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Biomedical subjects

A E Becker

Publications and source records attributed to A E Becker.

At least 127 records · Page 7Linked to original sources
PubMed1990

Ventricular tachycardia in the infarcted, Langendorff-perfused human heart: role of the arrangement of surviving cardiac fibers.

Electrophysiologic and histologic studies were performed on Langendorff-perfused human hearts from patients who underwent heart transplantation because of extensive infarction. In nine hearts, 15 sustained ventricular tachycardias could be induced by programmed stimulation. In all hearts, mapping of epicardial and endocardial electrical activity during tachycardia was carried out. Histologic examination of the infarcted area between the site of latest activation of one cycle and the site of earliest activation of the next cycle revealed zones of viable myocardial tissue. In two hearts in which the time gap between latest and earliest activation was small, surviving myocardial tissue constituted a continuous tract that traversed the infarct. In three other hearts in which the time gap was large, surviving tissue consisted of parallel bundles that coursed separately over a few hundred micrometers, then merged into a single bundle and finally branched again. The direction of the fibers within the bundles was perpendicular to the direction of the activation front in that area. A similar type of inhomogeneous anisotrophy and activation delay was found in an infarcted papillary muscle removed from one of the explanted hearts and studied in a tissue bath during basic stimulation. Histologic examination of this preparation revealed that the delay was caused by a zigzag route of activation over branching and merging bundles of surviving myocytes separated by connective tissue.

Cardiac Pacing, Artificial↗
PubMed1990

Renal angiomyolipomas: could the histology serve as a marker for tuberous sclerosis?

The histological features of 43 renal angiomyolipomas were studied in an attempt to evaluate whether the isolated forms and those that present as part of the tuberous sclerosis complex can be distinguished. In two patients the mass was classified as an angioleiomyoma, because no adipose tissue was present. All renal angiomyolipomas showed the same basic histological picture. The combined forms, however, showed additional features such as extension into pre-existent renal parenchyma, scattered foci of hamartomatous lesions, calcified spicules and tubular inclusions. The findings suggest that these features, in an otherwise classical angiomyolipoma, should alert the pathologist to the possibility of tuberous sclerosis.

Biomarkers↗
PubMed1990

Congenitally corrected transposition with normally positioned atria, straddling mitral valve, and isolated posterior atrioventricular node and bundle.

A heart is described with congenitally corrected transposition of the great arteries, normally positioned atria, and a straddling mitral valve. Instead of an anteriorly positioned atrioventricular node, a regularly positioned posterior node and bundle were observed. This observation has important clinical and surgical implications and underlines that close inspection of the alignment of atrial and ventricular septa during operations is mandatory.

Atrioventricular Node↗
PubMed1989

Ultrasound imaging and atherogenesis.

The in vivo detection of early atherosclerosis remains a problem. First, atherogenesis is a process with an insidious onset and course. Once clinical signs and symptoms have developed the lesion usually is in an advanced stage. Second, the detection of early atherosclerotic lesions creates the problem of distinguishing between almost natural, age-related intimal changes and intimal thickening as a precursor lesion of atherosclerosis. The hallmark of atherosclerosis is the abnormal deposition of lipids within the intima. This process is accompanied by a cellular response, composed of macrophages, lymphocytes and proliferating vascular smooth muscle cells. An increasing quantity of collagen and elastin fibers eventually will replace the cellular constituents. In other words, a changing histological picture with respect to component make up in time. Third, an adequate interpretation of intimal thickening may be complicated further by tissue characteristics of the arterial media. The elastin units of an elastic type artery produce an echo-dense image, whereas a muscular media is hypoechoic. All in all it seems fair to state that ultrasound imaging techniques, at least for the time being, will be inadequate to distinguish between 'early' atherosclerotic lesions and intimal thickenings which will not necessarily progress to the full blown lesion.

Arteriosclerosis↗
PubMed1989

The conduction bundle at the atrioventricular junction. An anatomical study.

The variability in the topographical anatomy of the conduction bundle at the site of the atrioventricular junction has been studied in four normal human hearts. The junctional area has been removed en bloc and serially sectioned. The conduction bundle and adjacent structures such as the posterior limb of the trabecula septomarginalis and the membranous septum have been reconstructed based on calculations from the histological sections. The study reveals marked variability particularly in the extent of the posterior limb of the trabecula septomarginalis. In one instance, the muscle was almost totally absent so that the branching bundle was located in a midline position and subendocardial both to the right and the left ventricular septal surface. In two hearts, the posterior limb of the trabecula septomarginalis had ramified so that only a small segment of the conduction bundle was covered by muscle. In the remaining case, a well-developed posterior limb of the trabecula septomarginalis completely covered the conduction axis thus accounting for the left-sided position of the bundle. The variability encountered may render the conduction bundle vulnerable to the tensile strain of the tricuspid valve apparatus, enhancing the natural process of wear and tear which may lead to disruption of conduction fibres and heart block, particularly in the elderly. Since the detailed topographical anatomy of the conduction bundle in the atrioventricular junctional area appears to be highly variable from one individual to another, meticulous inspection is mandatory once the area is manipulated at surgery.

