title: Hypertrophic Cardiomyopathy and Implantable Defibrillators in Sweden: Inappropriate Shocks and Complications Requiring Surgery.
abstract: BACKGROUND
  The expanded use of implantable cardioverter-defibrillators (ICDs) to prevent sudden cardiac death (SCD) in hypertrophic cardiomyopathy (HCM) based on risk stratification in individuals without known previous ventricular arrhythmia is justified by an acceptable risk of device-related adverse events. Such complications, leading to surgical procedures or inappropriate electrical shocks, may impact mortality, morbidity, quality of life, and cost-effectiveness.
  
  
  RESULTS
  From the Swedish ICD Registry, implants due to HCM since 1995 until November 2012 in patients aged ≥18 years were identified and medical records reviewed. Inappropriate ICD shock occurred in 14.3% (46 of 321 patients; mean follow-up 5.4 years) with a recurrent episode in 28.2% of them. In multivariable analysis, hazard ratio (HR) for atrial fibrillation was 3.5 (95% confidence interval 1.8-6.8; P < 0.001) but showed no significant association to male sex (HR = 0.77), age (HR = 0.99), secondary indication (HR = 1.02) or device, ICD-DR/CRTD vs. ICD-VR (HR 1.07). Inappropriate shocks were triggered by atrial fibrillation/flutter or ectopic tachycardia (56.5%), sinus tachycardia (14.5%), lead dysfunction (14.5%), and T-wave oversensing (13.0%). A reintervention, besides elective device replacement, occurred in 92 patients (totally 150 procedures). The majority were lead-related (70.0%) procedures, especially of the ICD lead. Reintervention was associated with female sex (HR = 1.6 P = 0.04).
  
  
  CONCLUSIONS
  Inappropriate ICD shock triggered by atrial arrhythmias, lead dysfunction, or complications requiring surgical interventions, is a concern in HCM patients who will be eligible for long-term prevention of sudden death. Efforts to avoid adverse events and provide balanced risk-benefit information are important, especially in primary prevention.
authors.affiliation: Cardiology Research Unit, Department of Medicine, Karolinska Institutet, Stockholm, Sweden.|Centre for Research and Development, Uppsala University/Region Gävleborg, Gävle, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Magnusson
authors.affiliation: Cardiology Research Unit, Department of Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Fredrik
authors.initials: F
authors.lastname: Gadler
authors.affiliation: Centre for Research and Development, Uppsala University/Region Gävleborg, Gävle, Sweden.
authors.forename: Per
authors.initials: P
authors.lastname: Liv
authors.affiliation: Cardiology, Heart Center and Department of Public Health and Clinical Medicine, Umeå University, Umeå, Sweden.
authors.forename: Stellan
authors.initials: S
authors.lastname: Mörner
mesh_terms: D002312:Cardiomyopathy, Hypertrophic / Q000401:mortality* / Q000628:therapy*; D015897:Comorbidity; D016757:Death, Sudden, Cardiac / Q000453:epidemiology* / Q000517:prevention & control*; D017147:Defibrillators, Implantable / Q000706:statistics & numerical data*; D020878:Device Removal / Q000401:mortality; D004556:Electric Injuries / Q000401:mortality*; D004868:Equipment Failure / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D019919:Prosthesis Implantation; D012307:Risk Factors; D017678:Sex Distribution; D015996:Survival Rate; D013548:Sweden / Q000453:epidemiology; D017211:Treatment Failure
keywords: Sprint Fidelis lead; complication; hypertrophic cardiomyopathy; implantable defibrillator; inappropriate shock; sudden cardiac death