Effects of Acetylstrophanthidin on Coronary Vascular Resistance and Myocardial Oxygen Consumption

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Abstract
The effects of acetylstrophanthidin on coronary circulation were studied in 31 dogs. Coronary blood flow was measured in empty beating hearts or in fibrillating hearts by collecting coronary venous return during perfusion of the systemic circulation (cardiopul-monary bypass). In 14 animals with ventricular fibrillation, acetylstrophanthidin caused an initial coronary constriction and fall in coronary blood flow. This was followed, after approximately 10 minutes, by a significant drop in resistance and a rise in coronary blood flow which persisted for the remainder of the experiment. Associated with the increase of blood flow was an increase of myocardial oxygen consumption. This effect was not abolished by ganglionic blockade, cardiac denervation or bilateral adrenalectomy. In nine dogs with beating but empty hearts, after the initial constriction of the coronary vessels, there was only a small change in coronary blood flow and resistance, although myocardial oxygen consumption was increased. The lack of coronary vasodilatation was attributed to increased mechanical resistance due to the augmented force of contraction produced by the drug.