Left and right-sided sympathetic paravertebral chains innervate the heart with each chain reported to have different electrophysiological effects (Winter et al., 2012), which are important factors in arrhythmia susceptibility. However, direct studies on differential left vs. right effects on electrical restitution and ventricular fibrillation (VF) inducibility are sparse. The effects of left (LSS) and right-sided (RSS) sympathetic chain stimulation on effective refractory period (ERP), action potential duration restitution (RT) and VF threshold (VFT) were studied. The innervated isolated heart preparation (Ng et al., 2001) from adult male New Zealand White rabbits (n=11, 2.0-3.2Kg) was used. Rabbits were sedated with Medetomidine Hydrochloride (0.2 mg/kg), Ketamine (10 mg/kg), and Butorphanol (0.05mg/kg) (s.c.) with anesthesia maintained using i.v. Propofol. Animals were a heparinized (1000 IU, i.v.) and euthanized with an overdose of Euthetal (111 mg/kg, i.v.). Preparations were perfused in constant flow Langendorff mode (100 ml/min). Left and right sympathetic chains were stimulated between T2-T3 at x2 threshold voltage (1-4V), at a frequency (4-6Hz) that produced a maximum heart rate increase. ERP and RT were performed with an extrastimulaus protocol and VFT with a rapid pacing protocol respectively at baseline (BL), RSS and LSS. Data are Mean±SEM; compared using ANOVA or paired t-test. LSS had a greater effect on left ventricular contractility (p<0.05) and RSS had a greater influence on sinus rate (p<0.001) (Table). There was a significantly greater change in ERP with LSS vs. RSS (p<0.001). LSS RT slope values were significantly larger than RSS at apex and base (p<0.05). The change in VFT was significantly greater for LSS than RSS (p<0.05). This study holds importance for arrhythmogenesis in cardiac disease and conditions of sympathetic imbalance and shows evidence to suggest that LSS is more likely to induce ventricular arrhythmia then RSS.