Comparative effects of three radiographic contrast agents in isolated normal and ischemic canine hearts.

Investigators have sought to improve contrast agents by changing the ionic content or decreasing osmolarity. This study compared the effects of meglumine sodium diatrizoate, sodium meglumine calcium metrizoate, and metrizamide on coronary blood flow, myocardial contractile force, and perfusion pressure under normal and ischemic conditions in eight isolated canine hearts. Diatrizoate had an initial negative inotropic effect, but contractile force returned to baseline within 1 minute during normal perfusion and within 2 minutes under ischemic conditions. Calcium-enriched metrizoate and metrizamide had only a positive inotropic effect under normal perfusion (127 +/- 3.9% and 116 +/- 2.9% of baseline, respectively). During ischemia, however, the positive inotropic effect of sodium meglumine calcium metrizoate was followed by a decrease in contractile force to 93 +/- 5% of baseline after 2 minutes. Metrizamide showed only a positive inotropic effect during ischemia. The myocardial depression that follows the initial positive inotropic effect of calcium may further alter the instability between normal and ischemic areas of the heart, thus increasing the risk of coronary arteriography in patients with severe coronary artery disease.