Lead & electrode materials for IBHRE®

True / False

Modern ICD leads are considered Multi-lumen.

True.

Individual sheaths of material (lumens) surround each conductor.

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What are anchoring sleeves made from?

MDX silicone rubber.

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In a co-axial lead design - does the inner conductor go to the ring or the tip?

Inner conductor goes to the Tip.

Its the Cathode = Negative.

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In a co-axial lead design - does the outer conductor go to the ring or the tip?

Outer conductor goes to the Ring.

Its the Anode = Positive.

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What is the major benefit of a Co-radial lead design vs. Co-axial?

Typically thinner diameter (can be <6F).

Good for CRT leads where CS can be tortuous.

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True / False

There are differences between Co-axial & Co-raidal leads with regard to durability and performance.

False.

There are no significant differences between the two lead designed with respect to durability and performance.

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Passive fixation leads rely on ‘Tines’ to become lodged to the trabeculae of the ventricle. Typically after what period of time do they become difficult to remove?

6 months.

Due to tissue growth around the lead tip.

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What is the name of the covering fixed helix leads possess to help prevent undesirable entrapment or perforation before fixation?

Mannitol (a type of sugar).

This substance typically dissolves within several minutes of insertion to the body.

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List two benefits of a Fixed Helix design vs the Retractable screw helix design.

Typically thinner diameter (no screw mechanism).
Less complexity - Screw mechanisms can and do break, rendering the lead useless.

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True / False

Historically active fixation leads (both fixed and screw helix type) show higher chronic pacing thresholds vs. passive fixation leads.

True.

This is due to inflammation caused by the unavoidable myocardial insult respondent to screwing in the helix. Modern corticosteroids such as dexamethasone have largely negated this however.

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True / False

Modern Epicardial leads are only available in a unipolar configuration.

False.

Epicardial leads are offered in bipolar configurations.

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What are the two different types of conductor materials used in modern leads?

MP35N
Silver

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MP35N is a multiphase alloy consisting of 4 different materials, what are they?

Cobalt
Nickel
Chromium
Molybdenum

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List the 3 important characteristics of MP35N that make it suitable as a lead conductor

Biocompatible with the human body
High tensile strength
Resistance to corrosion

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Why is MP35N combined with silver during lead construction?

MP35N has high resistivity (>1000ohms) Silver is an excellent conductor with low resistivity, thus blending the two results in optimal resistivity characteristics.

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MP35N & Silver are combined in two fashions during lead construction, what are they

Drawn brazed strand
Drawn filled tube

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The following statement best describes what type of lead construction?

‘Stranded wire which encompasses a core wire made from a softer, highly conductive material, such as silver. The wire is then brazed and drawn in the normal wire drawing process’.

Drawn brazed strand.

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The following statement best describes what type of lead construction?

‘Allows you to match dissimilar materials to provide a variety of properties in a single wire system. Most commonly, the outer sheath of the composite provides strength while the core material is used to provide conductivity’.

Drawn filled tube.

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These 3 benefits refer to which lead conductor manufacturing process?

Increased fatigue life
High conductivity
Withstands greater mechanical stress

Drawn brazen strand.

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True / False

Pacemaker leads are engineered with lead conductors manufactured using the Drawn Brazen Strand method.

False.

Pacemaker lead conductors are typically fashioned using the Drawn Filled Tube method.

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The following statement describes either Coil Pitch or Coil Filarity.

‘The number of separate wires within the coil’.

Coil Filarity.

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The following statement describes either Coil Pitch or Coil Filarity.

‘Filar diameter x number of filar in the set + space between filar sets’.

Coil Pitch.

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True / False

Most modern leads are Tri/Quadrifilar.

True.

Increasing complexity requires multiple lumens to encase each conductor.

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What are the two major types of Fluoropolymer insulation?

PTFE (Teflon // DuPont)
ETFE

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List two major advantages of Fluoropolymer insulation.

1. High resistance to solvents 2. Maximum biocompatibility with the human body

List two major advantages of Silicone rubber insulation.

1. Most common lead material (wealth of R&D) 2. Biostable and biocompatible

List two major disadvantages of Silicone rubber insulation.

