Differing susceptibilities to cold preservation of rat atria and ventricles

The susceptibilities of atria and ventricles to cold preservation were studied in rat hearts. Rat hearts were stored in Collins' solution at 4 degrees C for 0, 12, or 24 hours, and the atrial and ventricular function was measured in a working heart model and in isolated atrial and papillary muscle preparations. In working heart preparations, cardiac output decreased to 0 ml/min and other parameters of ventricular function (systolic and end-diastolic pressure and dP/dt of the left ventricle) markedly deteriorated after 12 hours of preservation. After 24 hours, no contraction of the left ventricle was observed despite the presence of atrial contraction. In isolated atrial muscle preparations, the rate of spontaneous beating of the right atrium was not affected by cold preservation. The twitch contractions of right and left atria were attenuated but elicited after 24 hours. In electrically driven papillary muscles, twitch contractions were also markedly attenuated by 12 hours of preservation and were abolished after 24 hours. The positive inotropic effect of isoproterenol was also markedly attenuated in the atrial preparations by cold preservation. However, the positive chronotropic response to isoproterenol and the negative chronotropic and inotropic responses to carbachol were little affected by cold preservation. Intramural cholinergic and adrenergic nerve stimulation produced first negative and then positive effects on the beating rate and twitch contraction in the isolated right atria. Cold preservation selectively attenuated and finally abolished the adrenergic responses. In the ventricles, the adenosine triphosphate and creatine phosphate content significantly decreased and the lactate content increased with an increase in the preservation period. On the other hand, changes of such metabolites in the atria were either not observed or were much smaller. These results suggest that atrial function is maintained better than ventricular function in the cold-preserved heart.