• Interventional Techniques & Devices
• Cardiology Clinical Trials

• Interventional Techniques & Devices
• Cardiology Clinical Trials
• Cardiology

Laurence D. Sterns, MD, Royal Jubilee Hospital, Victoria, British Columbia, Canada, presented results of the secondary prevention substudy of the Study to Evaluate System Safety and Clinical Performance of the Protecta Implantable Cardioverter Defibrillator (ICD) Plus Cardiac Resynchronization Therapy Defibrillator (CRT-D) trial [PainFree SST; NCT00982397]. This prospective, randomized, multicenter study demonstrated that defibrillators programmed with longer detection intervals are safe for secondary prevention in patients with ICDs.

Although previous studies have shown that extended ICD detection times for ventricular tachycardia or ventricular fibrillation (VF) reduce inappropriate therapies and mortality in primary prevention patients [Gasparini M et al. JAMA 2013; Moss AJ et al. N Engl J Med 2012; Wilkoff BL et al. J Am Coll Cardiol 2008], the effect of prolonged ICD detection in secondary prevention patients who have already experienced episodes of sudden cardiac arrest and are at increased risk for a deadly irregular heart rhythm had not been evaluated.

Prof. Sterns and colleagues conducted the PainFree SST trial to investigate the safety of prolonged detection for ventricular tachycardia or VF in secondary prevention patients. To be included in the study, patients were required to have secondary prevention indications for ICD.

Patients with mechanical tricuspid valves, those enrolled in concurrent drug or medical device studies, and those who were unwilling to provide written informed consent to participate in the study or who anticipated being unable to complete it were excluded from the trial.

The PainFree SST trial enrolled a total of 2790 patients receiving ICDs programmed with technology that enables the devices to discern whether an abnormal heart rhythm is life threatening. Of these participants, 705 were included in this substudy and were randomly assigned 1:1 to either standard interval detection (VF number of intervals to detect, 18 of 24; n=353) or extended interval detection (VF number of intervals to detect, 30 of 40; n=352) of ventricular tachycardia or VF ≥188 beats/minute.

The primary end point was freedom from arrhythmic syncope at 1 year. Secondary end points included time to first arrhythmic and all-cause syncope, appropriate therapy or inappropriate shock, and mortality.

At baseline, 35% of patients had atrial arrhythmias, and 33% had histories of syncope. At 1 year, 7 patients in the standard group and 11 in the prolonged group had arrhythmic syncope. The arrhythmic syncope-free rate was similar between the standard and prolonged groups (98.0% vs 96.9%; p=0.012 for noninferiority). There was no statistically significant increase in the time to first arrhythmic syncope (HR 1.52; 95% CI 0.66–3.52; p=0.32), incidence of all-cause syncope (HR, 1.17; 95% CI, 0.59–2.32; p=0.66), appropriate VF zone therapies (HR, 0.98; 95% CI, 0.67–1.43; p=0.91), time to first appropriate shock (HR, 1.04; 95% CI, 0.70–1.53; p=0.85), or incidence of inappropriate shocks (1.0% vs 1.3%, p=0.74). However, in the prolonged group, the VF therapy rate (1.5 vs 0.4, p=0.0001), VF shock rate (0.9 vs 0.27, p=0.0026), and VF antitachycardia pacing rate (0.57 vs 0.16; p=0.0019) were significantly lower.

The results of this substudy demonstrated that extended interval detections did not result in statistically increased risk for syncope in secondary prevention patients. Prof. Sterns concluded that the prolonged detection programming strategy may be considered as a strategy to reduce inappropriate shocks in patients with ICDs.

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