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Influence of storage volume on functional recovery and metabolism of explanted hearts following cold cardioplegia: studies in the rat.

STUDY OBJECTIVE
The aim was to characterise the metabolic and functional recovery after extended periods of hypothermic storage of hearts in varying volume of oxygenated cardioplegic solution.


DESIGN
Explanted rat hearts were arrested with and stored in 5, 10, or 100 ml of oxygenated (95% O2: 5% CO2) St Thomas's Hospital cardioplegic solution No 2 (STH) at 4 degrees C for 5 or 10 h. The isolated working heart model was used to determine the cardiac functions and the degree of functional recovery was expressed as a percentage of the prearrest value. Groups of hearts (n = 6) were rapidly freeze-clamped immediately after arrest, at end of storage, or after 30 min reperfusion for quantitation of the high energy phosphate content.


SUBJECTS
84 Male albino Wistar rats weighing 280 to 320 g (heart weight = 1.25 g) were used.


MEASUREMENTS AND MAIN RESULTS
All hearts in the three different volumes of STH recovered 80% or more [mean 90 (SEM 3)%] of their prearrest aortic output after 5 h storage but after 10 h, recovery was significantly reduced [23(7)%] with no significant difference among groups. During 5 h storage the phosphocreatine content of the hearts rapidly declined from 33.2(3.1) to 5.0(0.2) mumol.g-1 dry wt in the 5 ml group but only to 16.7(1.2) mumol.g-1 dry wt in the 100 ml group. Similarly ATP preservation was improved in the latter group (81% v 63%, p less than 0.02). Extending the storage time to 10 h resulted in a further decline in high energy phosphates (ATP + phosphocreatine) to 30% of normal values in the 100 ml group and to 9% in the 5 ml group (p less than 0.01). While the total nucleotide pool did not decrease the major catabolite was inosine monophosphate (IMP) which comprised 46% of the nucleotide pool in all groups. The extent of cardiac function recovered was correlated inversely with tissue IMP (R = 0.859) and positively with ATP (R = 0.835) but showed no significant correlations with the postischaemic ADP, AMP, or phosphocreatine.


CONCLUSIONS
Increased storage volume of oxygenated cardioplegic solution is superior in the preservation of ATP and phosophocreatine content in donor hearts with full recovery of cardiac function after the first 5 h of hypothermic (4 degrees C) storage.