Event rates were similar and extremely low when performing defibrillation testing (DT) versus not performing DT during de novo implantable cardioverter-defibrillator (ICD) implants, according to the prospective, observational SAFE-ICD study. The study authors suggested that their findings support a strategy of omitting DT during an ICD implant.
Historically, an effective DT has been considered part of standard procedures at insertion to ensure adequate sensing of ventricular fibrillation (VF), appropriate connection of high-voltage electrodes and the ability of the device to terminate VF with a shock. Implant techniques and technologies have evolved in recent years, and deviations from this clinical practice are “frequent,” according to Michele Brignole, MD, of the arrhythmia center in the department of cardiology at Ospedali del Tigullio in Lavagna, Italy, and colleagues.
Thus, the aim of the SAFE-ICD (Safety of Two Strategies of ICD Management at Implantation) study, published online Aug. 1 in the Journal of the American College of Cardiology, was to evaluate the safety, over a follow-up of two years, of two strategies, adopted at ICD implant in current clinical practice: induction, including patients who underwent DT at implant (DT+ group), and noninduction, including patients who did not undergo DT at implant (DT- group). The researchers said that they did not introduce any deviation from the centers' current practice.
In all, 2,120 consecutive patients (836 DT+ and 1,284 DT-) at least 18 years old were enrolled at 41 Italian centers from April 2008 to May 2009 and followed up for 24 months until June 2011. The primary endpoint was a composite of severe complications at ICD implant and sudden cardiac death or resuscitation at two years.
The researchers reported that the primary endpoint occurred in 34 patients: 12 intraoperative complications (eight in DT+ group; four in DT- group) and 22 during follow-up (10 in DT+ group; 12 in DT- group). Overall, the estimated yearly incidence was DT+ 1.15 percent and DT- 0.68 percent. The authors wrote that mortality difference between the two groups was “negligible” at 0.47 percent per year.
Although “fairly balanced,” Brignole et al said that DT+ patients had less severe underlying structural heart disease than DT- patients, as evidenced by a lower rate of congestive heart failure, New York Heart Association functional class III or IV, atrial fibrillation, higher ejection fraction, as well as less usage of diuretics and digoxin.
Finally, mortality from any cause at two years was slightly but not significantly lower among the DT+ patients than among DT- patients. The authors attributed the “slight, nonsignificant lower mortality” among DT+ patients as possibly being due to these patients having less severe underlying structural heart disease than DT- patients, partially because it disappeared when the two groups were analyzed after adjustment of their baseline clinical characteristics.
“The SAFE-ICD study shows that, on the one hand, current ICD recipients are very well protected from sudden cardiac death irrespective of performing DT or not and, on the other, that the DT strategy is unlikely to further decrease sudden cardiac death rate to a value that is clinically relevant, lower than that of 1 percent observed in the present study in DT- patients,” Brignole and colleagues wrote.
They added that the SAFE-ICD trial results support the increasing practice of omitting DT. “We expect that the results of this study may contribute to standardize the 'de novo' ICD implant procedure without DT for the majority of patients. However, it is possible that DT may continue to be utilized at implant or delayed after some months in difficult cases such as selected cases of nonstandard lead position, right-sided ICD pocket or pediatric implants.”
This study was funded by a grant from Boston Scientific, which is based in Natick, Mass.