Adult↗
PubMed1989

Intestinal endocrine cells in radiation enteritis.

In this study, the intestinal endocrine cells were investigated in 13 surgical specimens affected by radiation enteritis. Endocrine cells were studied by means of Grimelius' silver staining and immunostaining for chromogranin, a general marker of endocrine cells. Positively stained cells were quantified by counting their number per unit length of muscularis mucosa. Results in radiation enteritis were compared with matched control specimens by using Student's t test. Chromogranin immunostaining showed a statistically significant increase of endocrine cells in radiation enteritis specimens compared with controls both in small and large intestine (ileum, 67.5 +/- 23.5 cells per unit length of muscularis mucosa in radiation enteritis versus 17.0 +/- 6.1 in controls; colon, 40.9 +/- 13.7 cells per unit length of muscularis mucosa in radiation enteritis versus 9.5 +/- 4.1 in controls--p less than 0.005 in both instances). Increase of endocrine cells was demonstrated also by Grimelius' staining; however, without reaching statistical significance. It is not clear whether or not the increase of endocrine cells in radiation enteritis reported in this study is caused by a hyperplastic response or by a sparing phenomenon. We should consider that increased endocrine cells, when abnormally secreting their products, may be involved in some of the clinical features of radiation enteropathy. In addition, as intestinal endocrine cells produce trophic substances to the intestine, their increase could be responsible for the raised risk of developing carcinoma of the intestine in long standing radiation enteritis.

APUD Cells↗
PubMed1989

The morphology of the normal aortic valve as compared with the aortic valve having two leaflets.

We studied 30 normal aortic valves and 64 aortic valves with only two leaflets to examine their morphologic components. The components of the aortic valve are the leaflets, the sinuses, and the interleaflet triangles. The first part of our study shows the relationship of these component parts of the normal aortic valve to the other cardiac structures. The second part shows a wide variation in the architecture of valves having two leaflets. Having produced criteria for the number of sinuses and the number of leaflets, we discovered that previous criteria used in the definition of valves with two leaflets are inadequate when the whole valvular complex is considered. Only seven valves in the study have two leaflets supported by two sinuses. The evidence points to the other valves having started with three leaflets but becoming bicuspid during either intrauterine or postnatal life.

Adult↗
PubMed1989

Atherosclerotic lesions in humans. In situ immunophenotypic analysis suggesting an immune mediated response.

The immunophenotypical features of the cellular infiltrates in different types of human atherosclerotic lesions, including diffuse intimal thickening as a potential but controversial precursor lesion, have been examined using monoclonal antibodies. Special emphasis is put on monocytes/macrophages, lymphocytes, and their possible interactions. Immuno-double staining techniques have been employed to study these aspects. T lymphocytes and macrophages were detected in diffuse intimal thickening, fatty streaks, and atheromatous plaques. In some lesions a predominance of suppressor/cytotoxic lymphocytes was found, whereas in other lesions mixtures of T suppressor/cytotoxic cells and T helper/inducer cells were found in ratios varying from 1:1 to 4:1. A substantial number of T cells and macrophages was considered to be immunoactivated because of the expression of HLA-DR and, to a lesser extent, of I12 receptor molecules. The activation was particularly evident at sites of close cell-to-cell contact between monocytes/macrophages and lymphocytes. These observations suggest that a specific in situ immune mediated hypersensitivity reaction is associated with the development of atherosclerosis.

Adult↗
PubMed1989

Postmortem quantification of collateral vessels in the human heart. A new approach.

A technique is introduced to quantify the microvasculature of postmortem human hearts. The method combines coronary angiography with selective perfusion of the coronary arteries with differently labeled radioactive microspheres. The transmural distribution pattern of the microspheres (endocardium-epicardium ratios) reveals that rigor mortis is a factor that should be taken into account. In the majority of cases, however, noticeable effects of rigor mortis were absent. The results of the perfusion of 19 human hearts with 10 to 35 microns sized microspheres indicate that the distribution pattern of the microspheres is determined by arterioles with a minimal diameter of 35 microns. In a second series of 15 human hearts, a comparison in the pattern of distribution of microspheres was made between hearts with obstructive coronary artery disease (n = 9) and hearts without obstructive disease (n = 6). The results support the contention that the present technique allows us to quantify differences in collateral vascular supply. Hence, the method may be of use for the study of the microvascular bed in the zone at risk in hearts of patients who have died of myocardial infarction.

