A case of long QT syndrome type 2 that developed torsades de pointes two days after the initiation of oral β-blocker therapy

Figures

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  Figure 1. Pedigree, genotype, and a monitor electrocardiogram (ECG) of the proband (II-3). A: Family pedigree: arrow indicates the proband; filled circle, affected member; plus sign, KCNH2 p.G71W carrier. SD = sudden death. B: DNA sequencing of the proband. C: Topology of the hERG channel and the location of the KCNH2 variant, c.211G>T: p.G71W. D: ECG recording of the proband at the emergency department. Torsades de pointes was followed by a long-short sequence of R-R intervals.

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  Figure 2. Electrocardiograms (ECGs) of the proband (II-3). ECGs recorded A: before the initiation of nadolol, B: 2 days after the initiation of nadolol (0.45 mg/kg/d), C: immediately after intravenous administration of lidocaine (50 mg) at the emergency room, and D: under oral mexiletine (4.5 mg/kg/d). QTc values were calculated using Bazett’s formula.

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  Figure 3. Electrocardiograms (ECGs) of the second daughter (III-2). ECGs recorded A: at baseline, B: after the initiation of nadolol (0.64 mg/kg/d), C: after dose increase of nadolol (0.96 mg/kg/d), and D: after the addition of mexiletine (6.4 mg/kg/d). QTc values were calculated using Bazett’s formula.