Abstract

The results obtained in this study demonstrate a direct effect of pentylenetetrazol on the isolated cat heart. In the atria sinus bradycardia followed by bradycardic arrhythmias characterized by a bigeminal or trigeminal pattern occurred. In papillary muscles a decrease in conduction velocity, prolongation of refractory period and increase in threshold were observed prior to the development of spontaneous activity. The intact isolated heart showed sinus bradycardia, A-V block, ventricular fibrillation or asystole. However, the concentration of pentylenetetrazol required to produce these arrhythmias was 18 to 30 times higher than that used in intact animals to produce similar cardiac arrhythmias.