Subcutaneous Implantable Defibrillator



S-ICD vs. TV-ICD: 4-Year Results for the Landmark Head-to-Head Study



The PRAETORIAN Trial is an investigator-sponsored study (ISR)* initiated, designed and led by Academic Medical Center in Amsterdam (AMC) and Reinoud E. Knops, MD, PhD. It is the first prospective randomized head-to-head trial comparing the performance of S-ICD and TV-ICD.

The trial hypothesis was that the S-ICD is non-inferior to the TV-ICD with respect to major ICD-related adverse events, including:

  • Inappropriate shocks
  • ICD-related complications that require intervention
  • Lead-related complications

The trial enrolled 849 patients between March 2011 and January 2017 within the EU and US.



Data from the PRAETORIAN trial confirmed that the S-ICD can be the preferred therapy choice over the TV-ICD for protection from sudden cardiac arrest. The S-ICD offers comparable performance for the majority of ICD-indicated patients who do not have a need for pacing, while avoiding the serious complications associated with TV-ICDs such as serious infections and lead-related complications.


Primary Secondary Endpoints**

Mortality Rates

  • No significant difference in overall and arrhythmic mortality rates between the two groups.
  • Mortality rate was low in both groups, even though:
    • 90% had ischemic (68%) or non-ischemic heart failure
    • Secondary prevention for 19% of S-ICD patients and 20% of TV-ICD patients
    • Median EF was 30%
    • Median age was 63 years

Lead-Related Complications

  • Data showed a statistical difference in lead-related complications, with TV-ICD patients experiencing more than 4 times as many as S-ICD patients did.
  • The S-ICD leaves the vasculature untouched, thereby reducing the risk of acute and future complications associated with transvenous leads.
  • Eliminating device leads within the vasculature is particularly important for ICD-indicated patients with co-morbidities such as diabetes and renal disease who often are at an increased risk of infection and may have vascular access issues.2

Infections Requiring Device Extraction

  • Numerically, TV-ICD patients experienced twice as many infections that required device extraction as S-ICD patients did.
  • Data in >91,000 transvenous lead extractions demonstrated that those extracted for infection had significantly higher rates of complications and mortality.3

Device-Related Complications

  • No statistical difference in device-related complications at the median 4-year follow-up.
  • The trial authors have initiated an extended follow-up, PRAETORIAN XL, and anticipate that at 8 years the S-ICD will demonstrate superiority to TV-ICD for all device-related complications.1

Inappropriate Shock Rates

  • No significant difference in inappropriate shock rates between the two groups.
  • The PRAETORIAN trial used mainly devices available prior to 2016. Studies using modern S-ICDs like the EMBLEMTM S-ICD have demonstrated even lower rates of IAS.

S-ICD: A Smart Alternative to TV-ICD

Because it avoids some of the more major complications associated with the TV-ICD, including serious infection and lead-related complications, data shows that the S-ICD is an appropriate and potentially desirable alternative for primary and secondary ICD-indicated patients who do not require pacing. 


Reducing TV-ICD Infections Can Lower Mortality Rates

When it comes to reducing complications, lowering mortality rates and cutting costs, avoiding infected TV-ICD leads can go a long way.

  • Data in >91,000 transvenous lead extractions found that those extracted for infection had a higher overall complication rate and a higher in-hospital mortality rate compared to those without infection.3
  • In this same study, the median cost of lead extraction was $39,308 for infected devices and $14,916 for non-infected devices.

Contemporary S-ICDs Further Reduce Rates of Inappropriate Shock

SMART PassTM, included in the EMBLEM MRI S-ICD, has been shown to reduce IAS rates by 68%.4

  • In the more recent UNTOUCHED study, the 1-year IAS rate was 3.1%,5 which is comparable to or lower than the rates observed with TV-ICDs in other studies, including the PRAETORIAN trial.1, 6-8
  • In addition, the 1-year IAS rate was 2.4% for those who received an EMBLEM MRI with SMART Pass.5

S-ICD Procedures Are Becoming More Common Than Ever

Optimized implant techniques (such the intermuscular technique) and implant best practices have emerged as experience with S-ICD has increased to over 75,000 patients worldwide—and counting.



The PRAETORIAN trial is being extended to an 8-year follow-up, PRAETORIAN XL, that is due to complete in 2023. PRAETORIAN XL will be completed with the primary objective of establishing superiority of S-ICDs to TV-ICDs for acute and chronic complications.

*Supported by a research grant from Boston Scientific


1. Knops R. et al., A Randomized Trial of Subcutaneous versus Transvenous Defibrillator Therapy: The PRAETORIAN Trial. Heart Rhythm Society Late Breaking Clinical Trials LBCT-01 2020.

2. Polyzos KA, Konstantelias AA, Falagas ME. Risk factors for cardiac implantable electronic device infection: a systematic review and meta-analysis. Europace. 2015;17(5):767-777.

3. Deshmukh A, Patel N, Noseworthy PA, et al. Trends in Use and Adverse Outcomes Associated with Transvenous Lead Removal in the United States. Circulation. 2015;132(25):2363-2371.

4. Theuns D, Brouwer TF, Jones PW, et al. Prospective blinded evaluation of a novel sensing methodology designed to reduce inappropriate shocks by the subcutaneous implantable cardioverter-defibrillator. Heart Rhythm. 2018;15(10):1515-1522

5. Gold M. et al., Understanding Outcomes With The S-ICD In Primary Prevention Patients With Low Ejection Fraction (UNTOUCHED) Trial Primary Results. Heart Rhythm Society Late Breaking Clinical Trials LBCT-02 2020.

6. Gasparini M, Lunati MG, Proclemer A, et al. Long Detection Programming in Single-Chamber Defibrillators Reduces Unnecessary Therapies and Mortality. JACC: Clinical Electrophysiology. 2017;3:1275–82.

7. Kutyifa V, Daubert JP, Schuger C, et al. Novel ICD Programming and Inappropriate ICD Therapy in CRT-D Versus ICD Patients: A MADIT-RIT Sub-Study. Circ Arrhythm Electrophysiol. 2016;9(1):e001965.

8. Auricchio A, Hudnall JH, Schloss EJ, et al. Inappropriate shocks in single-chamber and subcutaneous implantable cardioverter-defibrillators: a systematic review and meta-analysis. Europace. 2017;19(12):1973-1980.