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Improved protection of chronically inflow-limited myocardium with retrograde coronary sinus cardioplegia
R M Lust1, C E Beggerly, R F Morrison
1Department of Surgery and Physiology, East Carolina University School of Medicine, Greenville, NC 27858.
Insights
Retrograde coronary sinus cardioplegia (CSC) offers superior myocardial protection compared to aortic route cardioplegia (ARC). CSC reduces energetic debt, particularly in collateral-dependent regions, indicating better preservation of heart muscle function.
Area of Science:
- Cardiovascular Surgery
- Myocardial Protection
- Surgical Techniques
Background:
- Coronary artery disease often involves compromised blood flow, necessitating effective myocardial protection strategies during cardiac surgery.
- Conventional aortic route cardioplegia (ARC) is standard, but its efficacy in regions with poor collateral circulation is debated.
- Retrograde coronary sinus cardioplegia (CSC) offers an alternative delivery method for cardioplegic solutions.
Purpose of the Study:
- To compare the effects of retrograde coronary sinus cardioplegia (CSC) and conventional aortic route cardioplegia (ARC) on myocardial reperfusion blood flow patterns.
- To evaluate the efficacy of CSC versus ARC in preserving myocardial function, especially in areas with pre-existing coronary collaterals.
- To assess the impact of each cardioplegia delivery method on reactive hyperemia and energetic debt post-ischemia.
Main Methods:
- 18 mongrel dogs with surgically induced coronary collaterals underwent cardiopulmonary bypass and systemic cooling.
- Hearts were arrested using hypothermic (4°C) hyperkalemic cardioplegic solution delivered via either the aortic root (ARC) or coronary sinus (CSC).
- Following 45 minutes of ischemic arrest, reperfusion blood flow was measured at multiple time points (1, 5, 10, and 60 minutes).
Main Results:
- Both CSC and ARC induced hyperemia in normal myocardial regions.
- Peak reactive transmural flow was significantly higher with ARC (4.55 ml/min/g) compared to CSC (2.12 ml/min/g) (p<0.05).
- ARC demonstrated sustained hyperemia in collateral-dependent regions, whereas CSC showed no significant blood flow changes, suggesting reduced energetic debt and potentially superior protection.
Conclusions:
- Retrograde coronary sinus cardioplegia (CSC) may provide superior myocardial protection compared to aortic route cardioplegia (ARC).
- The reduced hyperemic response with CSC suggests a lower energetic debt, particularly beneficial for chronically inflow-restricted myocardial regions.
- CSC's efficacy in collateral-dependent areas warrants further investigation for improved cardiac surgical outcomes.
Abstract:
The effects of retrograde coronary sinus cardioplegia (CSC) and conventional aortic route cardioplegia (ARC) on reperfusion blood flow patterns were compared in 18 mongrel dogs having ameroid-induced coronary collaterals. Animals were placed on cardiopulmonary bypass and cooled systemically. The aorta was clamped, and the hearts were arrested with a bolus infusion of hypothermic (4 degrees C) hyperkalemic cardioplegic solution delivered either into the aortic root or through a balloon catheter placed in the coronary sinus. After 45 minutes of ischemic arrest, hearts were reperfused, and blood flow patterns were measured at 1, 5, 10, and 60 minutes. In the normal region, a significant hyperemia occurred with both CSC and ARC. However, the peak reactive transmural flow was 120% more with ARC than with CSC (4.55 +/- 0.45 vs. 2.12 +/- 0.19 ml/min/g, respectively; p less than 0.05) and remained elevated after 60 minutes of reperfusion, when CSC flows had returned to control levels. In the collateral-dependent region, a significant hyperemia was observed with ARC that persisted throughout reperfusion. However, with CSC, no significant changes in blood flow were detected at any time during reperfusion. Thus, the decreased hyperemic response after arrest suggests a reduced energetic debt with CSC compared with ARC and may indicate superior myocardial protection with CSC. This is particularly evident in chronically inflow-restricted myocardial regions.