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Sinus slowing produced by intracoronary arterial injections of hyperosmotic solutions in man
Insights
Intracoronary injections of hyperosmotic agents like Urografin, glucose, and mannitol significantly slow sinus rate in patients. This sinus slowing is likely due to reflex parasympathetic stimulation, not direct effects on the sinus node.
Area of Science:
- Cardiology
- Physiology
Background:
- Intracoronary injections are common diagnostic and therapeutic procedures.
- The physiological effects of various injected solutions on cardiac function, particularly sinus rate, require thorough understanding.
Purpose of the Study:
- To investigate the impact of intracoronary injections of different osmolality solutions on sinus rate.
- To elucidate the mechanism behind observed sinus rate changes.
Main Methods:
- 18 patients underwent intracoronary arterial injections of normal saline, contrast agent (Urografin), hyperosmotic glucose, and mannitol.
- Sinus rate was monitored before and after injections.
Main Results:
- Isosmotic saline did not affect sinus rate.
- Hyperosmotic Urografin, glucose, and mannitol significantly decreased sinus rate (P < 0.001).
- Urografin, with the highest osmolality, caused the most pronounced sinus slowing; glucose and mannitol showed similar effects (P > 0.5).
- Injection site (ipsilateral vs. contralateral to sinus node artery) did not significantly alter sinus slowing (P > 0.2).
Conclusions:
- Hyperosmotic agents injected into coronary arteries can induce significant sinus slowing.
- The observed sinus slowing is unlikely due to direct sinus node effects (hypoxia, pressure) but may involve reflex-mediated parasympathetic stimulation.
Abstract:
The effect of intracoronary arterial injections of 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% Urografin (1.9 Osm. per kilogram of water), 20% glucose (1.3 Osm. per kilogram of water), and mannitol (1.2 Osm. per kilogram of water) decreased the sinus rate significantly (P less than 0.001). Among these solutions, Urografin with the highest osmolality produced the most marked sinus slowing, whereas no significant difference was detected between change in the sinus rate with hyperosmotic glucose and mannitol solutions (P greater than 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 greater than 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.