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Year 3 Cardiac physiology > CRM 1, 2, 3 - Introduction, Fundamental Basics, Devices and Leads > Flashcards

CRM 1, 2, 3 - Introduction, Fundamental Basics, Devices and Leads Flashcards

1
Q

What does ICD stand for?

A

-Implantable Cardioverter Defibrillator

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2
Q

Functions of device (pacemaker)

A

-Surgically implanted device which emits electrical signals to treat bradycardia
-Monitors intrinsic and paced beats
-Controls timing and system operations

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3
Q

Functions of device (ICD)

A

-Has capacitance to hold a high energy charge and is able to deliver a defibrillation shock
-ICD may form part of the shock vector (active can)

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4
Q

Functions of leads

A

-Acts as a conductor
-Deliver electrical stimuli from the impulse generator to the myocardium
-Carries intrinsic signals from the heart to the impulse generator
-Form part of shock vector (in ICD)

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5
Q

What are the different types of leads?

A

-Transvenous intracardiac
-Epicardial
-Coronary sinus
-Leadless

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6
Q

What type of rhythms would we think about pacing?

A

-Bradycardias

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7
Q

What rhythms would we think about shocking?

A

-VF

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8
Q

What are CRT (cardiac resynchronisation therapy) devices used for?

A

-Heart failure

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9
Q

Brief description of pacemaker

A

-Implanted electronic device
-That emits impulses to treat bradycardias

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10
Q

Brief description of ICD

A

-Implanted device
-Delivers anti-tachy pacing and shock therapy for ventricular arrhythmias
-Also treats bradycardias

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11
Q

Brief description of CRT

A

-Implanted device
-Treats heart failure by correcting electrical discordance by pacing both right and left ventricles

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12
Q

What happens at the anode?

A

-Electrons leave and move away

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13
Q

What happens at the cathode?

A

-Electrons enter or come towards

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14
Q

When does current flow?

A

-Only flows in a closed circuit

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15
Q

Describe electron and current flow

A

-Electrons flow from the negative pole to the positive pole
-Current flows from the positive pole to the negative pole

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16
Q

How does battery in pacemaker produce electricity to stimulate the heart?

A

-The battery has a positive and negative pole
-A chemical reaction between electrolytes produces an electron flow (energy)

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17
Q

What happens as battery ages?

A

-The oxidative and reductive processes between the electrolyte and the electrodes causes the internal resistance to increase

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18
Q

What type of battery do pacemakers use?

A

-Lithium-Iodine battery

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19
Q

What is the load in a pacemaker battery?

A

-The endocardium of the ventricle

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20
Q

Anode and cathode in load/battery

A

Load:
Anode = positive
Cathode = negative

Battery:
Anode = negative
Cathode = positive

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21
Q

How are electrons formed in a pacemaker battery?

A

Battery:
-Oxidation occurs at the anode
-Each atom of Li loses one electron
2Li -> 2Li+ + 2e-

-Reduction occurs at the cathode
-Each molecule of I combines with 2 electrons
I2 + 2e- -> 2I-

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22
Q

How does a pacemaker battery work?

A

-At the anode of the battery, electrons are released from lithium atoms - to form Li+ ions
-The electrons repel each other and are pushed outside of the battery and become the electrical flow (circuit)
-The electrons enter the cathode where they combine with iodine to form 2I- ions
-The positive lithium and negative iodine ions combine to form lithium iodide
-Lithium iodide is a poor conductor - the build-up of LiI increases the internal resistance of the battery over time

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23
Q

What can act as the anode in a pacemaker battery?

A

-The can (which contains the battery)
-The proximal pole on the pacing lead

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24
Q

What direction do electrons flow between anode and cathode?

A

-Electrons leave the anode (AWAY)
-Electrons enter the cathode (COME)

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25
Q

Where do leads for dual chamber ICD go?

A

-Right atrium
-Right ventricle

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26
Q

Unipolar vs Bipolar

A

Unipolar:
-Big circuit
-Anode is in can, Cathode in wire

Bipolar:
-Small circuit
-Anode and Cathode in wire

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27
Q

Voltage formula

A

V = IR

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28
Q

What is loss of capture?

A

-Pacing spike followed by no depolarisation

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29
Q

What is capture?

A

-Pacing spike followed by something

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30
Q

Explain pacing pulse width and height

A

Pulse duration = width
Voltage = height
Pulse duration x height = total amount of energy

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31
Q

What is the pacing threshold?

A

-The minimum amount of energy contained within the pulse width and voltage that is needed to pace the heart

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32
Q

What does pacing right ventricle look like on ECG?

A

-LBBB

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33
Q

What does pacing left ventricle look like on ECG?

A

-RBBB

34
Q

LBBB on ECG

A

-Negative in V1
-Positive in V6

35
Q

RBBB on ECG

A

-Positive in V1
-Negative in V6

36
Q

Why does Right ventricle pacing look like LBBB?

A

-In LBBB, left side is blocked so right side is depolarised first
-Right side is depolarised first in RV pacing

37
Q

What should you look out for during RV pacing

A

-Whether catheter has gone into LV
-Will look like RBBB

38
Q

What is the threshold test?

A

-Lowest voltage that produces capture
-Must state units (mV and mS)

39
Q

What are rheobase and chronaxie?

A

Rheobase
-Lowest stimulation voltage at any pulse width
Chronaxie
-Pulse duration at twice the rheobase
(Anything above the curve will be captured)

40
Q

What do we program the pacing device to?

A

2 x pulse amplitude (volts) (most common)
3 x pulse width (ms)

41
Q

Why shouldn’t pacemaker sense T waves

A

-It might think T waves are QRS complexes and reset timer for pacing

42
Q

What do we want to/not want to sense?

