Effects of ranitidine on ventricular refractory period and fibrillation threshold of normal and ischemic ventricle in rabbits

Effects of ranitidine (Ran) on ventricular refractory period and fibrillation threshold of normal and ischemic ventricle were investigated in pentobarbitone anesthetized rabbits. In saline-treated rabbits, relative refractory period (RRP) and effective refractory period (ERP) were shortened from 132 +/- 24 to 126 +/- 25 ms (n = 10, P < 0.05) and from 118 +/- 22 to 108 +/- 27 ms (n = 10, P < 0.05) in boundary zone of ventricular ischemic regions, respectively. The ventricular fibrillation threshold (VFT) was decreased from 5.5 +/- 1.4 to 2.8 +/- 1.1 V (n = 10, P < 0.01) after coronary artery ligation (CAL). Ran (25 mg.kg-1, i.v.) not only prevented these changes, but also lengthened RRP from 123 +/- 14 to 136 +/- 10 ms (P < 0.05) and ERP from 111 +/- 16 to 126 +/- 12 ms (P < 0.05), and increased VFT from 4.7 +/- 0.8 to 7.4 +/- 1.8 V (P < 0.01) in normal ventricle. The results suggest that Ran may have anti-arrhythmic effects in rabbits.