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Case Presentation
A 34-year-old female who is 4 months postpartum presents after a nocturnal seizure. She was awakened at night by an alarm clock to feed her baby, spoke briefly with her husband, and suddenly lost consciousness, appearing to have epileptic-type movements before spontaneously recovering. On further questioning, she reported several syncopal events over the past 15 years, once when standing suddenly, also thought at the time to be a seizure. Previous neurological investigations were normal. A 12-lead ECG (Figure 1A) revealed a corrected QT interval of 550 ms with low-amplitude, notched T-waves.
Electrocardiographic traces from leads II and V5 (A,C–F) and lead II (B) in patients with long QT syndrome. A, ECG traces from the initial patient described showing low-amplitude, notched T-waves characteristic of LQT2. B, Alternating T-wave axis and morphology (T-wave alternans) leading to an episode of torsades de pointes (TdP) triggered by a ventricular ectopic beat. C, Traces from a previously asymptomatic individual who suffered significant QT prolongation (QTc 570 ms) and ventricular fibrillation following a head injury and intracranial hemorrhage. D, On recovery his QT interval normalized (QTc 440 ms), but (E) showed marked prolongation 2 minutes into recovery on exercise testing (QTc 550 ms). Genetic analysis identified deletion of 10 amino acid residues in KCNQ1. F, Severe QT prolongation (QTc 740 ms) in a 9-year-old child presenting with nocturnal seizures. Despite propranolol therapy he continued to have short runs of TdP and underwent primary prevention ICD implantation. A functionally deleterious missense mutation previously associated with severe phenotype was identified in SCN5A (c.G1231A; p.V411M).
Background and Prevalence
Long QT syndrome (LQTS) is an inherited cardiac condition caused by genetically encoded abnormalities in cardiac ion channels, characterized clinically by palpitations, syncope, and sudden cardiac death, with varying degrees of QT prolongation and T-wave morphological …
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