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Components of Pacing Leads: Design and Performance Factors.

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Presentation on theme: "Components of Pacing Leads: Design and Performance Factors."— Presentation transcript:

1 Components of Pacing Leads: Design and Performance Factors

2 Pacing Lead Activity 70 bpm 100,000 beats / day 37,000,000 beats / year

3 Pacing Lead Components Objectives Be awareness of how leads play a critical role in the reliability of a pacing system -- A lead is not “just a wire”. Demonstrate an understanding of design and technology that influence potential performance and reliability of a lead -- All leads are not created equal. Demonstrate an understanding of lead assembly process

4 ConductorTip ElectrodeInsulationConnector Pin Pacing Lead Components Conductor Connector Pin Insulation Electrode Lead Assembly

5 Conductor Purpose –Deliver electrical impulses from IPG to electrode –Return sensed intracardiac signals to IPG Conductor

6 Conductor -- Types Types –Unifilar –Multifilar –Cable

7 Conductor -- Construction Unipolar Construction

8 Conductor -- Unipolar Construction Unipolar lead –1 pacing conductor –IPG case (“can”) for sensing

9 Conductor -- Unipolar Construction Unipolar Lead Characteristics –Larger pacing spikes on EKG –Small diameter lead body –Less rigid lead body –More susceptible to oversensing –May produce muscle and nerve stimulation

10 Conductor -- Construction Bipolar Construction –Co-axial –Co-radial Outer insulation Tip electrode coil Indifferent electrode coil Integral insulation Tip electrode coil Indifferent electrode coil

11 Conductor -- Construction Bipolar Construction –Parallel Coils –Coil / Cables

12 Conductor -- Bipolar Construction Bipolar –1 pacing conductor –1 sensing conductor

13 Conductor -- Bipolar Construction Bipolar Lead Characteristics –Larger diameter lead body –Tend to be stiffer –Less susceptible to oversensing –Unipolar programmable –Less likely to produce muscle and nerve stimulation

14 Conductor -- Material Typical Conductor Materials –MP35N (nickel alloy) –MP35N silver cored

15 Connector Purpose –Connects lead to IPG, and provides a conduit to: Deliver current from IPG to lead Return sensed cardiac signals to IPG Connector

16 Connector -- IS-1 Standard IS-1 Standard Connectors Sizes Prior to IS-1 Standard –3.2 mm low-profile connectors –5/6 mm connectors

17 Insulation Purpose: –Contain electrical current –Prevent corrosion Insulation

18 Insulation -- Properties Properties of Insulation Materials –Tensile strength –Elongation –Tear strength –Abrasion –Compression set –Crush (cyclic compression) –Creep

19 Insulation -- Type Insulation Types –Silicone –Polyurethane –Fluoropolymers (PTFE, ETFE)

20 Insulation -- Type Silicone –Advantages Inert Biocompatible Biostable

21 Insulation -- Type Silicone –Disadvantages High friction coefficient (sticky) Handling damage Size (for some types of silicone)

22 Insulation -- Type Polyurethane –Advantages Biocompatible High tear strength Low friction coefficient Less fibrotic Small lead diameter

23 Insulation -- Type Polyurethane Disadvantages  Environmental Stress Cracking (ESC) Crazing or cracking of the polyurethane due to exposure to the in-vivo environment and internal material stresses  Metal Ion Oxidation (MIO) Oxidative degradation of the polyurethane insulation

24 Insulation -- Small Size New Insulation Materials Facilitate the Benefits of Smaller Lead Diameters Smaller introducer size Easier insertion/passage through smaller veins More flexible lead bodies Two leads through one introducer Less intrusive

25 Electrodes Purpose –Deliver a stimulus to myocardium –Detect (sense) intracardiac signals Tip Electrode Ring Electrode

26 Electrodes Optimal Performance Factors –Low, Stable Thresholds –High Pacing Impedance –Low Source Impedance –Good Sensing

27 Electrodes Characteristics and Design Factors that Impact Electrical Performance –Fixation mechanism –Polarity –Surface material –Size –Surface structure –Steroid elution

28 Electrodes -- Fixation Mechanism Passive Fixation Mechanism – Endocardial –Tined –Finned –Canted/curved

29 Electrodes -- Fixation Mechanism Passive Fixation Applications – Endocardial –Trabeculated ventricle –Atrial appendage present –Traditional pacing sites

30 Electrodes – Fixation Mechanism Active Fixation Mechanism – Endocardial –Fixed screw –Extendible/retractable

31 Electrodes -- Fixation Mechanism Active Fixation Applications -- Endocardial –Smooth ventricular walls –Atrial appendage is missing/malformed –Alternate pacing site

32 Electrodes -- Fixation/Visualization Fluoroscopic Visual Quality of Passive Fixation Leads CapSure ® CapSure SP ® NovusCapSure Z ® Novus

