Figure 2.

ECGs of typical and atypical LQTS. ECGs of typical broad-based T waves in long QT 1 (A), bifid T waves in long QT 2 (B, enlarged box), and long horizontal ST-segment in long QT 3 (C). D, ECG of a 1-day-old infant found to carry a de novo variant in CALM3 (c.389A>G, p.Asp130Gly). A very prolonged QT interval with 2:1 atrioventricular block (full arrows) and T-wave alternans (hollow arrows) is present. Adapted with permission from Reed et al.³⁹ E, An ECG demonstrating QT prolongation and negative T waves in precordial leads of a 10-year-old girl homozygous for a loss-of-function variant in TRDN (c.53_56delACAG, p.Asp18Alafs). Adapted with permission from Altmann et al.⁴¹