Diltiazem in Jervell and Lange-Nielsen Syndrome

Inclusion Criteria: * Age greater than 18 years * Genetically confirmed diagnosis of Jervell and Lange-Nielsen syndrome * Able to provide written informed consent Exclusion Criteria: * Known hypersensitivity to diltiazem * Pregnancy * Congestive heart failure, angina, preexcitation, or chronic obstructive pulmonary disease * Sick sinus syndrome or atrioventricular block in the absence of a pacemaker/defibrillator * Any clinically significant ongoing medical or surgical condition that might jeopardize the subject's safety or interfere with the conduct of the study in the judgement of the investigator * Baseline systolic blood pressure less than 100 Hg or diastolic blood pressure less than 60 Hg