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Clinical and experimental studies in myocardial ischaemia
Başlık:
Clinical and experimental studies in myocardial ischaemia
Yazar:
Hutton, Ian, author.
ISBN:
9780438052352
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (113 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: T. D.V Lawrie.
Özet:
This thesis presents clinical and experimental studies in myocardial ischaemia and infarction. The introductory chapter consists of a brief historical review and a general survey of coronary heart disease. The cardiac performance of patients with acute myocardial infarction is assessed and the particular significance of renal haemodynamics is presented. Renal blood flow was measured in patients with acute myocardial infarction using a radio-isotope technique consisting of exteirial monitoring of I131 labelled hippuran disappearance. This technique was atraumatic, produced no discomfort in this ill group of patients, and gave comparable results in the control group to those accepted as normal, using conventional clearance techniques. Renal blood flow was normal in normo- tensive myocardial infarction patients but was significantly reduced in hypotensive myocardial infarction patients. The importance of this reduction in renal blood flow was assessed by measurement of other parameters of intrinsic renal function. Reduction in renal blood flow after myocardial infarction was found to be associated with the developmetnt of acute renal failure. The institution of the appropriate therapy in the early stages of potentially reversible acute renal failure. in addition to measures aimed at improving cardiac output and thus renal perfusion, was responsible for a slight reduction in mortality in the hypotensive myocardial infarction group of patients. In a search for pharmacological agents, which might be of value in the patient with hypotension in cardiac failure complicating acute myocardial infarction, the prostaglandin group of compounds which have significant vasodilating properties were assessed in a model of experimental myocardial ischaemia. The coronary and systemic haemodynamics of prostaglandin E1 were studied in the anaesthetised cat, before and after acute coronary artery ligation. Changes in myocardial blood flow were measured using a heat clearance technique, Prostaglandin E1was found to decrease systemic arterial pressure and systemic vascular resistance and to increase heart rate. There were small increases in cardiac output. The contractile state of the heart was enhanced and myocardial blood flow increased. After coronary artery ligation there were more pronounced decreases in systemic arterial pressure and vascular resistance, with no increase in myocardial contractility and only slight increases in coronary blood flow in the ischaemic area of the myocardium. It was concluded that prostaglandin E1would have little value other than as a peripheral vasodilator in the management of patients with acute myocardial infarction. Subsequent chapters deal with further experimental studies in myocardial ischaemia. The problems of extrapolation of information obtained from the various animal models of experimental myocardial ischaemia are discussed and a model is presented, which is considered to be an improvement on existing models, and perhaps more relevant to the clinical situation, The final chapters deal with a series of experiments in which the effects of hypertonic mannitol on the conscious dog, with and without myocardial ischaemia, and with established myocardial infarction. Total and regional myocardial blood flow was measured using a radioactive microsphere technique. with the heart rate held constant, there was an increase in myocardial contractility with increases in systemic arterial pressure and cardiac output, Mannitol significantly increased coronary blood flow to the right ventricle left ventricle and ventricular septum. Acute myocardial ischaemia was produced by proximal, reversible occlusion of the anterior descending branch of the left coronary artery. In the absence of significant haemodilution and plasma volume expansion j hypertonic mannitol produced generalised increases in coronary blood flow, including flow to the peri- ischaemic area of the left ventricle and the ischaemic area of the loft vcntricle, and also increases in flow to the ventricular septum and right vcntricle. In the presence of myocardial ischaemia, ventricular performance vas improved by mannitol. Despite the presence of myocardial infarction, after 48 hours of anterior descending left coronary artery occlusion, myocardial blood flow to the area of the occluded artery was normal This paradox vas explained by the extensive intracoronary anastomosis between the circumflex and the L.A.J). coronary artery systems. Hypertonic mannitol produced generalised increases in coronary blood flow including flow to the infarct area and to the peri-infarct area. These increases in coronary blood flow were not as marked as in the dogs with acute myocardial ischaemia, largely because there vas no change in coronary vascular resistance, as the coronary arteries were maximally dilated in response to chronic coronary artery occlusion, Mannitol was again found to have a positive inotropic effcct. These results are consistent with the concept that mannitol night be of value in protecting the ischaemic myocardium and reducing myocardial infarction size, after coronary artery occlusion.
Notlar:
School code: 0547
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684381.1) | 684381-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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