Trial Design

The EFFORTLESS S-ICD Registry is a non-randomized, standard of care, multicenter registry designed to collect long term system-related, clinical, and patient reported outcome data from S-ICD implanted patients since June 2009.

  • 1000 patients followed for 5 years post implant 
  • Includes both retrospective and prospective patients implanted since 2009
  • Centers to be included from all current commercial countries
  • QOL sub-study (not yet reported at the time of this interim analysis)

Inclusion Criteria

  • ≥ 18yrs at time of consent*
  • Eligible for implantation of an S-ICD System per local clinical guidelines or currently implanted with a S-ICD System
*A subset of countries implemented a protocol that allows patients under the age of 18

Exclusion Criteria

  • Participation in any other investigational study that may interfere with interpretation of the study results
  • Pace-terminable VT
  • Previously implanted unipolar pacemakers

Definition of Complications

  • Type I: caused by the S-ICD System
  • Type II: caused by the S-ICD System user’s manual or labeling of the S-ICD System
  • Type III: not caused by the S-ICD System but would not have occurred in the absence of the implanted S-ICD System

The interim results were published online in the European Heart Journal in March 2014.


The study population of 472 patients had a mean follow-up duration of 558 days, 72% were male, and mean age of enrolled patients was 49 ± 18 years. A broad spectrum of patients were represented with a significant proportion of congenital heart disease, ion channelopathy and non-ischaemic cardiomyopathy patients.
Demographics of EFFORTLESS study population

Trial Results

Complication-Free Rate

Complications were defined as clinical events where mitigation required an invasive procedure. There were no electrode failures, no systemic blood infections related to the S-ICD System or Procedure and no endocarditis. Complications occurred in 29 patients giving a patient complication event rate of 6.4% at an average follow-up of 558 days. In 14 patients (3%) complications occurred in the first 30-day post implant, for a peri-operative complication-free rate of 97%.

EFFORTLESS Complication-Free Rate
EFFORTLESS Complication Types

Implant conversion testing

Of 393 patients with complete data, in all but 1 patient VT/VF was successfully converted (99.7%). Implant testing with shock energy of ≤65J was successful in 95% of patients.

Spontaneous Conversion Efficacy 

Spontaneous Conversion Efficacy

Time to Therapy

Included15.1± 3.7 sec.
Spontaneous17.5 ± 4.4
  • Therapy withheld in 13% of patients and 46% of stored episodes due to longer time to therapy

Inappropriate Therapy

Inappropriate shocks were recorded in 32 patients over an average follow-up of 18 months (360 day inappropriate shock rate of 7%).

Dual zone programming (patients programmed with a conditional shock zone that applies SVT discrimination algorithms) had a 6.4% inappropriate shock rate (23/357) at an average follow-up of 558 days, while single zone programming had a 12% rate (9/74) [P = 0.09].

Inappropriate Shocks by Programming

Inappropriate Shocks by Programming

One inappropriate therapy due to VF/SVT discrimination error within the conditional zone.

Inappropriate vs Appropriate Therapies