Left Ventricular Function After Extended Hypothermic Preservation of the Heart Is Dependent on Functional Coronary Capillarity

Abstract

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°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 [Δd̄(c)], perfused capillary number per fiber area [Q A (0) P ], and perfused capillary surface area per fiber volume [S V (c,f) P ]. Capillaries were moderately compressed in both groups after reperfusion (group 1, 19±1%; group 2, 20±1%). Q A (0) P and S V (c,f) P were highly correlated with Δd̄(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 Q A (0) P and S V (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.