1. Prone to tearing and abrasion wear 2. High friction co-eficient

The following statement best describes what phenomenon? 'Silicone deformation under constant or cyclic compression'.

Cold Flow.

List three major advantages of Polyurethane insulation.

1. High tear strength 2. High elasticity 3. Low friction coefficient (This results in the ability to engineer smaller leads overall)

List three major disadvantages of Polyurethane insulation.

1. Lead calcification is possible 2. Environmental stress cracking 3. Chain scission (This is due to the low biocompatibility of Polyurethane)

Describe the process of environmental stress cracking (ESC) with respect to Polyurethane insulation.

Macrophages induce hydrogen peroxide formation on the polymer structure. This results in oxidation-induced chain breaks and resultant metal ion oxidation (MIO) leading to eventual failure.

What are the two most common types of Polyurethane used in lead construction.

1. Pellethane 80A = Bad 2. Pellethane 55D = Good

# True / False Pellethane 80A has an excellent track record of safety and longevity as an insulator of device leads.

False. ## Footnote *P80A is no longer used due to its poor biocompatibility and susceptibility to environmental stress cracking.*

# True / False Pellethane 55D has an excellent track record of safety and longevity as an insulator of device leads.

True. ## Footnote *P55D is the Polyurethane of choice for modern lead manufacturing.*

Manufactures are known to blend lead insulator materials to amplify positives and reduce negatives. What are the 3 materials Abbott OPTIM combines to create 'Elast-Eon'?

1. Silicone rubber 2. Polyurethane 3. Polyhexamethylene oxide

What are the purported benefits of 'elast-eon'

1. Greater strength 2. Greater fracture resistance 3. Greater redundancy 4. Non-compressible

Historically electrode surfaces were smooth. Modern day electrode surfaces are textured, why?

Textured (Fractionated) tips increase effective electrode surface area.

Electrode tips are fractionated in order to increase surface area. List the two benefits associated with a greater effective electrode size.

1. Reduced polarisation 2. Improved sensing and stimulation efficiency

# True / False Electrode Radius directly effects the Stimulation Threshold.

True. ## Footnote *The smaller the electrode radius, the lower the stimulation threshold.*

Fractionated electrodes allow for a smaller electrode radius without reducing the effective electrode size. List the 3 benefits of a reduced electrode radius.

1. Higher current density 2. Lower stimulation threshold 3. High sensing impedance

List the 6 major electrode materials currently in use.

1. Platinum-Iridium 2. Elgiloy (Cobalt, Chromium-nickel) 3. Platinum coated with platinised titanium 4. Platinum 5. Iridium-oxide 6. Titanium-nitride

Of the 6 currently used electrode materials, which has the lowest polarisation characteristics?

Titanium-nitride.

List the 4 materials historically used for electrode construction that are now abandoned.

1. Nickel 2. Copper 3. Silver 4. Elgiloy

Which of the 4 now defunct electrode materials has the unique characteristic of corroding when programmed as an anode, yet is stable when programmed as a cathode?

Elgiloy.

What is the most common corticosteroid applied at the lead tip?

Dexamethasone.

Why is a corticosteroid applied at the tip of a lead and how does it achieve its purpose?

To prevent gradually increasing stimulation thresholds historically seen post implant. ## Footnote *Inflammation at fixation side will increase stimulation threshold. Corticosteroids are an anti-inflammatory.*

Sealing rings prevent infiltration to the lead/device interface. Which lead type had sealing rings attached to the lead?

5mm Unipolar lead. ## Footnote *Largely redundant in modern practice however do crop up at box changes - check compatibility!*

Sealing rings prevent infiltration to the lead/device interface. How many sealing rings are present on a 3.2mm Low Profile Port?

Three sealing rings.

Sealing rings prevent infiltration to the lead/device interface. How many sealing rings are present on a modified 3.2mm Low Profile Port?

Two sealing rings.

Sealing rings prevent infiltration to the lead/device interface. Did the 3.2mm Low Profile system have sealing rings on the lead or in the header?

