60歳以上で診断された休止期依存性QT延長症候群の3例

Three Cases of Idiopathic Pause-dependent Long QT Syndrome in the Elderly

　QT延長症候群は，細胞膜のカリウムチャネルの異常で，その遺伝子異常がいくつも知られた先天性疾患である．今回，65歳以上で初めてQT延長症候群が診断された3例を報告する．症例は80,65,81歳の女性．いずれも心疾患の既往はない．3例中1例のみが失神発作の既往歴があった．3例とも誘因を特定できない失神発作により発症した．心電図でQT延長（それぞれQTc間隔0.55,0.52,0.52秒）およびtorsade de pointesを認めた．キシロカイン，マグネシウム製剤の投与，および一過性ペースメーカによる急性期治療を施行，後日永久的ペースメーカを植え込んだ．発作誘因として電解質異常，薬剤の使用は否定された．家族歴も明らかではなかった．いずれも，心室性期外収縮後の休止期に依存してtorsade de pointesを生じた．65歳以上の高齢で発症した点は，休止期依存性ゆえに，心室性期外収縮の頻発のような後天的要因が関与したためであると考えた．高齢者の失神であっても，散発性の休止期依存性のQT延長症候群の存在を念頭におく必要がある．

We report three elderly female patients with pause-dependent long QT syndrome (LQTS) which werediagnosed when they passed the age of 60. One was 80years old, another was 65 years old and the other was 81years old. They had not suffered from any other car-diovascular disease. However, the 80-year-old womanhad been prone to syncope since she was approximately20 years old. The ether two had been free from syncope.All of them were admitted to our department because ofsyncope. At that time, their electrocardiograms showedprolongation of QT interval (QT intervals 0.55 sec, 0.52sec, 0.52 sec), and also ventricular tachycardia, the socalled torsade de pointes. First of all, we gave themXylokine and Mg-sulfate intravenously, after that, weimplanted permanent pacemakers. Their laboratoryfindings showed almost normal range includingelectrocytes (Na, K, Cl, Mg). The causes for theirsyncope were neither heriditary nor drug-induced, so wesupposed that the causes were due to idiopathic factors.The common characteristics were that all of them werewomen more than 60 years old, whose syncope dependedon the pauses after ventricular premature heart beat.Considering these factors, we concluded that they wereall rare cases.