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Potential deleterious effect of [Beta]-adrenergic stimulation during warm-blood cardioplegia in rabbit hearts Cook, Richard Chung-Sop

Abstract

We hypothesized that β-adrenergic stimulation with isoproterenol during continuous normothermic cardioplegic arrest would enhance the regenerative and regulatory function of the myocardium, resulting in improved cardiac function. We studied isolated rabbit hearts paced at ~200 beats/minute and cross-circulated by a support rabbit. We measured ventricular pressure over a range of ventricular volumes to determine maximal elastance at baseline and 20 and 45 minutes after discontinuation of cardioplegia. Myocardial oxygen consumption measurements were performed simultaneously and during cardioplegic arrest. Hearts were prospectively randomized to receive either isoproterenol 0.1M or control in blinded fashion for 10 minutes during a 1 hour continuous warm blood cardioplegic arrest. Compared to control hearts, isoproterenol-treated hearts had trends towards longer time to first spontaneous heart-beat (control 141 ± 43 vs isoproterenol 200 ± 74 seconds, p = 0.07), and longer time to capture of atrial pacing (control 214 ± 52 vs isoproterenol 288 ± 91 seconds, p = 0.06). There was no difference observed in the myocardial oxygen consumption between isoproterenol-treated and control groups of hearts. Myocardial oxygen consumption decreased during administration of cardioplegia (p

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