Diltiazem in Jervell and Lange-Nielsen Syndrome

IV diltiazem (0.25 mg/kg) will be given over 2 minutes, with ECG and blood pressure measurements at baseline, 2, 5, 7, 10, 15 and 20 minutes. If at 10 minutes there is no QT shortening, and blood pressure is stable, an additional dose (0.35 mg/kg) will be given with ECG and blood pressure measurements at 17, 20, 22, 25, 30 and 35 minutes.