Biomedical subjects

R H Anderson

Publications and source records attributed to R H Anderson.

At least 109 records · Page 6Linked to original sources

PubMed1998

Formation of the atrioventricular septal structures in the normal mouse.

It is sometimes thought that formation of the atrioventricular septum is equated with fusion of the endocardial cushions and that failure of fusion can explain all deficiencies of atrioventricular septation. Clearly, this is simplistic, but the exact contribution of different primordia to atrioventricular septation is not well understood. To clarify this, we studied normal mouse embryos (days 10 to 15 of gestation), which were serially sectioned and examined by light microscopy. Another group of embryos was examined by scanning electron microscopy after microdissection. Our results show that development of the atrioventricular septal area is highly complex. Proper formation requires the following: remodeling of the inner heart curvature, rotation of the horns of the systemic venous sinus around the pulmonary portal, expansion of the right atrioventricular junction, formation of the muscular atrial and ventricular septa, bridging by the dextrodorsal outflow ridge and the superior endocardial cushion, fusion with the inferior margins of the venous valves, and formation of the mouth of the coronary sinus from the cranial muscular wall of the left sinus horn. Multiple primordia contribute to a central mesenchymal mass (the "septum intermedium"), including the mesenchyme on the leading edge of the primary atrial septum, the atrioventricular endocardial cushions, and the cap of mesenchyme on the spina vestibuli. Fusion of these components closes the ostium primum, completing atrial and atrioventricular septation. Additionally, the spina vestibuli has a mesodermal core, which contributes to the muscularization of the lower margin of the oval fossa. This contrasts with the formation of the upper rim, which occurs as a result of an infolding of the atrial wall itself.

Animals↗

PubMed1998

Development of the murine pulmonary vein and its relationship to the embryonic venous sinus.

BACKGROUND: Arguments concerning the development of the pulmonary vein, and its relationship to the embryonic venous sinus (sinus venosus) have continued for well over a century. Recently, attention has again been focused on the origin of the pulmonary vein. It has been suggested that, whereas the pulmonary vein originates from the left atrium in humans, in all other vertebrates it originates from the venous sinus, with subsequent transfer to the left atrium. The nature of this transfer has not, however, been elucidated, although there is speculation that the pulmonary vein is "pinched off" from the left side of the embryonic venous sinus. METHODS: We studied closely staged hearts of normal mouse embryos from a C57BL/6 x CBAcross days 10 and 11 of gestation (plug day = day 1). Two series of embryos were collected and fixed in 2% glutaraldehyde, 1% formaldehyde, buffered with 0.05 M sodium cacodylate pH 7.4 (adjusted to 330 mOsm with NaCl). One series was wax embedded, serially sectioned, and stained with Masson's trichrome. The second series was subject to microdissection and scanning electron microscopy. RESULTS: The atrial component of the heart tube is attached to the body of the embryo by reflections of the atrial myocardial wall. The attachment can be considered, from the outset, as the heart stalk, with the myocardial-mesodermal connections forming a horseshoe of tissue that projects ventrally into the lumen of the atrium, surrounding a single evagination in the midline of the embryo. This heart stalk is cranial to the connections of the tributaries of the embryonic venous sinus and ventral to the foregut. When traced through its developmental stages, the evagination in the centre of the stalk, which we describe as the pulmonary pit, is seen to become the portal of entry for the developing pulmonary vein. CONCLUSIONS: The heart stalk, representing the area used by the pulmonary vein to gain access to the heart, and analogous to the dorsal mesocardium, is, from the outset, discrete from the area occupied by the orifices of the horns of the embryonic venous sinus. The pulmonary vein does not, in the mouse, develop from the tissues that form the walls of the tributaries of the systemic venous sinus. Comparisons with other studies suggest that early events in the development of the pulmonary vein are likely to be the same in all mammals, including humans.

Animals↗

PubMed1998

Cross-sectional imaging of a cadaveric human heart.

The precise relationship of the components of the heart can be difficult to understand. With recent developments in cardiac ultrasound and other imaging modalities, most professionals need to be familiar with cross-sectional cardiac anatomy. We have created a teaching technique based on a normal human heart removed at autopsy. It was scanned using a computed tomography scanner and the images examined in different planes. The images were annotated and used in a computer-based teaching program to convey the details of cardiac anatomy. Images corresponding to planes typically used in echocardiography were also examined. The resulting images were of high resolution and illustrated many subtle structures rarely seen in conventional studies of cardiac anatomy. This system has benefits to both clinicians and anatomists.

