徐脈性不整脈に対するTA−064の効果

Effect of TA-064 on bradyarrhythmias

　徐脈性不整脈である洞不全症候群（sick sinus syndro—me：SSS）および房室ブロック（atrioventricular block：AVB）は徐脈によるlow outputあるいはその原因疾患のために心拡大などの心不全徴候を示すことがまれでない。これらの疾患の治療には，軽症例には硫酸アトロピン（AS）やβstimulantなどを用い，重症例には一時的pacemakerの使用やpermanent pacemakerの植え込みがなされている。心拍数の増加に伴い，心拡大等の心不全徴候は消失することが多いが，なかには，拡張型心筋症や心筋炎後遺症等の基礎疾患を有する例があり，刺激伝導系のみならず作業心筋にも変性をきたしているため，心不全が残存する場合もある。このような疾患には，陽性変時作用だけでなく陽性変力作用を有する治療薬が望ましい。今回われわれは，新しいβ₁-agonistであるTA−064（TA）^1）を徐脈性不整脈に用い，刺激伝導系および心機能への効果を検討した。

Objective: Effects of TA-064 (TA) on cardiac con-duction system of patients with bradyarrhythmias [sick sinus syndrome (SSS), atrioventricular block (AVB)] were studied.

Methods: Clinical electrophysiological study, Holter DCG and echocardiography were carried out in 9 patients with SSS and 5 patients with AVB to compare effects of TA-064 before administration of TA, after administration of 30mg/day and 60mg/day of. TA for 3 days and after administration of 2mg/day of atropine sulfate (AS) for 3 days.

Results: 1. Electrophysiological study; ,①Heart rates of the patients with SSS were 48/min, 60/min and 62/min before administration of TA, after administration of 30mg and 60mg of TA, respectively. While, heart rates of the patients with AVB were 76/min, 79/ min and 93/min before administration of TA, after administration of 30mg and 60mg of TA, respecti-vely. ② Corrected sinus node recovery time and sinoatrial conduction time seen in the patients with SSS tended to be shortened by administration of TA. ③ Wenckebach AVB appearance rate was improved in all patients with AVB after admini-stration of TA.

2. Holter DCG; ①Total heart beats of the patients with SSS counted through a whole day with Holter DCG was 74, 900 before administration of TA, and increased to 78,300, 84,800 and 92,200 after administration of AS, 30mg of TA and 60mg of TA, respectively. The same tendency was seen inthe patients with AVB. ②Minimum heart rate increased and maximum R-R interval was shorten-ed after administration of TA as compared to those before administration of TA. And improvement of subjective symptoms was seen in the patients with SSS.

3. Echocardiography; Ejection fraction was signifi-cantly improved after administration of 60mg of TA.

4. Arrhythmia; ① A certain tendency was not seen in a number of incidence and duration of atrial fibillation in patients with SSS. ② There was no significant difference in number of primature ventricular contraction (PVC) between before and after administration of TA. However, the grade of Lown's classification progressed in some patients. Conclusion: TA-064 is useful for treatment of bradyarrhythmias when attention is paid to the ap- pearance of arrhythmia.