Transient ischemia cannot precondition the rabbit heart against postischemic contractile dysfunction

Background. The rat heart is preconditioned against postischemic contractile dysfunction by a brief period of transient ischemia before a prolonged ischemic period. However, the rabbit heart does not receive such cardioprotection from pretreatment with a single transient ischemia periods. We hypothesized that in the rabbit heart, a multiple cycle of transient ischemia is required to reach a threshold necessary to precondition against postischemic contractile dysfunction. Methods. To test this hypothesis, we subjected isolated, perfused rabbit hearts to either one 5-minute transient ischemic period or three 5-minute transient ischemic periods followed by a 40-minute period of warm ischemia and 30 minutes of reperfusion. Control hearts (no pretreatment with transient ischemia) were examined simultaneously. Left ventricular developed pressure was measured with an intraventricular balloon. Results. Postischemic recoveries (expressed as percent of preischemic values) of left ventricular developed pressure for the group with one ischemic period and the group with three ischemic periods were 43% ± 5% (n = 5) and 38% ± 6% (n = 6), respectively. These values were not significantly different from control values. Conclusions. Neither one nor three periods of transient ischemia protect the isolated, perfused rabbit heart from postischemic contractile dysfunction. Therefore, the rabbit heart may not have the capacity to be ischemically preconditioned against postischemic contractile dysfunction.