• Cardiology Clinical Trials
• Interventional Techniques & Devices

• Cardiology Clinical Trials
• Cardiology & Cardiovascular Medicine
• Interventional Techniques & Devices

Shocks delivered by implantable cardioverter defibrillators (ICDs) can cause anxiety [Sears SF Jr et al. Clin Cardiol 1999], decreased quality of life [Schron EB et al. Circulation 2002], and mortality [Daubert JP et al. J Am Coll Cardiol 2008]. Although ICDs are intended to deliver a shock when needed, inappropriate shocks comprise 2% to 10% of ICD shocks [Schloss EJ et al. Heart Rhythm 2013; Moss AJ et al. N Engl J Med 2012; Gasparini M et al. JAMA 2013].

Painfree SmartShock Technology (SST) is designed to reduce the number of inappropriate shocks with dual- (DR), triple- (CRT), and single- (VR) chamber ICDs. According to Edward J. Schloss, MD, The Christ Hospital, Cincinnati, Ohio, USA, the Study to Evaluate System Safety and Clinical Performance of the Protecta Implantable Cardioverter Defibrillator (ICD) Plus Cardiac Resynchronization Therapy Defibrillator [Painfree SST; NCT00982397] is the first study to evaluate the SmartShock discrimination algorithms for reducing inappropriate shocks by VR-ICDs.

The SST programming for the study used out-of-the box nominal values in current ICDs. The primary endpoint was inappropriate shock-free rate at 1 year post implant. Dr. Schloss previously presented the results for DR- and CRT-ICDs at the Heart Rhythm Society (HRS) 2013 annual meeting [HRS 2013 (abstr 28–04)]. A total of 757 patients were included in the VR-ICD cohort. Follow-up was ≥1 year in 712 patients and <1 year in 45 patients.

At 1-year follow-up, the inappropriate shock-free rate was 97.6% (95% CI, 96.4 to 98.8; Figure 1).

Of the 757 patients, 15 had experienced 19 inappropriate shocks. The causes of the inappropriate shocks were atrial fibrillation or atrial flutter (10 patients, 14 episodes), other supraventricular tachycardia (2 patients, 2 episodes), and over-sensing (3 patients, 3 episodes). The risk of inappropriate shock was not affected by the ventricular tachycardia (VT) therapy zone. Patients with VT shock enabled were 98.1% inappropriate shock-free compared with 97.1% of patients with VT shock not enabled (p=0.38).

The all-cause shock-free rate at 1 year was 91.6% (95% CI, 89.5 to 93.8; Figure 2). There were 252 shock episodes in 53 patients, with 4.8±11.1 episodes per patient. Of these, 175 episodes in 41 patients were appropriate (4.3±6.9 episodes per patient) and 19 episodes in 15 patients were inappropriate (1.3±0.5 episodes per patient). An electrogram was not available for 58 episodes in 5 patients (11.6±17.8 episodes per patient). For the primary objective, patients were censored at the time of a first shock without an electrogram.

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Figure 1.

Inappropriate Shock-Free Rate at 1 Year

Reproduced with permission from EJ Schloss, MD.

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Figure 2.

All-Cause Shock-Free Rate at 1 Year

Reproduced with permission from EJ Schloss, MD.

Sixteen patients died during the 12 months following ICD implantation (mortality rate, 2.4%; 95% CI, 1.5% to 3.6%; Figure 3). There were 3 noncardiac deaths, 5 nonsudden cardiac deaths, and 8 deaths with an unknown cause.

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Figure 3.

Survival at 1 Year

Reproduced with permission from EJ Schloss, MD.

The 1-year results of the Painfree SST trial demonstrate that using SmartShock algorithms with VR-ICDs is effective for preventing inappropriate shocks. Use of this technology allows for flexibility in heart rate detection interval programming without resulting in a higher rate of inappropriate shocks.

• © 2013 MD Conference Express®