Investigations into the mechanisms of coronary vasodilation by contrast media in dogs.
OBJECTIVE
The study was performed to clarify the mechanisms underlying contrast-induced coronary vasodilation.


METHODS
The left anterior descending coronary artery of 14 open-chest dogs was perfused at constant pressure. Coronary blood flow (CBF) was measured electromagnetically and used to calculate myocardial oxygen consumption (MVO2). Responses were evaluated during intracoronary infusions (2 mL/ minute) of the ionic contrast medium, Hypaque-76, and the nonionic contrast medium, Isovue-370, and compared with those caused by hypertonic saline solutions with comparable osmolarities. Studies also were conducted using Isovist-300, which is a new nonionic and iso-osmolar contrast medium.


RESULTS
Hypaque-76 and Isovue-370 caused initial peak increases in CBF (reflecting decreases in coronary vascular resistance), which waned rapidly to achieve more modest steady-state increases within 2 to 3 minutes. Both the peak and steady-state increases in CBF were greater during Hypaque-76 than during Isovue-370. The increases in CBF caused by the contrast medium were greater than those caused by the corresponding saline solution. Neither Hypaque-76 nor Isovue-370 changed MVO2-Isovist-300 had no effect on CBF or MVO2.


CONCLUSIONS
The coronary vasodilation by contrast media is the result of a direct vasorelaxing effect rather than secondary to a metabolic mechanism. Hyperosmolarity can account only in part for contrast-induced coronary vasodilation.
Crystal
G J
GJ
Department of Anesthesiology, Illinois Masonic Medical Center, University of Illinois College of Medicine 60657, USA.
Salem
M R
MR
D000818:Animals; D003287:Contrast Media / Q000494:pharmacology*; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels / Q000187:drug effects*; D003973:Diatrizoate / Q000494:pharmacology; D003974:Diatrizoate Meglumine / Q000494:pharmacology; D004285:Dogs; D004338:Drug Combinations; D005260:Female; D007479:Iopamidol / Q000494:pharmacology; D008297:Male; D009206:Myocardium / Q000378:metabolism; D009994:Osmolar Concentration; D010101:Oxygen Consumption; D012462:Saline Solution, Hypertonic / Q000494:pharmacology; D014283:Triiodobenzoic Acids / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
D003287:Contrast Media; D004338:Drug Combinations; D012462:Saline Solution, Hypertonic; D014283:Triiodobenzoic Acids; D003973:Diatrizoate; C033300:iotrolan; D003974:Diatrizoate Meglumine; C027278:urovision; D007479:Iopamidol