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PAINFREE SST: Longer ICD detection intervals safe for secondary prevention patients
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SAN FRANCISCO — Extending the detection time of an implantable cardioverter defibrillator was safe in patients with ICDs for secondary prevention, according to study results presented at the Heart Rhythm Society Annual Scientific Sessions.
Researchers conducted an analysis to determine whether extending detection times for ventricular tachycardia (VT) or ventricular fibrillation (VF), which has been shown to decrease inappropriate therapies and mortality in patients with ICDs for primary prevention, could be performed safely in patients with ICDs for secondary prevention.
Laurence D. Sterns, MD, of the Royal Jubilee Hospital in Victoria, British Columbia, and colleagues enrolled 2,790 patients receiving Protecta ICDs with SmartShock Technology (Medtronic) in the PAINFREE SST study. In a substudy presented by Sterns, the researchers evaluated 705 patients from the study who had an ICD for secondary prevention and consented to interval detection randomization.
Patients were randomly assigned on a 1:1 basis to a standard-interval (number of intervals to detect=18/24) or prolonged-interval (number of intervals to detect=30/40) detection of VT/VF ≥188 bpm.
The primary endpoint was freedom from arrhythmic syncope at 1 year. Secondary endpoints included time to first all-cause syncope, appropriate therapy and inappropriate shock. Mean follow-up was 20 months.
Sterns and colleagues found no difference between the groups in freedom from arrhythmic syncope at 1 year (standard group, 97.7%; prolonged group, 96.9%; P for noninferiority<.01).
The groups also did not differ in freedom from all-cause syncope at 1 year (standard group, 96%; prolonged group, 96%; P for noninferiority<.01), appropriate VF zone therapies (standard group, 13.3%; prolonged group, 12.3%; P for noninferiority<.01), or inappropriate shocks (standard group, 1%; prolonged group, 1.3%; P=.93).
There was a trend toward reduced mortality for the prolonged-interval group compared with the standard group at 1 year (standard group, 5.6%; prolonged group, 3.8%; P=.07).
“The results of this study are important for secondary prevention patients, who often are treated with more aggressive ICD programming to address arrhythmic events as quickly as possible,” Sterns said in a Medtronic press release. “Previous studies have demonstrated that devices programmed to wait longer to deliver therapy do not increase the risk of fainting episodes among primary prevention patients, and now we know the same strategy can be used in more patients, even patients at increased risk based on their disease progression.” – by Erik Swain
For more information:
Sterns LD. LB03-01. Presented at: Heart Rhythm Society Annual Scientific Sessions; May 7-10, 2014; San Francisco.
Disclosure: Sterns reports serving on the speakers’ bureau for Medtronic.