DisopyramideによりAtypical Ventricular Tachycardiaをきたした一例

A case of atypical ventricular tachycardia induced by disopyramide

　Quinidineによる重篤な心室性不整脈は，"quinidinesyncope"としてよく知られているが，同様の作用のあるdisopyramideでも，心室性頻拍，心室粗動，細動等をおこすことが報告されている。我々は最近，常用量のdisopyramide投与中にAtypical Ventricular Tachycar—dia （以下AVTと略す）をきたした一例を経験し，diso—pyramide血中濃度の追跡より，発作時の血中濃度を推定しえたので報告する。

Atypical ventricular tachycardia (AVT) develop-ed in a 82 year old man who received conventional doses of disopyramide phosphate (300mg/day) for ventricular premature beats and paroxysmal supra-ventricular tachycardia. On the twelfth day of therapy, he had an episode of syncope. At that time electrocardiogram showed ventricular tachycardia with changes in QRS axis, which represents so call-ed "atypical ventricular tachycardia" or "torsade de pointes". This arrhythmia was avated by precor-dial thump. Serum concentrations of disopyramidewere 1.59 μg/ml and 0.6μg/ml at 28 and 44 hours after the episode of AVT, and from these data disopyramide level at the time of AVT was esti-mated to be 7-8 μg/ml. This toxic level was supposed to be the cause of AVT. This elevation of plasma disopyramide level may be induced by dehydration due to gastrointestinal disorders. Monitoring of electrocardiogram and serum concentration of disopyramide should be done in all patients receiving therapy with disopyramide even in patients without risk for toxicity. Patients showing prolonged QT intervals should be followed up closely and have the drug withheld.