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BOSTON -- An oversensing filter for Emblem subcutaneous implantable cardioverter-defibrillators (S-ICDs) halved the risk of inappropriate shocks in real-world practice, a European study found.

The rate of shocks given when there was no ventricular tachycardia or fibrillation or the tachycardia was below the zone rate fell from 9.7% without the SMART Pass filter to 4.3% with it enabled (age- and programming-adjusted HR 0.50, P<0.001), Tom Brouwer, MD, of the Academic Medical Center in Amsterdam, reported here at the Heart Rhythm Society (HRS) meeting and .

The number of inappropriate shocks per patient averaged 28 versus 7 per 100 patient-years (adjusted HR 0.32, P<0.001), driven by a reduction in cardiac oversensing but also with fewer non-cardiac oversensing cases as well.

For comparison, longer duration sensing with a conventional transvenous lead ICD in the brought the rate down from 18 to 10 inappropriate shocks per 100 patient-years, Brouwer noted.

"The inappropriate shock rate now in line with most recent transvenous ICD studies employing modern programming," he told attendees at the late-breaking clinical trial session. "Therefore the take-home message is turn SMART Pass on to avoid inappropriate shocks."

HRS session co-moderator Michael Gold, MD, PhD, of the Medical University of South Carolina in Charleston, called these "very interesting and exciting results as this has been one of the major limitations of the subcutaneous ICD."

Appropriate shocks, on the other hand, were not affected (5.2% vs 6.6%, P=0.21), nor was there a delay in sensing introduced by the filter in the analysis of 1,984 European patients with Emblem or Emblem S-ICDs implanted from 2015 through 2016 and using the LATITUDE system remote monitoring. SMART Pass was released in April 2016.

Gold noted that while the data was from Europe, the devices and filter examined are available in the U.S.

The findings confirmed in real-world practice what had been expected from a simulation study, Brouwer said, although he cautioned that it was not a randomized trial comparing strategies and had no mortality data.

Inappropriate shocks are "extremely debilitating," can result in anxiety disorders, and are also associated with increased mortality, John Day, MD, of Intermountain Heart Rhythm Specialists in Park City, Utah, commented at an HRS press conference chair.

"The goal would be zero inappropriate shocks," he said. "And I don' t know if we'll ever get to zero, but the closer we can get to zero, the better. And so any technology, any filter, anything that can get us closer to the goal of zero inappropriate shocks is really the goal. It's not just for patient satisfaction but it's also for survival."

Brouwer countered that he's not sure the mortality association with inappropriate shocks is causal but agreed that, with about a 5% appropriate shock rate and 5% inappropriate shock rate, there is a "lot of room for further improvement."

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