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Question 1

what is a heart attack and what is it caused by

Answer 1

heart blocked due to clogged arteries. deadly arrhythmia.

not an issue with the heart organ or blood, it is a conduction issue / electric disfunction.

Question 2

how are heart attacks usually treated

Answer 2

bypass surgeries, stents, catheter ablation

Question 3

what is systole and diastole

Answer 3

systole: contraction, polarisation
diastole: relaxation, depolarisation

Question 4

what is a ECG/EKG

Answer 4

measuring electrical activity of the heart using external electrodes. measures voltage over time

Question 5

What is the order of nodes/fibers in the heart that are activated during a contraction

Answer 5

SA node (pacemaker),
AV node,
Bundle of His, 
bundle branches,
Purkinje fibers

Question 6

Describe the order of locations activated during a contraction

Answer 6

Right atrium activated
both atria contract
bundles activated
both ventricles contract

Question 7

atria receive blood while ventricles pump out blood

describe the blood pumping function of the left & right atria & ventricles

Answer 7

right atrium: body => right ventricle

right ventricle: right atrium => lungs

left atrium: lungs => left ventricle

left ventricle: left atrium => body

Question 8

what is atrial fibrillation and why is it dangerous

Answer 8

the heart’s upper chambers (atria) beat out of coordination with the lower chambers (ventricles).

dangerous because of the side effects - blood may clot and cause a stroke

Question 9

what is the difference between early pacemakers and later pacemakers

Answer 9

early pacemakers had a fixed bpm (70 bpm). no proper encapsulation. mercury-zinc batteries. corroded and produced nuclear waste.

later changed so that the bpm is adaptable - needed because of age or excersise variability. titanium encapsulation.

Question 10

what pacemaker innovations were Telectronics responsible for

Answer 10

Titanium encapsulation
Use of ICs
Miniturising
Guardian defibrillator (implantable)
Laserpor and Laserdish Electrodes (electrode design)
Slimline tined leads (small thread sizes)
Elast-eon biostable polyurethane

Question 11

Where are the leads of implantable defibrillators implanted

Answer 11

the right chambers because it is easier to access the venous chamber from the collar bone region

Question 12

what is cardiac resynchronisation therapy (CRT-ICD)

Answer 12

use a third lead with an implantable cardiac defibrillator to stimulate the left ventricle when the left and right chambers are not in sync

Question 13

describe the lead-free design of implantable cardiac defibrillators

Answer 13

subcutaneous device - electrode array right above sternum delivers electrical pulses to the heart

Question 14

What are the pacemaker types and what part of the heart do they stimulate?

Answer 14

Single-chamber - the right atrium or the right ventricle

Dual chamber- both the right atrium and ventricle

Rate responsive - detects changes in HR and adjusts it accordingly

Question 15

what is the failliure rate of leads within 10 years?

Answer 15

20%

requires open heart surgery in 2% of cases

Question 16

what are the components of a pacemaker

Answer 16

Pulse generator
Lead
Programmer

Question 17

What (3) conditions are treated by pacemakers?

Answer 17

Bradycardia
Tachycardia
Heart failure

Question 18

What is the most common way by which pacemakers fail? i.e. “classic fatigue failure”

Answer 18

Through lead failure - weakening of the metal. Leads are not durable enough to survive either the pressure of implantation of the stresses exerted on them once they are in the body.

Question 19

what are the electrical properties of pacemakers

Answer 19

constant voltage stimulation
batteries are usually 2.8 V
output is around 3.5 V

Question 20

What was the cause of the Sprint Fidelis leads (Medtronic) failure?

what was the lead failiure rate?

what what the side effect of this failiure?

Answer 20

Suspected to be caused by “classic fatigue failure”

5.7% by 32 months

inappropriate shocks, alarm alerts, detection at follow up

Question 21

what was the cause of failure for Riata leads (St Jude)

Answer 21

inside-out insulation defects - the conductor cables wear through the silicone insulation (inside-out abrasion) and appear outside the lead body (externalized conductors).

Question 22

what are the different variables to consider when designing leads

Answer 22

Endocardial vs. epicardial

Unipolar vs. bipolar

Electrodes

Fixation mechanism

Insulation (Si or PU)

Pulse generator (connection)

Atrial vs. ventricular

Question 23

What are the epicardial leads?

Answer 23

Sutured outside the heart
Requires open-chest procedure
Typically has cockscrew mechanism
More invasive/difficult to implant
Pacing thresholds may increase over time

Question 24

when would epicardial leads be used

Answer 24

pediatric patients (vessels are too small for endocardial)

patients having open-chest surgery already

Question 25

describe the main elements of a pacemaker lead

Answer 25

two ends: connector pin (standardized size) and distal tip electrode. ~ 60 cm long. tip electrode has fixation mechanism. may have a ring electrode as an antenna if bipolar. may have drugs encapsulated at tip.

Question 26

what is lead polarity and what is the difference between unipolar and bipolar leads

Answer 26

All electricity travels in a circuit (circle) from a positive pole (anode) to a negative pole (cathode) A unipolar lead has a negative pole (cathode) on the lead itself (tip electrode) and uses the pulse generator can as the positive pole (anode, receives current). creates a large antenna => large pacing spike on ECG. A bipolar lead has both anode (ring electrode) and cathode (tip electrode) on the lead itself. creates a small antenna. small spike on ECG.

