Effects of intracoronary carbon dioxide on left ventricular function in swine

Abstract

Background and hypothesis: Carbon dioxide is currently used as an arterial and venous contrast agent; however, little is known of its effects on left ventricular function. This study was undertaken to investigate those effects. Methods: Ascending doses of 5, 10, and 20 ml of carbon dioxide were administered into the left main coronary artery of domestic swine with and without a continuous infusion of intravenous nitroglycerin (50 μg/min). Results: Carbon dioxide had an immediate and profound depressant effect on both systolic and diastolic left ventricular function associated with ischemic electrocardiographic changes. Compared with controls (% change), ascending doses of carbon dioxide decreased systolic pressure by −35 ± 7, −48 ± 8, and −53 ± 4 in the absence of nitroglycerin, and by −32 ± 9, −50 ± 9, and −60 ± 9 in the presence of nitroglycerin. Peak +dP/dt decreased by −54 ± 7, −61 ± 11, and −64 ± 3 in the absence of nitroglycerin, and by −36 ± 13, −55 ± 11, and −65 ± 11 in the presence of nitroglycerin. Minimum -dP/dt increased by 65 ± 8, 71 ± 8, and 77 ± 3 in the absence of nitroglycerin, and by 63 ± 7, 71 ± 8, and 78 ± 7 in the presence of nitroglycerin. No significant changes in heart rate were observed; however, widespread ST-segment elevation was observed in all animals. Coronary angiography following carbon dioxide injection revealed a marked decrease in coronary flow velocity until the gas was cleared from the microcirculation. This was also documented by direct measurement of flow velocity using a Doppler catheter in an additional animal. Left ventriculography demonstrated immediate global dilation and depression of systolic function. Conclusions: In the swine model, relatively small doses of intracoronary carbon dioxide cause profound yet reversible global left ventricular dysfunction which appears to be ischemic in origin.