RATIONALE AND OBJECTIVES
This study was designed to compare the effects of ionic contrast medium (CM), Renografin-76 (R76), and nonionic CM, Omnipaque-350 (OM350), on coronary hemodynamics and myocardial metabolism.
In 10 open-chest, atrial-paced dogs, 4 mL of R76 and OM350 were injected into the left anterior descending coronary artery. Coronary blood flow (CBF), myocardial oxygen consumption (MVO2), lactate extraction (LE), left ventricular (LV) dp/dt, and aortic systolic pressure (AOP) were measured.
The maximal CBF changes caused by OM350 and R76 were 23.7 ± 3.3 mL/minute and 18.3 ± 3.3 mL/minute (NS), respectively. OM350 produced an increase in LV dp/dt by 378 ± 85 mm Hg/second, which was different from – 244 ± 65 mm Hg/second by R76 (P < .05). The changes in MVO2 and LE after OM350 injection were 2.6 ± 0.6 mL/minute and 10.2 ± 5 μM/minute, respectively; those were different from – 0.1 ± 0.4 mL/minute, and –7.7 ± 5.1 μM/minute after R76 injection (P < .05).
Although both agents increased CBF, they appeared to act by different mechanisms. That a direct coronary vasodilator effect is the main action of R76 on coronary vascular response is suggested by decreasing myocardial contractility and oxygen consumption. However, OM350, by enhancing both parameters, may augment CBF at least in part by autoregulation.