Effects of intracoronary carbon dioxide on left ventricular function in swine

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.

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 micrograms/min).

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.

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.