title: Prolongation of the QTc interval predicts appropriate implantable cardioverter-defibrillator therapies in hypertrophic cardiomyopathy.
abstract: OBJECTIVE
  This study sought to determine factors predicting appropriate implantable cardioverter defibrillator (ICD) therapy in a large cohort of patients with hypertrophic cardiomyopathy (HCM).
  
  
  BACKGROUND
  HCM is the leading cause of sudden cardiac death in those age ≤35 years. ICD therapy is offered to select patients at increased risk for sudden cardiac death. Currently, there are no clinical predictors of appropriate ICD therapy in HCM.
  
  
  METHODS
  Patients attending the HCM clinic in Sydney, Australia, and who had undergone ICD insertion were included. Baseline data on clinical and ICD characteristics were collected. The primary endpoint was the proportion of patients who experienced at least 1 appropriate therapy from the ICD.
  
  
  RESULTS
  Of 164 HCM patients included (62% male; mean follow-up, 6 ± 4 years [range, 0 to 19 years]), 21 patients (13%) had at least 1 appropriate therapy. Corrected QT (QTc) interval was the strongest clinical predictor of appropriate ICD therapy (458 ± 30 ms vs. 430 ± 35 ms; p = 0.001). Multivariate logistic regression analysis demonstrated a 1.2-fold increased likelihood of appropriate therapy per 10-ms increase in QTc, independent of left ventricular wall thickness (LVWT) (odds ratio: 1.2; 95% confidence interval [CI]: 1.03 to 1.39; p = 0.02) and sex (odds ratio: 1.2; 95% CI: 1.07 to 1.42; p = 0.003). On analysis of cumulative event-free survival from appropriate ICD therapy, the risk for an appropriate ICD therapy in the subgroup with prolonged QT was >3-fold that in the subgroup without prolonged QT, after adjustment for LVWT (hazard ratio: 3.2; 95% CI: 1.02 to 9.88; p = 0.047) and sex (hazard ratio, 3.7; 95% CI, 1.22 to 11.41; p = 0.02).
  
  
  CONCLUSIONS
  The findings from this study suggest that QTc interval prolongation is a novel clinical predictor of appropriate ICD therapy in HCM.
authors.affiliation: Department of Cardiology, Royal Prince Alfred Hospital, Sydney, Australia; Sydney Medical School, University of Sydney, Sydney, Australia.
authors.forename: Belinda
authors.initials: B
authors.lastname: Gray
authors.affiliation: Sydney Medical School, University of Sydney, Sydney, Australia; Agnes Ginges Centre for Molecular Cardiology, Centenary Institute, Camperdown, Australia.
authors.forename: Jodie
authors.initials: J
authors.lastname: Ingles
authors.affiliation: Department of Cardiology, Royal Prince Alfred Hospital, Sydney, Australia; Agnes Ginges Centre for Molecular Cardiology, Centenary Institute, Camperdown, Australia.
authors.forename: Caroline
authors.initials: C
authors.lastname: Medi
authors.affiliation: Department of Cardiology, Royal Prince Alfred Hospital, Sydney, Australia; Sydney Medical School, University of Sydney, Sydney, Australia; Agnes Ginges Centre for Molecular Cardiology, Centenary Institute, Camperdown, Australia. Electronic address: c.semsarian@centenary.org.au.
authors.forename: Christopher
authors.initials: C
authors.lastname: Semsarian
mesh_terms: D000328:Adult; D002312:Cardiomyopathy, Hypertrophic / Q000503:physiopathology* / Q000628:therapy*; D017147:Defibrillators, Implantable; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D013997:Time Factors
keywords: QT interval; clinical predictor; hypertrophic cardiomyopathy; implantable cardioverter defibrillator