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持続性心室頻拍 (VT) の長期管理におけるホルター心電図 (HM) の有用性を治療選択と予後の面から電気生理検査 (EPS) と比較して検討した.対象は当科で経験した166例の単形性持続性VT症例のうち, EPSと48時間以上のHMを施行された120例で, 男性90例, 女性30例で, 年齢は51±17歳である.EPS上VTは90/120例で誘発され, EPS判定上の有効治療群 (55例) , 無効治療群 (35例) , 判定不能群 (30例) の3群間でVT再発率を比較した.HM上ESVEM基準 (心室性期外収縮 (VPC) >平均10拍/時間) を満たす症例は98/120例であり, 治療によって70%以上のVPOが抑制された場合にその治療を有効と判定し, 有効治療群 (40例) , 無効治療群 (58例) , 判定不能群 (22例) の3群間でVT再発率を比較した.また, EPS上有効治療の見出せなかった65例においてもHM結果別のVT再発率を比較した.統計的検討はKaplan-Meier曲線上, Wilcoxon法で行い, p more...

肺動脈弁直下から右室自由壁にかけた心筋切開の既往を有するファロー四徴症術後に発症した持続性心室頻拍 (VT) の興奮旋回路を詳細にマッピングし, 高周波力テーテル焼灼術の効果を検討した.電気生理学検査では右脚ブロック型と左脚ブロック型で同一周期長のVTが誘発された.いずれのVTもエントレインメント現象が認められ, 右室自由壁で分裂電位が記録された.右脚ブロック型VTの分裂電位の振幅は, 手術痕を境にカテーテルを僅かに移動すると大小変化し, 前半成分は搬痕の右房側, 後半成分は対側に由来する電位と解された.また頻回刺激時には, 前半成分が直接捕捉, 後半成分は緩徐伝導を介して捕捉された.マッピングにより心腔内電位の興奮旋回には, 手術痕周囲を時計周りに施回するマクロリエントリーが, また左脚ブロック型VTでは反時計回りのマクロリエントリーと考えられた.高周波力テーテル焼灼は肺動脈弁直下でマクロリエントリー路を横切るように行い, 本法によりVTが停止し, 以後誘発されなくなった. more...

Radiofrequency current catheter ablation was attempted for 17 morphologies of ventricular tachycardia (VT) in 14 patients. Five patients had underlying heart disease. The site of VT origin was determined as the earliest site of ventricular activation, or by pacing within the area of slow conduction. In 15 VTs, ablation was performed during VT, and 12 VTs (80%) were terminated within an average of 5.4±4.2 seconds. After ablation, 14 VTs (14/17=82%) of 11 patients (11/14=79%) could not be induced by electrical stimulation. Radiofrequency ablation appeared to be more effective in VTs without underlying heart disease (91%), and in VTs originating from the right ventricle (100%). Successful ablation sites usually showed a normal local electrograms during VT. Ablation in the slow conduction area was attempted in 3 VTs, and 2 VTs became noninducible. The mean number of applications of radiofrequency current for each VT origin was 7.7±6.4 at 20-50 Watts. In 4 patients, application of radiofrequency current was required 10 or more times because of a possible large arrhythmogenic area, or because of reinduction of VT, even though VT was terminated by radiofrequency current. No major complication was observed except for complete right bundle branch block in 1 patient. In conclusion: (1) Radiofrequency catheter ablation was considered to be effective and safe, especially for VT without underlying heart disease or VT originating from the right ventricle. (2) Ablation during VT was considered to be useful for identifying the proper ablation site and to avoid creating an unnecessary lesion. more...

(目的) 植込み式除細動器 (ICD) の除細動試験時における誘発から通電時までの不整脈の変化と通電成績を, 体表面心電図と心腔内電位の所見から解析し, 試験成績の有する問題点を検討した.(対象と方法) ICDの適応症例は治療が困難でショックをきたす持続性心室頻拍 (VT) 2例, 心室細動 (Vf) 4例 (男5例, 女1例, 平均年齢55.7歳: 陳旧性心筋梗塞2例, 拡張型心筋症1例, 特発性3例) であり, 検討には心腔内電位と体表面心電図ともに1誘導ずつを用いた.(結果) (1) 31回の除細動試験での誘発時の心電図所見は多形性VTが16回, Vfが15回であり, 誘発後, 通電までに多形性VTから単形性VTへの変化が4回, Vfから多形性VTへの変化が3回生じた. (2) 通電は単形性VTに対して4回 (13%) , 多形性VTに対して15回 (48%) , Vfに対して12回 (39%) 行なわれた.成功率は90% (28回) で, 単形性VT100%, 多形性VT93%, Vf83%であり, 多形性VTとVfの除細動閾値が異なる可能性が示唆された. (3) 心腔内電位上の持続電位は体表面心電図のVf移行より約2秒遅れて出現したが, これは誘導数がかぎられているためと考えられた.(結語) (1) 除細動試験時, 通電の半数以上は多形性VTに対して行なわれていた. (2) 多形性VTとVfの除細動閾値は異なる可能性が示唆された. more...

