Abstract: Objective: To investigate the electrophysiological effects of ischemia/reperfusion (I/R) on the spontaneous slow response action potentials in guinea-pig left ventricular outflow tract and the effects of antiarrhythmic drugs onI/R. Methods: The action potentials of pacemaker cells in guinea-pig left ventricular outflow tract were recorded by conventional intracellular microelectrode technique. The influences of ischemia(I) 10 min, reperfusion(R) 2 min, and R 15min on the spontaneous slow response potentials were investigated. The effects of lidocaine, propafenone, amiodarone, verapamil, adenosine, and sodium nitroprusside (SNP) on I/R were also studied. Electrophysiological parameters were examined:velocity of diastolic depolarization(VDD), rate of pacemaker firing(RPF), maximal diastolic potential(MDP), maximal rate of depolarization(V_max), amplitude of action potential(APA), 50% and 90% of duration of action potential(APD₅₀ and APD₉₀). Results: ①In I 10 min group, the values of VDD, RPF, V_max and APA were decreased markedly compared with control group (P<0.05, P<0.01).In R 2 min group, VDD and RPF were increased significantly(P<0.01), MDP was increased notably(P<0.05), APD₅₀ and APD₉₀ were shortened significantly compared with I 10 min and control group. V_max was increased markedly vs control group(P<0.05). APA was decreased notably vs I 10 min group (P<0.05), but was increased markedly vs control group(P<0.05). In R 15 min group, the action potentials recovered gradually to the levels of control group. ② Compared with I 10 min/R 2 min group, 1 μmol/L lidocaine, 10 μmol/L propafenone, 1 μmol/L amiodarone, 1 μmol/L verapamil, 50 μmol/L adenosine, and 10 μmol/L SNP decreased VDD and RPF significantly. Conclusion: I/R injury can trigger abnormal spontaneous activities of guinea-pig left ventricular outflow tract.The electrophysiological effects of I/R injury on left ventricular outflow tract can be treated by antiarrhythmic drugs.

Key words: ischemia/reperfusion, left ventricular outflow tract, electrophysiological effect, drug treatment, guinea-pig