連結期の短い心室性期外収縮で誘発されたと思われた特発性心室細動の1例

A Case of Idiopathic Ventricular Fibrillation Initiated a Short-coupled Ventricular Premature Beat

　症例は47歳，男性．1995年5月と1996年10月の2回，夜間に意識消失発作を起こした．安静時心電図で異常なく，ホルター心電図で連結期の短い（260msec）心室性期外収縮を認めた．12月に施行した右室心尖部からのプログラム電気刺激試験（PES）で多形性心室頻拍が誘発され心室細動に移行した．心エコー，¹²³I-MIBG心筋シンチグラム，MRI，心臓カテーテル検査で異常を認めず，特発性心室細動と診断した．心室性期外収縮の頻度が少なく薬物療法の効果判定が困難のため，われわれは突然死の予防目的で植込み型除細動器（ICD）を使用した．特発性心室細動は種々のタイプが発表されているが，安静時心電図で異常なく，連結期の短い心室性期外収縮で誘発される特発性心室細動と考えられた．報告例と比較すると，発作が治まった時点でのPESで多形性心室頻拍が誘発された点が稀少な症例と思われた．

　The case presented was that of a 47-year-old man losing consciousness at night on 2 separate occasions. Although the electrocardiogram (ECG) at rest and other examinations, such as echocardiography and cardiac catheterization, all showed normal, short-coupled ventricular premature beats (260 msec) appeared on Holter's ECG, and polymorphic ventricular tachycardia developed and degenerated into ventricular fibrillation when examined with programmed electric stimulation (PES) to the right ventricular apex. Thus the patient was diagnosed as having idiopathic ventricular fibrillation initiated by a short-coupled ventricular premature beat and he was given an implantable cardioverter defibrillator (ICD) as a prophylactic against sudden death. This measure was taken because it was difficult to evaluate the efficacy of drug medication due to the very low frequency of the ventricular premature beat. Although various types of idiopathic ventricular fibrillation have been reported, no definitive classification ha yet been established. Compared with previous reports of this type, our case seems to have a rarity value in its PES-induced polymorphic ventricular tachycardia during the non-paroxysmal period. Among cases with idiopathic ventricular fibrillation of this type, the incidence of sudden death and/or therapeutic regimens may differ. For this reason we report our case to add it to the data necessary for the precise classification of idiopathic ventricular fibrillation and for the establishment of therapeutic indications, particularly ICD.