Case Report: Nadolol–mexiletine combination therapy for refractory neonatal long QT syndrome: a case series beyond sodium channelopathies

Figures

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  Figure 1. Electrocardiographic findings of case 1. (A) Initial 12-lead recording on the day of birth, prior to any antiarrhythmic medication: sinus rhythm with frequent PVCs, broad T waves, and a markedly prolonged QTcB of 542 ms (tangent method, lead II; HR 136 bpm). At slower sinus rates within the same recording (HR 65 bpm; QTcB 503 ms), 2:1 atrioventricular conduction emerged with blocked P waves visible within the broad T waves. (B) On flecainide and nadolol therapy (post-natal day 2): 1:1 atrioventricular conduction restored; HR 65 bpm; QTcB 503 ms. (C) One-month follow-up on nadolol and mexiletine (flecainide discontinued): normalization of QTcB to 381 ms; HR 151 bpm; sinus rhythm with 1:1 conduction. All QTc values measured by the tangent method on lead II (or V5 when lead II was not interpretable) with Bazett's correction; conducted sinus beats only.

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  Figure 2. Electrocardiographic findings of case 2. (A) Initial 12-lead ECG on the day of birth: sinus rhythm with frequent PVCs, broad-based T waves consistent with LQT1 morphology, and 1:1 atrioventricular conduction; HR 90 bpm, QTcB 539 ms. (B) Post-natal day 3: bigeminal PVCs with broad-based T waves; HR 122 bpm (underlying sinus rate), QTcB 542 ms; 1:1 atrioventricular conduction preserved. (C) One-month follow-up on nadolol and mexiletine (flecainide discontinued): near-normalization of QTcB to 435 ms; HR 126 bpm. All QTc values measured by the tangent method on lead II (or V5 when lead II was not interpretable) with Bazett's correction; conducted sinus beats only.