of the gross arrangement of the atrial musculature with earlier echocardiographic measurements showed that this arrangement of the muscle explains movement of the atrioventricular ring and overall atrial contraction, and provides a suitable substrate for preferential conduction. CONCLUSION: The anatomical features of the atrial musculature explain the known facts concerning atrial contraction and preferential conduction.

Autopsy↗
PubMed1995

Comparison of three dimensional echocardiographic findings with anatomical specimens of various congenitally malformed hearts.

OBJECTIVE: To compare the reconstructions obtained by three dimensional echocardiography with the anatomical specimens used to generate the echocardiograms. DESIGN: The heart specimens were immersed in a water bath and imaged with a 5 MHz echocardiographic transducer mounted into a scan frame which allowed the transducer to travel a total distance of 4.4 cm in steps of 0.25 mm. The transducer records a tomographic slice at each incremental level thus producing 176 parallel slices of the heart to form the dataset. Reconstruction of the anatomical structures of the heart in a three dimensional format is achieved by means of different grey scales. MATERIALS: 72 specimens of either normal or various congenitally malformed hearts. RESULTS: Good quality echocardiographic pictures were obtained, permitting three dimensional reconstructions in each heart. The cardiac chambers and valves could be displayed in a three dimensional format which accurately displayed the internal anatomy of the specimens. No artefacts, such as spurious septal defects, were produced in specimens with intact septums. The atrioventricular valvar leaflets, however, appeared thicker in the images than they were in the specimens. CONCLUSIONS: Three dimensional echocardiography accurately displays the anatomy of normal and congenitally malformed hearts.

Echocardiography↗
PubMed1995

Morphology of the sinus node in human and mouse hearts with isomerism of the atrial appendages.

BACKGROUND: The location of the sinus node is known to be at best abnormal, or at worst unknown, in patients with isomerism of the morphologically left atrial appendage. In contrast, the sinus node is known to be an excellent histological marker of the morphologically right appendage, being duplicated in those with right isomerism. The aim of the study was to investigate this condition further in fetal human and mouse hearts. METHODS: Serial histological sections of the area anticipated to contain the sinus node were studied in hearts with isomerism of the atrial appendages taken from 14 human fetuses and 13 iv/iv mice, using 12 mouse hearts with normally arranged or mirror imaged atrial chambers for controls. RESULTS: All hearts with isomerism of the right appendages (two human and four mouse) had bilateral sinus nodes. The cases with isomerism of the left appendages (12 human and nine mouse) showed absence of a recognisable sinus node except in four cases (19%) in which a small remnant of the node was found. In three of these cases, it was related postero-inferiorly to the superior cavoatrial junction. CONCLUSIONS: The concept of isomerism of the atrial appendages is endorsed by findings on the morphology of the sinus node, this being the most reliable histological criterion for existence of a morphologically right atrium. A small proportion of hearts with left isomerism had a structure resembling the sinus node, but it was hypoplastic and displaced postero-inferiorly, distant from its expected position had the hearts possessed an incompletely formed morphologically right appendage.

Adult↗
PubMed1995

Echocardiographic-anatomical correlations in aorto-left ventricular tunnel.

OBJECTIVE: To investigate the echocardiographic, morphological, and histological appearances of aorto-left ventricular tunnel observed in four fetal hearts and compare the findings with those reported in older patients with the malformation. BACKGROUND: Previous studies have concentrated on clinical features of the malformation from birth to adult life and have speculated on either its embryological formation or its acquisition during late intrauterine life. The presentation of a large series of cases in fetal life is a unique opportunity to study the malformation at an early stage in its natural course. METHODS: A retrospective study was performed of four cases of aorto-left ventricular tunnel discovered among 872 cases of congenital abnormalities diagnosed at a tertiary centre for fetal echocardiography. Detailed echocardiographic and anatomical observations were made of the malformation as identified during fetal life. The precise anatomical arrangement was determined and compared with previous descriptions found in journals published in English. RESULTS: In fetal life, as after birth, the malformation is characterised by enlargement and hypertrophy of the left ventricle, enlargement of the aortic root, and free regurgitation at the level of the aortic valve. Anatomical abnormalities are found at the aortic ventriculoarterial and sinutubular junctions as well as in the intervening aortic wall. These are unrelated to necrosis, ischaemia, or the presence of mucopolysaccharides. CONCLUSIONS: The lesion is a developmental abnormality that should be reliably diagnosed by fetal echocardiography combined with colour flow Doppler echocardiography during the mid-trimester. The exact anatomical relations clarified by this study are pertinent to diagnosis and subsequent surgical correction.

Aorta↗
PubMed1995

An immortalized mouse neuroepithelial cell line with neuronal and glial phenotypes.

