Heart-block and nodal rhythm in the acute infections / by John Cowan, Geoffrey B. Fleming and Alexander M. Kennedy.

  • Cowan, John, 1870-
Date:
[1912?]
Catalogue details

Licence: In copyright

Credit: Heart-block and nodal rhythm in the acute infections / by John Cowan, Geoffrey B. Fleming and Alexander M. Kennedy. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    ■{Case 5) found them in interstitial nodules. The arteries, too, in these cases may be thrombosed (Romberg), most often in the vicinity of the auriculo-ventricular junction. We have found arterial thrombosis with arteritis and periarteritis in one case of acute myocarditis. Cellular infiltrations are very commonly present in the tissues at the bases of inflamed valves, especially the mitral valve, a circumstance vsrhich is important on account of their proximity to the primitive tissue of the heart. Bacteria have pot hitherto been found in the non-suppurative myocardial nodules, which thus seem to be the result of a local toxaemia. As regards their ultimate fate, the smaller nodules are probably completely absorbed, but it seems certain that the larger lesions may become the foundation of a subsequent fibrosis of the myocardium. The cardiac muscle in cases of chronic valvular disease is frequently fibroid, patches of sclerosed connective tissue of varying size being scattered here and there throughout the wall. In the majority of cases the fibrosis is the result of arterial occlusion and consequent necrosis of the muscle cells. In mitral disease, ho wever, other causes are often active, and the fibrosis of the tips of the musculi papillares is generally believed to be often the result of a spread of the inflamma- tion from the valves to the papillfe, and not infrequently the connective tissue at the base of the valves is excessive in amount and infiltrates into the adjacent structures. It is evident, too, that some of the more distant fibrous tissue owns a similar origin, and is the re.sult of the healing of the sub- miliary nodules which we have just described. The patches are peri-arterial in site, multiple and widespread, and indi- vidually are of little practical importance, but their multi- plicity may interfere considerably with the cardiac action, and they may, accidentally, involve important structures. It is now generally believed that the rhythm of the heart and the proper sequence of contraction of its various chambers are intimately associated with the integrity of the undifferentiated cells which are present in certain places, the sino-auricular node of Keith and Flack, the auriculo- ventricular node of Tawara, and the auriculo-ventricular bundle of Stanley Kent. It has been repeatedly shown that heart-block may be due to lesions in the auriculo-ventricular bundle, though in certain cases this has been found to be normal, and the block has been ascribed to vagal lesions. James Mackenzie^'^ has suggested that extra-systoles occur as the result of impulses which arise in the primitive tissue. It has been shown that the normal contractions originate in the immediate vicinity-of the sino-auricular node, and pre- sumably in it, and that the region of the au riculo-ventricular tissue is more irritable than the muscle elsewhere, stimulation of the former being followed by a series of contractions (Gaskell), while stimulation of the latter only produces an isolated beat. 12 Diseases of the Heart, London, 1908.