Adult↗
PubMed1988

Cardiomyopathies with particular reference to the diagnostic relevance of endomyocardial biopsies.

A distinction is made between heart muscle diseases with a known cause, or occurring as part of a systemic disease, and those of unknown cause. The first category is termed "specific heart muscle disease". The term "cardiomyopathy" is then limited to the latter category. Cardiomyopathies are categorized as dilated cardiomyopathy, hypertrophic cardiomyopathy and restrictive cardiomyopathy. The pathology of dilated cardiomyopathy depends on the clinical stage of the disease. Basically, the histology shows hypertrophic myocytes, often with degenerative signs, and interstitial fibrosis. Lymphocytes may be observed, particularly in cases studied shortly after the onset of symptoms. Endocardial thickening may occur in time. The role of endomyocardial biopsies in the clinical setting is limited and relates mainly to excluding other diseases, such as myocarditis. The pathology of hypertrophic cardiomyopathy is characterized by myocardial wall thickening, either asymmetric or symmetric, and disorganization of the normal myocardial texture. The latter phenomenon should be distinguished from disarray, since it may occur as a natural phenomenon. The differentiation between these two may be extremely difficult on the basis of only small tissue samples, as with endomyocardial biopsies. This, therefore, poses serious limitations in the use of endomyocardial biopsies. The pathology of restrictive cardiomyopathy also depends on the stage of the disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Biopsy↗
PubMed1988

Segmental aortic hypoplasia or how to interpret the flow concept.

The development of elastin lamellae in the media of elastic type arteries such as the aorta appears to be modulated by mechanical factors such as flow. On that basis, decreased aortic flow during fetal development is held responsible for the occurrence of tubular hypoplasia of the aortic arch. Underdevelopment of the ascending aorta in aortic atresia likewise is considered due to diminished retrograde flow from the aortic arch. The present study has examined this hypothesis by comparing the number of elastic lamellae in hypoplastic segments of the aortic arch and ascending aorta with corresponding segments from normal aorta. In both situations the underdeveloped segments show a paucity of cellular and supportive connective tissue constituents, leading to a densely packed layer of elastic lamellae and, thus, contributing to the diminished dimensions. A major difference, however, was noted with respect to the number of elastic lamellae. In the hypoplastic ascending aorta in aortic atresia, the number was not different from that encountered in normal specimens. In tubular hypoplasia, on the other hand, the number of elastic lamellae was significantly lower than in the corresponding segments of normal specimens (P less than 0.01). Taking the stance that flow is a major factor in proper development of the aortic media, it seems that the findings in tubular hypoplasia fit well with a chronic lack of tension from early development and, hence, relate directly to the cardiac malformation. The findings in the ascending aorta of aortic atresia are less easy to understand from this point of view.(ABSTRACT TRUNCATED AT 250 WORDS)

Aorta, Thoracic↗
PubMed1988

Long-term follow-up of idiopathic mitral valve prolapse in 300 patients: a prospective study.

A prospective long-term follow-up study was made of 300 patients with idiopathic mitral valve prolapse, diagnosed by clinical, cineangiographic and echocardiographic criteria. There were 136 male and 164 female patients, ranging in age from 10 to 87 years (mean 42.2). The study included all patients with primary mitral valve prolapse, irrespective of clinical condition at the onset, and excluded only those patients with "secondary" mitral valve prolapse attributable to an accompanying established disorder. The average follow-up period was 6.1 years (range 6 months to 20 years). Two patients died of a noncardiac cause. The clinical condition of 153 patients remained stable. In 27 patients a supraventricular tachycardia occurred that was readily controlled with medication and caused no serious clinical complications. In 20 patients signs of mitral regurgitation appeared, but the patients remained clinically asymptomatic. Serious complications developed in 100 patients. Sudden death, most likely due to ventricular fibrillation, occurred in three patients; documented ventricular fibrillation was seen in two. Ventricular tachycardia developed in 56 patients, but in all instances the rhythm disorder was managed effectively and durably with medication. Infective endocarditis occurred in 18 patients, 4 of whom died during treatment and 6 of whom needed mitral valve replacement. The remaining eight patients suffer from severe mitral regurgitation that will require surgery in the near future. Twenty-eight patients underwent mitral valve operation because of progressive regurgitation. Cerebrovascular accidents occurred in 11 patients, but lifelong treatment with coumarin derivatives or antiplatelet aggregation agents was not considered necessary.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Collateral blood supply to the myocardium at risk in human myocardial infarction: a quantitative postmortem assessment.

