Clinical Electrophysiology -> Ventricular Arrhythmias -> Physiology-Pharmacology D-PO01 - Featured Poster Session (ID 11) Poster

D-PO01-015 - Mexiletine Suppresses Ventricular Arrhythmias In In Andersen-tawil Syndrome With Kcnj2 Mutations (ID 881)

 Y. Jing: Nothing relevant to disclose.


Background: Andersen-Tawil syndrome(ATS) ,also classified as long QT-7 syndrome manifested as ventricular arrhythmias, periodic paralysis and dysmorphic features. In expert consensus β-adrenergic blocker is the first-line option,flecainide is an alternative agent not available in China.The class-Ib antiarrhythmic drug mexiletine was proposed as an effective therapy.We present a recurrent syncope boy diagnosed with ATS and successfully treated with oral mexiletine.
Results: A 7-year-old boy experienced syncope during exercising, climbing stairs.Physical examination revealed dysmorphologies including mandibular hypoplasia and long bone over hyperextension.His past medical history included lower limb myasthenia with hypokalemia and recovered after potassium supplement.The surface electrocardiograms demonstrated sinus rhythm with prolonged terminal T-wave in limb leads ,enlarged U waves, and wide T-U junction (Tp-Up, 240ms) in leads V2-V3.He had QTc of 360 ms and QUc of 671 ms. Furthermore,frequent PVCs(38% of total beats) in bigeminy and recurrent asymptomatic nonsustained bidirectional or polymorphic ventricular tachycardia(bVT/pVT) (2659 times VT)were shown in 24-hour Holter recording.The clinical diagnosis of congenital long QT syndrome (LQTS) was made based on the prolonged QTU interval and enlarged U waves with ECG patterns typical to LQT7. The boy received metoprolol 11.25mg twice a day just for two days, he felt apparent fatigue.With the intolerance of β-blockers, he was given oral medications of mexiletine starting from 300 mg/day,and gradually increased to 450 mg/day. Three days after taking mexiletine, continues electrocardiograph monitoring showed kinds of ventricular arrhythmias was suppressed. 24-hour Holter was conducted after treatment showed PVCs burden decreased from 38% to 3% of total beats and there was no more ventricular tachycardia.Genetic testing identified a heterozygous missense mutation named c.652C>T(p.R218W) in the coding region of KCNJ2. At the 6-month follow-up,he has remained event-free.
Conclusion: Mexiletine effectively suppresses ventricular arrhythmias in in ATS probably by suppresses INa-L and arrhythmia triggers in phase 4.