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PubMed1982

On the ultrastructure of the ventricular endocardium and bulbar endothelium in 3 teleostean species.

The endocardium in the ventricle and the endothelium in the bulbus arteriosus are described in 3 phylogenetically distant teleostean species, Betta splendens, Pistella riddlei, and Xiphophorus maculatus. The ventricular endocardial cells are attenuated and contain a number of bristle-coated vesicles (BCV). In the former 2 species these cells contain numerous ribosomes, a low number of moderately electron dense bodies (MDB) and a poorly developed agranular endoplasmic reticulum (AER). In the latter species, however, these cells are poor in ribosomes, but very rich in MDB and AER. In the species studied the bulbar endothelial cells contain high numbers of ribosomes, whereas BCV and AER are poorla developed. In P. riddlei these cells have a height of 3-7 microns and are closely packed by MBD, whereas in B. splendens and X. maculatus they appear to be flat and contain a very low number of MDB. The results of the present work are compared with those scare findings previously reported for the teleostean ventricular endocardium. The structural differences described may reflect phylogenetical distances.

Animals↗
PubMed1991

Catheter ablation of the atrioventricular junction using a helical microwave antenna: a novel means of coupling energy to the endocardium.

Catheter ablation with either direct current defibrillator discharges or radiofrequency energy produces tissue injury via current flow from an electrode into the adjacent myocardium. In order to affect tissue at a distance, excessive power density may be produced at the electrode-tissue interface with the possibility of explosive gas formation or coagulum formation. A novel microwave catheter was developed with a helical antenna distally. This coil, although not in direct contact with the endocardium, radiates an electromagnetic field into the tissue that, in turn, causes thermal injury. The utility of this system for ablation was assessed in six dogs. The antenna catheter was introduced percutaneously and positioned so as to record the largest His electrogram. Microwave power (50 watts at 2,450 MHz) was applied for 114 +/- 118 seconds. Complete AV block was produced in all six animals with 1.8 +/- 1.2 applications. There was no ventricular ectopy or change in blood pressure during microwave ablation. One dog died 6 days after ablation. The remaining five dogs had persistent, complete AV block during 6 weeks of follow-up. Pathological analysis at 6 weeks revealed a large (mean 2.8 x 4.7 mm) fibrovascular scar in the region of the AV junction. Percutaneous microwave ablation of the endocardium appears feasible. By radiating an electromagnetic field without direct contact, this system can produce large lesions without being limited by desiccation of tissue and impedance rise.

Animals↗
PubMed1982

Ultrastructural alterations in the fibrous sheath, endocardium, and myocardium of dogs shocked with chronically implanted automatic defibrillator leads.

Catheter-mounted automatic implantable defibrillator leads were implanted in 10 dogs for 11 to 21 months (mean 15.0 months). Single shocks of 10 A, 20 A, or 30 A (peak current) were then delivered through the chronically implanted leads. Two days after the shock, the dogs were euthanatized and necropsied. The intracardiac segment of the lead was covered by a fibrous sheath, the endocardium in contact with the lead was thickened by fibrous tissue, and shock-induced myocardial necrosis was present surrounding the distal pair of electrodes, with the largest amount of damage found in the dogs given the large shocks. Ultrastructurally, the fibrous sheath was covered by endothelium and contained numerous spindle cells and identified as smooth muscle cells by their prominent cytoplasmic filaments and external laminae or myofibroblasts with prominent endoplasmic reticulum. The spindle cells were surrounded by abundant collagen fibrils but not by elastic fibers. The thickened endocardium contained numerous fibroblasts, abundant collagen fibrils, and a few small elastic fibers. The shock-induced myocardial alterations included necrosis of cardiac muscle cells with prominent mitochondrial mineralization, interstitial edema, and infiltration of macrophages.

Animals↗
PubMed1978

Starch granulomata of the endocardium.

Two cases of granuloma of the endocardium following cardic catherterisation are described. In each case the granuloma consisted essentially of macrophages associated with intracellular and extracellular starch granules, derived presumably from the glove powder used at operation. No previous cases of this condition have been found in the literature.

Adult↗
PubMed1984

Occurrence of long non-myelinated axonal segments intercalated in myelinated, presumably sensory axons: electron microscopic observations in the dog atrial endocardium.

Electron microscopy of serial sections revealed the occurrence of long non-myelinated segments in myelinated, presumably sensory axons running in the left atrial endocardium of normal adult dogs. Four such non-myelinated segments were analysed in three myelinated axons. They varied from 20 to 150 microns in length, and differed from nodes of Ranvier in being invested by Schwann cells in the manner of unmyelinated nerve fibers. Short non-myelinated portions (20-25 microns long) were associated with a single Schwann cell, whereas the longest such segment (150 microns) had five. The non-myelinated axonal segments were non-varicose and similar in diameter (1.2-3.0 microns) to adjacent myelinated segments, which had myelin sheaths 6-25 lamellae thick. The cytoplasm of the non-myelinated axonal segments contained numerous neurofilaments and microtubules, some mitochondria and smooth endoplasmic reticulum. The short non-myelinated segments were enclosed by perineurium, whereas the long non-myelinated segment was devoid of perineurium at its mid-portion; instead fibroblast-like cells made a loose boundary around the axon at this level. The significance of these non-myelinated segments was discussed with special emphasis on the question of whether they result from focal degeneration of the myelin sheath (demyelination) or are generally present in the preterminal regions of some axons.

Animals↗
PubMed1985

Eosinophilic disorders affecting the myocardium and endocardium: a review.

A wide range of disorders give rise to eosinophil counts greater than 1.5 X 10(9)/l (hypereosinophilia) and cardiac injury. The best known of these is eosinophilic endomyocardial disease (Löffler's endomyocardial fibrosis), which occurs as a major complication of the idiopathic hypereosinophilic syndrome. Here the heart damage appears to be a direct result of tissue injury produced by toxic eosinophil granule proteins within the heart. However, it is not known what causes the eosinophilia in these patients, why the eosinophils degranulate, or why the endocardium is especially susceptible to this type of injury. A number of parasitic infections may give rise to eosinophilic myocarditis. This is usually the result of the presence of the parasites within the myocardium where they die within inflammatory lesions, which may be extensive. Occasionally, drug reactions and rejection of a transplanted heart may produce eosinophilic myocarditis. Allergic granulomatosis and vasculitis (the Churg-Strauss syndrome), which gives rise to granulomas involving the myocardium, and eosinophilic (hypersensitivity) myocarditis usually respond rapidly to treatment with steroids. However, diffuse myocardial involvement may lead to heart failure, and some of these patients may later develop dilated cardiomyopathy. It is concluded that the heart may be affected by a variety of diseases in which eosinophils are a prominent component in the inflammatory cell infiltrates. Eosinophils themselves may contribute to some of the myocardial cell injury which occurs in these diseases, and attempts to limit this with steroids may be worthwhile in some patients.

Cardiomyopathies↗
PubMed2000

[Determining left and right ventricular volume ejection fractions (VEF) with MRI at 1.0 T. Comparison of manual and semi-automated endocardium detection].

PURPOSE: To evaluate method- and user effects as well as the required time in the determination of left- and right ventricular ejection fractions in comparing manual and semiautomatic border detection of the endocardium. METHODS: In 22 patients with varying cardiac diseases endocardial borders were detected either manually or semi-automatically (seeded ROI) and subsequently the right and left ventricular volume ejection fractions were computer-calculated. Two investigators defined the endocardial borders for both ventricles using both methods. For statistical analysis two-factorial analyses of variance were performed for the four variables: VEF right ventricle, VEF left ventricle, required time right ventricle, required time left ventricle (SAS, Anova). RESULTS: There was no user or method effect detectable for both ventricles. The required time for both ventricles also did not reveal a user effect, but there was a dramatic method effect concerning a reduction of the required time for analysis for both ventricles > 50%. CONCLUSIONS: The semiautomatic mode for detecting the endocardial borders in determining right and left ventricular ejection fractions did not demonstrate results differing from the results of the manual method, but is significantly superior concerning the time required for analysing ejection fractions of both ventricles with a reduction of over 50%. This might significantly reduce the expenditure for personnel.

Adult↗
PubMed1981

Digital image processing of two dimensional echocardiograms: identification of the endocardium.

Digital computer image-processing techniques were applied to two dimensional echocardiograms to improve the accuracy of cardiac spatial measurements by enhancing endocardial recognition. Images were photographed from the two dimensional echocardiographic monitor and digitized using an optical densitometer. Image-processing algorithms were applied to the digitized images as follows: (1) Multiple images were averaged; (2) a gray level threshold was chosen to separate the image into tissue and cavity regions on the basis of amplitude (brightness) of the returning echoes; (3) endocardium was traced between the regions; (4) endocardial position was confirmed by matching this boundary with a contrast edge map of the original images; and (5) the endocardial boundaries were tested by comparison with simultaneous M mode echocardiograms. A linear correlation was found between M mode and computer-processed two dimensional echocardiographic measurements of ventricular septal thickness (r = 0.88); this was superior to the correlation between M mode and unprocessed two dimensional echocardiographic septal measurements (r = 0.55). The correlations between M mode and processed or unprocessed two dimensional echocardiographic measurements of left ventricular internal dimension were similar (r = 0.89 and 0.85, respectively), but the slope of the regression line for the processed data more closely approximated the line of identity (p less than 0.05). It is concluded that endocardial outlines derived with use of digital image-processing techniques lead to left ventricular measurements that correlate more closely with M mode measurements than do dimensions derived from unprocessed two dimensional echocardiography.

Computers↗
PubMed1995

Novel technique to bioassay endocardium-derived nitric oxide from the beating heart.

Nitric oxide is a potent vasodilator and antiplatelet substance released by the vascular endothelium. In the current study, isolated rabbit hearts were perfused retrograde in the aortic root with a balanced salt solution using a Langendorff technique. To perfuse the right cardiac chambers, an inflow cannula was placed in the superior vena cava and an outflow cannula in the right ventricular apex via the pulmonary artery. To detect endocardial vasodilator production, right heart perfusate was used to bathe a "bioassay" segment of canine coronary artery denuded of endothelium. Perfusate from unstimulated hearts did not alter smooth muscle tone in the bioassay tissue. Calcium inophore, a potent stimulus for endothelial nitric oxide production, produced relaxation of the bioassay smooth muscle when added to the cardiac perfusate but not when applied directly to the bioassay segment. Cardiac effluent vasodilator activity was abolished by removal of the endocardium or addition of nitric oxide synthesis inhibitors, but not by prostanoid inhibitors. These experiments describe a practical method to bioassay endocardial nitric oxide production in the beating heart.

Animals↗
PubMed1986

Effect of nicotine on prostacyclin formation in human endocardium in vitro.

The effect of nicotine on the formation of prostacyclin by human endocardium was studied in vitro. Slices of cardiac valve cusps were incubated in a saline medium and the prostacyclin-like activity generated spontaneously by the tissue specimens was assessed in terms of its capacity to inhibit ex vivo platelet aggregation. In separate experiments supernatants of valvular tissue homogenates were incubated with [14C]arachidonate. This resulted in the appearance of labelled 6-keto-prostaglandin F1 alpha in the radiochromatograms, indicating the formation of prostacyclin in the homogenates. Nicotine inhibited dose-dependently the spontaneous generation of prostacyclin-like activity (I50 approximately equal to 2 X 10(-4) M), as well as the formation of 6-keto-prostaglandin F1 alpha (I50 approximately equal to 2 X 10(-5) M), indicating an inhibitory effect of the drug on endocardial prostacyclin production.

6-Ketoprostaglandin F1 alpha↗
PubMed2006

Computerized evaluation of echocardiographic stress tests in patients with poorly visualized endocardium using analysis of color-encoded contrast-enhanced images.

AIMS: We hypothesized that real-time color encoding of contrast-enhanced images would allow objective detection of stress-induced wall motion abnormalities (WMA). METHODS: We studied 117 patients with poorly visualized endocardium undergoing dobutamine stress tests. Color-encoded images (Philips, color kinesis) were obtained at rest and peak stress in four standard views during i.v. infusion of Definity. Images were reviewed without color overlays by two expert readers, who graded regional wall motion as normal or abnormal. In 101/117 patients (86%), in whom contrast enhancement allowed endocardial tracking, regional fractional area changes were calculated from the color overlays, and thresholds for calling a stress-induced WMA were optimized in a randomly selected subgroup of 34 patients (ROC analysis) to achieve maximum agreement with expert grades. This computerized detection of stress-induced WMA was then tested prospectively in the remaining 67 patients, using the expert grades as a "gold standard". RESULTS: 20/67 patients had resting WMA and 13/67 patients developed WMA at peak stress. The automated technique detected stress-induced WMA in at least one vascular territory with a sensitivity, specificity and accuracy of 0.80, 0.65 and 0.69, while the level of agreement between the two experts was 0.62, 0.91 and 0.85, respectively. CONCLUSION: Analysis of color-encoded, contrast-enhanced images allows objective, accurate, automated detection of stress-induced WMA in patients with poor acoustic windows.

Cardiotonic Agents↗
PubMed2004

The structure and ultrastructure of the sinus venosus in the mature dogfish (Scyliorhinus canicula): the endocardium, the epicardium and the subepicardial space.

The sinus venosus of fish is the most caudal chamber of the heart. It is often reduced in teleosts but well developed in elasmobranchs. The sinus venosus of the dogfish (Scyliorhinus canicula) is vital, since it harbours key elements such as a little known neuroendocrine system and the nodal tissue. However, the study of its structure is still incomplete. We examined the endocardium, epicardium and subepicardium of the sinus venosus in mature dogfishes. The wall is 100-250 microm thick and comprises three main layers. Large bundles of myocardial cells occupy the middle layer. The endothelial ensheathing is composed of thin endocardial cells with prominent nuclei towards the lumen, whose cytoplasm contains numerous dense bodies and moderately dense bodies, 150-800 nm in diameter and large vacuoles. The possible functions of these organelles are discussed. The outermost layer is made of a robust sheet of cuboidal epicardial cells separated from the subepicardium by a conspicuous basal lamina. Numerous microvilli towards the pericardial cavity and elliptical vesicles are located in the apex of epicardial cells. A thick layer richly endowed with dense bundles of collagen fibres forms the subepicardial space. This structure should be contrasted with the venous return mechanism of elasmobranchs.

Animals↗
PubMed1985

Laser photoablation of pathological endocardium: in vitro findings suggesting a new approach to the surgical treatment of refractory arrhythmias and restrictive cardiomyopathy.

In selected patients, malignant ventricular tachyarrhythmias have been successfully abolished by excision of subendocardial arrhythmogenic foci. Likewise, in certain patients in whom restrictive cardiomyopathy is due to endocardial thickening, endocardial resection has resulted in hemodynamic improvement. The present study was designed to explore the utility, in vitro, of laser photoablation of pathologically thickened endocardium. Endocardial photoablation was easily accomplished regardless of etiological or anatomical variations using either the focused beam of a carbon dioxide laser or argon laser light delivered through a 200-microns optical fiber. Photoablation of areas as large as 3.9 X 1.3 cm was performed within 40 seconds. The extent or depth of endocardial photoablation could be limited to 2 mm2 in area or 1 mm in depth using either form of laser therapy. These in vitro results suggest that either carbon dioxide or argon laser phototherapy can be successfully applied to the surgical treatment of refractory arrhythmias and restrictive cardiomyopathy. Advantages of laser photoablation include speed and precision. Furthermore, laser photoablation obviates the difficulty associated with conventional techniques in establishing tissue planes.

Argon↗
PubMed1987

Endocytosis of horse-spleen ferritin by bony fish endocardium.

The endocytic uptake of horse-spleen ferritin by the endocardial cells in 2 bony-fish species, Xiphophorus helleri and Pollachius virens, is described. In specimens of X. helleri injected intraperitoneally by a ferritin solution 1/10 h before the sacrifice, the endocardial bristle-coated vesicles, cytoplasmic tubules, and endosomes (smooth vesicles of variable size) contain a number of ferritin particles. These particles are taken up by the bristle-coated vesicles, transferred through the cytoplasmic tubules, and emptied into the endosomes. The latter get more tightly packed by ferritin and increase in size with the time elapsed between the injection and sacrifice. After 9 h, most ferritin-packed endosomes (4 to 6 micron) contain fragments of those inclusion bodies (0.5 to 1.5 micron) which normally occur in the teleostean endocardium, and are therefore regarded as lysosomes. The ferritin-rich lysosomes increase greatly in size with time and display a width of 6 to 12 micron after 28 h. The number of cytoplasmic tubules declines rapidly with time, whereas there is a constant production of new endosomes, which probably are derived from the former. The ferritin particles are not accumulated in the endothelium of the bulbus arteriosus, whereas the hepatic endothelial cells take up some small amounts of ferritin. A similar uptake of ferritin as described above was also observed in the heart of P. virens when perfused by a ferritin solution for 3 h. The present results are discussed and compared with those previously reported for the uptake of ferritin in various tissues in fishes and mammals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

Left atrial endocardium and prostacyclin.

In patients with rheumatic mitral stenosis, intracardiac thrombi are found mostly, for reasons still unknown, in the left atrium. We compared the release of PGI2 from the endocardium of the left atrium with that of the right ventricle and from the endothelium of the pulmonary arteries. Endocardial endothelial cells (EECs) were isolated from right ventricles (RV) and left atrial appendages (LAA) of porcine hearts, and vascular endothelial cells (VECs) from pulmonary arteries (PA) were obtained from the same animals. Cultured EEC and PA-VEC monolayers were placed in a pressure loading apparatus and incubated for 30 min under various pressures. After incubation, the supernatants were sampled and the 6-keto-PGF1 alpha contents measured. PGI2 release from LAA-EEC was much less than from RV-EEC or from PA-VEC. Moreover, transmural pressure did not enhance PGI2 release from LAA-EEC, although it did from RV-EEC and PA-EEC in a pressure-dependent manner. These results may explain why the left atrium is a common site for intracardiac thrombus formation in patients with mitral valve disease.

6-Ketoprostaglandin F1 alpha↗
PubMed1998

Comparison of the cellular electrophysiological characteristics of canine left ventricular epicardium, M cells, endocardium and Purkinje fibres.

Electrophysiological differences among M cells, epicardium, endocardium and Purkinje fibres of the canine ventricle were studied over a wide range of stimulation cycle lengths, and the pharmacological response of these cell types to the sodium channel blocker tetrodotoxin, calcium channel blocker nifedipine and ATP-sensitive potassium channel activator pinacidil was compared. The experiments were carried out by applying standard intracellular microelectrode technique in isolated dog left ventricular preparations. The results confirmed the existence of M cells in the canine ventricle, in addition, the distribution of the rate of rise of the action potential upstroke and action potential amplitude values reflecting probably the inhomogeneity of the fast sodium current in these cells was revealed. It was also demonstrated that M cells differ from Purkinje fibres in some aspects which were not expected from previous investigations: (1) The early portion of the action potential duration restitution curve in M cells is more similar to that of endocardial and epicardial cells than to Purkinje fibres. (2) The plateau phase of the action potentials in Purkinje fibres developed at a more negative potential range than that in the other cell types studied. (3) The pharmacological response to tetrodotoxin and pinacidil in M cells resembles to that in the endocardial and epicardial cells more than in the Purkinje fibres. Our results provide further evidence in support of the existence of M cells but also indicate that there are important electrophysiological as well as pharmacological differences between M cells and Purkinje fibres.

Action Potentials↗
PubMed1999

Localisation and quantitation of autonomic innervation in the porcine heart II: endocardium, myocardium and epicardium.

The immunological problems of pig hearts supporting life in human recipients have potentially been solved by transgenic technology. Nevertheless, other problems still remain. Autonomic innervation is important for the control of cardiac dynamics and there is evidence suggesting that some neurons remain intact after transplantation. Previous studies in the human heart have established regional differences in both general autonomic innervation and in its component neural subpopulations. Such studies are lacking in the pig heart. Quantitative immunohistochemical and histochemical techniques were used to demonstrate the pattern of innervation in pig hearts (Sus scrofa). Gradients of immunoreactivity for the general neural marker protein gene product 9.5 were observed both within and between the endocardial, myocardial and epicardial plexuses throughout the 4 cardiac chambers. An extensive ganglionated plexus was observed in the epicardial tissues and, to a lesser extent, in the myocardial tissues. The predominant neural subpopulation displayed acetylcholinesterase activity, throughout the endocardium, myocardium and epicardium. These nerves showed a right to left gradient in density in the endocardial plexus, which was not observed in either the myocardial or epicardial plexuses. A large proportion of nerves in the ganglionated plexus of the atrial epicardial tissues displayed AChE activity, together with their cell bodies. Tyrosine hydroxylase (TH)-immunoreactive nerves were the next most prominent subpopulation throughout the heart. TH-immunoreactive cell bodies were observed in the atrial ganglionated plexuses. Endocardial TH- and NPY-immunoreactive nerves also displayed a right to left gradient in density, whereas in the epicardial tissues they showed a ventricular to atrial gradient. Calcitonin gene-related peptide (CGRP)-immunoreactive nerves were the most abundant peptide-containing subpopulation after those possessing NPY immunoreactivity. They were most abundant in the epicardial tissues of the ventricles. Several important differences were observed between the innervation of the pig heart compared with the human heart. These differences may have implications for the function of donor transgenic pig hearts within human recipients.

Acetylcholinesterase↗
PubMed1978

Permanent cardiac pacing with electrodes of a new type of fixation in the endocardium.

To improve electrode construction the following main problems have been considered: (1) reliable initial fixing in the endocardium, and (2) reducing the area of contact surface and improving threshold values. In this article we have described three original electrodes: 1) an endocardial electrode with a multi-edged tip (contact area 28 mm2), which gives high electric field strength and low thresholds; 2) a spreading tip electrode, which was created on the basis of morphological data. The tissues grow into the spread spaces of this tip and ensure better stability (contact area 17.8 mm2); and 3) a double-screw-in electrode which differs from the other corkscrew types. The contact end (surface area--10.4 mm2) consists of two sickle-shaped hooks. The sickle handle is 0.7 mm in length which prevents further hook penetration in the wall of the heart. It was found that a multi-edged electrode and electrodes supplied with a fixation device are, in terms of energy consumption, more effective compared to electrodes with spherical or cylindrical tips of the same area of contact surface. The double-screw-in endocardial electrode has useful features: reliable fixation and a small contact surface area and, therefore, a low threshold value. Thirty-five double-screw-in electrodes were inserted into an atrial position and 28 into a ventricular position. We have not observed any displacement of such electrodes during the past two years.

Cardiac Pacing, Artificial↗