The effects of intracoronary Renografin injection on coronary flow and distribution in dogs following coronary occlusion

To study the effects of a contrast agent commonly used in coronary angiography (Renografin) on myocardial flow distribution, the main left coronary arteries of 9 dogs were cannulated and perfused from the carotid arteries. The left anterior descending coronary artery (LAD) was ligated and cannulated to monitor peripheral coronary pressure (PCP). Myocardial blood flow and distribution were determined with radioactive microspheres before Renografin administration and after resolution of the brief period of hypotension following injection of 2-3.5 cm3 of the contrast agent directly into the coronary perfusion tubing. Renografin significantly increased blood flow to normal myocardial regions (0.90 to 1.51 cm3 . g-1 . min-1, p less than 0.001). Despite this flow augmentation and normal aortic and coronary perfusion pressures. PCP decreased from 28.0 +/- 3.4 to 24.4 +/- 2.8 mm Hg (p less than 0.001), and myocardial blood flow to the central ischemic LAD area halved from 0.17 +/- 0.04 to 0.09 +/- 0.03 cm3 . g-1 . min-1 (p less than 0.025). The inner/outer left ventricular wall blood flow ratio in the central ischemic region increased from 0.28 to 0.39 (p less than 0.05). Thus the contrast agent causes a coronary steal or redistribution of coronary flow away from already ischemic regions, and the endocardium appears to be less affected than the epicardium.