Cardiac slowing occurring during diagnostic coronary arteriography was studied in 78 patients. Comparable degrees of slowing occurred with
injections into the right and into the left coronary arteries into the contralateral artery, and with
injections into the coronary artery giving rise to the sinus node artery and into the contralateral artery. Rapid intracoronary
injections of isosmotic
dextrose solution produced significantly less slowing than comparable
injections of contrast medium. Slow
injections of contrast medium produced cardiac slowing comparable to that caused by rapid
injections of contrast medium. However, the cardiac slowing was significantly greater than that produced by rapid
injections of
dextrose solution. Inhalation of 100%
oxygen did not alter the heart rate response to
injections of contrast medium.
Atropine produced dose-related attenuation of cardiac slowing.
Bradycardia persisting after
cholinergic blockade was significantly greater after
injections into the coronary artery supplying the sinus node than it was after
injections into the contralateral artery. Coronary arteriography produced transient, occasionally profound, arterial
hypotension in 38 of 41 patients in whom arterial pressures were recorded. Arterial pressure did not change in three patients. This study suggests that the cardiac slowing which occurs during coronary arteriography in man is due primarily to a
cholinergic reflex which may be a human counterpart of the Bezold-Jarisch reflex, observed heretofore only in experimental animals. This slowing appears to be mediated primarily by receptors sensitive to contrast medium, rather than by changes of coronary artery pressure, and secondarily, by direct depression of sinus node function by contrast medium.