Question 27

describe the conductor coil design for unipolar electrodes

Answer 27

One conductor coil + outer insulation Conductor coil may consist of multiple (3-4) strands or filars (multifilar leads)

Question 28

what is the difference between using silicone vs PU outer insulations

Answer 28

Silicone - stable, softer, flexible, but weak, stickier. No environmental stress cracking, No metal ion oxidation. PU - stronger, fatigue resistant, more slippery, can be manufactured thinner, but may degrade in the body, stiffer. environmental stress cracking, metal ion oxidation (leeching metal ions degrade the PU).

Question 29

describe the conductor coil design for bipolar electrodes

Answer 29

two conductor coils (inner cathode and outer anode) inner and outer layers of insulation. typically thicker than unipolar

Question 30

What are the advantages and disadvantages of unipolar leads?

Answer 30

Advantages: Smaller diameter, Easier to implant, Larger ECG spike, Reliability due to 1 coil Disadvantages: No programming flexibility, Possible pocket stimulation (twitch), Far-field over-sensing (the right atrial appendage is close to the right ventricular outflow tract, resulting in the atrial lead picking up far-field signals from ventricular depolarization. The consequence are (1) inappropriate mode switching in a dual-chamber system and (2) pacing below the programmed rate).

Question 31

What are the advantages and disadvantages of bipolar leads?

Answer 31

Advantages: No pocket stimulation, Less susceptible to electromagnetic interference, Programming flexibility. Disadvantages: Larger diameter, Smaller ECG spike, Stiffer lead body.

Question 32

What is the electrode performance affected by?

Answer 32

``` Materials Polarisation (want to minimise) Impedance (want within lower range) Pacing (voltage) tresholds (want to minimise) Steroids ```

Question 33

What is the ideal electrode material?

Answer 33

Porous to allow for tissue ingrowth (increased stability). Does not corrode or degrade. Should be small in size but with large surface area.

Question 34

what are common materials for electrodes

Answer 34

Platinum and alloys (titanium coated platinum iridium) Vitreous carbon (pyrolytic carbon) Stainless steel alloys such as Elgiloy

Question 35

What is impedance and what factors can influence it?

Answer 35

The sum of all forces opposing the flow of current in a circuit. Resistance of the conductor coils, Size and shape of the tip electrode, Electrode's surface area, Tissue between anode and cathode, The electrode/ myocardial interface

Question 36

describe the properties of charge build up (Polarization)

Answer 36

charge builds up at the stimulation electrode. The amount of the charge build up is directly proportional to pulse duration and inversely proportional to the functional electrode size (i.e. smaller electrodes cause higher polarisation) High polarisation distorts the pacing pulse and reduces or masks the quality of sensed signal (makes signal noisy)

Question 37

what is the effect of large vs small electrode sizes

Answer 37

large: Increased voltage threshold, Decreased impedance, Decreased polarisation small: Decreased voltahe threshold, Increased impedance, Increased polarisation

Question 38

What is the difference between active and passive fixation?

Answer 38

Active fixation leads use a corkscrew mechanism. Extendable-retractable. Passive fixation leads use tines or projections that can snag onto and get embedded in trabeculae

Question 39

What are some of the advantages and disadvantages of active fixation?

Answer 39

Advantages: Easy fixation, Lower rate of dislodgment, Easy to reposition, Chronic lead removability. Disadvantages: More complicated to implant, More expensive.

Question 40

What are some of the advantages and disadvantages of passive fixation?

Answer 40

Advantages: Cheaper, Simpler to implant, Minimal trauma to patient, Potentially lower thresholds Disadvantages: Higher rate of dislodgement, Difficult to remove chronic lead, Affected by change in anatony from heart attack

Question 41

What are some examples of passive fixation mechanisms?

Answer 41

Tines, Fins, and flexible projections Works well when there is a lot of trabeculae and where tissue ingrowth is likely to secure the lead

Question 42

What are some examples of active fixation mechanisms?

Answer 42

Cockscrew, Helix, Screw-in tip Works well when there is not much trabeculae (enlarged ventricle or atrium) and where there is a stronger gravitational pull on the lead

Question 43

what is the pacing threshold

Answer 43

The minimum amount of voltage required to reliably pace the heart (cause contraction) => want to require less battery energy

Question 44

how will inflammation affect the pacing threshold

Answer 44

increases it

Question 45

why are steroids used in pacemakers

Answer 45

To decrease inflammation => decreases threshold (from .8 V to .5 V)

Question 46

what are the three types of lead caps

Answer 46

dish - no holes laserpor - lots of flat holes laserdish - angled holes on dimpled top

Question 47

Which lead cap type produces the lowest (pacing & sensing) impedance?

Answer 47

Laserpor

Question 48

Which lead type produces the lowest voltage threshold & stimulation energy per pulse?

Answer 48

Laser porous dish

Question 49

how are steroids delivered to the heart tissue

Answer 49

Medtronic: drug sits inside electrode Developed: drug eluding collars (outside of electrode)

Question 50

what is Elast-Eon

Answer 50

copolymer of Si and PU

Question 51

What are some of the current research developments for pacemakers?

Answer 51

``` Remote monitoring, MRI compatible pacemakers, New algorithms (heart failure), Stimulation via ultrasound, Miniaturisation ```

Question 52

what are some considerations for leadless pacemakers

Answer 52

implantation complication: venous access, embolation, perforation retrival/extraction of chronic devices implantation of multiple devices rate response characteristics