[Quinidine plasma concentration-cardiac electrophysiologic effects relationships in anesthetized dogs (author's...

1. The electrophysiologic effects of quinidine (Q)were studied in 15 pentobarbital-anesthetized dogs using intracardiac electrography and programmed stimulation. With four successive bolus i.v. injections of Q gluconate (1, 3, 9, 18 mg/kg cumulative doses) at 30 min intervals, Q plasma concentration (Cp) ranged from 1.02 +/- 0.1 micrograms/ml to 5.7 +/- 0.6 micrograms at the time of electrophysiologic measurements 20 min after each injection. 2. In six control dogs, heart rate (HR), sinus node recovery time (TRS), conduction times (StH, HV, QRS), ventricular repolarization time (QTc) Wenckebach cycle length (L.W), and atrial refractory periods (RP) did not change significantly while the functional nodal (PRFN) and the effective ventricular (PREV) RPs significantly increased with time. 3. Quinidine produced a significant log- Cp related decrease in HR and increase in TRS corresponding to a decreased sinus automaticity. 4. StH and HV conduction times increased proportionally to log CpQ while the increase in QRS was not Cp-dependent. QTc did not increase significantly. 5. Quinidine resulted in significant log Cp-related increases in atrial RP PRFN and LW while the Q-induced changes in PREV were not Cp-dependent.