特発性心室頻拍症の電気生理学的検討

Electrophysiological findings in patients with idiopathic ventricular tachycardia

　心室頻拍（以下VT）は，心疾患に伴う致死的不整脈として知られているが，この中にはidiopathic VT^1）と呼ばれる器質的心疾患によらない特殊なVTが知られている。この心室性不整脈は基礎的心疾患を有しない比較的若年者にみられ，その多くは自然寛解すると考えられているが^2），頻拍中の心不全や^3），まれに突然死^4）も報告されており，未だその病態は明らかでない。

　著者らは特発性VTと考えられる4例に対し，電気生理学的検査を行い，若干の検討を加えたので報告する。

Electrocardiographic and electrophysiologic char-acteristics were evaluated in 4 patients who demon-strated idiopathic ventricular tachycardia (VT). The patients were young (mean age 32 years) and asymptomatic during the episode of VT. In 2 pa-tients, VT lasted more than 30 complexes. VT terminated spontaneously in all cases. No patients had obvious organic heart disease. The electrocar-diogram during sinus rhythm were within normal limit. QRS morphology during the episode of VT showed a pattern of right bundle branch block andright axis deviation. Heart rate ranged between 128 and 164 (mean 146) beats,/min during the attack.

At electrophysiologic study, all patients had nor-mal AH, 4-1V, QRS and QT intervals during sinus rhythm. Refractory period of right atrium, AV node and right ventricle were within normal limit. Right ventricular endocardial mapping during the episode of VT revealed that the site of the earliest activa-tion was located in the outflow tract of the ven-tricle in all patients.

In only one patient, VT could be induced with electrical stimulation. In 2 patients, VT could be terminated with programmed electrical stimulation. Aggresive techniques of programmed electrical stim-ulation, including right ventricular burst pacing (pacing cycle length between 400 and 240 msec) were employed to induce sustained VT. In spite of this protocol, sustained VT could not be induced in all patients. Therefore, the failure to induce sus-tained VT suggests the electrical stability in these patients with idiopathic VT.