Effect of cardioplegic arrest and reperfusion on coronary reserve and autoregulation.
BACKGROUND
The effects of cardioplegic arrest and reperfusion on the coronary vasculature remain to be characterized. This study was designed to investigate changes in coronary reserve and autoregulation after hypothermic cardioplegic arrest and reperfusion.


METHODS
Isolated rabbit hearts were perfused in a retrograde manner with Krebs-Henseleit bicarbonate buffer solution at a pressure of 80 cm H2O. Baseline measurements were performed for (1) coronary flow; (2) vasodilatory response to 5-hydroxytryptamine (10(-7) mol/L) and nitroglycerin (10(-4) mol/L); (3) autoregulatory capacity, quantified as closed-loop gains; and (4) isovolemic left ventricular function. Hearts were then subjected to cardioplegic arrest for 90 minutes. Twenty minutes after reperfusion, measurements were repeated.


RESULTS
Coronary flow decreased significantly after reperfusion (6.2 +/- 1.1 versus 5.3 +/- 1.1 mL.min-1.g-1; p < 0.01). The response to 5-hydroxytryptamine as percentage increase of flow decreased significantly after reperfusion (134.0% +/- 12.0% versus 109.1% +/- 6.8%; p < 0.01). However, there was no significant change in the response to nitroglycerin after reperfusion (121.3% +/- 17.6% versus 136.6% +/- 13.3%). The closed-loop gain demonstrated negative values before arrest but became positive after reperfusion, indicating loss of autoregulation after reperfusion. There was no significant change in left ventricular function.


CONCLUSIONS
The coronary flow reserve in response to 5-hydroxytryptamine and autoregulation were impaired after cardioplegic arrest and reperfusion, whereas nitroglycerin-induced vasodilatory response and left ventricular function were preserved.
Gohra
H
H
First Department of Surgery, Yamaguchi University School of Medicine, Japan.
Tsuboi
H
H
Sasaki
G
G
Minami
Y
Y
Hamano
K
K
Katoh
T
T
Fujimura
Y
Y
Esato
K
K
D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006324:Heart Arrest, Induced; D006706:Homeostasis; D066298:In Vitro Techniques; D015425:Myocardial Reperfusion; D005996:Nitroglycerin / Q000494:pharmacology; D011817:Rabbits; D012701:Serotonin / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013318:Stroke Volume; D014665:Vasodilator Agents / Q000494:pharmacology; D016277:Ventricular Function, Left
D017366:Serotonin Receptor Agonists; D014665:Vasodilator Agents; D012701:Serotonin; D005996:Nitroglycerin