Funasako Moritoshi, Aiba Takeshi, Ishibashi Kohei, Nakajima Ikutaro, Miyamoto Koji, Inoue Yuko, Okamura Hideo, Noda Takashi, Kamakura Shiro, Anzai Toshihisa, Noguchi Teruo, Yasuda Satoshi, Miyamoto Yoshihiro, Fukushima Kusano Kengo, Ogawa Hisao, Shimizu Wataru
Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center.
Circ J. 2016;80(2):340-5. doi: 10.1253/circj.CJ-15-0984. Epub 2015 Dec 3.
Mexiletine is often used for medical therapy in LQT3 patients, however, the usefulness of mexiletine infusion test for LQT3 patients has not been reported. The aim of this study was to evaluate the usefulness of mexiletine infusion test for detecting LQT3 patients.
We analyzed response in 12-lead electrocardiogram parameters measured in II or V5 to i.v. mexiletine infusion (2 mg/kg) during sinus rhythm among 31 genotype-positive LQT patients (29 ± 18 years, 12 male). Change in QTc interval after mexiletine was compared between LQT3 (n=15, 24 ± 21 years, 9 male) and other LQT patients (4 LQT1 and 12 LQT2; 34 ± 14 years, 3 male). Baseline RR, QT, and QTc interval were not different between the 2 groups (981 ± 182 vs. 1,023 ± 192 ms; 550 ± 94 vs. 524 ± 75 ms; 556 ± 66 vs. 520 ± 62 ms, respectively). While QTc interval was shortened with mexiletine in both groups (P<0.0001 vs. baseline), degree of QTc shortening (∆QTc) was significantly larger in LQT3 than in LQT1/LQT2 patients (99 ± 39 vs. 48 ± 32 ms; P=0.0004). The sensitivity, specificity and predictive accuracy of mexiletine infusion test for differentiating LQT3 from LQT1/LQT2 were 86.7%, 81.3% and 81.3%, respectively, and the optimal cut-off for ∆QTc was 69 ms on receiver operating characteristic analysis. No pro-arrhythmic event was observed.
Pronounced shortening of QT interval with mexiletine may facilitate genetic testing in patients with LQT3 syndrome.
美西律常用于长QT综合征3型（LQT3）患者的药物治疗，然而，美西律输注试验对LQT3患者的有效性尚未见报道。本研究旨在评估美西律输注试验在检测LQT3患者中的有效性。
我们分析了31例基因阳性的长QT综合征（LQT）患者（年龄29±18岁，男性12例）在窦性心律下静脉输注美西律（2mg/kg）期间II导联或V5导联12导联心电图参数的反应。比较了LQT3患者（n=15，年龄24±21岁，男性9例）和美西律输注后QTc间期的变化与其他LQT患者（4例LQT1和12例LQT2；年龄34±14岁，男性3例）。两组的基线RR、QT和QTc间期无差异（分别为981±182 vs. 1023±192ms；550±94 vs. 524±75ms；556±66 vs. 520±62ms）。虽然两组美西律均使QTc间期缩短（与基线相比P<0.0001），但LQT3患者QTc缩短程度（∆QTc）显著大于LQT1/LQT2患者（99±39 vs. 48±32ms；P=0.0004）。美西律输注试验区分LQT3与LQT1/LQT2的敏感性、特异性和预测准确性分别为86.7%、81.3%和81.3%，在接受者操作特征分析中，∆QTc的最佳截断值为69ms。未观察到促心律失常事件。
美西律使QT间期显著缩短可能有助于LQT3综合征患者的基因检测。
