title: Clinical characteristics of patients with drug-induced QT interval prolongation and torsade de pointes: identification of risk factors.
abstract: The present study aimed to investigate the causative medications and underlying risk factors that predispose to drug-induced QT interval prolongation. Twenty-one patients with drug-induced long QT (90% females, mean age 64.3 +/- 14.1 years) were included in the study. Transthoracic echocardiography as well as continuous or ambulatory 48-h electrocardiographic monitoring was carried out in all patients during their hospitalization. The mean corrected QT (QTc) interval was 542 +/- 56.8 ms. Known cardiac agents (mainly class III antiarrhythmics) were implicated in 13/21 (62%), antipsychotics in 8/21 (38%), and antibiotics in 5/21 patients (24%). Potential drug-interactions through inhibition of cytochrome P450 isoenzymes were considered responsible in 5/21 cases (24%). The underlying cardiovascular diseases included hypertension (57%) with left ventricular hypertrophy (29%), paroxysmal atrial tachyarrhytmias (48%), heart failure (14%), valvular heart disease (10%), and coronary artery disease (5%). Torsade de pointes (TdP) was recorded in 6/21 of patients, and cardiac arrest necessitating resuscitation occurred in five of them. A significant correlation was observed between administration of cardiac agents and TdP events (P < 0.05). TdP and cardiac arrest events were both associated with a QTc interval >510 ms (P < 0.05). Advanced age (>60 years), female gender, hypertension and paroxysmal atrial tachyarrhytmias were the most common identifiable pre-existing factors for drug-induced long QT in our patient cohort. Marked QTc interval prolongation should be considered of prognostic significance for TdP and cardiac arrest events.
authors.affiliation: Second Department of Cardiology, Evangelismos General Hospital of Athens, Athens, Greece. k.letsas@mail.gr
authors.forename: Konstantinos P
authors.initials: KP
authors.lastname: Letsas
authors.forename: Michalis
authors.initials: M
authors.lastname: Efremidis
authors.forename: Stavros P
authors.initials: SP
authors.lastname: Kounas
authors.forename: Loukas K
authors.initials: LK
authors.lastname: Pappas
authors.forename: Gerasimos
authors.initials: G
authors.lastname: Gavrielatos
authors.forename: Ioannis P
authors.initials: IP
authors.lastname: Alexanian
authors.forename: Nikolaos P
authors.initials: NP
authors.lastname: Dimopoulos
authors.forename: Gerasimos S
authors.initials: GS
authors.lastname: Filippatos
authors.forename: Antonios
authors.initials: A
authors.lastname: Sideris
authors.forename: Fotis
authors.initials: F
authors.lastname: Kardaras
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000889:Anti-Arrhythmia Agents / Q000009:adverse effects*; D000900:Anti-Bacterial Agents / Q000009:adverse effects; D014150:Antipsychotic Agents / Q000009:adverse effects*; D003577:Cytochrome P-450 Enzyme System / Q000187:drug effects / Q000378:metabolism; D004347:Drug Interactions; D004452:Echocardiography; D005260:Female; D006323:Heart Arrest / Q000209:etiology; D006801:Humans; D006973:Hypertension / Q000150:complications; D008133:Long QT Syndrome / Q000139:chemically induced*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012307:Risk Factors; D012737:Sex Factors; D013614:Tachycardia, Paroxysmal / Q000150:complications; D016171:Torsades de Pointes / Q000139:chemically induced*
chemical_list: D000889:Anti-Arrhythmia Agents; D000900:Anti-Bacterial Agents; D014150:Antipsychotic Agents; D003577:Cytochrome P-450 Enzyme System