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J Mol Cell Cardiol. 1993 Dec;25(12):1391-402.

"Dose"-dependency and temporal characteristics of protection by ischaemic preconditioning against ischaemia-induced arrhythmias in rat hearts.

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Rayne Institute, St Thomas' Hospital, London, UK.


Brief episodes of ischaemia and reperfusion (preconditioning) can increase the resistance of the myocardium to ischaemic injury. We investigated the temporal characteristics of anti-arrhythmic protection by preconditioning. Rat hearts underwent regional ischaemia (+/- reperfusion) of the left coronary territory. Control isolated blood-perfused hearts underwent 40 min ischaemia; in the preconditioned groups this was preceded by one, two or three cycles of 5 min ischaemia and 5 min reperfusion. Control anaesthetized rats underwent 60 min ischaemia; this was preceded by three cycles of 3 min ischaemia and 3 min reperfusion in the preconditioned group. Preconditioning led to: (i) the abolition of ventricular fibrillation in both in vivo and in vitro preparations; (ii) a reduced incidence of ventricular tachycardia (from 100% to 8% in vitro and 100% to 25% in vivo); and (iii) a reduced incidence of ventricular premature beats (from 246 +/- 36 to 8 +/- 5 in vitro and 85 +/- 21 to 24 +/- 13 in vivo). In isolated hearts protection was proportional to the number of preconditioning cycles. Although preconditioning caused a dramatic reduction in the severity of arrhythmias it did not result in any significant alteration in their temporal profiles. We conclude that protection by preconditioning against ischaemia-induced arrhythmias is "dose"-dependent in rat hearts in vitro and results in an absolute reduction in the severity of ischaemia-induced arrhythmias rather than an alteration in their time-course, both in vivo and in vitro.

[Indexed for MEDLINE]

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