Abstract

Summary: Angiographic contrast media induce changes in cardiac and circulatory function. Their effect on the extent of aortic regurgitation in closed-chest sedated dogs was studied. Ascending aortic flow was measured by an electromagnetic transducer, implanted five to ten days earlier when aortic regurgitation had been produced. Sodium iothalamate 80% or 76% sodium methylglucamine diatrizoate (0.5 ml/kg body weight) were injected into the left ventricle. Seconds later there was a decrease in peak rate of left ventricular pressure rise and inconsistent elevation of trans-mural left ventricular end-diastolic pressure but no change in aortic regurgitation. Twelve to sixteen seconds after injection significant hypotension, due to decreased systemic vascular resistance, appeared and was usually accompanied by tachycardia. Diastolic regurgitant volume fell 48‡ 13 (SD)% (p < 0.001) but total stroke volume fell only 10%, regurgitant fraction decreasing 43‡ 11% (p < 0.001). Duration of regurgitation per minute fell, but not consistently (8‡ 11%; p < 0.1), and most of the decrease in regurgitation was due to a fall in regurgitant flow rate early in diastole (36‡ 16%p < 0.001) associated with decrease in aortoventricular pressure difference. Effective cardiac output increased 84‡ 50%. Hypotension and tachycardia disappeared by one minute; then persistent increase in forward flow parameters became associated with variable increase in regurgitation. Left ventricular end-diastolic pressure became elevated. The early changes are consistent with mild depression of left ventricular contractility, but there was no change in aortic regurgitation. Thereafter, hypotension, with or without prominent tachycardia, led to decrease in aortic regurgitation. Subsequently, regurgitation tended to increase above the control value, other concomitant changes being consistent with expansion of intravascular volume. Changes induced in aortic regurgitation by angiographic contrast media are importantly time dependent and secondary to other haemodynamic effects.

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