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Figure 1 Electrocardiographic (A) and Holter (B) recordings of a one-day-old neonate with bradycardia attributable to 2:1 atrioventricular block (AVB). The Holter recording showed 1:1 sinus rhythm periods, thus demonstrating that the AVB was intermittent. Furthermore, the notched T-wave morphology pointed to a mutation in HERG, which was identified.