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Myocardial protection during cardiac surgery from the viewpoint of coronary endothelial function
1Division of Cardiothoracic Surgery, Grantham Hospital, University of Hong Kong, Hong Kong. gwhe@hkucc.hku.hk
Insights
Cardiac surgery can cause heart injury through ischemia-reperfusion. Protecting heart myocytes and coronary circulation with optimized cardioplegia and supplemental therapy is crucial for patient recovery.
Area of Science:
- Cardiovascular Surgery
- Cardiology
- Physiology
Background:
- Cardiac surgery necessitates heart arrest, inducing ischemia-reperfusion injury.
- Cardioplegia is administered to arrest the heart, minimizing energy consumption and facilitating precise surgery.
- Ischemia-reperfusion injury affects both cardiac myocytes and the coronary circulation, including endothelium-smooth muscle.
Discussion:
- Cardioplegia, while protective, can potentially injure the coronary circulation due to its hyperkalemic components.
- Coronary circulation injury involves endothelium-derived nitric oxide (EDNO) and endothelium-derived hyperpolarizing factor (EDHF) pathways.
- EDNO pathways are vulnerable to ischemia-reperfusion, while EDHF pathways can be affected by hyperkalemic cardioplegia.
Key Insights:
- Understanding the dual injury mechanisms (myocyte and coronary circulation) is vital for comprehensive cardiac protection.
- The EDNO mechanism's susceptibility to ischemia-reperfusion necessitates targeted protective strategies.
- Hyperkalemic cardioplegia's impact on the EDHF mechanism requires careful consideration and potential optimization.
Outlook:
- Supplemental therapy targeting EDNO pathways may enhance myocardial protection.
- Optimizing cardioplegia composition is essential to preserve EDHF-mediated coronary vasodilation.
- Further research into these protective strategies can improve outcomes for patients undergoing cardiac surgery.
Abstract:
1. During cardiac surgery, the heart is arrested and subject to ischaemia-reperfusion 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 but, more importantly, minimizes the energy consumption 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 should also involve these two aspects. 4. Injury to the heart involves: (i) ischaemia-reperfusion injury to the myocytes and coronary circulation; and (ii) possible injury to the coronary circulation 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) mechanisms. The EDNO mechanism is susceptible to ischaemia-reperfusion, whereas the EDHF mechanism may be altered by hyperkalaemic cardioplegia. 6. To further protect the heart, supplemental therapy for EDNO and optimizing the components of cardioplegia to restore the EDHF mechanism may be important.