3.2mm Low Profile has sealing rings in the header.

Is an IS1 lead compatible with a 3.2mm Low Profile header port?

No. ## Footnote *They're incompatible. IS1 is engineered with two sealing rings, this clashes with the 3 rings of 3.2mm*

How many mm is an IS1 connection?

3.2mm.

What is the major anatomical characteristic of IS4 vs DF4 connectors that prevents incorrect insertion?

IS4 pins are larger diameter with no step down. ## Footnote *DF4 pins step down to smaller diameter.*

The following statement best describes what type of bipolar pacing configuration? 'RV tip to RV Defibrillator Coil'.

Integrated Bipolar.

# True / False True bipolar pacing through an ICD lead employs the RV Tip and Ring electrodes.

True.

# True / False True bipolar pacing through an ICD lead employs the RV Tip and Coil electrodes.

False. ## Footnote *True bipolar is akin to a normal pacing lead - Tip to Ring.*

Integrated bipolar pacing through an ICD lead employs the RV Tip and Ring electrodes.

False. ## Footnote *Integrated bipolar uses TIP and COIL electrodes.*

# True / False Integrated bipolar programming effectively encompasses three electrodes for pacing and defibrillation purposes.

False - no dedicated ring electrode. ## Footnote *RV Defib coil = Sensing Anode = Positive* *RV Defib coil = Pacing Anode = Positive* *Tip electrode = Cathode = Negative*

Integrated Bipolar pacing recruits which electrode site as the Sensing anode?

RV Defib Coil.

Integrated Bipolar pacing recruits which electrode site as the Pacing anode?

Coil Electrode.

Integrated Bipolar pacing recruits which electrode site as the Cathode?

Tip Electrode.

Which of the 3 main sensing configurations is least likely to detect impulses of non cardiac origin?

True bipolar. ## Footnote The sensing field of view is small \<5cm.

# Integrated bipolar / Unipolar Which is more likely to detect impulses that are non-cardiac in origin?

Unipolar. ## Footnote *It has a greater sensing field of view and crosses skeletal muscle. Lead tip to device can is approximatelty 30cm vs Lead tip to Coil which is approximately 10cm.*

Is it possible to program an ICD to sense unipolar?

No. ## Footnote *High risk of oversensing that could lead to inappropriate therapy. ICDs sense in Bipolar or Integrated bipolar only.*

What is a negative associated with integrated bipolar ICD sensing?

Oversensing. ## Footnote *Larger field of view compared to true bipolar, thus means its more likely to detect impulses that aren't of cardiac origin.*

What is the major positive of true bipolar ICD sensing?

Least likely configuration to oversense. ## Footnote *Smallest possible field of view reduces risk of detecting impulses that aren't of cardiac origin.*

# True / False Lead electrode tips are generally manufactured from smooth, non-porous metal.

False. ## Footnote *Lead tip will resemble sandpaper with porous surface. This increases surface area without having to increase the size of the electrode (which would increase effect of polarisation phenomenon and result in low current density).*

List two benefits of manufacturing leads with electrode tips that have large active surface areas (but small geometric areas).

1. Larger surface area = Greater contact with electrolyte = Reduced threshold 2. Increased sensing sensitivity

List two benefits of manufacturing leads with electrode tips that have small geometric surface areas (but large active surface areas).

1. High current density = lower stimulation threshold 2. Higher operating impedances = Reduced battery drain

# True / False The Tip electrode is almost always the negative pole (Cathode).

True.

# True / False An advantage of polyutherane lead construction is a reduction of interlead friction.

True.

What differentiates a 3.2mm LP bipolar lead from an IS-1 bipolar lead?

Longer terminal pin.

A main benefit of bipolar leads vs. unipolar is what? 1. Cause less muscle stimulation 2. Thinner 3. Handle better 4. Smaller device headers 5. Less susceptible to EMI

5 - Less susceptible to EMI. ## Footnote *Due to smaller sensing window vs. unipolar configuration.*

Lead & electrode materials Flashcards

Highlights lead manufacture technique and alludes to the pros/cons associated with different construction materials. Currently weighted 6% in the CCDS exam.