reversal of ischemic damage with secondary blood cardioplegia after severe ischemic injury it is usually necessary to prolong bypass to enhance recovery this study tests the hypothesis that the best reversal of ischemic damage is achieved by briefly rearresting the postischemic heart with a continuous infusion of an oxygenated cardioplegic solution secondary blood cardioplegia during the period when bypass must be prolonged twenty dogs underwent 45 minutes of normothermic ischemic arrest fifteen minutes after unclamping no heart could support the systemic circulation in all dogs oxygen demands were lowered by extending bypass for 30 minutes in 10 of these dogs demands were further lowered by rearresting the heart for 5 minutes with a continuous infusion of a 37 degrees c blood cardioplegic solution k28 meql ph 76 ca 1 meql at a pressure of 50 mm hg hearts treated with secondary blood cardioplegia showed greater recovery in the rate of contraction dpdt 75 versus 62 p less than 005 and relaxation dpdt 76 versus 58 p less than 005 better recovery of compliance 85 versus 51 p less than 005 a higher stroke work index 072 versus 050 gmmkg p less than 005 and more ability to augment oxygen uptake 85 versus 45 p less than 005 to meet the demands of the working heart than hearts treated by prolonging bypass alone we conclude that rearresting the heart with a brief continuous infusion of a blood cardioplegic solution results in more complete reversal of ischemic damage than possible by prolongation of a bypass alone we believe that the increased recovery with secondary cardioplegia results from diversion of delivered oxygen toward reparative processes rather than its being expended needlessly on electromechanical work during the time when bypass must be prolonged