This is an early-stage feasibility study. This study seeks to characterize the performance of the new electrode shock configuration with the S-ICD

Background: The subcutaneous implantable cardioverter-defibrillator (S-ICD, EMBLEM®, Boston Scientific Corp) delivers 80 J shocks from an 8 cm left-parasternal coil (LPC) to a 59 cc left lateral pulse generator (PG). A system that defibrillates with lower energy could significantly reduce PG size. Computer modeling and animal studies suggest a 2nd shock coil either parallel (P) to LPC or transverse (T) from xiphoid to PG pocket would significantly reduce shock impedance and defibrillation threshold (DFT).

Objective: Acutely test defibrillation efficacy of P and T configurations in patients receiving an S-ICD.

Methods: Testing was performed in patients receiving a conventional S-ICD system (C) for standard indications. Patients at risk for conversion failure, stroke or infection were excluded. A 65 J success with the conventional S-ICD was required prior to investigational testing. A second electrode was temporarily inserted from the xiphoid incision using the same introducer and sheath tools and connected to the PG with an investigational Y-adapter (Model 3598, Boston Scientific). Phase 1 (n=11) tested only P at a starting energy of 50 J with subsequent tests at 65 or 30 J then 40 or 20 J depending upon outcome. Phase 2 (n=21) tested both P and T in random order, starting at 30 J then either 40 or 20 J.

Key Inclusion Criteria:

1. Subject is scheduled to receive a de novo S-ICD system implant per labeled indication.
2. Passing S-ICD screening ECG performed per applicable user's manual.
3. Subject is willing and capable of providing informed consent specific to local and national laws.
4. Subject is age 18 or above, or of legal age to give informed consentspecific to local and national law.

Key Exclusion Criteria:

1. Subject has an unusual chest anatomy (eg. pectus excavatum and pectus carinatum) that might impede the ability to temporarily insert a second S-ICD electrode.
2. Subject has a left ventricular ejection fraction ≤ 20% within 3 months prior to enrollment.
3. Subject has NYHA Class IV or unstable Class III heart failure.
4. Subject that, in the opinion of the investigator, cannot tolerate the DFT testing required by this protocol.
5. Subject is morbidly obese, defined as BMI ≥ 35.
6. Subject has an active infection or has been treated for infection within the past 30 days.
7. Subject that, in the opinion of the investigator, has an increased risk of infection.
8. Subject is currently requiring/receiving dialysis.
9. Subject has insulin-dependent diabetes.
10. Subject had/has any prior or planned other surgical procedure within ±30 days of enrollment.
11. Subject that, in the opinion of the investigator, has an increased risk for thromboembolic event.
12. Subject that, in the opinion of the investigator, has an increased risk of excessive bleeding.
13. Subject is currently on an active heart transplant list.

35 subjects began the S-ICD implant with the intention of perfroming acute investigational testing

Reporting of events occurred during the period the subject was considered to be enrolled in the study: from implant up to 3 months after implant.

The study excluded certain patients believed to have the potential for higher DFTs and greater risk for AE.2 subjects were not tested with either two-electrode configuration due to requirement that VF must first be successfully converted in the Single configuration with 65 J. The sample size was small,subjects may have characteristics that do not perfectly match S-ICD recipients. In this cohort of patients from the Netherlands, age younger and BMI somewhat lower than what might occur in the US