Therapy of Venous Hypertension in Calves with Total Artificial Heart (TAH)

Abstract

Vasomotor disregulation, preponderantly expressed by a pathological increase of central venous pressure (CVP) in calves with total artificial heart (TAH), starts to be evident from about the 50th day of pumping. The main cause of this state is an imbalance in cardiac receptor areas. Ventricular vasodepressor mechanisms are eliminated with the ventricular tissue, which is replaced by the artificial blood pump. In the stumps of both atria, which remain in situ, all neural elements disappear immediately after TAH implantation, but within two months they are fully regenerated. Regenerated atrial receptors are the starting points of afferent neural stimuli, which in the vasomotor center of the brainstem, increase the activity of the vasoconstricting functional component. A general tendency to vasoconstriction, now not well counterbalanced, increases, and the progressive venous hypertension causes loss of liver function and morphology. Two therapeutic approaches were tried: afferent therapy by atrial electrical stimulation, and efferent therapy by the administration of antihypertensives. Both kinds of this therapy were sufficiently effective in reducing CVP, protecting the liver, and prolonging average survival.