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Biomedical subjects

A C Wenink

Publications and source records attributed to A C Wenink.

At least 19 recordsLinked to original sources
PubMed1992

Quantitative morphology of the embryonic heart: an approach to development of the atrioventricular valves.

In 32 human embryos ranging from 4.0 to 42 mm CR-length, the volumes of the atrioventricular endocardial cushions and of the ventricular myocardium were estimated by the point counting method. The surface densities of the left and right ventricular apical trabeculations were estimated by the point and intersection counting method. It is concluded that the cushions do not grow after the 25 mm stage, by that time having reached the maximal value of 0.074 mm3. This supports the concept that the cushions do not materially contribute to the definitive atrioventricular valves. In young embryos, the left ventricular trabeculations are thicker (as concluded from their higher surface density) than the right ventricular trabeculations. Only around the 25 mm stage, the ratio becomes 1. After this stage, right ventricles have thicker trabeculations than left ventricles have. This supports the concept that the trabecular pattern is changed during the period of valve formation, which process is characterized by delamination of the inner myocardial layers.

Endocardium↗
PubMed1992

New findings concerning ventricular septation in the human heart. Implications for maldevelopment.

BACKGROUND: The mechanics involved in development of the inlet component of the morphologically right ventricle are, as yet, undecided. Some argue that this component is derived from the descending limb of the ventricular loop, and that the inlet and apical trabecular components of the muscular ventricular septum have separate developmental origins. Others state that the entirety of the right ventricle grows from the ascending limb of the loop, and that the muscular septum, apart from its outer component, has a unitary origin. We now have material from human embryos at our disposal, which, we believe, solves this conundrum. METHODS AND RESULTS: We used a monoclonal antibody against an antigen to neural tissue from the chick to demarcate a ring of cells separating the descending (inlet) and ascending (outlet) limbs of the developing ventricular loop of the human heart. Preparation of serial sections of graded human embryos enabled us to trace the fate of this ring, and hence the formation of the inlet of the right ventricle, to the completion of cardiac septation. Eight embryos were studied, encompassing stages 14-23 of the Carnegie classification. The ring of cells initially separating the ascending and descending limbs of the ventricular loop were, at the conclusion of ventricular septation, located within the atrioventricular junction, sequestrated for the most part in the terminal segment of atrial myocardium. CONCLUSIONS: Our study conclusively shows that the inlet component of the morphologically right ventricle is derived from the ascending limb of the embryonic ventricular loop, and that the inlet and apical trabecular components of the muscular septum are derived from the same primary ventricular septum.

Antibodies, Monoclonal↗
PubMed1991

Myocardial capillaries: increase in number by splitting of existing vessels.

To study myocardial vascular development, stereological parameters were estimated in 24 Wistar rat hearts of six different age groups, from newborn to adult. The vascular surface density showed a sharp increase in the first 2 weeks, a peak around the age of 2 weeks, and then a steady decrease until it flattened in adulthood. In contrast, the vascular volume percentage, when plotted against age, decreased continuously with the greatest change in the first week, after which the curve flattened. These findings are compatible with an increase in the number of capillaries with a concomitant decrease of their diameters. Qualitative scrutiny of the histology did indeed support the idea that vessels become thinner. Reconstructions of the histological sections showed the same change three dimensionally. The reconstructions also demonstrated very small holes that seemed to go through the capillaries in the younger stages. Corrosion casts of the blood vessels were made using a casting resin. This was injected into the umbilical artery of rat embryos from 15 days gestation to birth. In postnatal rats of six age groups methacrylate was injected directly into the left ventricle. These casts supported the stereological data by showing an increase in number and decrease in diameter of capillaries, while during pre- and postnatal development, the intervascular spaces lengthened from small, irregular spaces to long, rectangular ones. Small holes, the probable precursors of such spaces, were clearly visible in the wider vessels of the youngest stages. All data point to an interesting mode of capillary growth, i.e. growth by division of existing vessels.

Age Factors↗
PubMed1991

Anterolateral muscle bundle of the left ventricle in atrioventricular septal defect: left ventricular outflow tract and subaortic stenosis.

The anatomy of the left ventricular outflow tract (LVOT) in 77 hearts with atrioventricular septal defect (AVSD), 36 with a separate A V orifice and 41 with a common A V-orifice, were investigated. In all specimens, an anterolateral muscle bundle of the left ventricle was identified between the superior bridging leaflet and the left coronary aortic cusp. It displaced the attachment of the superior bridging leaflet, resulting in its clockwise rotation. The muscle bundle frequently bulged into the LVOT, but was never prominent enough to have caused significant subaortic stenosis. Measurement of the LVOT aortic ratio was possible in 54 hearts and ranged from 36-100%. In 23 cases (43%), there was mild to moderate subaortic narrowing with a ratio ranging from 53-88%. In six cases (11%), unequivocal subaortic stenosis was present, mainly in AVSD with separate A V orifices (five of six) and iatrogenic in one case with surgically corrected complete defect. A decreased ratio was mainly due to decreased anteroposterior width of the septum in the subaortic area, with anterior displacement of the superior bridging leaflet in cases with dense septal attachment of the superior bridging leaflet (i.e., in AVSD with separate A V orifices, type A complete defect with small ventricular septal defect, or surgically corrected complete defect). Significant subaortic stenosis was caused by hypertrophy of the ventricular septum in the subaortic area with anteroseptal twist in four cases, by anomalous chordal insertion of the superior bridging leaflet in one case, and iatrogenic in one case after surgical correction with left A V valve replacement in type C complete defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Single papillary muscle ("parachute valve") and double-orifice left ventricle in atrioventricular septal defect convergence of chordal attachment: surgical anatomy and results of surgery.

