常用量のchlorpromazineを服用中にT wave alternansとTorsade de Pointesを生じた1例

Torsade de Pointes with T wave alternans in a patient receiving moderate dose of chlorpromazine:report of a case

　常用量の向精神薬を服用中に，心電図のQT間隔が延長し，Torsade de PointesとT wavealternansを生じた1例を経験した。

　患者は31歳，女性。精神分裂病にて長期間chlorpromazine（100mg／day）を服用していたが，失神発作を頻発して緊急入院した。心電図にて著明なQT延長とともに，T wave alternansとTorsade dePointesを認めた。lidocaine（50mg）の静注にてT wave alternansとTorsade de Pointesは消失し，その後は失神も生じなかった。QT間隔はchlorpromazineの投与中止にて漸減したが，再投与にて再び延長した。

　常用量の向精神薬を服薬中に，Torsade de Pointesを生じたことは，突然死の子防のためにも重要であるとともに，まれなTwave alternansを記録し得たので報告した。

A case is presented of Torsade de Pointes (TDP) with T wave alternans in a 31-year-old female re-ceiving a moderate dose of chlorpromazine.

She was treated in an another hospital for shizo-phrenia with chlorpromazine (100mg daily) for several years and admitted to Pujisawa city hospital for numerous episodes of syncope. The electro-cardiogram immediately after admission revealed a marked QTc prolongation to 0.81 seconds, T wave alternation without any obvious change in morpho-logy of the QRS complex, and reccurent ventricular tachycardia called TDP. The T wave alternans and TDP were easily abolished by intravenous adminis-tration of a bolus of 50 mg lidocaine infusion. The QT interval however, remained prolonged.

Physical examination, including cardiac examina-tion, was normal. Serum potassium was 3.6/mEq. Chlorpromazine was discontinued immediately after admission and no further episodes of TDP were seen after the first day.

After the QT interval returned to almost normal, chlorpromazine (50mg daily) was re-administered. Two days after the re-administration, the electro-cardiogram revealed marked QT interval prolonga-tion with prominent T waves.

Psychotropic drugs, such as chlorpromazine, pro-long the QT interval and cause TDP. Chlorproma-zine appears to have been responsible for TDP and the T wave alternans in this case. TDP caused by a moderate dose of chlorpromazine has not been previously reported. Lone T wave alternans unac-companied by changes in the QRS complex is a rare phenomenon and the mechanism underlying T wave alternans remains unknown.