INFLUENCE OF ACETYLCHOLINE, ISOPROTERENOL, QUINIDINE AND OUABAIN ON EFFECTIVE REFRACTORY PERIODS OF ATRIAL AND VENTRICULAR MYOCARDIUM IN DOG

  • 1 January 1977
    • journal article
    • research article
    • Vol. 227  (2) , 206-219
Abstract
During total cardiopulmonary bypass and after removal of the interventricular septum to obtain independent atrial and ventricular contractions, acetylcholine-, isoproterenol-, quinidine- and ouabain-induced variations of the effective refractory period (ERP) of nonspecialized atrial and ventricular tissues were studied by the extra-stimulus method. Acetylcholine significantly shortens ERP of atrial fibers but does not provoke any change in ventricular tissue, whereas parallel decrease of atrial and ventricular ERP is observed with isoproterenol. Quinidine induces greater increase in the refractory period in atrial contractile tissue than in ventricular tissue. Quabain exerts biphasic action on atrial ERP depending on dose and time after injection, and the initial decrease it produces on atrial ERP is more marked than the decrease recorded for ventricular ERP. Indirect actions appear responsible for disparity between respective actions of quinidine and ouabain on atrium and ventricle. The relation between results and respective influences of the 4 drugs on fibrillation (inducing, prevention, treatment) are considered.