Evidence from retroviral marking techniques and immortalized cell lines indicates that multipotential stem cells exist in many areas of the developing central nervous system. However, the factors that influence the commitment of these stem cells into distinct neuronal or glial lineages are not known. We have created an immortalized hypothalamic cell line derived from embryonic day 14 hypothalamic cells with a replication-defective retroviral construct containing a temperature-sensitive allele (tsA58) of the large T antigen of the simian virus 40. The clonality of this cell line, which we have named V1, was established by single cell cloning and by Southern blot analysis. V1 cells exhibit two different morphologies: the vast majority of cells are flat and stellate, and a smaller number are phase-bright round cells with processes. V1 cells express nestin and neural-cell adhesion molecule, typical of proliferating neuroepithelial cells. They also express glial fibrillary acidic protein and S100 as well as the low molecular weight neurofilament protein. In addition, the phase-bright, process-bearing V1 cells stain intensely for many typical neuronal proteins, such as low, medium and high molecular weight neurofilament proteins, tau protein, microtubule-associated protein-2, and neuron-specific enolase. The phase-bright cells also have condensed chromatin and display mitotic spindles, indicating that they are in mitosis. When V1 cells are transferred from the permissive temperature (33 degrees C) to the restrictive temperature (39 degrees C), there is a decrease in expression of NF-L and an increase in expression of NF-H and glial fibrillary acidic protein in the flat V1 cells. The enhanced expression of neuronal antigens in mitotically active V1 cells is novel and may represent a more general property of the differentiation process. We suggest that V1 cells arise from a mixed neural/glial neuroepithelial progenitor cell that expresses both neuronal- and glial-specific proteins in the developing hypothalamus.

Animals↗
PubMed1995

[Vasopressin facilitates aortic baroreceptor activity in the rat].

Effect of arginine vasopressin (AVP) on the aortic baroreceptor activity of anesthetized rats was studied in 25 aorta arch-aortic nerve preparations. The results obtained were as follows: (1) By perfusing the isolated aortic arch with AVP (10(-8) mol/L), at constant intra-aortic pressure (IAP) of 13.3 kPa, the integrated aortic nerve activity (IANA) was increased by 40 +/- 4.7% (P < 0.0001), and the stepwise increase or decrease of IAP were accompanied correspondingly by changes of IANA. The function curve of aortic baroreceptor was shifted to the left and upward, and the peak into grated value (PIV) of the curve was increased from 621 +/- 85 to 711 +/- 81%.kPa-1 (P < 0.01). There were no changes in threshold pressure (TP), saturation pressure (SP), operating range (OR) and peak slope (PS). After washing out of AVP, the IANA returned to the control level. (2) The above effects of AVP were abolished by pretreatment with V1-antagonist [d (CH2)5Tyr- (Me) AVP, 10(-7) mol/L]. (3) By perfusing the aorta-arch preparation with five different concentrations of AVP (10(-11)-10(-7) mol/L), at the same constant IAP, IANA were respectively 190%, 160%, 150%, 130% and 103% of the control. After pretreatment with V2-antagonist [d (CH2) (d-Ile2Abu4] AVP (10(-7) mol/L), the perfusions with five different concentrations of AVP increased the IANA respectively to 130%, 150%, 160%, 170% and 180% of the control. When the V2-receptor-mediated vasodilating effect of AVP was blocked, the facilitatory effect of AVP on aortic baroreceptors via V1 receptors was significantly exhibited in a dose-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗
PubMed1995

Is the morphologically right atrioventricular valve tricuspid?

BACKGROUND AND AIM OF STUDY: Classification of the components of the right atrioventricular valve by its anatomical configuration is problematic and needs clarification. METHODS: Fifty hearts were studied so as to analyze carefully the structure of the right atrioventricular valve and to define its component parts. Cross-sectional echocardiograms were reviewed to demonstrate the valve in closed position, and reconstructed in three-dimensional fashion. RESULTS: The majority of specimens (62%) had three readily identifiable leaflets, but some (30%) could be described as having two leaflets while (8%) had four leaflets. The cross-sectional echocardiograms reviewed showed three definite lines of closure in all cases. CONCLUSIONS: The eccentric placement of the anterior papillary muscle causes the leaflets to close with three lines of apposition, and this makes the valve readily distinguishable from its mitral partner. When present, extra "scallops" in the structure of the right atrioventricular valve merely allow better coaption of the leaflets. So, although the term "cusp" is less than adequate as the descriptive basis for the structure of an atrioventricular valve, the right atrioventricular valve should still be considered to be tricuspid.

Echocardiography↗
PubMed1994

Clinical anatomy of the atrioventricular junctions.

