Immediate effects of graded ionic and nonionic contrast injections on coronary blood flow and myocardial function. Implications for digital coronary angiography.

The comparative immediate effects of ionic and nonionic contrast agents on coronary blood flow and regional function have not been studied. Therefore, subselective intracoronary injections of iohexol and sodium meglumine diatrizoate (Renografin 76) were compared at different rates (1, 3, and 4 mL/sec) and volumes (2 and 4 mL). Open chest dogs were instrumented with electromagnetic flow probes, subendocardial ultrasonic crystals, and a subselective intracoronary catheter. The 2- and 4-mL volumes of Renografin infused at 3 mL/sec, caused reductions in coronary blood flow that were maximal at 2 to 3 seconds after injection. These changes were significant for the 4-mL dose (61 +/- 19 at control vs. 23 +/- 12 mL/min, mean +/- SD, P less than .01) but not for the 2-mL dose. Iohexol produced identical flow responses but regional function was not significantly altered, whereas Renografin caused significant depression at both dose levels. Injections of 4 mL of Renografin at 1 and 4 mL/sec caused maximal flow decrements at 4.5 and 2 seconds after injection, respectively. Again, iohexol caused identical responses. At these doses, the effects of iohexol on regional function were also identical to those of Renografin. Thus, despite differences in physical properties, no significant differences in early blood flow changes were detected between these two agents.