非虚血性心室頻拍 (以下VT) 例においてエントレーメント現象を利用しIa群抗不整脈薬のリエントリー回路への定量的評価を試みた.VTはいずれもプロカインアミド (以下PA) の投与前後で誘発され, 同一QRS波形を示し, VT中の頻回刺激でエントレーメント現象が認められた.リエントリー回路を介する順行性伝導時間 (以下CTo) はエントレーメント中の刺激から最早期興奮部位までの時間とし, 逆行性伝導時間 (以下CTa) は洞調律時の両者間の伝導時間とした.VTを停止させる最長の刺激周期をBlook CLとし, リエントリー回路外の心筋の不応期 (以下ERP) を刺激部位で求めた.PA投与後, VT周期とCToは有意に延長し, 両者の変化は高い相関を示した.しかし, CToの変化はCTaの変化に比べ有意に大で, PAは緩徐伝導路により選択的に作用すると考えられた.Block CLも有意に延長したが, 正常心筋でのERPの変化はそれより有意に小であった.PAは緩徐伝導路の伝導速度を低下させ伝導途絶をきたす周期を延長させるが, この作用はより緩徐伝導路に選択的と考えられた. more...

症例は21歳男性.15歳時より動悸発作出現, 左軸偏位+右脚ブロック型の持続性心室頻拍 (VT) が記録された.諸検査で心臓に異常は認めず, VTはverapamil静注で停止したが, 同薬360mg内服にても再発を繰り返した.右室心尖部よりの心室早期刺激で, 自然発作と同一のVTが誘発され, 頻回刺激でエントレーメント現象が確認され, 機序はリエントリーと考えられた.頻拍中のマッピングで左室心尖部中隔側にQRS波の開始より30～60msec先行する電位が1.0×1.0cm以上の領域に同定された.VT中のペーシングで融合のないエントレーメント現象を示す部位での通電でVTは数秒後に停止したが, 再誘発され, このときわずかにORS波形の変化を認めた.その近傍で脚様の電位がQRS波の開始に45msec先行する部位での通電によりVTは停止し, 以後誘発不可能となった.術中, 術後に合併症はなく, 特発性心室頻拍例に対する本法の有用性が示唆されたが, 小さな局所電位の意義とリエントリー回路の必須な部位の同定には, いまだ検討の余地があると思われる. more...

頻回刺激による持続型心室頻拍 (VT) の停止の機序が, リエントリー回路での川頁行伝導途絶による可能性が示唆された2症例を提示する.2例とも自然発作と同一波形のVTが誘発され, 頻拍周期より短い周期のペーシングで, constant fusionとProgressive fusionが確認され, さらに短い周期でVTは停止した.VT停止時には以下の所見が観察された. (1) リエントリー回路の出口において, 各々の刺激に対応する局所電位が欠如し, 電位出現間隔が延長した. (2) その後の刺激で同部位の局所電位の形態が変化し, (3) 体表面QRS波形もoonstant fusionの波形から洞調律時のペーシング波形に変化した.これらの所見はVTを停止させる周期のペーシング中に, リエントリー回路を経て回路外で融合波を形成していた興奮が途絶し, そこにペーシング部位からの逆行性興奮が伝導したための現象と考えられた.これらの所見が確認された症例の頻拍停止は, リエントリー回路内緩徐伝導路での順行伝導途絶が一次的な原因と考えられた. more...

Electrophysiologic testing was performed in 31 patients with ventricular tachycardia (21 cases) and fibrillation (10 cases) to characterize the electrophysiologic properties of patients responding or not responding to therapy with class III antiarrhythmic drugs. At the baseline, there were no differences among the patients in the monomorphic VT cycle length (CL), block CL or the width of the zone of entrainment. Ventricular tachyarrhythmias after the administration of class III drugs (sotalol: 9, amiodarone: 15 and E-4031/MS-551: 7) were inducible (non-responders) in 17 patients and non-inducible (responders) in 14 (45%). The class III drugs prolonged the sinus cycle length (SCL), QT interval and right ventricular effective refractory period (VERP), but had little effect on ventricular conduction time in the responders and non-responders. The SCL, QT interval and VERP at the three drive cycle lengths of 600, 400 and 300 msec were significantly longer in the responders than in the non-responders, but the class III drug action on VERP showed a reverse use-dependency. Isoproterenol administered to the responder did not fully reverse the class III antiarrhythmic drug-induced prolongation of QT, QTc and VERP, which remained significantly prolonged compared to the baseline values. Furthermore, when the VERP after the administration of class III drugs were greater than 270, 250 and 240 msec at the three drive cycle lengths of 600, 400 and 300 msec, respectively, it was associated with the non-inducibility of VT/VF. Though the precise mechanism of the drug efficacy is not yet known, these observations help to clarify the ability of class III drugs to prevent the induction of ventricular tachyarrhythmia. more...

