心室性不整脈に対する抗不整脈薬長期療法に関する提案—休薬による再評価，左心機能評価の必要性についてコハク酸シベンゾリンを用いた検討

An Assessment of Long-term Antiarrhythmic Therapy for Ventricular Arrhythmias:A study with cibenzoline:necessity of washout period and intermittent evaluation of left ventricular function

　心室性不整脈（PVC）に対するシベンゾリン（C）の抗不整脈効果と心機能への影響を，またPVCの経時的な変化を検討した．ホルター心電図（HM）で3,000／日以上のPVCを有する（観察期）47例を対象とし，C 300mgを投与（治療期）した．4〜8週後のHMでPVC数が観察期の25％未満に減少した有効27例（57％）に対して7日以上の休薬後にHMを再検した．PVC数が観察期の50％以上再出現した14例（54％）中11例にC 300mgを再投与した．再治療の有効率は64％であった．C投与で左室駆出率（EF），fractional shortening（FS）は変化せず左室機能への影響は少なかった．PQ時間，QRS幅は有効27例でのみC投与後に延長した．初回治療の有効例と無効例で観察期，治療期のEF,FS,C血中濃度に差がなく，再治療有効例と無効例で観察期のEF,FS，治療期のPVC減少率に差はなく，これらの因子から治療効果は予測しえなかった．PVCの出現には経時的変化が大きく有効例での休薬の必要性，再治療時の薬効再評価の必要性が示された．

We evaluated effects of cibenzoline (class la agent) on premature ventricular contractions (PVCs) and left ventricular function. 47 patients who had a minimum of 3000 PVCs/day detected by Holter monitoring (HM) received 300 mg of cibenzoline. HM was repeated during 4 to 8-weeks active therapy. For the initial responders whose PVCs suppressed by 75% or more, HM were repeated after a washout period of 7 days or more and during the second active (more than 12 weeks) therapy. Among the initial responders (27 patients, 57%), 50% or more PVCs recurred in 14 patients (54%) during washout period. Among those 14, 11 patients received cibenzoline again and only 7 patients (64%) responded. NYHA functional class did not change and major clinical events did not occur during this protocol. New couplets in one patient and new salvos (less than 5 beats) in two patients wereobserved as the adverse effects of cibenzoline therapy. Active cibenzoline therapy prolonged PQ interval and QRS width especially among the responders, but did not affect left ventricular ejection fraction (EF) or frac-tional shortening (FS) detected by echocardiogram (even in moderately compromised left ventricle whose EF were less than 50% or whose FS were less than 25%). The efficacy of cibenzoline on PVCs could not be predicted from EF or FS during the entry period or the initial active therapy, serum cibenzoline concentration and PVC suppression rates during the initial therapy. Intermittent evaluation with Holter monitoring is nec-essary to assess continued need for antiarrhythmic therapy and continued efficacy of the therapy.