Myocardial protection during cardiac surgery from the viewpoint of coronary endothelial function

1. During cardiac surgery, the heart is arrested and subject to ischaemia-r eperfusion injury. 2. To protect the heart, cardioplegia is usually used to initially stop and then maintain the still condition of the heart, which not only facilitates the precise operation hut, more importantly, minimizes the energy consumpt ion of the heart during this period, 3. The ischaemia-reperfusion injury may involve both myocytes and coronary endothelium-smooth muscle and, therefore, the protection of the heart shoul d also involve these two aspects, 4. Injury to the heart involves: (i) ischaemia-reperfusion injury to the my ocytes and coronary circulation; and (ii) possible injury to the coronary c irculation by cardioplegia due to its hyperkalaemic components. 5. Injury to the coronary circulation may involve both endothelium-derived nitric oxide (EDNO) and endothelium-derived hyperpolarizing factor (EDHF) m echanisms, The EDNO mechanism is susceptible to ischaemia-reperfusion, wher eas the EDHF mechanism may be altered by hyperkalaemic cardioplegia, 6. To further protect the heart, supplemental therapy for EDNO and optimizi ng the components of cardioplegia to restore the EDHF mechanism may be impo rtant.