The relation between the type and size of myocardial infarcts and collateral development was studied in postmortem human hearts with a new approach that allows quantification of vascular beds. The coronary arteries were perfused with radioactive microspheres and were visualized by injecting a barium-gelatin mixture. The collateral supply was assessed in 6 reference hearts without infarction, 4 hearts with a transmural infarct and 12 hearts with a total of 16 subendocardial infarcts. The distribution pattern of microspheres in hearts in the reference group did not differ significantly from that in hearts with a transmural infarct but was significantly different (p less than 0.01) from that in hearts with a subendocardial infarct, which had a much greater number of microspheres in the collateral-dependent area. Moreover, the lateral zone of myocardium at risk--defined as the area containing viable myocardium but within the distribution zone of the occluded artery--was small in hearts with a transmural infarct (less than or equal to 2 mm), but showed a much wider range in hearts with a subendocardial infarct. This study strongly suggests that collateral vessels play an important role during the development of myocardial infarction, both in determining infarct type (transmural versus subendocardial) and in preserving the viability of the lateral zone of the myocardium at risk.

Aged↗
PubMed1988

A histological study of the atrioventricular junction in hearts with normal and prolapsed leaflets of the mitral valve.

The mitral annulus is the point at which the atrial and ventricular walls meet the base of the mitral valve cusps. The suggestion that a variant of this arrangement termed "disjunction" was associated with prolapse of the leaflets prompted examination of the mitral atrioventricular junctions in seven normal hearts and six with prolapse owing to floppy mitral valves. A complete cord-like ring of connective tissue that encircled the atrioventricular junction and into which the three components were inserted at the same point was found in only one heart. The remaining hearts all showed a mixture of segments in which either the three components were inserted into a cord or simply met. Disjunction, defined as a separation of the atrial wall-mitral valve junction from the other component, the left ventricular wall, can occur both with and without a cord-like annulus. There was no significant difference in the number of segments around the left atrioventricular junction which showed disjunction in hearts with normal or prolapsing leaflets. The feature termed disjunction is an anatomical variation of the normal morphological characteristics of the left atrioventricular junction.

Aged↗
PubMed1988

Reentry as a cause of ventricular tachycardia in patients with chronic ischemic heart disease: electrophysiologic and anatomic correlation.

In this report we describe electrophysiologic and histologic findings in hearts and endocardially resected preparations from patients with sustained ventricular tachycardias in the chronic phase of myocardial infarction. We recorded simultaneously from 64 endocardial sites during tachycardia in 72 patients that were operated on for medically intractable ventricular tachycardias. Two other patients underwent heart transplantation, and mapping was performed on the explanted isolated heart connected to a Langendorff perfusion set-up. During operation 139 tachycardias with different morphologies could be induced. Although the majority of evidence supports the concept of a reentrant mechanism for these tachycardias, we found that 105 tachycardias appeared to arise at a focal area of less than 1.4 cm2. In only three cases macroreentry around the infarction scar could be detected. Of 21 tachycardias in which the "origin" appeared to be focal, earliest subendocardial activation was preceded by discrete electrograms of low amplitude (presystolic activity). In three tachycardias presystolic activity was detected at several sites, permitting reconstruction of its route. Histology of the endocardial resected preparation in one of these cases revealed separate zones of viable myocardial fibers in areas in which presystolic activity was recorded. These zones were located intramurally and subendocardially, supporting the concept that reentry occurred via isolated bundles of surviving myocytes at the border of the infarct and the larger subendocardial muscle mass. Conduction velocity through the isolated tracts was on the order of 25 cm/sec. Similar reentrant pathways were found in the two isolated hearts. Extracellular and intracellular recordings were made from 20 endocardial preparations that were excised from areas in which tachycardia originated. Preparations were superfused in a tissue bath. These experiments showed that action potentials were usually close to normal, but occasionally action potentials with reduced amplitude and slow upstrokes were found. In addition, there were cells that exhibited both fast and slow upstrokes, depending on the direction of the wavefront. Histology of seven resected preparations and the isolated hearts showed subendocardially as well as intramurally located zones of viable myocardium. Fractionation of extracellular electrograms and slow conduction were found in areas where surviving muscle fibers and strands of fibrous tissue were interwoven, and in zones where muscle fibers were oriented in parallel but isolated by strands of connective tissue.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