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Programming an implantable cardioverter-defibrillator (ICD) for high-rate, delayed firing not only cuts down on inappropriate shocks but also improves survival, researchers found.

Inappropriate discharge was 79% less common with devices programmed to ignore tachyarrhythmias under 200 beats per minute and 44% less common when set to wait a little longer to discharge for slower 170 beats per minute or higher, reported Arthur Moss, MD, of the University of Rochester Medical Center in Rochester, N.Y., and colleagues.

These strategies cut all-cause mortality by 55% and 44%, respectively, compared with standard programming (P=0.01 and P=0.06).

The Multicenter Automatic Defibrillator Implantation Trial -- Reduce Inappropriate Therapy (MADIT-RIT) appeared online in the New England Journal of Medicine.

"These are practice changing results," Gregg Fonarow, MD, director of the UCLA Cardiomyopathy Center, commented in an interview with 麻豆传媒 from the American Heart Association meeting in Los Angeles where the results were released simultaneously.

He predicted rapid dissemination as patients come in to device clinics for checkups over the next several months because it's a quick noninvasive procedure for any existing standard ICD.

"This is the good kind of alert," Fonarow said. "Even with the conventional programming, an ICD is a lifesaving device compared with not having it. This, through the programming, is making it even better so additional lives can be saved."

The results came as no surprise based on prior nonrandomized studies, noted Bruce Wilkoff, MD, of the Cleveland Clinic, in an accompanying editorial.

"The programming choices or very similar ones have been available for almost 2 decades," he wrote.

"The implication of these data is that the previous trials may have underestimated the potential beneficial effects of ICD therapy, and the new findings should clearly influence the way that ICDs are programmed," Wilkoff agreed, urging clinicians, "Choose wisely!"

The researchers pointed out that while the trial wasn't designed to compare high-rate versus delayed therapy, it does provide some guidance in choosing among programming options.

"It is obvious from the reported findings that the overall results of these two methods of programmed therapy were similarly superior to the results of conventional programming," the group wrote.

"However, programming delayed therapy together with enhanced rhythm detection is quite complex, whereas programming therapy at a heart rate of 200 beats per minute or higher is simple."

The trial wasn't designed for mortality endpoints either, but an impact was plausible, Moss' group pointed out.

"While controversial, there is evidence that defibrillator shocks can cause myocardial damage, and the shocks have been associated with increased mortality," they wrote.

The MADIT-RIT findings add further support for a causal link between inappropriate pacing or shocks and mortality risk rather than a spurious association due to confounding, Fonarow said.

"That's why this trial is so critical," he told 麻豆传媒. "To see an actual difference in survival is very compelling."

The trial included 1,500 patients receiving an ICD for a primary-prevention indication randomized to the following programming configurations:

• High-rate therapy, with a 2.5-second delay before the initiation of therapy at a heart rate of 200 beats per minute (bpm) or higher
• Delayed therapy, with a 60-second delay at 170 to 199 bpm, a 12-second delay at 200 to 249 bpm, and a 2.5-second delay at 250 bpm or higher
• Conventional therapy, with a 2.5-second delay at 170 to 199 bpm and a 1.0-second delay at 200 bpm or higher

During an average follow-up of 1.4 years, the primary endpoint of first occurrence of any inappropriate therapy occurred in 20% of the conventional therapy as compared with 4% under high-rate programming and 5% with delayed therapy programming (both P<0.001).

The hazard ratios were 0.21 for high-rate therapy (95% CI 0.13 to 0.34) and 0.24 with delayed therapy (95% CI 0.15 to 0.40).

A similar pattern was seen for first occurrence of any device-delivered therapy and total occurrences of appropriate and inappropriate therapy.

Total cumulative inappropriate shock or pacing energy delivered over the course of the trial was 77% lower with high-rate programming and 54% lower with delayed programming (P=0.01 and P=0.03), whereas appropriate therapy delivery didn't differ.

Notably, "appropriate anti-tachycardia pacing was significantly less frequent in the high-rate and delayed-therapy groups than in the conventional therapy group, a finding that suggests that many episodes of nonsustained ventricular tachycardia that would have terminated spontaneously were treated prematurely in the conventional-therapy group," the researchers noted.

"In retrospect, such therapy could be considered unnecessary," they added.

Procedure-related adverse events didn't differ among the treatment groups.

The researchers cautioned about the small number of deaths -- 34 with conventional therapy compared with 16 and 21 in the high-rate and delayed groups, respectively, which may have left the trial underpowered to look at mortality.

From the American Heart Association:

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