Effects of calcium antagonists on the alternation of the ST-T complex and associated conduction abnormalities during coronary occlusion in dogs.
1 The effects of Ca2+ -antagonists on the relationships between alternate changes in the ST-T complex in the epicardial electrogram, ST-T alternans, and associated excitation-conduction abnormalities during coronary occlusion were examined in anaesthetized dogs. 2 Epicardial unipolar electrograms, bipolar electrograms (BPEG) and monophasic action potentials (MAP) were recorded with unipolar, composite and suction electrodes, respectively. 3 ST-T alternans was associated with serious conduction delay. During the period of ST-T alternans, the amplitude of MAP changed alternately and the negative deflection of the ST-T complex was associated with a larger MAP. A depression of the TQ level and decrease in the resting potential of MAP were marked. 4 Verapamil (0.2 mg/kg) and diltiazem (0.5 mg/kg) inhibited ST-T alternans, conduction abnormalities, TQ depression and changes in MAP. However, after these drugs, the TQ depression and the decrease in the resting potential were evident after a longer period of occlusion at a time when ST-T alternans, conduction abnormalities and alternate changes in MAP were still inhibited. Dipyridamole (0.5 mg/kg) had no effect on either ST-T alternans or the conduction abnormalities. 5 Verapamil and diltiazem inhibited ST-T alternans and the associated excitation and conduction abnormalities. The effects of these two drugs cannot be explained on the basis of attenuation of the decrease in the resting potential.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D003327:Coronary Disease / Q000503:physiopathology*; D004110:Diltiazem / Q000494:pharmacology; D004176:Dipyridamole / Q000494:pharmacology; D004285:Dogs; D004562:Electrocardiography; D006329:Heart Conduction System / Q000187:drug effects*; D014700:Verapamil / Q000494:pharmacology
D002121:Calcium Channel Blockers; D004176:Dipyridamole; D014700:Verapamil; D004110:Diltiazem