Role of the Alternans of Action Potential Duration and Aconitine-Induced Arrhythmias in Isolated Rabbit Hearts

Under conditions of Na(+) channel hyperactivation with aconitine, the changes in action potential duration (APD) and the restitution characteristics have not been well defined in the context of aconitine-induced arrhythmogenesis. Optical mapping of voltage using RH237 was performed with eight extracted rabbit hearts that were perfused using the Langendorff system. The characteristics of APD restitution were assessed using the steady-state pacing protocol at baseline and 0.1 µM aconitine concentration. In addition, pseudo-ECG was analyzed at baseline, and with 0.1 and 1.0 µM of aconitine infusion respectively. Triggered activity was not shown in dose of 0.1 µM aconitine but overtly presented in 1.0 µM of aconitine. The slopes of the dynamic APD restitution curves were significantly steeper with 0.1 µM of aconitine than at baseline. With aconitine administration, the cycle length of initiation of APD alternans was significantly longer than at baseline (287.5 ± 9.6 vs 247.5 ± 15.0 msec, P = 0.016). The functional reentry following regional conduction block appears with the progression of APD alternans. Ventricular fibrillation is induced reproducibly at pacing cycle length showing a 2:1 conduction block. Low-dose aconitine produces arrhythmogenesis at an increasing restitution slope with APD alternans as well as regional conduction block that proceeds to functional reentry.