Preconditioning during warm blood cardioplegia

Objective: Preconditioning describes the cardioprotective effects of multiple brief episodes of warm ischemia. The purpose of the study was to determine whether warm ischemia, during the intermittent delivery of warm blood cardioplegia, would induce preconditioning during cardioplegia arrest. Methods: Dogs, 15, were randomized to a preconditioning protocol or to serve as controls. The control group received 60 min of continuous warm blood cardioplegia (WBC) followed by 30 min of warm arrested ischemia. The preconditioned group were arrested with WBC and then underwent three consecutive cycles consisting of 10 min of warm ischemia followed by 10 min of reperfusion. Reperfusion was provided by a continuous infusion of WBC. The preconditioning protocol was followed by 30 min of warm arrested ischemia. Myocardial functional recovery was assessed before cardiopulmonary bypass and cardioplegia arrest and again 30, 60 and 90 min after the arrest. Pressure-volume loops were used to measure the maximum elastance of the left ventricle (E_max), diastolic compliance, and used to calculate preload recruitable stroke work area. Results: Myocardial functional recovery was better preserved after 30 min of warm arrested ischemia in those animals that had been preconditioned. Conclusion: Preconditioning may be induced when warm blood cardioplegia is delivered intermittently during cardioplegia arrest.