UNLABELLED We performed electrophysiological studies in 13 patients with idiopathic VT and attempted radiofrequency (RF) catheter ablation in 4 of them. RESULTS VT was induced by programmed stimulation in all patients and the mean cycle length was 363 +/- 58 msec. In 8 of 13 patients (62%), alternation of either the cycle length and/or morphology of VT was observed. Transient entrainment was achieved in all patients by rapid pacing from the right ventricular outflow tract so reentry was considered the underlying mechanism of VT. The site of earliest activation (EAS) during VT was located at the apicoposterior portion of the left ventricular septum and used as the target site for RF catheter ablation. Spikelike presystolic activity was detected 20-40 msec prior to the large deflection of the local electrogram in four patients. VT was terminated by a few seconds of RF current in all four patients, but subsequently new VTs with a slightly different morphology were induced in three of them and re-mapping showed a shift of the EAS. After additional RF ablation at the new EAS, VT was no longer induced. No complication was noted and VT did not recur during a follow-up period for a mean of 9.3 +/- 5.2 months. CONCLUSION RF catheter ablation seems useful and safe for idiopathic VT. The alternation of QRS morphology and the findings at the time of catheter ablation suggest that an alternative pathway or multiple exists may be present in some patients with idiopathic VT, because the change in VT morphology was associated with a shift of the EAS. more...

In a patient with sustained ventricular tachycardia (VT), we observed two different conduction times through the reentry circuit at the critical paced cycle length. The cycle length of the VT was 420 msec and overdrive pacing initially performed at a paced cycle length of 400 msec and repeated at decrements of 10 msec until the VT was interrupted at a paced cycle length of 320 msec. During rapid pacing, constant fusion and progressive fusion were confirmed. The first post-pacing return cycle was identical to each paced cycle length. The conduction time between the stimulus artifact and the orthodromically captured electrogram at the left ventricle was constant at 350 msec in each paced cycle length. However, only at a pacing cycle length of 360 msec two conduction times were alternatively observed, one of 350 msec and the other of 365 msec. When the conduction time changed from 350 msec to 365 msec, morphological alternation both in the surface QRS complex and in the orthodromically captured electrogram was evident. Dual slow pathways or a single slow pathway with plural exits from the reentry circuit is a likely mechanism of the alternation. more...

BACKGROUND Information concerning the electrophysiological characteristics of the reentrant circuit is still limited. To understand the incidence and mechanism of pacing-induced interruption of ventricular tachycardia (VT), rapid pacing was performed to entrain VT, and the local electrogram at the VT origin and the surface electrocardiogram were analyzed. METHODS AND RESULTS Among 25 patients, evidence of transient entrainment was confirmed in 20 patients, but the critical paced cycle length at which VT was interrupted was obtained in 13 patients when the paced cycle length was decreased in steps of 10 msec. During pacing at the critical cycle length (defined as block cycle length), changes in the local electrogram at VT origin were confirmed in all of the 13 patients; that is, 1) a change in morphology and 2) a change in the timing of activation: a sudden shortening in the stimulus to local electrogram time (third entrainment criterion by Waldo). The two changes mean that the exit is activated from a different direction (retrograde capture) because of an orthodromic block in the slow conduction zone. The QRS complex in the surface electrocardiogram showed a change in configuration from the fusion complex to the fully paced one at the same time when the exit was captured antidromically. CONCLUSIONS Based on our observations in these patients, ventricular tachycardia interruption is very often associated with orthodromic block in the reentrant circuit at a critical cycle length of rapid pacing. more...

In two patients with arrhythrnogenic right ventricular dysplasia (ARVDJ, sustained ventricular tachycardia (VT) was induced by programmed stimulations during serial drug testings. One patient had five and the other had two VT morphologies, and the sites of origin were determined by endocardial catheter mappings. When overdrive pacing was performed, constant fusion in the QflS complex was observed in the two patients. Constant fusion of a different degree was also observed at different paced cycle lengths. Both patients had dilated right ventricles and wall-motion abnormality, and the diagnosis of ARVD was further confirmed by the specimen resected at the site of origin of VT. Therefore, VT in ARVD can be entrained and reentry is the most likely mechanism of such VT. more...