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Left ventricular function after extended hypothermic preservation of the heart is dependent on functional coronary
L H Manciet1, K A Fox, J G Copeland
1University of Arizona Health Sciences Center, Department of Surgery, Tucson 85724, USA.
Insights
Hypothermic preservation can injure heart microcirculation. Recovery of heart function after preservation is directly linked to coronary capillary perfusion, regardless of reperfusate composition.
Area of Science:
- Cardiovascular Science
- Physiology
- Biomedical Engineering
Background:
- Hypothermic myocardial preservation is crucial for cardiac surgery.
- Injury to the microcirculation during this process may impair post-reperfusion heart function.
Purpose of the Study:
- To investigate the relationship between microcirculatory no-reflow and left ventricular function after hypothermic cardiac preservation.
- To compare the effects of reperfusion with dilute whole blood (DWB) versus washed red blood cells (K2RBC) on capillary perfusion and cardiac function.
Main Methods:
- Rat hearts underwent hypothermic preservation (6 hours) followed by reperfusion with K2RBC or DWB/K2RBC mixtures.
- Left ventricular developed pressure (LVDP) was measured.
- Morphometric analysis quantified capillary compression, perfused capillary number, and perfused capillary surface area.
Main Results:
- Capillary compression occurred in both reperfusion groups.
- Perfused capillary number and surface area strongly correlated with capillary compression in K2RBC-reperfused hearts.
- A weaker correlation was observed in DWB-reperfused hearts, suggesting additional factors contribute to no-reflow.
Conclusions:
- Factors beyond capillary compression influence no-reflow in DWB-reperfused hearts.
- Recovery of left ventricular function post-hypothermic ischemia is directly dependent on coronary capillary perfusion upon reperfusion.
Background:
A growing body of knowledge has led to the hypothesis that injury to the microcirculation during hypothermic myocardial preservation may result in decreased contractility of hearts upon reperfusion.
Methods And Results:
To test this hypothesis, we examined the relationship between no-reflow and left ventricular function after hypothermic cardiac preservation after reperfusion with solutions containing dilute whole blood (DWB) or washed red blood cells (K2RBC). Rat hearts were arrested with high-potassium cardioplegia, then flushed and stored for 6 hours in low-potassium cardioplegia at 4 degrees C. Hearts were reperfused at a constant flow rate (4 mL/min) with K2RBC for 60 minutes (group 1, n = 5) or DWB for 7 minutes followed by 53 minutes of K2RBC (group 2, n = 5). Left ventricular developed pressure (LVDP) was measured with an intraventricular balloon. Immediately after functional assessment, hearts were perfused with an india ink solution to mark flow, then glutaraldehyde. Morphometric techniques were used to determine the degree of capillary compression [delta d(c)], perfused capillary number per fiber area [QA(0)P], and perfused capillary surface area per fiber volume [Sv(c,f)P]. Capillaries were moderately compressed in both groups after reperfusion (group 1, 19 +/- 1%; group 2, 20 +/- 1%). QA(0)P and Sv(c,f)P were highly correlated with delta d(c) in hearts reperfused with K2RBC (r = .92 and r = .92; P < .01). Although statistically significant, the correlation was not as strong in DWB-reperfused hearts (r = .66 and r = .67; P < .05). LVDP was correlated to QA(0)P and Sv(c,f)P (r = .86 and r = .87, respectively) for groups 1 and 2.
Conclusions:
The weaker correlation between capillary perfusion and capillary compression in DWB-reperfused hearts suggests that factors other than compression contribute to no-reflow after hypothermic preservation. Regardless of the composition of the reperfusate, recovery of left ventricular function after hypothermic ischemia is directly related to coronary capillary perfusion upon reperfusion.