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Figure 4 Diagnostic value of Ex QTc-max in patients with a borderline baseline QTc interval. A 23-year-old male asymptomatic family member shows a baseline QTc of 440 ms during sinus bradycardia. An Ex QTc-max of 480 ms at 9 min of the bicycle exercise test identifies his affected status. Genetic testing revealed he was a T1945+6C mutation carrier.