Figure 2.

Distribution of long QT syndrome (LQTS) children and controls according to corrected QT (QTc) and T-wave morphology in leads V₄–V₆. Top: All LQTS children and controls. Bottom: Children without an obvious QTc prolongation at baseline (eg, <480 ms, LQTS children n = 33 and control n = 84). At baseline, abnormal QTc (denoted as QTc+), defined as ≥440 ms, and abnormal T waves (denoted as T-wave+) include broad, notched, and late-onset T waves. During maximal QT stretching, the respective abnormal values are QTc ≥490 ms and “abnormal T-wave response to standing” as defined in the text.