title: Multifactorial QT interval prolongation.
abstract: Acquired long QT interval has been widely reported to be a consequence of drug therapy and electrolyte disturbances. We describe two cases of multifactorial acquired QT interval prolongation and torsades de pointes. In the first case, the drugs venlafaxine, amiodarone and domperidone may have contributed to QT interval prolongation in a patient with hypokalemia and hypomagnesaemia. In the second case, QT interval prolongation occurred in a patient taking quetiapine and citalopram, and whose use of hydrocholorothiazide and history of chronic alcohol abuse likely contributed by rendering the patient hypokalemic. These cases highlight the potential risks associated with polypharmacy and demonstrate that though torsades de pointes is an uncommon arrhythmia, the combination of multiple factors known to prolong QT interval may precipitate this life-threatening arrhythmia.
authors.affiliation: Division of Cardiology, Kingston General Hospital, Queen's University, Kingston, Ontario, Canada.
authors.forename: Geneviève
authors.initials: G
authors.lastname: Digby
authors.forename: Jimmy
authors.initials: J
authors.lastname: Machaalany
authors.forename: Paul
authors.initials: P
authors.lastname: Malik
authors.forename: Michelle
authors.initials: M
authors.lastname: Methot
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Simpson
authors.forename: Damian
authors.initials: D
authors.lastname: Redfearn
authors.forename: Adrian
authors.initials: A
authors.lastname: Baranchuk
mesh_terms: D000437:Alcoholism / Q000150:complications; D000638:Amiodarone / Q000009:adverse effects; D014150:Antipsychotic Agents / Q000009:adverse effects; D001145:Arrhythmias, Cardiac / Q000097:blood / Q000209:etiology* / Q000503:physiopathology / Q000628:therapy; D015415:Biomarkers / Q000097:blood; D015283:Citalopram / Q000009:adverse effects; D003511:Cyclohexanols / Q000009:adverse effects; D003987:Dibenzothiazepines / Q000009:adverse effects; D004232:Diuretics / Q000009:adverse effects; D004294:Domperidone / Q000009:adverse effects; D018492:Dopamine Antagonists / Q000009:adverse effects; D004562:Electrocardiography; D005260:Female; D006801:Humans; D006852:Hydrochlorothiazide / Q000009:adverse effects; D007008:Hypokalemia / Q000150:complications; D008274:Magnesium / Q000097:blood; D008875:Middle Aged; D019338:Polypharmacy; D000069348:Quetiapine Fumarate; D012307:Risk Factors; D017367:Selective Serotonin Reuptake Inhibitors / Q000009:adverse effects; D016171:Torsades de Pointes / Q000097:blood / Q000209:etiology* / Q000503:physiopathology / Q000628:therapy; D016896:Treatment Outcome; D000069470:Venlafaxine Hydrochloride
chemical_list: D000638:Amiodarone; D014150:Antipsychotic Agents; D015415:Biomarkers; D015283:Citalopram; D003511:Cyclohexanols; D003987:Dibenzothiazepines; D004232:Diuretics; D004294:Domperidone; D018492:Dopamine Antagonists; D006852:Hydrochlorothiazide; D008274:Magnesium; D000069348:Quetiapine Fumarate; D017367:Selective Serotonin Reuptake Inhibitors; D000069470:Venlafaxine Hydrochloride