HRS: NID 30/40 detection window safe in reducing unnecessary ICD therapy
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Maurizio Gasparini, MD, of Istituto Clinico Humanitas in Milan, Italy, presented the findings May 10 during a late breaking clinical trial at the 33rd annual scientific sessions of the Heart Rhythm Society.
As a primary endpoint, Gasparini hypothesized using NID 30/40 could achieve a 20 percent or less reduction of combined antitachycardia pacing (ATP) and shocks delivered for all device-detected spontaneous episodes with a short cycle length.
“We need[ed] a global, perspective, randomized, single-blind, multicenter trial,” Gasparini stated.
A total of 1,902 patients were enrolled, and randomized patients were implanted at 94 centers in Europe, South Africa, Asia and Russia from 2008 to 2010. The median follow-up was 12 months. Nine hundred and forty-eight patients were randomized to NID 30/40 and 954 were randomized to NID 18/24. Eighty-four percent of patients were male and patients had a mean age of 65.
To minimize bias, randomization was stratified by prevention, history of atrial arrhythmias and device type. Devices in both arms were programmed to treat ventricular arrhythmias with ATP during charging before shocks for episodes with a cycle length between 320 ms and 200 ms and shock only for episodes with cycle lengths less than 200 ms.
Mortality and syncope were adjudicated by an independent and blinded committee. The total number of therapies delivered over all episodes was compared between arms using a negative binomial regression model.
The device mix was 28.7 percent single chamber, 30.6 percent dual chamber and 40.7 percent received cardiac resynchronization therapy-defibrillator (CRT-D). There were 346 therapies in the 30/40 arm and 557 in the 18/24 arm, resulting in a 37 percent reduction.
Kaplan-Meier estimates showed a significant difference in patient probability of therapy occurrence. Patient mortality and arrhythmic syncope rates between the 30/40 and 18/24 arms were low (3.9 patients/year vs. 4.6 patients/year and 2.2 patients/year vs. 1.1 patients/year, respectively) and not significantly different.
In a discussion following the presentation, Gasparini clarified that there was no statistical difference in syncopy events associated with ventricular arrthymic episodes.
The research is still being combed to adjudicate mortality. On the subject of acceleration, he concluded there was no statistically significant difference between the two groups.