title: Incidence of Sustained Ventricular Tachycardia in Patients with Prolonged QTc After the Administration of Azithromycin: A Retrospective Study.
abstract: BACKGROUND
  Azithromycin has been associated with abnormalities of cardiac repolarization and development of torsades de pointes. Observational data suggest that the risk of death from cardiovascular causes is increased in patients taking azithromycin. Little is known regarding the risk of ventricular arrhythmia in patients with prolongation of the corrected QT interval who receive azithromycin.
  
  
  OBJECTIVE
  The purpose of this study was to determine the incidence of sustained ventricular tachycardia in patients with prolonged corrected QT (QTc) who subsequently received azithromycin.
  
  
  METHODS
  We performed a retrospective cohort analysis of the incidence of sustained ventricular tachycardia in patients with prolonged QTc (greater than 450 ms) who successively received intravenous (IV) and/or oral azithromycin. Patients hospitalized in a tertiary care teaching hospital between November 2009 and June 2012 were included in the study. The primary outcome was sustained ventricular tachycardia documented in patients on telemetry.
  
  
  RESULTS
  Of the 103 patients enrolled in the study, only one patient experienced the primary outcome (0.97 %). The event occurred 1 day after the administration of a single dose of 500 mg IV azithromycin.
  
  
  CONCLUSIONS
  The risk of sustained ventricular tachycardia was 0.97 % in our cohort of patients with prolonged QTc who subsequently received azithromycin. Given the small size of this study, additional research is needed to determine the true incidence of arrhythmia in the population.
authors.affiliation: Department of Internal Medicine, Mayo Clinic, 4500 San Pablo Road S, Jacksonville, FL, 32224, USA. sears.steven@mayo.edu.
authors.forename: Steven P
authors.identifier: http://orcid.org/0000-0001-7257-1599
authors.initials: SP
authors.lastname: Sears
authors.affiliation: CRISP Investigative Research Program, Mayo Clinic, Jacksonville, FL, USA.
authors.forename: Trevor W
authors.initials: TW
authors.lastname: Getz
authors.affiliation: Department of Cardiology, Mayo Clinic, Jacksonville, FL, USA.
authors.forename: Christopher O
authors.initials: CO
authors.lastname: Austin
authors.affiliation: Department of Gastroenterology and Hepatology, Mayo Clinic, Jacksonville, FL, USA.
authors.forename: William C
authors.initials: WC
authors.lastname: Palmer
authors.affiliation: CRISP Investigative Research Program, Mayo Clinic, Jacksonville, FL, USA.
authors.forename: Evelyn A
authors.initials: EA
authors.lastname: Boyd
authors.affiliation: Department of Internal Medicine, Mayo Clinic, 4500 San Pablo Road S, Jacksonville, FL, 32224, USA.
authors.forename: Fernando F
authors.initials: FF
authors.lastname: Stancampiano