Experimental studies of the pharmacology of quinidin

It has recently been shown that in certain patients suffering from fibrillation of the auricles, the normal cardiac mechanism may be restored by the oral administration of quinidin sulphate. Knowledge concerning the pharmacological action of this drug is desirable for the clinic and is important insofar as it may furnish information concerning the nature of the fibrillatory process. Experiments were done on 12 dogs. Anesthesia was accomplished by intratracheal etherization. The thorax was opened in the median line. A myocardiograph of the Roy and Adami type was sewed into the tip and base of the ventricles and connected with a system of Marey tambours. Changes in the degree of cardiac contraction obtained by this method may be taken to represent alterations in volume output. The blood pressure was recorded from the right femoral artery; injections of the drug were made into the left femoral vein. In eight experiments the threshold for the production of transient auricular fibrillation was determined by faradization of the right auricle. Electrocardiograms were made at frequent intervals. 1. Rate.—No constant effect was noted. There was acceleration 4 times, slowing 4 times and fluctuation in the remainder of the animals. 2. P-R (conduction) Time.—The changes were slight and relatively insignificant. There was prolongation four times and shortening once. 3. T-wave.—A change in this portion of the electrocardiogram occurred eight times. This consisted either of reversal in the direction of the deflection, or of increase in the voltage of the original wave. 4. Blood Pressure.—In all of the animals a striking fall in blood pressure was observed, the extent of the fall depending in a measure on the amount of the drug injected. There was partial, but never complete return to the former pressure level.