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CHICAGO -- Long detection intervals reduce shocks for patients with single-chamber implantable cardioverter-defibrillators (ICDs), a subanalysis of the ADVANCE III study showed.

Prolonging the threshold for delivery of therapy from 18 of 24 beats to 30 of 40 beats (112 therapies in 34 patients versus 257 in 60 patients, IRR 0.52, 95% CI 0.36-0.76, P=0.002), and for antitachycardia pacing and shocks separately, Maurizio Gasparini, MD, of the Humanitas Clinical and Research Center in Rozzano, Italy, reported here at the Heart Rhythm Society meeting.

The long-detection algorithm reduced appropriate therapies delivered by 55% (30 versus 74 per 100 patient-years, IRR 0.45, P=0.001), but with no significant difference in inappropriate therapy, which occurred infrequently (6.1%).

"Many different studies reported that ICD therapies -- both appropriate and inappropriate -- may be associated with potential side effects like heart failure or increased mortality," Gasparini said at the meeting.

"Our data here support the hypothesis that treatment of arrhythmias which may otherwise self-terminate may cause long-term patient harm and erode the survival benefit of the ICD," the researchers wrote in a paper released simultaneously online in .

Indeed, allowing more time for nonsustained events to self-terminate was associated with no greater risk of syncope but rather a benefit in outcomes in the ADVANCE III analysis. Hospitalization risk at 1 year was 27% with long detection versus 36% with standard detection (P=0.04) -- mainly driven by fewer cardiovascular-related hospitalizations (20% versus 28% risk, P=0.04).

And, while the study was not powered for mortality, it did show 59% fewer deaths in the long-detection group (3.0% versus 7.2% over 12 months, HR 0.41, P=0.047).

The overall trial had not shown a difference in mortality between treatment arms. Gasparini noted that the dual chamber device patients in the trial showed no increased risk of death with the intervention.

The analysis included 545 patients who got single-chamber (VVI) ICDs, which was 28.7% of the overall ADVANCE III trial population of 1,902 patients implanted with commercially available Medtronic VVI, DDD, and cardiac resynchronization therapy ICDs for primary or secondary prevention of sudden cardiac death. Patients were randomized and stratified by type of ICD to intervention in which detection was prolonged to 30/40 intervals to permit delay in therapy or standard-interval detection programmed to 18/24 intervals.

"Our results have particular gravity, since the 'standard' intervals (18/24) we applied in our control arm are longer than nominal ICD settings ('conventional' in MADIT RIT), indicating that even further prolongation of time to delivered therapy extends the advantages of this programming strategy further," the researchers noted in the paper.

However, despite several major trials pointing to better outcomes with long detection in patients implanted with an ICD (albeit largely excluding single chamber devices), too few patients are getting their devices reprogrammed, commented Andrew Krahn, MD, chair in cardiology at the University of British Columbia in Vancouver and co-chair of the late-breaking clinical trial session at which the study was presented.

"We've known about this for a long time," he said at the session. "This is another iteration of this in a specific patient population. But when you look at devices -- for example, those that come for replacement -- a lot are still programmed to short durations. How do we change the health system to implement this?"

Gasparini responded: "When you receive the device from the company in the box, you at the beginning have 1 second for VF [ventricular fibrillation]. This is incredible. But there are some difficulties to change and convince the company and the FDA that it is necessary in the box to change the programming. Now we know for Medtronic that it's possible, but it's not so easy."

"We need more education and talks to get it out into the hands and consciousness of the implanting clinicians, certainly," added the session's co-chair, Jeanne Poole, MD, of the University of Washington in Seattle.

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