33 Electrodes -- Fixation/Visualization Fluoroscopic Visual Quality of Active Fixation Leads SureFix CapSureFix ® Extended Retracted Fixed Screw space

34 Electrodes -- Fixation Mechanism Fixation Mechanism – Myocardial / Epicardial –Stab-in –Screw-in –Suture-on

35 Electrodes -- Polarity Characteristics and Design Factors that Impact Electrical Performance –Fixation mechanism –Polarity –Surface material –Size –Surface structure –Steroid elution

36 Electrodes -- Surface Material Characteristics and Design Factors that Impact Electrical Performance –Fixation mechanism –Polarity –Surface material –Size –Surface structure –Steroid elution

37 Electrodes -- Surface Material Surface Material –Polished platinum –Activated carbon –Platinized metal

38 Electrodes -- Surface Material Surface Material Characteristics –Corrosion Resistant –Biocompatible –Reduced Polarization

39 Electrodes -- Size Characteristics and Design Factors that Impact Electrical Performance –Fixation mechanism –Polarity –Surface material –Size –Surface structure –Steroid elution

40 Electrodes -- Size Reducing Electrode Size –Increases Impedance –Reduces Current Drain –Increases Longevity

41 Electrodes -- Size/Impedance Pacing Impedance (Ohms) Geometric Tip Electrode Surface Area (mm 2 ) Size = Impedance

42 Electrodes -- Size/Current Drain Reducing electrode size –Increased impedance –Lower outputs, reduces current drain –Increases longevity Larger current drain Increased impedance at the tip electrode Smaller current drain (less current does same amount of work)

43 Electrodes -- Size/Longevity Impact of Pacing Impedance on Longevity TotalPulse Width 0.4 ms in both chambers LeadA = 3.5 VA = 2.5 VA = 2.5 V ImpedanceV = 3.5 VV = 2.5 VV = 1.5 V 500  6.3 Yr7.7 Yr8.1 Yr 600  6.6 Yr8.0 Yr8.3 Yr 1000  7.7 Yr8.6 Yr8.8 Yr 1200  8.0 Yr8.8 Yr9.0 Yr 100% pacing at 60 ppm Medtronic.Kappa ™ DR Model KDR701

44 Electrodes -- Size/Polarization Reducing Electrode Size –Increases polarization

45 Electrodes -- Size/Polarization Current Tissue  Polarization Layering Effect

46 Electrodes -- Surface Structure Characteristics and Design Factors that Impact Electrical Performance –Fixation mechanism –Polarity –Surface material –Size –Surface structure –Steroid elution

47 Electrodes -- Surface Structure Porous Electrode Surface CapSure ® 8.0 mm 2 Porous Electrode CapSure ® SP Novus 5.8 mm 2 Platinized Porous Electrode CapSure ® Z Novus 1.2 mm 2 Platinized Porous Electrode 15KV x V Medt

48 Electrodes -- Surface Structure Benefits of a Porous Electrode Surface –Reduces Polarization –Improves Sensing –Promotes Tissue In-Growth

49 Electrodes -- Size and Surface Structure Increased Porosity Smaller Size Longevity Increases! Reduces polarization Increases electrode tissue impedance Decreased current drain

50 Electrodes -- Steroid Elution Characteristics and Design Factors that Impact Electrical Performance Fixation mechanism Polarity Surface material Size Surface structure Steroid elution

51 Electrodes -- Steroid Elution Tines for Stable Fixation Silicone Rubber Plug Containing Steroid Porous, Platinized Tip for Steroid Elution Type - Steroid in matrix

52 Electrodes – Steroid Elution IMPLANTCHRONIC (8 weeks or longer) Excitable Cardiac Tissue Non-Excitable Fibrotic Tissue Excitable Cardiac Tissue

53 Electrodes -- Steroid Elution Benefits of Steroid Elution Excellent Electrode-tissue Biocompatibility: –Fewer and less active inflammatory cells –Less fibrotic development Improved Electrode Performance: –No significant threshold peaking nor chronic threshold increases –Improved consistent sensing characteristics

54 Electrodes -- Steroid Elution Effect of Steroid on Stimulation Thresholds Pulse Width = 0.5 msec Implant Time (Weeks) Textured Metal Electrode Smooth Metal Electrode Steroid-Eluting Electrode Volts

55 Electrodes -- Steroid Elution Steroid Enhances Sensing –Steroid elution stabilizes electrode sensing performance –Improved r-wave sensing: mV –Improved p-wave sensing: mV –Stable, acute atrial sensing –Clinical benefits Less postoperative atrial sensing loss Can use higher atrial sensitivities

56 Electrode -- Summary Design Factors that Impact Lead Electrical Performance Fixation Mechanism Polarity Surface Material Size Surface Structure Steroid Elution

57 Lead Summary Lead environment is hostile Leads are complex Lead performance ConductorTip ElectrodeInsulationConnector Pin


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