Adult↗

PubMed1998

Anatomic conundrum in a case of complete transposition of the aorta and pulmonary trunk.

An unusual cord-like structure was found on postmortem examination of the heart of a 30-year-old woman who had complete transposition of the great arteries. This extended from the posterior aspect of the right side of the base of the aorta to the posterior wall of the distal part of the arch immediately proximal to the insertion of the arterial ligament. The nature and origin of this is discussed.

Adult↗

PubMed1998

Anatomical conundrum: unusual position of the aortic arch.

At autopsy on a 72-year-old woman, the aortic arch showed an unusual arrangement, passing behind the trachea and esophagus and descending on the left side. The heart was normal, and death was due to unrelated causes. The nature of this anomaly is considered in respect of embryological development.

Aged↗

PubMed1998

The nature of the superior sinus venosus defect.

The location, and morphology, of the superior sinus venosus interatrial communication remains contentious. As part of a clinical study, we examined anatomic specimens and echocardiograms so as to clarify the arrangement of the normal atrial septal structures, and compared them with the arrangement found in the superior sinus venosus defect. The pathognomonic diagnostic criterion in the abnormal hearts was overriding of the intact muscular rim of the oval fossa by the mouth of the superior caval vein. This muscular rim is, in reality, a tube of myocardium which encloses a core of extracardiac adipose tissue. Understanding of this anatomic conundrum clarifies the understanding of the structures of both the normal atrial septum and sinus venosus defects.

Cadaver↗

PubMed1998

Surgical anatomy of aorto-left ventricular tunnel.

BACKGROUND: Owing to the rarity of aorto-left ventricular tunnel, surgical experience with this condition is generally limited. The anatomic configuration remains to be clarified in the light of better understanding of the normal aortic root. METHODS: Two autopsied hearts with aorto-left ventricular tunnel were examined and compared with four normal heart specimens. The normal hearts were sectioned in a variety of planes to display the ventriculoarterial junction. RESULTS: The leaflets of the pulmonary valve in both normal and abnormal hearts have semilunar attachments to a sleeve of freestanding ventricular musculature, the infundibulum. An extensive fibrofatty tissue plane then interposes between the freestanding infundibulum and the aortic sinuses. The aorto-left ventricular tunnels in the abnormal hearts pass within this tissue plane. The aortic orifice of the tunnel is distal to the level of the sinutubular junction, whereas the ventricular orifice is located within the interleaflet triangle between the right and left aortic sinuses. CONCLUSIONS: Aorto-left ventricular tunnels bypass the normal ventriculoarterial junction but do not penetrate the septal musculature. This has implications for the fine-tuning of surgical repair.

Aorta↗

PubMed1998

Cephalad resuspension of aortic leaflet of the mitral valve in hypertrophic obstructive cardiomyopathy.

A young child with hypertrophic obstructive cardiomyopathy, who was reoperated on for recurrent left ventricular outflow tract obstruction, underwent myectomy with patch augmentation of the ventricular septum. Cephalad resuspension of the aortic leaflet of the mitral valve resulted in abolishment of residual obstruction occurring secondary to its systolic anterior motion.

Aortic Valve↗

PubMed1998

What is a ventricle?

BACKGROUND: The concept of "one and a half" ventricular repair is to use "half" a ventricle to support the pulmonary circulation. The component makeup of any ventricle needs clarification for us to understand the nature of the so-called half ventricle. METHODS: The components of normal and abnormal ventricles are reviewed. RESULTS: Normal ventricles possess an inlet, an apical trabecular component, and an outlet. This tripartite approach is also logical in the description of congenitally malformed ventricles. Rudimentary and incomplete ventricles lack one or more of its component parts, and are usually hypoplastic. The location and morphology of the rudimentary ventricles correlate with the disposition of the atrioventricular conduction system. CONCLUSIONS: Recognition of the ventricular components permits determination of ventricular morphology and guidelines for the location of the atrioventricular conduction axis.

Heart Defects, Congenital↗

PubMed1998

Pathologic substrates for 1 1/2 ventricular repair.

BACKGROUND: The concept of "one and a half ventricular repair" relates to situations where one ventricle is capable of pumping one half of the circulation while the other ventricle is deemed inadequate and requires off-loading by means of a shunt. The inadequate ventricle is usually assigned the role of pumping the pulmonary circulation. The majority of hearts potentially amenable to this repair will have one large ventricle associated with a smaller and more-or-less rudimentary ventricle. METHODS: In this review, we focused on hearts in which the morphologically left ventricle will continue to support the systemic circulation. RESULTS: Among the hearts with univentricular atrioventricular connections, a few cases of classic tricuspid atresia and cases of double-inlet left ventricle coexisting with concordant ventriculoarterial connections would be suitable for incorporating the right ventricle into the pulmonary circulation. This procedure may be feasible in some cases of straddling and overriding tricuspid valve. Hearts with pulmonary atresia and intact ventricular septum display a wide range of sizes of the right ventricular cavity. Although biventricular repair is an option for those with good-sized cavities, patients with hypoplastic right ventricles may be candidates for one and a half ventricular repair. CONCLUSIONS: For the lesions reviewed, and many others, one and a half ventricular repair can be an option.

Heart Defects, Congenital↗

PubMed1998

The pathology of subaortic obstruction.

BACKGROUND: In hearts having the atriums connected only to a dominant left ventricle, typified by double-inlet left ventricle but seen also in lesions such as tricuspid atresia, subaortic obstruction, when it exists, is usually found at the level of the ventricular septal defect when the aorta is supported by the rudimentary right ventricle. METHODS: Heart specimens were examined to determine the nature and position of the ventricular septal defect existing between dominant left and rudimentary right ventricles when the ventriculoarterial connections are discordant. RESULTS: Most commonly, the ventricular septal defect is positioned between the muscular apical trabecular septum and the muscular outlet septum. This type of defect is found not only in double-inlet left ventricle, but also in hearts with absence of either the right or left atrioventricular connection when the other atrium is connected to a dominant left ventricle, irrespective of the position of the rudimentary and incomplete right ventricle. Obstructive lesions within the aortic arch are commonly associated with restriction at the site of the ventricular septal defect. The atrioventricular conduction bundle takes a constant course relative to the margin of the septal defect. CONCLUSIONS: Because subaortic obstruction is almost always caused by a restrictive ventricular septal defect, relief of the obstruction can be achieved by surgical enlargement of the septal defect, bearing in mind the course of the atrioventricular conduction system.

Aorta, Thoracic↗

PubMed1998

Which hearts are unsuitable for biventricular correction?

BACKGROUND: The surgical option of biventricular repair requires two ventricles, each fully capable of supporting the systemic or pulmonary circulation. The morphologic substrates that may preclude some hearts from biventricular repair need to be assessed. METHODS: Heart specimens were reviewed to assess the morphologic mechanisms that produce an unbalanced ventricular mass and to identify features that would, potentially, be a contraindication for biventricular repair. RESULTS: Hearts with solitary and indeterminate ventricles, and hearts with essentially solitary ventricles, often have associated abnormalities of venoatrial connections and arrangement of the atrioventricular valves. In the majority of hearts with univentricular atrioventricular connections, the rudimentary and incomplete ventricle of either right or left morphology may be too small to support either the systemic or the pulmonary circulation. Straddling with overriding of the atrioventricular valve, unbalanced atrioventricular septal defect, and gross hypoplasia of one of the ventricles in hearts with biventricular connections are other mechanisms producing ventricular imbalance, which could preclude biventricular repair. CONCLUSIONS: The morphologic mechanisms that result in ventricular imbalance are mainly related to the sizes and morphology of the ventricles, septal malalignment, valvar morphology, and component make-up of the ventricles. These features will influence decision-making in considering the option of biventricular repair.

Heart Defects, Congenital↗

PubMed1998

Interventricular communication in complete atrioventricular septal defect.