A review of 59 anatomical specimens and of the findings in 65 surgically repaired patients with atrioventricular septal defect (AVSD), revealed four patients with a single papillary muscle and 11 with a double-orifice left ventricle. A single papillary muscle of the left ventricle occurred in 1.7% (1 of 59) of the anatomical specimens, and 6% (4 of 65) of the surgical cases. A double orifice of the left ventricle was found in 13.6% (8 of 59) of the anatomical specimens, and 7.7% (6 of 65) of the surgical cases. A single papillary muscle was only seen in cases with a complete defect. Double orifice was associated with partial, complete, or intermediate type of defect, with the highest incidence in the intermediate forms: 40% (4 of 10) of the anatomical specimens and 22% (2 of 9) of the surgical cases. In the anatomical study the specimens, with either single papillary muscle or double-orifice left ventricle, appear to be variants of the same malformation characterized by convergence of chordal insertion and underdevelopment of the left lateral leaflet. Pathology belonging to this spectrum was seen in 15% of our autopsy specimens and 14% of the surgical cases. In the surgical series good operative results were obtained with a conservative approach in cases with a favorable surgical anatomy.

Adolescent↗
PubMed1988

Thoughts on concepts of development of the heart in relation to the morphology of congenital malformations.

In the past, it has often been the case that congenital malformations have been categorized in terms of their presumed embryologic development. The knowledge of development, however, has itself often been derived from studies of the normal heart during its development coupled with inferences drawn from the morphology of the abnormal hearts. This can lead to circular thinking which, often, has little basis in fact. It is our belief that cardiac embryology is an important science which should stand in its own right, but that knowledge of abnormal development should be derived from observation rather than inference. The potential dangers of concepts derived by extrapolation are illustrated with reference to hearts having deficiencies of atrioventricular septation ('endocardial cushion defects') and those with double inlet left ventricle ('single ventricle'). It is shown that description of these hearts is greatly facilitated by eschewing those concepts derived from 'armchair embryology'. Once a clear description is established, the scene is set to understand the real mechanisms underscoring the maldevelopment of these lesions.

Endocardial Cushion Defects↗
PubMed1979

Muscular ventricular septal defects: a reappraisal of the anatomy.

Among 79 autopsy specimens of heart with an isolated ventricular septal defect, there were 29 cases of muscular defect. Among 60 hearts with complete transposition of the great arteries and a ventricular septal defect, there were 13 cases with a muscular defect. All muscular defects could be classified in three different types, based on the specific pathologic anatomy of the ventricular septum. The central and posterior defects were usually large and single, the marginal defects were frequently small and multiple. In hearts with transposition, central muscular defects were extremely rare, whereas these defects were by far the most frequent muscular defects in isolated ventricular septal defect. Alternatively, the posterior type was more common in cases of transposition. Marginal muscular defects were rare in both groups of malformations.

Heart↗
PubMed1979

Two-dimensional echocardiography in atrioventricular canal malformation: a diagnostic approach.

Two-dimensional echocardiographic studies were performed in 20 children with various forms of atrio-ventricular canal malformation. Both sagittal and transverse cross-sections were evaluated. The most typical finding in all patients was the visualization of the cleft anterior mitral leaflet (AML) represented by a diastolic break of AML echoes in the sagittal cross-section. - In cases where the AML is attached to the interventricular septum, varying degrees of left ventricular outflow tract narrowing and elongation were observed. In the transverse cross-section mitral-tricuspid alignment could be observed at the level of the aortic root. The ventricular septal defect in complete AVC was visualized as an echo-free space between the common anterior leaflet and the interventricular septum.

Adolescent↗
PubMed1979

Congenitally complete heart block with an interrupted Mönckeberg sling.

The conducting tissues are described in a case of congenitally corrected transposition. The patient was known to have suffered from congenital complete atrioventricular block. In the heart, both anterior and posterior nodes and bundles were found to coexist. The two bundles shared a common bifurcation. Neither of the two nodes connected with their respective bundles. The different morphology of the two sites of fibrous interruption may be explained by differences in embryonic development.

Atrioventricular Node↗
PubMed1978

Double outlet right ventricle in a human embryo.

A human embryo of 14 mm crown-rump length is described to exemplify the anomaly of double outlet right ventricle with subaortic defect. The configuration of endocardial swellings in the outflow portion of the heart are compatible with the general architecture of full-grown examples of the anomaly. This configuration differs considerably from normal embryonic anatomy, but is still supported by the architecture of the myoepicardial mantle. It is concluded that endocardial swellings play a secondary role in the determination of fullgrown cardiac anatomy.

Embryo, Mammalian↗
PubMed1978

The conducting tissues in primitive ventricle with outlet chamber. Two different possibilities.

The conducting tissues have been studied in two cases of primitive ventricle with outlet chamber. In one case the outlet chamber was to the right and in the other, to the left. In both cases there was an anterior node related to the anterior part of the right atrioventricular anulus. In the specimen with a left-sided outlet chamber (l-loop), the bundle passed through the atrioventricular-semilunar fibrous continuity and was intimately related to the posterior artery. Such a relation was absent in the specimen with a right-sided outlet chamber (d-loop), wherein the bundle directly descended on the posterior part of the septum between the main and outlet chambers. The septum is not considered to be the true ventricular septum but rather a hypertrophied trabecula septomarginalis.

Aorta↗
PubMed1977

The medial papillary complex.

The anatomy of the papillary muscle of the conus, also known as Lancisi's muscle, was studied in 100 normal hearts from pathological collections and in 8 embryonic and fetal hearts. Wide morphological variations were observed and because of this the name medial papillary complex is proposed. It is concluded that the value of this complex as an anatomical landmark in the right ventricle is a very restricted one. The development of the medial papillary complex is described.

Adolescent↗