Histogram of the aconitine-induced arrhythmia time threshold (NS: n=10; Andro: VPC, n=10; VT, n=7) (A). Histogram of the aconitine threshold (NS: n=10; Andro: VPC, n=10; VT, n=7) (B). VPC and VT appeared in all 10 NS group rabbits, and in 10 and 7 Andro group rabbits, respectively. Rabbit mortality before and after andrographolide treatment (NS: n=10, Andro: n=10) (C). Incidence of aconitine-induced multiple ventricular arrhythmias in the two groups (D). VPC was triggered successfully in all animals, but VT and VF incidences were reduced in the Andro group. Time-dosage threshold curve of various types of ventricular arrhythmias (E). VPC, VT and VF were observed in all 10 NS group rabbits, and in 10, 7, and 1 of 10 Andro group rabbits, respectively. Typical ECG tracings showing various types of ventricular arrhythmias before (Fa) and after aconitine treatment (2 μg/kg/min) (Fb–d) VPC, VT, and VF began to appear at 17, 23, and 47 min (F). Typical ECG tracings before (Ga) and after andrographolide (10 mg/kg) and aconitine (2 μg/kg/min) treatment (Gb–d). The times of the four ECG tracings in (G) were consistent with those in (F). After andrographolide treatment, VPC appeared at 47 min, and arrhythmia did not appear at either 17 or 23 min. *p<0.01 vs NS. NS: normal saline; VPC: ventricular premature contraction; VT: ventricular tachycardia; VF: ventricular fibrillation.