Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

b5995 > w10 > Flashcards

w10 Flashcards

1
Q

what is a heart attack and what is it caused by

A

heart blocked due to clogged arteries. deadly arrhythmia.

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

how are heart attacks usually treated

A

bypass surgeries, stents, catheter ablation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is systole and diastole

A

systole: contraction, polarisation
diastole: relaxation, depolarisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is a ECG/EKG

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

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

A 
SA node (pacemaker),
AV node,
Bundle of His, 
bundle branches,
Purkinje fibers
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe the order of locations activated during a contraction

A

Right atrium activated
both atria contract
bundles activated
both ventricles contract

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

atria receive blood while ventricles pump out blood

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

A

right atrium: body => right ventricle

right ventricle: right atrium => lungs

left atrium: lungs => left ventricle

left ventricle: left atrium => body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is atrial fibrillation and why is it dangerous

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the difference between early pacemakers and later pacemakers

A

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.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what pacemaker innovations were Telectronics responsible for

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Where are the leads of implantable defibrillators implanted

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is cardiac resynchronisation therapy (CRT-ICD)

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

describe the lead-free design of implantable cardiac defibrillators

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

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

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the failliure rate of leads within 10 years?

A

20%

requires open heart surgery in 2% of cases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the components of a pacemaker

A

Pulse generator
Lead
Programmer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What (3) conditions are treated by pacemakers?

A

Bradycardia
Tachycardia
Heart failure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

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

A

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.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what are the electrical properties of pacemakers

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

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?

A

Suspected to be caused by “classic fatigue failure”

5.7% by 32 months

inappropriate shocks, alarm alerts, detection at follow up

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

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

A

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

22
Q

what are the different variables to consider when designing leads

A

Endocardial vs. epicardial

Unipolar vs. bipolar

Electrodes

Fixation mechanism

Insulation (Si or PU)

Pulse generator (connection)

Atrial vs. ventricular

23
Q

What are the epicardial leads?

A 
Sutured outside the heart
Requires open-chest procedure
Typically has cockscrew mechanism
More invasive/difficult to implant
Pacing thresholds may increase over time
24
Q

when would epicardial leads be used

A

pediatric patients (vessels are too small for endocardial)

patients having open-chest surgery already

25
Q

describe the main elements of a pacemaker lead

A

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.

26
Q

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

A

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.

27
Q

describe the conductor coil design for unipolar electrodes

A

One conductor coil + outer insulation

Conductor coil may consist of multiple (3-4) strands or filars (multifilar leads)

28
Q

what is the difference between using silicone vs PU outer insulations

A

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).

29
Q

describe the conductor coil design for bipolar electrodes

A

two conductor coils (inner cathode and outer anode)

inner and outer layers of insulation.

typically thicker than unipolar

30
Q

What are the advantages and disadvantages of unipolar leads?

A

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).

31
Q

What are the advantages and disadvantages of bipolar leads?

A

Advantages: No pocket stimulation, Less susceptible to electromagnetic interference, Programming flexibility.

Disadvantages: Larger diameter, Smaller ECG spike, Stiffer lead body.

32
Q

What is the electrode performance affected by?

A 
Materials
Polarisation (want to minimise)
Impedance (want within lower range)
Pacing (voltage) tresholds (want to minimise)
Steroids
33
Q

What is the ideal electrode material?

A

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

34
Q

what are common materials for electrodes

A

Platinum and alloys (titanium coated platinum iridium)

Vitreous carbon (pyrolytic carbon)

Stainless steel alloys such as Elgiloy

35
Q

What is impedance and what factors can influence it?

A

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

36
Q

describe the properties of charge build up (Polarization)

A

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)

37
Q

what is the effect of large vs small electrode sizes

A

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

38
Q

What is the difference between active and passive fixation?

A

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

39
Q

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

A

Advantages: Easy fixation, Lower rate of dislodgment, Easy to reposition, Chronic lead removability.

Disadvantages: More complicated to implant, More expensive.

40
Q

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

A

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

41
Q

What are some examples of passive fixation mechanisms?

A

Tines, Fins, and flexible projections

Works well when there is a lot of trabeculae and where tissue ingrowth is likely to secure the lead

42
Q

What are some examples of active fixation mechanisms?

A

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

43
Q

what is the pacing threshold

A

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

44
Q

how will inflammation affect the pacing threshold

A

increases it

45
Q

why are steroids used in pacemakers

A

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

46
Q

what are the three types of lead caps

A

dish - no holes

laserpor - lots of flat holes

laserdish - angled holes on dimpled top

47
Q

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

A

Laserpor

48
Q

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

A

Laser porous dish

49
Q

how are steroids delivered to the heart tissue

A

Medtronic: drug sits inside electrode

Developed: drug eluding collars (outside of electrode)

50
Q

what is Elast-Eon

A

copolymer of Si and PU

51
Q

What are some of the current research developments for pacemakers?

A 
Remote monitoring, 
MRI compatible pacemakers, 
New algorithms (heart failure), 
Stimulation via ultrasound, 
Miniaturisation
52
Q

what are some considerations for leadless pacemakers

A

implantation complication: venous access, embolation, perforation

retrival/extraction of chronic devices

implantation of multiple devices

rate response characteristics

b5995 (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions