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At least 397 records · Page 22Linked to original sources
PubMed1989

Histopathologic changes in the heart including the conduction system after catheter ablation.

The pathology of the heart, including that of the conduction system, after various catheter techniques used to ablate the various parts of the conduction system and the myocardium, were examined histologically by serial sections. The experiments were conducted on canines. The conduction system studies included the approaches to the AV node, the AV node, the AV bundle and bundle branches, as well as, the central fibrous body, the tricuspid, mitral and aortic valves. The methods of ablation were DC shock, laser and radio frequency energy. Production of the complete AV block clinically was associated with fibrosis with or without cartilage formation of the approaches to the AV node, the AV node, the bundle and the beginning of the bundle branches in most cases. On the other hand, creation of first degree AV block was associated with fibrotic changes in the approaches to the AV node and the AV node, and second degree block with more changes to the AV node. Coronary sinus ablation resulted in necrosis and fibrosis of the coronary sinus wall with occasional thrombosis of the coronary sinus. The adjacent atrial and/or the ventricular myocardium also showed fibrosis. Likewise, ventricular septal ablation was associated with focal areas of fibrosis of the myocardium. The conduction system was intact in both of the above experiments. In one human where complete AV block was created to manage intractable atrial fibrillation, the AV node, the bundle, and the bundle branches were fibrosed. In addition, there was a fibrosed atrio-Hisian connection and the patient died suddenly six weeks after the ablative procedure. The surrounding structures close to the vicinity of the conduction system, such as the aortic, tricuspid, mitral valve, the central fibrous body, and the summit ventricular septum are involved to a varying degree. In summary, (1) Whatever the method of ablation may be, the end result was fibrosis with or without cartilage formation of the ablative area. (2) Congenital anomalies of the conduction system such as an atrio-Hisian connection may remain elusive for ablative methods, and arrhythmias may persist and may cause sudden death in some cases.

Animals↗
PubMed1987

Angiotensin II binding sites in the conduction system of rat hearts.

Angiotensin II binding sites were localized and quantified in the conduction system of the rat heart by autoradiography in combination with computerized microdensitometry. Tissue sections (16-microns thick), containing cardiac vagus ganglia, sinus node, and atrioventricular node, were incubated with 125I-Sar1-angiotensin II to generate autoradiograms that were compared with other autoradiograms from 125I-labeled standards. Angiotensin II binding sites were highly localized in both the sinoatrial and atrioventricular nodes and in the cardiac vagus ganglia. In contrast, binding to the angiotensin converting enzyme, determined by incubation of adjacent tissue sections with the specific enzyme inhibitor 125I-351A, was very low in these areas but high in the cardiac endothelium. Our results suggest that angiotensin II may have direct chronotropic effects through stimulation of specific receptors in the conduction system of the heart and in intrinsic parasympathetic ganglia.

Angiotensin II↗
PubMed1970

Transitional cardiac cells of the conductive system of the dog heart. Distinguishing morphological and electrophysiological features.

Cardiac cells with distinctive electrophysiological and morphological features were found at the junctional region between Purkinje and ventricular cells of the dog heart. The electrophysiological exploration of these "transitional" cells revealed action potentials markedly different in configuration from those generated by Purkinje or by ventricular cells. The impaled cardiac cells which generated transitional action potentials were identified in serial sections and studied with the light and the electron microscopes. The transitional cells were found to be characterized cytologically by: (a) their subendocardial location, (b) their small diameter, (c) the absence of T system and sarcoplasmic reticulum, and (d) the lack of intercalated discs under the light microscope and the sparsity of specialized intercellular junctions under the electron microscope. Purkinje, transitional, and ventricular cells were found to be joined by gap junctions permeable to lanthanum. A quantitative difference in the extent and distribution of specialized intercellular junctions may be one of the factors responsible for the slow velocity of conduction characteristic of the Purkinje-ventricular junctional region.

Action Potentials↗