Hemodinamiese veranderinge as gevolg van eksperimentele hartversaking by skape soos waargeneem met 99m.-Technetium
Van Rooyen, Johannes Marthinus
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1. Gousiekte is a congestive cardiomyopathy that occurs in ruminant animals. It is characterised by a latent period of 2-6 weeks followed by a sudden death. Typical symptoms such as arrhythmia, systolic murmurs and gallop rhythm can be heard by means of auscultation. It appears that during gousiekte the stroke volume decreases with about 40% and the PFI increases with more than a 100%. The decrease in stroke volume is observed by means of an electromagnetic bloodflow meter. The decrease in stroke volume during gousiekte is a sign that there is congestive failure of the left ventricle. A decrease in ejection fraction has been observed by a loss of value lower than 30% after the final congestive phase has been reached. The parameter ejection fraction is of more importance to accademic interest because it describes what takes place during congestive heart failure in sheep that have gousiekte, than what it is used for diagnostic criterion for heart failure during gousiekte. Normally 714 ~ 0,3 contractions of a sheep's heart are needed to pump the blood from the right to left side of the heart. Complete congestive fa i lure during gousiekte can decrease the effectiveness of the heart so that 50 contractions are needed, in other words a PFI value of 50. Two phases can be distinguished during the development of gousiekte namely a compensation phase and a decompensation phase. The PFI as criterion is used to establish the influence of certain medicines with aninotropie effect and to establish whether a gousiekte heart can potentiate after administration of the medicines. The findings are positive which shows that energy abnonnalities are not primary causes of gousiekte. As a model for heart failure gousiekte can be compared with other well known models of heart failure such as volume overload, pressure. overload and coronary ligatures in sheep. Similarity between volume overload as model and gousiekte has been found with a basic difference namely a limited compensation and pulmonary congestion with high PFI in sheep with gousiekte. Pressure overload as a model for heart failure has very little in common with gousiekte because the hypertrophy that is causes is obstructive and not dilating. Where gousiekte has been compared with a familiar criterion such as coronary arterie ligations it has been established that the rate of heart failure in gousiekte i.s much higher than during a drastic coronary ligature. 2. The by-product of this research is the development and possible application of the technetium isotope method to diagnose heart failure in sheep.