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Subcutaneous Implantable Defibrillator

S-ICD Clinical Data

Explore clinical study and real-world data on inappropriate shock rates, complication rates and more. Plus, learn about the ATLAS and PRAETORIAN trials which are both prospective, randomized, head-to-head, clinical trials comparing S-ICD to TV-ICD.

ATLAS Randomized Controlled Trial: S-ICD Superior to TV-ICD1

Study overview

The ATLAS Trial is an investigator-sponsored research study (ISR) initiated, designed and led by Population Health Research Institute (PHRI), Jeff S. Healey MD, MSc, FHRS, and the ATLAS Steering Committee. It is the first prospective randomized controlled trial where the primary objective was to evaluate lead-related complication rates between the S-ICD and single chamber TV-ICD devices at six months after implant.


The trial hypothesis is that S-ICD is superior to TV-ICD with respect to serious lead-related complications*, including:

  • Moderate-severe or severe tricuspid regurgitation
  • Hemothorax or pneumothorax
  • Cardiac perforation, tamponade, or pericardial effusion or pericarditis
  • Ipsilateral upper extremity deep vein thrombosis
  • Lead dislodgement or loss of sensing or pacing requiring revision


Sample Size and Timing

The trial randomized 503 patients, who passed electrocardiographic screening, from clinical centers across Canada between February 2017 and July 2021.


Primary Outcomes

Patients in the S-ICD group showed significantly fewer serious lead-related complications* than patients implanted with a single-chamber TV-ICD.

The ATLAS trial met its primary superiority endpoint demonstrating a highly significant 92% reduction in serious lead-related complications* at six months for the EMBLEM™ S-ICD compared to any manufacturers single chamber TV-ICD devices. p=0.0031
Serious lead-related complication* occurred in 12 times as many patients in the single chamber TV-ICD arm (4.8%) at six months compared to 1 patient (0.4%) in the S-ICD arm.1

Secondary Analysis: Effects of Implantable Cardioverter-Defibrillator Leads on the Tricuspid Valve and Right Ventricle: A Randomized Comparison of Transvenous versus Subcutaneous Leads.24

Data from a secondary analysis of the investigator-sponsored research ATLAS trial evaluated in nearly 450 patients the severity of Tricuspid Regurgitation (TR) at six months following the implantation of a transvenous implantable cardioverter-defibrillator (TV-ICD) versus the EMBLEM S-ICD.

At six months, patients in the TV-ICD group were seven times more likely to have worsening tricuspid regurgitation (p<0.001) than those in the S-ICD group. 24
Of those with worsening tricuspid regurgitation, moderate or severe TR developed in 6.9% of patients receiving a TV-ICD versus 2.3% of those receiving an S-ICD (p=0.02).24


PRAETORIAN is the first prospective, randomized, head-to-head, non-inferiority clinical trial that compares S-ICD to TV-ICD. The trial followed 850 patients at 40 centers across Europe and the United States. Full results were published in 2020.

First results of the randomized PRAETORIAN-DFT trial

Prospective validation of the PRAETORIAN score for prediction of defibrillation test success after subcutaneous ICD implant

The findings from this first analysis demonstrate that a low (<90) PRAETORIAN score is 99% predictive for a successful DFT and a high (≥90) PRAETORIAN score is the strongest predictor for DFT-failure (odds ratio of 34 ).25

While the study investigators concluded their presentation by stating that the PRAETORIAN score could be used as an alternative for DFT in cases when DFT-testing is not possible or desirable, omitting DFT’s in S-ICD implants cannot be advised until the full PRAETORIAN-DFT results are available.

Analysis of the UNTOUCHED Study


The incidence of inappropriate shocks in primary prevention, LVEF ≤ 35% patients will be non-inferior to the rate in transvenous ICD patients with similar programming observed in MADIT-RIT Arms B and C.

Study Design

  • Follow-up for 18 months
  • Device programming with a conditional zone of 200 bpm and a shock zone of 250 bpm
  • Primary endpoint of inappropriate shock-free rate at 18 months
  • Secondary endpoints of all cause shock-free rate at 18 months and system and procedure complications at 30 days

Key Takeaways

1. The inappropriate shock rate of 2.4% at 1 year for EMBLEM™ MRI S-ICDs is the lowest reported for S-ICD, despite a cohort with more left ventricular dysfunction and heart failure.2

acute outcomes
2. The appropriate shock rate of 5.7% over 18 months was low with a high conversion success of 98.4%, similar to that reported with TV-ICD trials.2
S-ICD-Conversion Rates
3. Complication rates remain very low (95.8% complication free rate at 30 days, 92.7% at 18 months, and no systemic infections), despite enrolling a sicker patient population.2
EMBLEM complication rates

TV-ICD Lead Complications in the Real World

The transvenous lead is the most common source of complications in a TV-ICD system. Data from over 40,000 patients from the OptumLabs Data Warehouse demonstrated that the incidence of mechanical and infectious complications of transvenous leads over long-term follow-up is much higher in the real world than in clinical studies. 
3-4% of patients with TV-ICD suffer lead malfunctions in the first year of implant15
About 25% mechanical failure rate for TV-ICD at 10 years15
4% infection rate for TV-ICD at 10 years15
freedom from complication
 Kaplan-Meier plot of lead revision associated with a diagnosis of infection or mechanical complication for patients with an implantable cardioverter-defibrillator or cardiac resynchronization therapy defibrillator. 

S-ICD is Guideline Recommended

The S-ICD is now guideline recommended for patients at high risk of infection, inadequate venous access, and any patient without a pacing indication – the majority of ICD indicated patients.16

75% of ICD-Indicated Patients Have ≥1 Comorbidity Associated with Device Infection17-19
70% of DR & VR ICD Patients Under 75 Have No Pacing Indication at Implant7, 20
61% of Patients May Have Venous Stenosis Following Initial Device Implantation21

Analysis of MADIT RIT Data22

A new analysis of data from MADIT RIT demonstrates patients are more likely to develop complications from transvenous leads than they are to benefit from ATP.

  • There is a statistically significant reduction in ATP with contemporary programming, suggesting that many VTs are self-terminating and earlier interventions may lead to an overestimation of the value of ATP. 
  • Despite the use of significantly more ATP in the conventional programming arm of MADIT RIT, there was no reduction in the final shock rate when compared to the contemporary programming arms.

SMART Pass Significantly Reduces IAS

Real-world LATITUDE data for 1,984 patients demonstrated the annual rate of inappropriate shocks (IAS) went down to 4.3% when SMART Pass was enabled. This is a reduction of over 67% compared to the IAS rate seen in the original IDE study.23

Clinical Data Resources

Dr. Michael Gold Discusses the UNTOUCHED Study at HRS 2020

EFFORTLESS Midterm Outcomes

The Impact of SMART Pass on IAS

S-ICD and Patients at High Risk for Infection


Bradycardia Pacing Need in ICD Patients

Real-World Longevity Projections


Training & Education

Explore continuing education courses, best practices modules and other training and resources for S-ICD.



Why S-ICD?

See how S-ICD helps protect patients at risk for sudden cardiac death while also eliminating the risk of TV-ICD lead complications.

Implant Procedure

Implant Procedure

Learn about advancements in the S-ICD implant procedure, including the 2-incision and intermuscular implant techniques.

Videos & Resources

Videos & Resources

Hear physician perspectives about S-ICD, find media information, and download product images, patient videos and more.