Trends and Variation in Use of Defibrillation Testing

Study Questions:

What are the temporal trends and variation in the use of defibrillation threshold testing (DFT) in contemporary practice in the United States?

Methods:

This was an analysis of data from the National Cardiovascular Data Registry ICD Registry. Patients undergoing first-time implantable cardioverter-defibrillator (ICD) implantation were included. Defibrillation testing rates and median odds ratios (MORs) were assessed over time. The MOR represents the odds that a randomly selected patient receiving testing at a hospital with high testing rates would be tested compared with if he or she had received care at a hospital with low testing rates.

Results:

Among 499,211 patients, the mean age of the population was 66 years and 71% were men. The use of DFT declined from 71.6% in the first calendar quarter of 2010 to 36.4% in the fourth quarter of 2015 (p < 0.001). Patients undergoing DFT were more likely than those without testing to have ischemic heart disease (58.1% vs. 56.6%), ventricular tachycardia (31.2% vs. 28.7%), and less advanced heart failure (New York Heart Association class I and II, 52.2% vs. 44.4%) (p < 0.001 for all). The MOR for the use of defibrillation testing was 3.78 (95% confidence interval [CI], 3.54-4.03) in 2010, increasing to 6.05 (95% CI, 5.61-6.52) in 2015, indicating that by 2015, a randomly selected patient receiving testing at a hospital with high testing rates would have a sixfold higher odds of being tested than if he or she had received care at a hospital with low testing rates.

Conclusions:

Defibrillation testing at the time of ICD placement in the United States may have declined over time; however, institutional variation in its use appears to be marked and increased. This variability in the reduced use of defibrillation testing could reflect differences in individual or institutional cultures of practice.

Perspective:

The purpose of DFT is to confirm proper detection of fine ventricular fibrillation and to ascertain that there is a sufficient amount of energy to reliably convert ventricular fibrillation to a nonshakable rhythm. The practice used to be performed in all patients undergoing ICD implantation. However, with enhancements in detection, introduction of biphasic defibrillation, and high energy generators, contemporary ICDs rarely fail in their ability to detect and treat ventricular arrhythmias. It is reasonable to withhold DFT among patients with severe heart failure, valvular disease, or atrial fibrillation or flutter and subtherapeutic anticoagulation. Patients at the highest risk of a serious complication from DFT may be some of the same ones for whom the defibrillation energy and vector may be inadequate. The present study shows that there is tremendous interphysician and interhospital variation in the rates of DFT testing, independent of patient characteristics, likely reflecting differing practice cultures and experiences.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure

Keywords: Arrhythmias, Cardiac, Defibrillators, Implantable, Diagnostic Imaging, Electric Countershock, Heart Failure, ICD Registry, Myocardial Ischemia, National Cardiovascular Data Registries, Tachycardia, Ventricular, Ventricular Fibrillation, ICD Registry, National Cardiovascular Data Registries


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