Use of implantable cardioverter defibrillators in Canadian and US survivors of out-of-hospital cardiac arrest

Abstract

Background: Cardiac arrest due to ventricular arrhythmia in the absence of a reversible cause or contraindication has been a class I indication for insertion of an implantable cardioverter defibrillator since 1998. We compared and contrasted the use of implantable cardioverter defibrillator therapy in Canada and the United States among adults who survived a cardiac arrest.

Method: Data on hospital separations from April 1, 1994 through March 31, 2003 were obtained from the Health Person-Oriented Information Database maintained by Statistics Canada and from the US National Hospital Discharge Survey on all patients with a primary diagnosis of cardiac arrest, ventricular fibrillation or ventricular flutter for the same 9-year period. We excluded all records of patients with a secondary diagnosis of acute myocardial infarction.

Results: In Canada, 3793 patients survived to discharge after a cardiac arrest; 628 (16.6%) of these were implanted with a cardioverter defibrillator before discharge. The implant rate rose steadily from 5.4% in 1994/95 to 26.7% in 2002/03. In the United States, 23 688 (30.2%) of 78 538 such survivors received an implantable cardioverter defibrillator before discharge. Logistic regression analysis indicated that sex, age, fiscal year, the hospital's teaching status, hospital size and patient history of heart failure were positive predictors of implantable cardioverter defibrillator implantation. Age, renal failure, liver failure and cancer were negative predictors of receiving an implantable cardioverter defibrillator.

Interpretation: The rate of use of implantable cardioverter defibrillator therapy for cardiac arrest survivors in Canada is increasing, but still is lower than the rate in the United States.

Figure 1: Cardioverter defibrillator implant rates in survivors of out-of-hospital cardiac arrest in the United States and Canada. Data points centre on fiscal years, which end on March 31. Vertical lines indicate the publication of major secondary-prevention trials and guidelines, as follows. AVID = Antiarrhythmics Versus Implantable Defibrillators trial, published November 1997: N Engl J Med 1997;337:1576. ACC–AHA = American College of Cardiology–American Heart Association guidelines, April 1998: J Am Coll Cardiol 1998;31:1175. CIDS = Canadian Implantable Defibrillator Study, March 2000: Circulation 2000;101:1297. CASH = Cardiac Arrest Hamburg Study, August 2000: Circulation 2000;102:748.

Figure 2: Odds ratios, both unadjusted and adjusted for all variables in the model, for predictors of cardioverter defibrillator implantation in Canadian survivors of out-of-hospital cardiac arrest. All other variables considered for the model, including presence of acute myocardial ischemia, were not predictive for use of this therapy.

Figure 3: Cardioverter defibrillator implant rates in male and female survivors of out-of-hospital cardiac arrest in Canada by year, 1994–2003. (Data points centre on fiscal years, which end on March 31.)