Comparative effects of continuous warm blood and intermittent cold blood cardioplegia on coronary reactivity.
BACKGROUND
Cardioplegia is known to affect coronary vascular reactivity. We examined the effects of intermittent cold and continuous warm blood cardioplegia on beta-adrenoceptor-mediated, adenosine triphosphate-sensitive K+ (K+ATP)-channel-mediated, and endothelium-dependent relaxation and on the myogenic tone of coronary arterioles.


METHODS
Pigs were placed on cardiopulmonary bypass. Hearts were arrested for 1 hour with a cold blood cardioplegic solution administered intermittently (n = 12; iCB-CP) or with a warm blood cardioplegic solution delivered continuously (n = 12; cWB-CP). Selected hearts (n = 6 in each group) were then reperfused for 1 hour. In vitro relaxation responses of precontracted microvessels (50 to 160 microns) were studied in a pressurized no-flow state.


RESULTS
Relaxation in response to isoproterenol (beta-adrenergic agonist) was similar after iCB-CP and cWB-CP, whereas forskolin (adenylate cyclase activator)-induced relaxation was impaired more after iCB-CP than after cWB-CP. After reperfusion the respective responses were similar. Both iCB-CP and cWB-CP preserved receptor-mediated, endothelium-dependent relaxation in response to adenosine, 5'-diphosphate; non-receptor-mediated endothelium-dependent relaxation in response to A23187; endothelium-independent cyclic guanosine monophosphate-mediated relaxation in response to sodium nitroprusside, and K+ATP-channel-mediated relaxation. Relaxations in response to 8-bromo-cyclic guanosine monophosphate (a cyclic guanosine monophosphate-dependent protein kinase activator) and to 8-bromo-cyclic adenosine monophosphate (a cyclic adenosine monophosphate-dependent protein kinase activator) were impaired after iCB-CP alone and after reperfusion, whereas the respective responses were not affected after cWB-CP. Myogenic tone was decreased similarly after iCB-CP and cWB-CP but was not further altered after reperfusion. Cardiac function was similar after iCB-CP and cWB-CP.


CONCLUSIONS
These results suggest that cWB-CP is similar to iCB-CP in its ability to preserve endothelium-dependent relaxation and K+ATP-channel function. The superior preservation of beta-adrenergic-cyclic adenosine monophosphate-mediated coronary responses after cWB-CP is brief and associated with minimal improvement of myocardial function and myogenic tone.
Tofukuji
M
M
Department of Surgery, Beth Israel-Deaconess Medical Center, Boston, MA 02215, USA.
Stamler
A
A
Li
J
J
Hariawala
M D
MD
Franklin
A
A
Sellke
F W
FW
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D001769:Blood; D000001:Calcimycin / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006152:Cyclic GMP / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000502:physiology; D004789:Enzyme Activation; D006146:Guanidines / Q000494:pharmacology; D006324:Heart Arrest, Induced / Q000379:methods*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008833:Microcirculation / Q000187:drug effects / Q000502:physiology; D020110:Pinacidil; D015221:Potassium Channels / Q000378:metabolism; D013552:Swine; D013696:Temperature; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology
D000318:Adrenergic beta-Agonists; D006146:Guanidines; D015221:Potassium Channels; D014665:Vasodilator Agents; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000001:Calcimycin; D000244:Adenosine Diphosphate; D020110:Pinacidil; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases; D006152:Cyclic GMP; D007545:Isoproterenol