XDH and ventricular fibrillation: Use of allopurinol significantly decreased the inducibility of ventricular tachycardia and ventricular fibrillation in infarcted rats by down-regulating sympathetic innervation through a superoxide-dependent pathway, but the uricosuric agent benzbromarone had no beneficial effects on oxidative stress, sympathetic hyperinnervation or arrhythmia vulnerability at the similar levels of uric acid [27], indicating that uric acid functions only as an indicator of xanthine oxidase (XO) activity and is not directly involved in the arrhythmogenic process.