Direct chronotropic and dromotropic actions of contrast media: ineffectiveness of atropine in the prevention of bradyarrhythmias and conduction disturbances.

Methyl glucamine sodium diatrizoate (Renografin 76) was directly infused into the isolated arteries to the sino-atrial and atrioventricular nodes of anesthetized dogs, causing a dose-related inhibition of sino-atrial nodal automaticity and atrioventricular nodal conductivity; these effects were not attenuated by autonomic blockade or cervical vagotomy. The important negative chronotropic and dramatropic effects of contrast media used for coronary angiography are direct actions and cannot be effectively blocked by premedication with atropine.