Sinus slowing produced by intracoronary arterial injections of hyperosmotic solutions in man

Summary The effect of intracoronary arterial injectionsof normal saline, contrast agent, hyperosmotic glucose, and mannitol solutions on the sinus rate was studied in 18 patients. Sinus slowing was not produced by isosmotic saline (0.3 Osm. per kilogram of water) when injected into either coronary artery, whereas 76 per cent Urografin (1.9 Osm. per kilogram of water), 20 per cent glucose (1.3 Osm. per kilogram of water) decreased the sinus rate significantly (P 0.5). Moreover, there was no significant difference between the degree of sinus slowing produced by intracoronary injections into the coronary artery of the side which the sinus node artery originated from and the slowing produced by contralateral injections with hyperosmotic solutions (P>0.2). Therefore, it seems unlikely that this sinus slowing would be a result of a direct action on the sinus node including hypoxia and elevated perfusion pressure. Reflex-mediated parasympathetic stimulation may be operative.