Molecular and cellular biochemistry
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Mol. Cell. Biochem. · Dec 1993
Dissociation between myocardial relaxation and diastolic stiffness in the stunned heart: its prevention by ischemic preconditioning.
The effects of myocardial stunning and ischemic preconditioning on left-ventricular developed pressure and end-diastolic pressure (diastolic stiffness) as well as on coronary-perfusion pressure were examined in isolated isovolumic rabbit hearts. The isovolumic relaxation was evaluated, and the time constant of pressure decay during the isovolumic period was calculated. Our experimental protocol comprised: 1) myocardial stunning-global ischemia (15 min) followed by reperfusion (30 min); 2) myocardial stunning-global ischemia (20 min) followed by reperfusion (30 min); and 3) ischemic preconditioning--a single cycle of brief global ischemia and reperfusion (5 min each), before a second ischemic period, of 20-min duration. ⋯ They were increased after stunning, as also was the coronary perfusion pressure. When the heart was preconditioned with a single episode of ischemia, the systolic and diastolic alterations were completely abolished. We thus concluded that diastolic abnormalities incurred by myocardial stunning consist in both an increase in diastolic stiffness and an early impairment of isovolumic relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)