Bar chart showing the number of patients with any QT-prolonging medical conditions excluding female gender, electrolyte disturbances, and medication (A), number of patients who were taking any QT-prolonging drugs (B), distribution of pro-QTc scores (C), and number of patients taking at least one drug from the four subgroups of drugs from the CredibleMeds QTdrugs lists (D). CLQTS, congenital long-QT syndrome; QTc, corrected QT interval.