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Figure 1 Electrocardiographic parameters in lead V₅ before and after exercise in LQT1 patients with mutations located in the transmembrane region (A341V, non-proband, 16-year-old male) (A and B) and in the C-terminal region (D611Y, non-proband, 16-year-old male) (C and D). The baseline corrected Q-Tend (cQ-Tend), Q-Tpeak (cQ-Tpeak), and Tpeak-end (cTpeak-end) intervals were greater in the patient with a transmembrane mutation than in the patient with a C-terminal mutation (A and C). Exercise produced more prominent increases in the cQ-Tend and cTpeak-end in the patient with a transmembrane mutation than in the patient with a C-terminal mutation (B and D).