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Figure 1 Electrocardiographic lead I4 of the body-surface map, which corresponds to lead V6 of the standard 12-lead electrocardiogram, at the baseline condition (A), with oral propranolol (B), during epinephrine infusion at baseline (C) and during epinephrine infusion with oral propranolol (D) in a patient with LQT1 syndrome. Both cQTe and cQTp were prolonged (584 and 461 ms, respectievly) and cTp-e was increased (123 ms) at the baseline condition. Propranolol produced no significant change in cQTe (588 ms), but prolonged cQTp (488 ms), resulting in a decrease in cTp-e (100 ms). Epinephrine produced a remarkable prolongation in cQTe (710 ms), but a mild prolongation in cQTp (532 ms), resulting in an increase in cTp-e (178 ms), and this was completely suppressed by oral propranolol. HR = heart rate.
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