OBJECTIVES: This study reevaluated the anatomy of the areas anterior and posterior to the atrioventricular (AV) septal structures, previously said to represent anterior and posterior septal areas. BACKGROUND: In descriptions of the locations of accessory AV pathways within the AV junctions, four regions have been recognized: the left and right free walls and the anterior and posterior septums. On the basis of known facts concerning cardiac structure, it is questionable whether these so-called septums are truly septal. METHODS: Ten human hearts were dissected to elucidate the clinical anatomy of these purportedly septal regions, together with the overall arrangement of the AV junctions. RESULTS: The true septal components of the AV junctions are the muscular and membranous AV septal areas. These separate the cavity of the right atrium from that of the left ventricle. The region previously designated as the anterior septum is part of the right parietal junction. It is contiguous with the membranous part of the septum but extends anteriorly and laterally from the septum as part of the supraventricular crest of the right ventricle ("crista supraventricularis"). In the region posterior to and beneath the mouth of the coronary sinus, only the most anterior extent, in continuity with the central fibrous body, is part of the muscular AV septum. The posterior extent of this area roofs over the diverging right and left ventricular walls and is filled in with fibroareolar tissue of the AV groove. CONCLUSIONS: The larger part of the regions anterior and posterior to the true AV septal areas are not septal but are parts of the parietal AV junctions. An understanding of these anatomic relations is essential for those wishing to modify conduction across the AV junctions.

Atrioventricular Node↗
PubMed1994

The surgical anatomy of ventricular septal defects with univentricular atrioventricular connection.

Hearts that do not possess one-to-one connections at the segmental junctions almost always produce a univentricular atrioventricular connection. One ventricle is usually large and dominant and the other small, lacking one or two of its components. The ventricular septal deficiency forms part of the circulatory pathway. We take the stance that only hearts that possess a truly solitary ventricular chamber are univentricular. They cannot have a ventricular septal defect, and so are excluded from this study. This review, therefore, is concerned with the morphology of septal defects in hearts in which both atrioventricular junctions are connected exclusively to a dominant left or a dominant right ventricle, and those lacking one atrioventricular connection, where the remaining valve is connected to a dominant ventricle. This morphology in the absence of one atrioventricular connection can be modified when there is overriding of the solitary atrioventricular valve. The ventricular septal defects are analyzed and categorized for the various groups, and the position of the conduction axis is described for the well-recognized entities.

Heart Atria↗
PubMed1994

[Effects of atrial natriuretic peptide on aortic baroreceptor activity in rats].

Effects of atriopeptin III (AP III) on the aortic baroreceptor activity in rats were studied in the isolated aorta arch-aortic nerve preparation in situ. By perfusing the isolated aortic arch with AP III (2.0 micrograms/ml) in rats, at constant intra-aortic pressure (IAP) of 13.3 kPa, the integral of aortic nerve activity (IANA) was increased by 64 +/- 27% (P < 0.001), the stepwise increases and decreases of IAP were correspondingly accompanied by increase and decrease in IANA, while the saturation pressure (SP) and the operating range (OR) of aortic baroreceptor activity were decreased from 22.5 +/- 0.5 to 21.3 +/- 0.5 kPa (P < 0.05) and 12.1 +/- 0.4 to 10.6 +/- 0.4 (P < 0.05), respectively, and the threshold pressure (TP) did not show any changes. The function curve of aortic baroreceptor was shifted to left and upward, and the peak integral value (PIV) and the peak slope (PS) of the curve were increased from 508 +/- 66 to 730 +/- 52% (P < 0.05), 55.6 +/- 7.5 to 93.2 +/- 6.8%.kPa-1 (P < 0.05), respectively. After washing out of AP III, the IANA returned to the control level. By perfusing the aortic arch with sodium nitroprusside (NP, 1.0 microgram/ml), at constant intra-aortic pressure (IAP) of 13.3 kPa, although the IANA was decreased as compared with the control, there was no statistical significance (P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Morphology of the cardiovascular system in conjoined twins: spatial and sequential segmental arrangements in 36 cases.

Thirty-six pairs of conjoined twins are reviewed from the joint experience of the authors. The external forms of conjunctions were 18 thoracopagus (joined at chest), eight cephalothoracopagus (joined at head and chest), eight dicephalus (single trunk and two heads), one craniopagus (joined at head), and one omphalopagus (joined at abdomen). There was one case with a single conventional heart in association with isomerism of the left lungs and absence of the heart in the left-side twin. Six cases had two conventional hearts. All of them had associated lesions, which were more severe in three cases (50%) with abnormal laterality. All of the cephalothoracopagus (eight cases) had two shared hearts. Cardiac lesions were commonly seen in the posterior heart, but the arrangement of atrial appendages were normal in every heart. Twenty-one cases of either dicephalus or thoracopagus had a compound heart. Three cases (14%) had fusion only at the level of venous sinus; three others (14%) were fused at the atrial level only, but 15 cases (71%) had fusion at both atrial and ventricular levels. Abnormal laterality was an associated lesion in ten cases (48%) with a compound heart. The fusion at the atrial level always occurred between right atriums, but ventricular fusion was more commonly between two left ventricles. Four atrial or ventricular chambers, if fused, were arranged in a cruciate arrangement. Mode of conjunction was as important, in the formation of the cardiovascular system, as was the degree of fusion. Abnormal laterality, which is commonly associated in lateral or mixed lateral/facing conjunction, was the most important factor affecting the general morphology of the cardiovascular system.

Female↗