This study assesses the 18-month incidence of inappropriate shocks in subjects implanted with the EMBLEM Subcutaneous Implantable Defibrillator (S-ICD) for primary prevention of sudden cardiac death. Devices are to be programmed with zone cutoffs at 200 bpm and 250 bmp in order to mimic the programming settings for transvenous ICDs in the MADIT RIT study. The incidence of inappropriate S-ICD shocks will be compared to the incidence of inappropriate shocks observed in the MADIT RIT study.

Implantable cardioverter defibrillator (ICD) therapy is highly effective for reducing mortality in patients with clinical markers for elevated risk for ventricular arrhythmias. However, inappropriate shocks and unnecessary appropriate shocks remain an important side effect that can significantly affect an ICD recipient's quality of life and may be deleterious to the myocardium.

The MADIT RIT study demonstrated that the incidence of inappropriate and unnecessary appropriate ICD therapy can be reduced in primary prevention patients through two different programming strategies: 1) High Rate Zone Cutoff, i.e., raising the lowest rate detection cutoff to 200 bpm; and 2) Delayed Therapy Initiation, i.e., increasing the time to therapy initiation to 60 seconds for arrhythmias detected between 170-199 bpm and 12.5 seconds between 200-249 bpm. Both strategies effectively reduced the amount of ICD therapy delivered when compared to conventional programming, where the lowest rate detection cutoff was 170 bpm and the delay to therapy initiation was programmed to 2.5 seconds. Importantly, neither treatment arm was associated with significantly increased syncope or mortality. The results of MADIT RIT established preferred device settings for reducing shocks in transvenous ICD (TV-ICD) patients with a primary prevention indication.

Preferred settings for subcutaneous ICDs, however, have not been established with data from prospective studies. The UNTOUCHED study will test a programming scheme designed to minimize inappropriate and unnecessary shocks in patients who have an indication for primary prevention of sudden cardiac death and low ejection fraction. Although S-ICD programming options do not permit exact replication of the programmed settings previously shown to reduce shocks in the MADIT RIT treatment arms, key elements are combined into the UNTOUCHED settings to be tested in this protocol. It is hypothesized that despite the lack of anti-tachycardia pacing, the EMBLEM S-ICD settings utilized in this study will result in an overall shock incidence similar to that observed in ICD patients from MADIT RIT.

Inclusion Criteria:

• Patient with ischemic or non-ischemic heart disease who meets current guidelines for ICD therapy and intends to undergo a de novo implant procedure for an EMBLEM™ S-ICD (or newer generation BSC S-ICD)
• Left ventricular ejection fraction ≤ 35%
• A passing EMBLEM™ S-ICD (or newer generation BSC S-ICD) screening ECG
• Patient ≥ 21 years of age willing and capable of giving informed consent
• Patient willing and capable of complying with follow-up visits

Exclusion Criteria:

• Patient with a history of spontaneous sustained VT or VF
• Patient with bradycardia pacing indication
• Patient eligible and scheduled for cardiac resynchronization implant
• Patient with a previous S-ICD or a previous transvenous pulse generator (pacemaker or defibrillator)
• Patient in NYHA Class IV documented in the medical records within 90 days before enrollment
• Patient with life expectancy shorter than 18 months due to any medical condition (e.g., cancer, uremia, liver failure, etc…)
• Patient receiving hemodialysis within 180 days before to enrollment
• Patients unable to give consent in person, including patients unable to read or write
• Patient who is known to be pregnant or plans to become pregnant over the course of the trial
• Patient unwilling or unable to cooperate with the protocol
• Participation in concurrent clinical study without prior approval from Boston Scientific
• Medical status (e.g., hemodynamic conditions ) of the patient doesn't allow programming devices with a conditional shock zone at 200 bpm and a shock zone at 250 bpm, in the judgment of the implanting physician and/or according to (inter) national guidelines