Protection of the ischemic myocardium. Ultrastructural, enzymatic, and functional assessment of the efficacy of various cardioplegic infusates.

The increasing use of cardioplegic protective infusates for reducing ischemic tissue injury requires that all infusates be carefully assessed for any protective or damaging properties. This study describes ultrastructural, enzymatic, and functional assessments of the efficacy of three infusates (Bretschneider, Kirsch, and St. Thomas' Hospital) in a rat heart model of cardiopulmonary bypass and ischemic cardiac arrest. The study reveals a close concordance of results as assessed by the three totally different indices of tissue damage. The results also indicate that, in the rat heart model, the St. Thomas' Hospital solution is an effective protective agent under all conditions studied but the Bretschneider solution is effective only under hypothermic conditions and the Kirsch solution is ineffective under all conditions studied and may exacerbate tissue injury. The studies further suggest that the potentially damaging effects of calcium-free myocardial infusates may be due to their induction of a "calcium paradox."