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Figure 2 Maximal QT end intervals (higher two lines) and QT end intervals at stable heart rates (lower two lines) at specified heart rates before the treatment with beta-blockers (broken lines) and during the treatment with beta-blockers (solid lines) in 24 long-QT syndrome type 1 (LQT1) patients. **p < 0.01 before the treatment versus during the treatment with beta-blockers at RR intervals from 600 to 700 ms.