BACKGROUND: Little attention has been paid to whether the interventricular communication in complete atrioventricular septal defect is different beneath the superior and inferior bridging leaflets, a feature of obvious surgical significance. METHODS: We searched for a defect under the bridging leaflets and examined the valve morphologies in 98 autopsied and 86 surgical patients. Of the overall specimens, 27 were associated with Fallot's tetralogy, and a further 20 had subaortic stenosis, aortic coarctation, or both. In the autopsied specimens, we also measured the degree of deficiency of the ventricular septum. RESULTS: No communication was found under the inferior bridging leaflet in 30% (29 of 98) of the specimens. All 29 hearts except two without such communications showed an undivided inferior leaflet. In contrast, all patients undergoing operation except 1 had a communication beneath both bridging leaflets (p < 0.001). The absence of a communication beneath the inferior leaflet was observed more in hearts with Fallot's tetralogy (seven of 14) or those with subaortic stenosis, aortic coarctation, or both (eight of 18) than in those without associated anomalies (14 of 66; p < 0.01). Those with a communication under the inferior leaflet showed a greater deficiency of the inlet ventricular septum than did those without it (p < 0.001). CONCLUSIONS: In a certain percentage of patients with complete atrioventricular septal defect, there will be no communication under the inferior bridging leaflet. Surgeons should be aware of this possibility, particularly when confronted with a patient with obstruction in either ventricular outlet.

Child↗

PubMed1998

The mouse with trisomy 16 as a model of human hearts with common atrioventricular junction.

OBJECTIVE: To establish if the mouse with trisomy 16 is a suitable animal model with which to elucidate the development of a common atrioventricular junction. METHODS: The junctional morphologies in the normal human heart and those with a common atrioventricular junction are compared and contrasted. These are then related to observations made in normal mice and those with trisomy 16. So as better to understand development, a full description is given first of the normal atrioventricular junctions. Developmental implications are discussed because failure of fusion of the endocardial cushions cannot account for all the anomalies found in RXR alpha knockout, and in iv/iv mice. RESULTS: Mice with trisomy 16 showed evidence of deficiencies of atrioventricular septation and possessed a common atrioventricular junction, but the valvar orifices were not balanced between the ventricles as is the case in humans. Whilst some mice showed affinities with human tricuspid atresia, other cardiac malformations in the mice had no counterparts in human cardiac pathology. In humans both "partial" and "complete" forms of "atrioventricular canal malformations" share a basically common muscular junctional morphology, the differences being due exclusively to the way the bridging leaflets are fused to each other and/or the septum. CONCLUSIONS: It is simplistic to use the mouse with trisomy 16 as a model for cardiac abnormalities seen in humans. A spectrum more comparable to humans is found in RXR knockout mice. Study of the iv/iv mouse may help elucidate the genetic steps involved in normal and abnormal atrioventricular septation.

Animals↗

PubMed1998

Conotruncal repair for tetralogy of Fallot: midterm results.

OBJECTIVE: Because of the left-sided location of the main atrioventricular conduction axis, the membranous flap can be safely used for closure of the ventricular septal defect in tetralogy of Fallot. METHODS: Conotruncal repair consists of (1) precise closure of the defect using the membranous flap and (2) outflow reconstruction of the right ventricle by a wide monocusp patch. This method has been followed in 233 patients from October 1985 to March 1997. The age of patients ranged from 2 months to 53 years, with a mean of 4.6 years; 44% were younger than 2 years of age, and 11% were less than 12 months of age. RESULTS: A membranous flap was present in 86%, 12% had a muscle bar between the defect and the tricuspid valve, and only 2% had neither a membranous flap nor a muscle bar. There was no early death; two late deaths occurred over a mean follow-up period of 7.3 years. The actuarial survival was 99.1%. No patients required reoperation except for two with residual anomalously connecting pulmonary veins. All 233 patients were in sinus rhythm postoperatively. No patient has had a significant residual defect. The mobility of the polytetrafluoroethylene monocusp was echocardiographically detected in 85% and pulmonary regurgitation was less than mild in 82% at the late phase. The late right and left ventricular pressure ratio was 0.40 +/- 0.14 (n = 30) and the late central venous pressure was 5.6 +/- 2.2 mm Hg (n = 30). CONCLUSION: Conotruncal repair has provided good midterm results with a low central venous pressure, well-reconstructed outflow tract of the right ventricle, no residual defect, and no heart block.

Actuarial Analysis↗

PubMed1998

Isolated congenitally complete heart block attributable to combined nodoventricular and intraventricular discontinuity.

