Background: Modulation of ischemia-dependent pathways alters electrophysiological evolution of ventricular fibrillation(VF). Hypothesis: 1)There is regional disease-related expression of KATP-channels in human cardiomyopathic hearts. 2)KATP-channel blockade promotes spontaneous VF termination by attenuating spatiotemporal dispersion of refractoriness(ΔERP). Methods and Results: Electric mapping of control(n=6) and treatment(n=9) (10 μmol/L glibenclamide) isolated human cardiomyopathic hearts was performed. Spontaneous defibrillation and KATP-subunit gene expression were studied. Spontaneous VF termination occurred in 1/6 control and 7/8 treated hearts (P=0.026). After 180 seconds of ischemia, LV transmural dispersion in VF cycle length was observed(p=0.001), which was attenuated by glibenclamide. There was greater gene expression of all KATP-subunit on the endocardium compared with the epicardium(P<0.02). In ischemic rat heart model, ΔERP was verified with pacing protocols (36±5ms vs 4.9±4ms, p=0.019). Conclusions: KATP channel subunit gene expression is heterogeneously altered in the cardiomyopathic human heart. Blockade of KATP channels promotes spontaneous defibrillation by attenuating ischemia-dependent ΔERP during VF.

Background: Modulation of ischemia-dependent pathways alters electrophysiological evolution of ventricular fibrillation(VF). Hypothesis: 1)There is regional disease-related expression of KATP-channels in human cardiomyopathic hearts. 2)KATP-channel blockade promotes spontaneous VF termination by attenuating spatiotemporal dispersion of refractoriness(ΔERP). Methods and Results: Electric mapping of control(n=6) and treatment(n=9) (10 μmol/L glibenclamide) isolated human cardiomyopathic hearts was performed. Spontaneous defibrillation and KATP-subunit gene expression were studied. Spontaneous VF termination occurred in 1/6 control and 7/8 treated hearts (P=0.026). After 180 seconds of ischemia, LV transmural dispersion in VF cycle length was observed(p=0.001), which was attenuated by glibenclamide. There was greater gene expression of all KATP-subunit on the endocardium compared with the epicardium(P<0.02). In ischemic rat heart model, ΔERP was verified with pacing protocols (36±5ms vs 4.9±4ms, p=0.019). Conclusions: KATP channel subunit gene expression is heterogeneously altered in the cardiomyopathic human heart. Blockade of KATP channels promotes spontaneous defibrillation by attenuating ischemia-dependent ΔERP during VF.

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Calcium tolerant pig and rabbit cardiomyocytes were isolated using retrograde aortic perfusion of nominally calcium-free collagenase. Preconditioning protocols used 1 or 3 x l0-min episodes of ischemic pelleting or pre-incubation with 100 μM adenosine, followed by a 15-min post-incubation and 180-240-min ischemic pelleting. Control cells were incubated and washed in parallel with the experimental groups. Injury was assessed by determination of cell morphology, trypan blue permeability following osmotic swelling, lactate and HPLC analysis of adenine nucleotides. Preconditioned pig cardiomyocytes had a reduced rate of ischemic contracture, but protection occurred without conservation of ATP. Preconditioned rabbit cardiomyocytes were protected without significant changes in rates of ischemic contracture or ATP depletion. Incubation of ischemic cells with the protein phosphatase inhibitor, fostriecin, at PP2A-selective concentrations (0.1-10 μM), mimicked preconditioning in both rabbit and pig cardiomyocytes. In rabbits, the K(ATP) channel blocker, 5-hydroxydecanoate (5-HD), did not block preconditioning or fostriecin protection. In the pig, 5-HD blocked both preconditioning and fostriecin protection, with return of the rates of ischemic contracture to control. However, 5-HD was an effective blocker of protection only in early ischemia. Fostriecin mimicked preconditioning in the rabbit and the early responses of the preconditioned pig. Preconditioning appears associated with protein phosphorylation in both the rabbit and the pig, but major pathways leading to protection may differ in the two species.