Preconditioning Attenuates the Shortening of Recovery During Coronary Occlusion in Isolated Rabbit Hearts With d-Sotalol-Induced Long QT Intervals

The effects of 20-min ligations of the anterior branch of the left coronary artery were studied in Langendorff-perfused rabbit hearts with 92 microM D-sotalol added to the perfusate to induce long QT intervals and triggered arrhythmias. Epicardial electrograms, a left ventricular endocardial monophasic action potential, and simulated X and Y lead electrocardiograms were used to characterize ventricular conduction and recovery. In contrast to previous work showing that global ischemia eliminated triggered activity, coronary occlusion did not alter its mean incidence. Although the anatomic distribution of earliest sites of epicardial activation by triggered beats was altered, triggered beats still appeared on the epicardial surface in the nonperfused regions. Coronary occlusion had a small and variable effect on epicardial conduction velocity but caused a significantly greater percent shortening of epicardial activation-recovery intervals in the nonperfused region of hearts given D-sotalol than in control hearts. In hearts given D-sotalol, preconditioning significantly attenuated the shortening of epicardial activation-recovery intervals in response to coronary occlusion. However, preconditioning had no effect on the mean incidence of triggered activity during coronary occlusion. Thus, the persistence of triggered activity and the shortened myocardial recovery time associated with coronary occlusion could contribute to increasing the likelihood of occurrence of malignant ventricular arrhythmias. Preconditioning by attenuating the shortening of recovery would be anti-arrhythmic.