Coronary ligation and reperfusion arrhythmias, which are thought to be produced by reentry of excitation occurring at and around the acutely infarcted myocardium , were also used. Results showed that E-4031 , D-sotalol , MS-551 and KCB 328 were effective, but other drugs listed in Table 1 were not effective in suppressing the reperfusion VF. There were also differences in the effect of D-so-talol and KCB 328 where these two drugs suppressed reperfusion VF in pentobarbital anesthetized dogs only. Because QT prolongation was more pronounced in halothane anesthetized dogs with lower heart rates, the drug effect on the antifibrillatory mechanism may not be directly related to QT or ERP prolongation. Also, reverse use-dependent QT prolongation was demonstrated in MS-551, while there was no reverse use-dependent prolongation with D-sotalol . These characteristics of class III drugs may not be responsible for their different antifibrillatory effects.
With regard to the arrhythmogenic effect of class III drugs in the control period of the coronary ligation and reperfusion experiments, PVC and/or VT occurred before coronary ligation was applied in halothane anesthetized beagle dogs, but not in the pentobarbital anesthetized beagles. This may be due to halothane because more severe arrhythmogenic effects were observed only in halothane anesthetized dogs. Halothane is known not only to decrease the sinoatrial rate and intensify QT prolongation, but also to induce arrhythmias, especially with catecholamines . Such side effects of class III drugs may explain the clinical occurrence of arrhythmias, when the QT interval is dramatically increased by the drugs. You will always find birth control alesse click here, shopping online with pleasure every time.