Reliance 4-Frontᵀᴹ

Implantable Defibrillation Lead

Reliance 4-Front leads

RELIANCE 4-FRONT leads are 7.3F (2,4 mm), steroid-eluting, endocardial cardioversion/defibrillation and pace/sense leads. 4-FRONT is built on the reliable RELIANCE™ platform and has a smart size reduction while maintaining insulation thickness.

Key Resources


Product Specifications

Lead Specifications

RELIANCE 4-Front™, Single-coil

RELIANCE 4-Front™, Dual-coil

The RELIANCE 4-FRONT leads are 7.3F (2.4 mm) (8F / 2.6 mm introducer), steroid-eluting, endocardial cardioversion/defibrillation and pace / sense  leads available in extendable/retractable models as well as in passive fixation models. These leads utilize the DF4 connector and incorporate the IROX™ (iridium oxide) coating. The silicone lead body has a lubricious coating and the electrode coils are covered with an anchored GORE™ expanded polytetrafluoroethylene (ePTFE) covering.


ProductDual-coil ActiveSingle-coil ActiveDual-coil PassiveSingle-coil Passive
Model/Length0695 59 cm
0696 64 cm
0658 70 cm
0692 59cm
0693 64cm
0657 70cm*
0685 59 cm
0686 64 cm
0655 70 cm*  
0682 59 cm
0683 64 cm
0654 70 cm*
Terminal Configuration1DF4-LLHHDF4-LLHO2DF4-LLHHDF4-LLHO
PG CompatibilityRELIANCE 4-FRONT leads with the DF4-LLHH / LLHO label are equivalent and are compatible with a device containing either a GDT-LLHH or DF4-LLHH port 
Lead Introducer without Guide Wire8F4 (2.6 mm)8F4 (2.6 mm)8F4 (2.6 mm)8F4 (2.6 mm)
Lead Introducer with Guide Wire10.5F (3.5 mm)10.5F (3.5 mm)10.5F (3.5 mm)10.5F (3.5 mm)
Isodiametric Lead Body Diameter7.3F (2.4 mm)7.3F (2.4 mm)7.3F (2.4 mm)7.3F (2.4 mm)
Rotations Expected to Extend/Retract Helix31111n/an/a
Tip/Helix Electrode Surface Area (mm2)
Proximal Coil Active Electrode Surface Area (mm2)660n/A660n/a
Distal Coil Active Electrode Surface Area (mm2)450450450450
Tip to Proximal Coil Electrode Length (mm)180n/a180n/a
Tip to Distal Coil Electrode Length (mm) 12121212
Lead Body Insulation Materiallayer of silicone, layer of polyurethane (for the first ~ 12 cm) and then the silicone trilumen
Terminal Pin MaterialMP35N nickel-cobalt alloy
Pace/Sense Conductor Materiallow titanium, MP35N nickel-cobalt alloy, PTFE sleeve
Conductive Ring MaterialMP35N nickel-cobalt alloy
Shocking Conductor Material1X19 Low titanium MP35N nickel-cobalt alloy, silver-core, drawn filled tube, ETFE coated
Tip Electrode MaterialIROX coated platinum / iridium
Coil Electrode Covering MaterialePTFE
Shock Coil MaterialPlatinum clad tantalum clad titanium
Steroid MaterialApproximately 0.96 mg dexamethasone acetate nominally


Lifetime Warranty: The RELIANCE 4-FRONT defibrillation lead family is backed with a lifetime warranty5.

Terminal configuration: The RELIANCE 4-FRONT lead is DF4-LLHH for dual-coil leads and DF4-LLHO for single-coil leads, this suffix provides functional identifications of conductors:

L = Low Voltage

H = High Voltage

O = Inactive Ring Contact (Single-Coil Leads Only)


Rings 1 and 2 are electrically connected within the terminal for integrated bipolar pacing / sensing. Cable conductors

are utilized for both shock coils. Ring 2 is connected to the distal shock coil and ring 3 connects to the proximal coil.


