Alterations in Cardiac Mechanism. 89 



(about 50 per cent.), oral administration of quinidine sulphate 

 serves to restore the normal rhythm. It is the purpose of this 

 communication to record the mechanism of the heart's action 

 which has been observed in the first eleven patients who have 

 received quinidine in this hospital. 



Five hundred and seven electrocardiograms taken on eleven 

 patients have been measured and analyzed. After a preliminary 

 dose of .2 to .4 gm. of quinidine to test for the presence of an 

 idiosyncrasy to members of the cinchona group, .4 gm. of the 

 drug has been given by mouth, in gelatin capsules, either three 

 times daily or every two hours, until either the establishment of 

 normal rhythm or the appearance of untoward symptoms indicated 

 cessation of therapy. No more than 2.0 gm. of quinidine were 

 administered in twenty-four hours, though treatment has been 

 continued daily for as long as ten days. 



Electrocardiograms were taken in some instances as often as 

 every five minutes during the time when a change in rhythm was 

 anticipated. Usually curves were made at two-hour intervals on 

 the days on which the drug was given, and at least daily throughout 

 the periods of observation. 



Cases in which the Normal Mechanism was Restored. — Three 

 patients received ten courses of quinidine. Restoration of the 

 normal mechanism was accomplished nine times. The first effect 

 noted was usually an acceleration of ventricular rate. This was 

 followed at times by the appearance of premature beats, arising 

 more commonly in the right, but occasionally in the left ventricle, 

 and at times in both. If electrocardiograms were taken at suffi- 

 ciently frequent intervals, the transitional mechanisms in the 

 common order of their appearance were: coarse fibrillation, impure 

 flutter, flutter, and normal rhythm. This sequence was not 

 invariably demonstrated in all its phases, and it is possible that 

 one or more of the intermediate mechanisms may be omitted. 

 In one patient the transition from auricular flutter to the normal 

 rhythm was photographed in the second lead. The change was 

 rather abrupt, there being a period of altering auricular activity, 

 slowing of ventricular rate for several beats, a relatively long 

 period of a systole of both auricles and ventricles and then prompt 

 resumption of the sinus rhythm. The P waves, denoting auricu- 



