Objective: To investigate the changes of g ui nea pig heart electrophysiological properties caused by increasing left ventricu
lar preload, and to assess the effects of
tetradrine on these changes. Method: Working model preparation of guinea pig hearts in vitro was used, and the preload of left ventricle was increased by adjusting the prefusio n pressure of left atria. The changes of heart electrophysiologic parameters inc luding monophasic action potential duration(MAPD90), monophasic action potential amplitude(MAPA), effective refractory period(ERP) and
ventricular fibrillation threshold(VFT) were observed before and after altering the preload of left ventr icle, and compared in the absence and presence of tetradrine,streptomycin or ve rapamil. Result: The rising of left ventricular preload le d to shortening of MAPD90, ERP, and to descent of MAPA, VFT(all P<0.01). Bot h Tetradrine and streptomycin inhibited these changes of heart electrophysiologi c parameters caused by elevation of left ventricular afterload (all P<0.01) . In contrast, verapamil had no effects on the preload-related electrophysiolo gical changes(all P>0.05). Conclusion: Electrophysiolo gic changes caused by increasing left ventricular preload may be inhibited by te trandrine, through inhibition of stretch-activated ion channels.