Isodiametric lead body:

The isodiametric lead body contains one conductor for pacing / sensing. For defibrillation, the lead has two conductors in dual coil models and one for the single coil models leaving one lumen empty in single coil models. The conductors are insulated in separate lumens within the silicone rubber lead body. A second layer of silicone covers the lead body, providing additional insulation and a uniform body diameter. RELIANCE 4-FRONT has a 7.3F (2.4 mm) lead body which fits through an 8F (2.6 mm) non-hemostatic introducer when not retaining a guide wire.


• Silicone construction: Silicone has been used in Boston Scientific leads for nearly 4 decades.

• Polyurethane sleeve: The first 12 cm of the lead distal to the terminal boot incorporates a polyurethane sleeve underneath the outer silicone rubber insulation for enhanced abrasion resistance within the pocket.

• Lubricious coating: The RELIANCE 4-FRONT lead family utilizes a proprietary coating that makes the silicone lead surface more lubricious. This reduces both the static and dynamic coefficients of friction, making the lead surface feel and handle like polyurethane while providing the time-tested reliability of silicone.

GORE ePTFE-covered coils: The GORE ePTFE covering enhances the lead’s extractability by preventing fibrotic tissue from forming around and between the individual coil filars. The GORE is anchored to the lead body so it can be used with standard hemostatic introducers without the use of additional implant tools.

IROX coating: RELIANCE 4-FRONT features an IROX coated pace/sense cathode electrode, which may improve pacing performance. Lower and more predictable pacing thresholds may increase the longevity of the pulse generator.

Steroid distal tip: The tip electrode contains a nominal dose of steroid that elutes upon exposure to body fluids. The steroid suppresses the inflammatory response believed to cause threshold rises typically associated with implanted pacing electrodes. Lower thresholds are desirable because they can increase pacing safety margins and reduce pacing energy requirements, potentially increasing pulse generator longevity.

Pullback: Pullback is the distance the defibrillation electrode is removed from the lead tip, a critical factor in helping to direct energy deep into the ventricular apex. Standard for multiple generations of Boston Scientific defibrillation leads, the 12 mm RELIANCE 4-FRONT pullback design is important for low defibrillation thresholds, while optimizing sensing characteristics.

Radiopaque suture sleeve: The radiopaque suture sleeve is visible under fluoroscopy and is used to secure and protect the lead at the venous entry site after lead placement. The window feature is designed to aid compression of the sleeve onto the lead during suturing.

Passive-Fixation Features

Design leveraged from successful FINELINE 2 family. 12 mm Tip to RV Coil spacing is identical to RELIANCE.

Incorporates a flexible neck region and IROX coating for improved pacing performance.

Active-Fixation Features

Terminal pin-driven extendable/retractable fixation helix: Rotating the knob of the EZ-4 Connector tool rotates the terminal pin which extends / retracts the helix. The IROX coated platinum-iridium helix anchors the pacing electrode to the endocardial surface without support of trabecular structures, offering various lead placement possibilities for the tip electrode in the right ventricle.

Fluoroscopic markers: The RELIANCE 4-FRONT active fixation model incorporates a radiographic marker system to enable clear visualization of the helix position under fluoroscopy.


Mapping: The RELIANCE 4-FRONT tip and helix design allows mapping even with the helix fully retracted. Helix is flush to prevent snagging while enabling mapping.

EZ-4 ™ Connector Tool

When connected to the lead, the EZ-4 Connector Tool performs the following functions:

1. Protects the lead terminal during the implant procedure.

2. Provides a safe and secure connection between the pacing system analyzer (PSA) patient cables and

the lead terminal.

3. Guides the stylet into the lead through the stylet funnel.

4. For leads with an extendable / retractable helix, rotates the terminal pin clockwise or counterclockwise to extend or retract the helix.

The EZ-4 Connector Tool is intended to be left on the lead for the duration of the implant, until the lead terminal is inserted into the header.

Key Benefits

After 5 years of development, RELIANCE 4-FRONT is the latest in ICD lead technology, built on the proven RELIANCE platform to provide:

  • The most reliable lead on the market6
  • A modest size reduction
  • An improved implant experience
  • Enhanced extraction capability