Must not have a family history of long corrected QT interval (QTc) syndrome Consistent corrected QT (QTc) > msec on more than one screening electrocardiography (ECG). Patients with a history of long QTc syndrome or personal or family history of ventricular arrhythmias will be excluded. Participants with a personal or family history of long QT syndrome Participants with a personal or family history of long QT syndrome Consistent corrected QT (QTc) > msec on more than one screening electrocardiograms (ECGs); patients with a history of long QTc syndrome or personal or family history of ventricular arrhythmias will be excluded Participants with a personal or family history of long QT syndrome. Patients with a prior history of drug-induced serotonin syndrome, or a family history of long-QT syndrome Known family history of hereditary heart disease Presence of risk factors for torsade de pointes, including family history of Long QT Syndrome or uncorrected hypokalemia. Family or personal history of long QT syndrome History of risk factors for TdP, including family history of long QT syndrome. History of risk factors for torsades de pointes (e.g., heart failure, hypokalemia, family history of long QT syndrome); concomitant use of medications with a low risk of QT/QTc prolongation (including, but not limited to diphenhydramine, famotidine, ondansetron) is permissible Known family or personal history of long corrected QT (QTc) syndrome or ventricular arrhythmias including ventricular bigeminy History of serious ventricular arrhythmia (VT or VF, ? beats in a row) and/or risk factors (e.g., heart failure, hypokalemia, family history of Long QT Syndrome) History or family history of long QT syndrome. History of serious ventricular arrhythmia (VT or VF, ? beats in a row) and/or risk factors (e.g., heart failure, hypokalemia, family history of Long QT Syndrome) A history of additional risk factors for torsades de pointes (e.g., heart failure, hypokalemia, family history of long QT syndrome, etc.) A history of additional risk factors for torsade de pointes (e.g., heart failure, hypokalemia, family history of long QT syndrome) Must not have a family history of long QTc syndrome A history of additional risk factors for Torsade de Pointes (e.g., clinically significant heart failure, hypokalemia, family history of long QT syndrome) A history of additional risk factors for torsade de pointes (e.g., heart failure, hypokalemia, family history of Long QT Syndrome). Personal or family history of long QT syndrome A history of additional risk factors for torsade de pointes (e.g., clinically significant heart failure, hypokalemia, family history of long QT syndrome) History of additional risk factors for torsade de pointes (e.g., family history of long QT syndrome). History of long QT syndrome or a family member with this condition History of risk factors for TdP, including family history of long QT syndrome Presence of risk factors for torsade de pointes, including family history of Long QT Syndrome or uncorrected hypokalemia A history of additional risk factors for torsade de pointes (e.g., heart failure, hypokalemia, family history of long QT syndrome) Personal or family history of long QT syndrome Family history of long QTc syndrome Family history of long QTc syndrome Personal or family history of established Brugada syndrome; if pre-enrollment electrocardiogram (ECG) demonstrates abnormal findings (ST elevation in precordial leads), cardiology consultation should be obtained to rule out presence of this inherited syndrome; patients with family history of unexplained sudden death before the age years; personal history of unexplained syncope or history of unexplained ventricular tachycardia or fibrillation should have a cardiology evaluation to rule out the diagnosis of Brugada syndrome Personal or family history of long QT syndrome Patients with unexplained syncope, history of or known risk factors for torsade des pointes, including congenital long QT syndrome, or family history of LQTS. History of clinically significant cardiac disease, including but not limited to a history (personal or family) of congenital long QT syndrome Must be willing to complete demographic, family history, personal health and medication history, and informed consent Subject has a history (or family history) of long QT syndrome. Personal or family history of porphyrias Personal or family history of porphyrias Personal or family history of porphyrias History of Brugada syndrome, risk factors for TdP, or family history of long QT syndrome.