Implantable cardioverter-defibrillators (ICDs) are effective in decreasing mortality in patients at high risk for sudden cardiac arrest. However, previous studies have reported that 20 percent of ICDs for primary prevention to not adhere to current criteria. Now, a new study presented on May 14 at Heart Rhythm 2015 finds that the majority of ICD patients meet trial-based criteria, while many of those that do not may have clinical circumstance to warrant one.

Researchers, led by Daniel W. Kasier, MD and Mintu P. Turakhia, MD, MS, FACC, from the Stanford University School of Medicine, examined data from the ACC’s ICD Registry. All patients who underwent first-time ICD or cardiac resynchronization therapy defibrillator (CRT-D) implantation for a primary prevention indication between January 2006 and December 2008 were included. The primary outcome was meeting inclusion criteria of at least one of the primary prevention ICD trials – MADIT I, MADIT II, SCD-HeFT or MUSST. If none of the criteria for these trials was reported, the patient was considered to have undergone ICD implantation for primary prevention not meeting trial-based criteria. For CRT-D patients, researchers only examined whether they met trial-based indications for the ICD component of their therapy.

Of 150,264 patients, 128,821 (85.7 percent) met inclusion criteria for at least one of the primary prevention trials at the time of implantation. 21,433 (14.3 percent) patients received ICDs outside of trial inclusion criteria. The proportion of ICD implantations not meeting inclusion criteria increased as patient age decreased. The characteristics associated with not meeting inclusion criteria included prior cardiac transplantation, high-grade conduction disease and those with procedures performed by certain medical specialties such as a cardiothoracic surgeon or pediatric electrophysiologist. These results suggest that some of these implantations may have been appropriate without meeting inclusion criteria for primary prevention trials, which were comprised of mostly older patients with heart failure and vascular risk factors.

“[While] these seminal trials represent the evidence base for the majority of ICD implants, there are many other clinically accepted reasons that ICD implantation would be considered clinically and medically appropriate,” the authors said. “In some cases, situations that seem like deviations from the seminal trial criteria could potentially have valid clinical justifications.”

Based on the results, researchers caution the use of trial-based indications to determine site quality metrics which could penalize sites that care for younger patients. The NCDR is currently working to update the ICD Registry, which will better incorporate updated Appropriate Use Criteria (AUC) for implants. The authors add that this update will “help clarify when ICD implants are appropriate rather than mapping based in trial inclusion criteria.”  

Keywords: Arrhythmias, Cardiac, Cardiac Resynchronization Therapy, Death, Sudden, Cardiac, Defibrillators, Implantable, Heart Conduction System, Heart Failure, Heart Transplantation, Primary Prevention, Registries, Surgeons, National Cardiovascular Data Registries, ICD Registry

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