Intraventricular together with atrial-axis and nodoventricular discontinuity, in which various parts of the conduction system are replaced by fibrous or fatty tissue, constitute the three major pathological categories of isolated congenitally complete heart block. Intraventricular discontinuity is distinctly rare, with only two previous cases reported in the literature, one of which was associated with a familial history of heart block. The cardiac conduction systems of two cases of isolated congenitally complete heart block were serially sectioned and analyzed histopathologically. The findings were correlated with the clinical features, in particular, the family histories and maternal serum anti-Ro antibodies. Both cases, a 9-day-old neonate and an 8-year-old schoolgirl, showed a combination of nodoventricular and intraventricular discontinuity, with absence of the atrioventricular penetrating bundle, the entire right, and the proximal portion of the left bundle branch. The branching bundle was absent in the first case and replaced by fatty tissue in the second. In contrast to the commoner atrial-axis discontinuity in which the atrioventricular node itself is usually replaced by fibrous or fatty tissue with variable involvement distally, the sinus node, and in particular, the atrioventricular node were normal in both of our cases. There was no family history in either case, whereas tests for the maternal serum anti-Ro antibody were positive in the first but negative in the second case. Intraventricular discontinuity as a cause of isolated congenitally complete heart block is very rare. In our cases, it co-existed with nodoventricular discontinuity. It can be sporadic, familial, or associated with positive maternal serum anti-Ro antibodies.

Atrioventricular Node↗

PubMed1998

Morphometric analysis of atrioventricular septal defect with common valve orifice.

OBJECTIVES: We sought to analyze morphometric features of atrioventricular septal defect (AVSD) in autopsy specimens and to consider the developmental implications of obstruction in either ventricular outflow tract. BACKGROUND: Left ventricular outlet obstruction (LVO) is more prevalent in patients with Rastelli type A morphology. When tetralogy of Fallot (ToF) complicates this malformation, there is usually a free-floating superior bridging leaflet. The reasons for these associations are uncertain. METHODS: In 133 hearts with AVSD and common atrioventricular (AV) valve orifice, we measured the degrees of horizontal and anterior deviation of the great arteries from the AV valve, the diameters of the ventricular outlets and the great arteries and the degree of deficiency of the ventricular septum. RESULTS: In Rastelli type A morphology, the great arteries were deviated more leftward than in type C morphology (p < 0.01). Type A hearts also had a relatively small aorta, with a long and narrow subaortic tract. The presence of obstruction in either ventricular outlet was associated with a more oblique arrangement of the great arteries, with the pulmonary trunk being more leftward than in hearts without LVO (p < 0.01). In combination with ToF, the aorta was dextroposed and the pulmonary trunk was located more posteriorly (p < 0.01). No heart with type A morphology showed ToF (p < 0.01). CONCLUSIONS: The geometric arrangement of the great arteries correlated significantly with obstruction in either ventricular outflow tract and with the Rastelli subtypes. Malrotation of the developing outlet septum may be an embryologic factor producing obstruction, with horizontal deviation of the outlets also influencing the morphology of the superior bridging leaflet.

Aorta↗

PubMed1998

Clinical anatomy of the normal pulmonary root compared with that in isolated pulmonary valvular stenosis.

OBJECTIVES: This study aimed to clarify the clinical anatomy of the pulmonary root. BACKGROUND: Many descriptions of valvular anatomy have focused on the annulus, leading to varied interpretations of abnormal valves. METHODS: Twenty-two heart specimens with isolated pulmonary valvular stenosis were examined to analyze the gross structure of the pulmonary root. For comparison, we examined a normal series of a similar age range together with nine adult hearts. Serial histologic sections were prepared from five specimens. RESULTS: The normal pulmonary valve is enclosed in a proximal sleeve of free-standing right ventricular infundibulum supporting the fibroelastic walls of the pulmonary sinuses at the anatomic ventriculoarterial junction. The valvular leaflets are attached in semilunar fashion across this junction, delimiting the extent of the valvular sinuses. The stenotic valves were separated into dome-shaped valves, dysplastic valves and a third group of less typical cases. In the dome-shaped valves, which had a relatively circular origin of their leaflets, three raphes were tethered to the arterial wall at the sinutubular junction, producing a waistlike narrowing. The leaflets of the dysplastic valves were attached in a relatively normal semilunar fashion, but stenosis was caused by thickening of the leaflets at their free edges. Serial histologic sections through normal and abnormal valves failed to demonstrate any well defined fibrous "annulus" that could be of clinical relevance. CONCLUSIONS: Unlike the normal and the dysplastic valves, the dome-shaped valves have circular rather than semilunar lines of attachment of the valvular leaflets. Liberation of the fused zones of apposition of the leaflets within the dome is unlikely to restore such abnormal valves to normal structure, even if this procedure relieves the stenosis.

Cadaver↗