The use of defibrillation testing (DFT) when inserting an implantable cardioverter defibrillator (ICD) declined significantly in US hospitals between 2010 and 2015; during the same time period there was an increase in institutional variability in performing DFT that was not based on patient characteristics. Writing in the Journal of the American Medical Association (JAMA), Ryan T Borne (University of Colorado, Colorado, USA) et al say: “This variability in de-adoption of DFT could reflect differences in practice culture, despite mounting evidence and guidance that DFT may not be necessary at the time of ICD implantation.”
DFT is performed during implantation to assess the capacity of the ICD to detect and terminate ventricular arrhythmias, but it can cause complications and it has been shown to be safe to omit its use. The authors point out: “Contemporary ICDs rarely fail in their ability to detect and treat ventricular arrhythmias. Improvements in device technology provide defibrillation thresholds that are typically 10 to 20J less than the maximum ICD output, such that successful defibrillation occurs in more than 90% of clinical shocks. Given the evolution of the evidence and guidelines, we sought to evaluate contemporary temporal trends and institutional variation in DFT at the time of initial ICD implantation and determine patient and hospital characteristics associated with DFT within the National Cardiovascular Data Registry (NCDR) ICD Registry.”
Borne and colleagues performed a multi-centre cross-sectional study of 499, 211 patients undergoing first-time ICD implantation between April 2010 and December 2015 in 1,794 different facilities. Data were analysed from May 2015 to August 2019. 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.
The mean age of the population was 65.5 years (standard deviation [SD] 13.4) and 356, 681 (71.4%) were men. The use of DFT declined from 71.6% in Q1 2010 to 36.4% in Q4 2015 (p <0 .001). Compared to those who were not tested, patients undergoing DFT were more likely to have ischaemic heart disease (170, 569 [58.1%] DFT vs. 116, 295 [56.6%] no DFT), ventricular tachycardia (91, 500 [31.2%] tested vs 58 ,949 [28.7%] not tested), and less advanced heart failure (New York Heart Association class I and II, 153,188 [52.2%] vs 91,215 [44.4%] for DFT and no DFT, respectively) (p < 0.001 for all).
There was significantly lower use of DFT among patients who had NYHA class IV (odds ratio [OR] 1.35, 95% CI 1.30–1.40) and those with atrial arrhythmias (OR 1.52, 95% CI 1.47–1.56) and higher use in patients with NYHA class I categorisation (OR 0.89, 95% CI 0.87–0.91), sinus rhythm (OR 0.72, 95% CI 0.7–0.74), and antiarrhythmic agent therapy (OR 0.91, 95% CI 0.9–0.93).
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, say the authors that “by 2015, a randomly selected patient receiving testing at a hospital with high testing rates would have a six-fold higher odds of being tested than if they had received care at a hospital with low testing rates”.
Those who had a secondary prevention indication and structural abnormalities were more likely to undergo testing than patients who had a primary indication and no structural abnormalities. In contrast, the number and severity of comorbidities appeared to be related DFT not being performed, reflecting that omitting DFT was preferred in patients who are sick and/or frail. “Paradoxically, say the authors, “these patients who are not undergoing DFT may be more likely to benefit. Further studies are needed to determine which patients gain the most benefit from DFT.”
They add: “A fundamental aspect to quality improvement is reducing unwarranted variation in care. Identifying hospital-level variation is a first step in understanding the extent to which patient factors influence variation in care compared with institutional factors, which can serve to be processes for interventions in attempts to improve the quality of care. The present study may provide a perspective on the pace of de-adoption of a once-held belief that DFT needs to be performed during ICD implantation. As with adoption, de-adoption 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.”