Arrhythmia Single Shock Defibrillation Threshold Testing Versus Upper Limit of Vulnerability: Risk Reduction Evaluation With Implantable Cardioverter Defibrillator Implantations - ASSURE
The goal of the trial was to compare single versus multiple ventricular fibrillation (VF) induction/defibrillation tests at implantation on the device's ability to sense, detect, and convert VF in patients receiving an implantable cardioverter defibrillator (ICD) or cardiac resynchronization therapy defibrillator.
Patients Enrolled: 328
Mean Follow Up: Mean 9.5 months
Mean Patient Age: Mean age, 66 years
Age ≥18 years with standard inclusion criteria for initial ICD/cardiac resynchronization therapy defibrillator implantation or replacement
During implantation, patients were randomized to vulnerability safety margin (VSM) or defibrillation safety margin (DSM) screening at 14 J. Each group then crossed over to the opposite testing. Patients then underwent confirmatory testing that required two VF conversions without failure at ≤21 J. If the first 14 J and confirmatory tests were passed, the devices were programmed to a 21 J shock for ventricular tachycardia (VT) or VF ≥200 bpm, irrespective of the results of their second 14 J test (the crossover testing).
At study entry, 68% of patients had an ejection fraction ≤30%. New York Heart Association classification was predominantly class II (35%) or class III (48%). Coronary artery disease was present in 71% of patients, with 49% having had a prior myocardial infarction. Device type was ICD in 51% of patients and cardiac resynchronization therapy defibrillator in 49%.
Of those who underwent VSM, 75.5% passed the 21 J conversion; of those who underwent DSM, 81.3% passed 21 J conversion. There was a discrepancy between VSM and DSM screening following crossover in 65 patients, 94% of whom passed their 21 J confirmation testing. Testing results were similar when randomized to VSM versus DSM screening first.
During follow-up, the clinical VT/VF episode rate was 13.3% per year. The majority of clinical VT/VF episodes (86%) were terminated by the first shock, with no difference in first shock success by randomization group (92% in the VSM first group and 75% in the DSM first group). In all observed cases in which the first shock was unsuccessful, subsequent shocks terminated VT/VF.
Among patients receiving an ICD or cardiac resynchronization therapy defibrillator, device testing at the time of implantation using either vulnerability safety margin or defibrillation safety margin screening at 14 J was associated with similar rates of termination of clinical VT/VF episodes by the first shock.
While important to determine the function and integrity of the device, repeated VF induction at the time of device implantation can result in severe complications, particularly in certain high-risk populations such as those with advanced heart failure. VSM or DSM screening at 14 J were both shown to have similar positive predictive accuracy in the present trial.
Day JD, Doshi RN, Belott P, et al. Inductionless or limited shock testing is possible in most patients with implantable cardioverter-defibrillators/cardiac resynchronization therapy defibrillators: results of the multicenter ASSURE Study (Arrhythmia Single Shock Defibrillation Threshold Testing Versus Upper Limit of Vulnerability: Risk Reduction Evaluation With Implantable Cardioverter-Defibrillator Implantations). Circulation 2007;115:2382-9.
Keywords: Myocardial Infarction, Tachycardia, Ventricular, Follow-Up Studies, Ventricular Fibrillation, Electric Countershock, Heart Failure, Defibrillators, Implantable, Cardiac Resynchronization Therapy
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