title: Acquired long QT interval: a case series of multifactorial QT prolongation.
abstract: BACKGROUND
  Acquired long QT (LQT) interval is thought to be a consequence of drug therapy and electrolyte disturbances.
  
  
  OBJECTIVE
  We characterize the potential effects of polypharmacy in a case series of acquired LQT and torsades de pointes (TdP) in order to determine whether multiple risk factors play a role in the development of LQT.
  
  
  METHODS
  The case series consisted of 11 patients presenting to 4 tertiary care hospitals with LQT and ≥ 2 risk factors for developing LQT. Clinical characteristics, medications, electrolyte disturbances, and course in hospital were analyzed.
  
  
  RESULTS
  Mean age was 49.1 ± 5.8 years. Eight patients were female. Four had hypertension, 1 had a history of dilated cardiomyopathy, and 1 patient demonstrated complete atrioventricular block. Average QTc interval at presentation was 633.8 ± 29.2 ms. Nine patients developed TdP. In 3, LQT was not initially detected and amiodarone was administered, followed by development of TdP. Patients were taking an average of 2.8 ± 0.3 QT-prolonging medications-an antidepressant in 6 cases and a diuretic in 8 cases. All patients had an electrolyte abnormality; 8 patients presented with severe hypokalemia (<3.0 mmol/L). Average serum potassium and magnesium were 2.82 ± 0.10 mmol/L and 0.75 ± 0.03 mmol/L, respectively. There were no deaths.
  
  
  CONCLUSIONS
  This case series highlights the risks of polypharmacy in the development of LQT and TdP. It illustrates the importance of early detection of LQT in patients with multiple risk factors in ensuring appropriate treatment.
authors: Department of Cardiology, Kingston General Hospital, Queen's University, Kingston, Ontario, Canada. genevieve.digby@gmail.com
authors: Geneviève C
authors: GC
authors: Digby
authors: Andrés Ricardo
authors: AR
authors: Pérez Riera
authors: Raimundo
authors: R
authors: Barbosa Barros
authors: Christopher S
authors: CS
authors: Simpson
authors: Damian P
authors: DP
authors: Redfearn
authors: Michelle
authors: M
authors: Methot
authors: Francisco
authors: F
authors: Femenía
authors: Adrian
authors: A
authors: Baranchuk
mesh_terms: D000328:Adult; D000368:Aged; D000638:Amiodarone / Q000009:adverse effects; D000889:Anti-Arrhythmia Agents / Q000009:adverse effects; D005260:Female; D006801:Humans; D008133:Long QT Syndrome / Q000139:chemically induced* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D019338:Polypharmacy; D015221:Potassium Channels; D012189:Retrospective Studies; D012307:Risk Factors; D016171:Torsades de Pointes / Q000139:chemically induced* / Q000473:pathology; D055815:Young Adult
chemical_list: D000889:Anti-Arrhythmia Agents; D015221:Potassium Channels; D000638:Amiodarone