The effect of cardioplegic oxygenation on the correlation between the linearized Frank-Starling relationship and myocardial energetics in the ejecting postischemic heart.

To ascertain whether oxygenated cardioplegia is beneficial during surgically induced global ischemia, 27 canine hearts underwent sonomicrometric determination of cardiac mechanics and energetics during volume loading on right heart bypass before and after 2 hr of potassium cardioplegic arrest with crystalloid, oxygenated crystalloid, or blood vehicles. The slope of the linear stroke work vs end-diastolic volume relationship, an index of contractility, was preserved by each vehicle. Similarly, oxygen utilization to perform external mechanical work during reperfusion was unaffected in all groups. However, there were significant 119% and 122% increases in basal oxygen utilization after both unoxygenated and oxygenated crystalloid cardioplegia (p less than .05) that were prevented by the blood-based vehicle. These data suggest that the salutary effects of blood cardioplegia on postischemic myocardial energetics may not be solely mediated by its oxygen-carrying capacity.