Defibrillation testing losing ground as a safety check for ICDs

A cross-sectional study of heart patients undergoing implantable cardioverter-defibrillator (ICD) implantation revealed a marked decline in the use of defibrillation testing over time in the U.S., suggesting the precaution might be losing its value as a clinical tool.

First author Ryan T. Borne, MD, of University of Colorado Anschutz Medical Campus, and colleagues wrote in JAMA Network Open that defibrillation testing (DFT)—a means to assess the ability of a newly implanted ICD to detect and put an end to ventricular fibrillation—is included in the FDA’s labeling of ICDs and was once used routinely in clinical practice. But while it may have been regarded as a safety necessity in the past, the utility of DFT has been questioned in recent years.

“The benefits of DFT have not routinely been demonstrated,” Borne et al. wrote in the journal. “Several studies published between 2008 and and 2012 found no association between routine testing and the efficacy of ICD shocks during follow-up or the risk of arrhythmic death. Furthermore, contemporary ICDs rarely fail in their ability to detect and treat ventricular arrhythmias.”

Newer-generation ICDs are capable of high-energy, biphasic and tunable defibrillation waveforms, the authors said, meaning successful defibrillation now occurs in around 90% of clinical shocks. The team studied contemporary temporal trends and institutional variation in DFT use between 2010 and 2015 in an attempt to determine whether the added effort of defibrillation testing is still worth it.

Borne and colleagues used data from the National Cardiovascular Data Registry ICD Registry for their work, enrolling 499,211 first-time ICD patients from 1,794 different facilities. The researchers assessed defibrillation testing rates and median odds ratios (MORs) over time, where MOR represented the odds that a randomly selected patient receiving DFT at a hospital with high testing rates would be tested compared with if they received care at a hospital with low testing rates.

The authors found the use of DFT among the study population, who were a majority male and in their mid-sixties, declined over time, from 71.6% in the first calendar quarter of 2010 to 36.4% in the fourth quarter of 2015. Patients who underwent DFT were more likely than no-DFT patients to have:

  • Ischemic heart disease (58.1% of DFT patients vs. 56.6% of no-DFT patients)
  • Ventricular tachycardia (31.2% vs. 28.7%)
  • Less advanced, NYHA class I or II heart failure (52.2% vs. 44.4%)

The MOR for the use of defibrillation testing was 3.78 in 2010 and 6.05 in 2015, suggesting that by 2015 a randomly selected patient receiving DFT at a hospital with high testing rates would see six-fold higher odds of being tested than if they’d received care at a hospital with low testing rates.

While the use of DFT declined significantly over time, the authors reported that testing in certain populations varied. The numbers couldn’t be attributed to patient characteristics, meaning recent variability in DFT use likely reflects differences in individual or institutional practices.

“The evolution of medicine occurs through a process of adoption and/or deadoption of practices,” Borne and co-authors said. “More often, there is a focus on adoption of newer interventions that outperform established practices. However, there must also be deadoption of established standards, not because a better intervention has been developed, but because what was once thought to be beneficial is not.”

The team’s study could provide perspective on the pace of deadoption of DFT as a necessity before ICD implantation, they said. The noted variability in the deadoption of DFT might reflect differences in practice culture despite increased evidence that testing might not be necessary at the time of implantation.

“Despite mounting evidence that omission of DFT is safe, there is still significant variation in its use, with some institutions continuing to apply DFT frequently, which is independent of patient characteristics,” Borne et al. wrote. “As with adoption, deadoption requires a focus on the cultural aspects of practice, which have evolved from not only evidence-based practices but also personal experiences, conflicts and biases.”