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Comparative effects of continuous warm blood and intermittent cold blood cardioplegia on coronary reactivity
1Department of Surgery, Beth Israel-Deaconess Medical Center, Boston, MA 02215, USA.
Insights
Continuous warm blood cardioplegia (cWB-CP) better preserves coronary vascular responses mediated by beta-adrenergic-cyclic adenosine monophosphate pathways compared to intermittent cold blood cardioplegia (iCB-CP). However, this benefit is short-lived, with no significant impact on overall cardiac function.
Area of Science:
- Cardiovascular Physiology
- Cardiac Surgery
- Vascular Biology
Background:
- Cardioplegia strategies impact coronary vascular reactivity.
- Understanding the effects of different cardioplegia types on coronary arterioles is crucial for preserving cardiac function during surgery.
Purpose of the Study:
- To compare the effects of intermittent cold blood cardioplegia (iCB-CP) and continuous warm blood cardioplegia (cWB-CP) on coronary arteriolar function.
- To assess the impact on beta-adrenoceptor-mediated, K+ATP-channel-mediated, and endothelium-dependent relaxation, as well as myogenic tone.
Main Methods:
- Pigs underwent cardiopulmonary bypass with hearts arrested for 1 hour using either iCB-CP or cWB-CP.
- Microvessels were pressurized in vitro to study relaxation responses to various agonists.
- Studies were conducted both immediately after arrest and after 1 hour of reperfusion.
Main Results:
- Both iCB-CP and cWB-CP preserved endothelium-dependent and K+ATP-channel-mediated relaxations.
- Continuous warm blood cardioplegia (cWB-CP) showed superior preservation of beta-adrenergic-cyclic adenosine monophosphate-mediated relaxation compared to iCB-CP, although this effect was transient.
- Myogenic tone was reduced similarly by both methods and was not altered by reperfusion.
Conclusions:
- Continuous warm blood cardioplegia (cWB-CP) offers comparable preservation of endothelium-dependent relaxation and K+ATP-channel function to intermittent cold blood cardioplegia (iCB-CP).
- The enhanced beta-adrenergic-cyclic adenosine monophosphate-mediated coronary responses with cWB-CP are short-lived and do not significantly improve overall myocardial function or myogenic tone post-reperfusion.
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.