Medtronic Fidelis lead
-Class 1 recall
-Higher than expected conductor fracture rate with frequent episodes of inappropriate shocks as well as inhibition of pacing
St Jude Riata lead
-Class 1 recall
-Lead cables may become exteriorized as high voltage and/or low voltage conductor cables wear through the silicone insulation and appear outside the lead body (i.e. inside out abrasion)
Class 1 recall
There is a reasonable probability that the use of or exposure to a violative product will cause serious adverse health consequences or death
Class II recall
Use of or exposure to a violative product may cause temporary or medically reversible adverse health consequences or in which the probability of serious adverse health consequences is remote
Class III recall
The use of or exposure to a specific product is not likely to cause adverse health consequences
Capacitor
Component that stores electrical charge and releases it quickly when needed
Stores energy from the battery
Measured in farads (F)
-Pacemaker: Releases energy as the pacing pulse
-ICDs: Accumulate and store charge before shock delivery (because battery is unable to deliver the high level of voltage and current needed over the shock interval)
-CIEDs use electrolytic capacitors - they have a high energy density which allows a small size
Anode
-Positive
-In a unipolar system: the can
-In a bipolar system: the ring electrode
-Capture occurs at the trailing edge of the stimulus -> myocardial refractory period tends to be shorter so concern at faster HR for R on T
-At higher outputs it’s possible to have anodal stimulation from the RV ring:
-Can be a problem in CRT devices as this could lead to 3 wavefronts with RV tip, RV ring, and LV tip and suboptimal pacing
-Potential for capturing surrounding tissues (phrenic nerve, diaphragm, etc)
Cathode
-Negative
-Capture occurs at the tip electrode
-Electrons enter the muscle from the electrode, resulting in relatively low capture thresholds and minimal electrode corrosion
-Capture occurs at the onset of the impulse
Bipolar
Sensing between tip and ring electrodes
Cathode: lead tip
Anode: lead ring electrode
Produces high frequency, lower amplitude electrograms with reduced susceptibility to far-field signals, myopotential oversensing, and EMI.
Integrated bipolar
Sensing between distal tip electrode and distal defibrillation coil
The wider spacing compared to true bipolar sensing creates a larger sensing field with greater susceptibility to T wave oversensing and myocardial detection
Unipolar
Cathode: lead tip
Anode: pacemaker can
Pros:
-Produces larger amplitude signals
Cons:
-Can sometimes cause extra cardiac stimulation at the pulse generator (pectoral is muscle stimulation) due to current returning to the generator
-Increased susceptibility to myopotential oversensing, EMI, and far field detection
Standard pacemaker lead/connectors per guidelines
IS-1: single pin, bipolar or unipolar, 3.2 mm diameter in-line bipolar connector pin
IS-4: (CS lead) single in line connection of 4 low voltage pace/sense electrodes (allows 4 pacing sites). Can go into a DF-4 port but won’t connect
Standard ICD lead/connectors per guidelines
DF-1: Has separate IS-1 pin and 1 or 2 DF-1 pins
DF-4: single pin with 4 connectors (pace/sense tip, pace/sense ring, RV coil, +/- SVC coil). Can go into a LV-4 port and be able to pace
Lead electrodes
Lead electrode materials currently in use:
-Platinum-iridium, platinized titanium coated platinum, iridium oxide, and platinum
-Carbon electrodes seem to be the least susceptible to corrosion
-Optimal stimulation and sensing thresholds favor an electrode with a small radius and a large surface area
-Electrodes with an irregular, textured surface allow for increased surface area without an increase in electrode radius
Lead conductors
-Alloys such as MP35N (cobalt, nickel, chromium, and molybdenum) and nickel silver
Bipolar coaxial conductor
-Inner and outer multifilar coils with inner and outer insulation
-Inner coil extends to the distal electrode
-Outer coil terminates at the proximal electrode
-Conductor coils are separated by a layer of inner insulation
Multilumen lead
ICD lead
-Each conductor has its own lumen
-Pacing conductor, sensing conductor, and high voltage conductor
Coradial conductor
“Parallel-wound”
-Two insulated coils are wound next to each other
Conductor coil designs
Unifilar
Multifilar
Cable
Cable conductor coil design
-Allows a smaller lead body
-Allows the conductor to be more flexible and resistant to fracture
Multifilar conductor design
-Allow the conductor to be more flexible and resistant to fracture
-Conductors are commonly multifilament design to provide tensile strength and reduce resistance to metal fatigue
Types:
-Coaxial
-Multiluminal
-Coradial (parallel wound)
Lead insulation materials
-Silicone
-Polyurethane
Silicone insulation material
Pros
-More flexible
-Good biostability
-More tolerant of electrocautery heat damage
Cons
-More vulnerable to tear, cut, and ablation
-Higher friction in blood
-Subject to cold flow (mechanical failure)
-More thrombogenic
-Unable to manufacture smaller diameters
Polyurethane insulation material
Two types: P80A and P55D
-P80A can develop microscopic cracks, which initially occured as the heated polymer cooled during manufacturing and worsened with stress over time causing the cracks to go deeper into he insulation, resulting in failure of the lead insulation
Pros:
-Better mechanical properties. Tear, cut, and abrasion resistance
-Lower friction in blood
-Better at tolerating compression
-Less thrombogenic
-Smaller diameter is possible
Cons:
-Stiffer (P55D)
-More susceptible to metal ion oxidation (chemical degradation)
-More susceptible to environmental stress cracking (combined chemical/mechanical degradation)
-More susceptible to electrocautery heat damage
