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Gross and microvascular distribution of retrograde cardioplegia in explanted human hearts
R N Gates1, H Laks, D C Drinkwater
1Department of Surgery, University of California, Los Angeles, Medical Center 90024.
Insights
Retrograde blood cardioplegia effectively perfuses all ventricular regions. However, significant shunting through thebesian veins limits nutrient delivery to the right ventricle microvasculature during cardiac surgery.
Area of Science:
- Cardiovascular Surgery
- Cardiomyology
- Transplantation Medicine
Background:
- Idiopathic cardiomyopathy is a leading cause for heart transplantation.
- Preservation of the coronary sinus venous system is crucial for effective cardioplegia delivery.
- Understanding cardioplegia distribution is vital for optimizing myocardial protection.
Purpose of the Study:
- To evaluate the distribution and efficacy of retrograde blood cardioplegia in explanted human hearts.
- To assess the extent of microvascular perfusion in both ventricles during retrograde infusion.
- To identify potential shunting pathways affecting cardioplegia delivery.
Main Methods:
- Explanted hearts from transplant recipients underwent retrograde blood cardioplegia infusion.
- Coronary sinus and coronary arteries were cannulated for infusion and effluent collection.
- Hearts were fixed and perfused with an inert marker (NTB-2) for histological analysis.
- Histologic sections from 12 sites were examined to quantify capillary perfusion.
Main Results:
- No significant difference in cardioplegia perfusion between left and right ventricular regions.
- A substantial portion (67.2%) of retrograde cardioplegia shunted through thebesian veins, bypassing microvasculature.
- Myocardial perfusion was observed in 29.3% of the left ventricle and 3.5% of the right ventricle.
- Nutrient flow to the right ventricle microvasculature was found to be minimal.
Conclusions:
- Retrograde blood cardioplegia ensures perfusion of all ventricular regions.
- Thebesian venous shunting significantly impacts cardioplegia distribution and efficacy.
- Further strategies may be needed to enhance microvascular nutrient delivery to the right ventricle.
Abstract:
In this report, explanted hearts from transplant recipients with the diagnosis of idiopathic cardiomyopathy underwent a blood cardioplegia arrest and extended subatrial resection to preserve their coronary sinus venous system. The coronary sinus and left and right coronary arteries were then cannulated and warm blood cardioplegia retrograde infused at a pressure of 30 to 40 mm Hg. Effluent from the coronary arteries and thebesian veins was then collected. Hearts were subsequently fixed with retrograde glutaraldehyde perfusion and perfused retrograde with NTB-2 (an inert intracapillary marker). Histologic sections were examined from 12 separate sites. There was no significant difference in the percentage of capillaries perfused by retrograde-delivered cardioplegia between corresponding regions of the left and right ventricles. However, effluent analysis indicated that 67.2% +/- 6.4% of retrograde-delivered blood cardioplegia was shunted through thebesian veins, thereby bypassing the microvasculature, whereas 29.3% +/- 6.3% and 3.5% +/- 3.1% traversed the myocardium supplied by the left and right coronary arteries, respectively. The results indicate that all regions of both ventricles are perfused by retrograde blood cardioplegia. However, they also suggest that nutrient flow to the microvasculature of the right ventricle is minimal during retrograde cardioplegia.