A

+ atrial depolarisation
+Ventricular depolarisation
-Noise
-T waves
-Myopotential

43
Q

What would happen if RV lead fell into the RA

A

-It would sense P waves as QRS complexes
-As a result, it would not pace

44
Q

Benefits of sensing

A

-No inappropriate pacing
-Saves battery
-Reduces risk of arrhythmias
-Allows intrinsic arrhythmias/ectopics to be identified/measured

45
Q

Which is the most/least sensitive?

A

-Most sensitive = right (little number)
-Least sensitive = left

46
Q

Components of a pacemaker

A

-Can - casing
-Header - connector
-Battery - power source
-Diodes/resistors/microchips/oscillators

47
Q

Components of CRT/ICD

A
48
Q

Describe the can and header in a pacemaker

A

-Hermetically sealed
-Titanium - biocompatible, light, strong
-Houses all the components
-Protects the components and the lead connectors from bodily fluids
-Can act as a conductor (e.g. in unipolar pacing configurations, as part of the shocking vector in ICDs
-Leads are attached via the header

49
Q

Function of diodes and resistors

A

-Manage current flow and direction
-Restricts/limits the flow of current

50
Q

Function of crystal oscillator

A

-time clock for timing cycles

51
Q

Function of microchip

A

-A mini computer for sensing, pacing, memory, demographics, programmable algorithms
-Can have uploads via a programmer

52
Q

Function of sensors

A

-Used in rate response
E.g.
-Piezoelectric crystal
-Accelerometer

Metabolic sensors:
-minute ventilation
-QT
-temperature

53
Q

Function of battery

A

-Provides energy

54
Q

Function of capacitor

A

-ICD component
-Charges up
-Holds charge for shock therapy of VF

55
Q

What type of battery is used in ICD?

A

-Vanadium iodide

56
Q

What type of battery is used in pacemaker

A

-Lithium iodide

57
Q

Why do pacemaker batteries use lithium iodide?

A

-High electrochemical potential
-High energy density - powerful
-Low cost
-Lightweight
-Predictable discharge and predictable impedance rise as it ages

58
Q

What happens to lithium battery as it ages?

A

-It gets coated as it ages
-The more coating, the higher the impedance

59
Q

What does ERI stand for?

A

Elective Replacement indicator (low battery)

60
Q

What does EOL stand for?

A

End Of Life (no battery)

61
Q

What impacts battery life?

A

-Type
-Discharge
-Consumption
-Tissue resistance (Higher resistance, battery lasts longer)
-Use

62
Q

Battery life expectancy equation

A

-Battery capacity / Current drain expressed in ampere hours

63
Q

Example of battery life equation

A

-Convert to same units
-Convert hours to years

64
Q

What type of battery in ICD?

A

Lithium Silver Vanadium
-Large charge stored in a small volume
-Distinctive discharge curve - ERI has a distinct ‘point’

65
Q

Features of ICD leads

A

Insulation:
-Prevents electrical current escaping to the tissue, protects conductor from corrosion
-Separates conductors in bipolar and ICD leads

Conductor:
-Carries electrical impulse to the heart and carries intracardiac signals to the device.
-In ICDs - delivers shock therapy

Connector:
-Attaches the pacing lead to the impulse generator and assures safe transmission of current without electrical leakage

Lead electrodes:
-Deliver the impulse and record intracardiac signals. Are part of the shock vector in ICD

Distal tip electrode - Cathode
Proximal ring electrode - Anode

66
Q

What are the black dots?

A

Electrodes
-Gives options to pace across different areas

67
Q

Features of pacing/shocking leads

A

-Flexible
-Strong - subjected to loading forces
-Reliable - Perform continuously in a hostile environment
-Biocompatible - must not be rejected or cause clots
-Insulated - electrical conductive wires must be insulated
-Thin - to pass down a vein

68
Q

Features of the conductor

A

-Thin
-Nickel or silver alloy
-Low resistance to electrical current
-Corrosion resistant
-Flexible and durable

69
Q

Features of connector

A

-Attaches pacing lead to the impulse generator/device
-Assures safe transmission of current and intracardiac signals without current leakage
-Different connectors for different systems

70
Q

Different types of connector

A

IS-1 International Standard 1
DF-1 Defibrillation lead 1-3 connectors
DF-4 Defibrillation - 1 connector

71
Q

Features of IS-1 connector

A

-3.2mm short pin, sealing rings
-Can be bipolar or unipolar - bipolar will have a terminal ring (anode) and a second lead sealing ring
-Can be bipolar or unipolar - the ‘modern’ lead for pacemaker systems

72
Q

Advantages/disadvantages of polyurethane and silicone as leads

A
73
Q

What are the different methods of implantation for a pacemaker

A

-Transvenous - introduced to the RV or RA via a vein (cephalic, subclavian)

-Epicardial - placed directly on the heart on the epicardium (Thoracotomy surgery)

74
Q

Polarity in unipolar and bipolar circuits

A

Unipolar:
-Tip of lead is negative pole
-Can is positive pole

Bipolar:
-2 poles on lead itself
-Proximal pole ring (positive)
-Distal pole tip (negative)

75
Q

Advantages/disadvantages of unipolar/bipolar circuits

A
76
Q

What are the different types of lead electrode fixation?

A

Passive - placed in the endocardium without penetrating the muscle - tined

Active - fixated into the muscle - helix, corkscrew

77
Q

Advantages/disadvantages of active/passive fixation

A
78
Q

Length of atrial leads vs ventricular leads

A

-Atrial leads are shorter than ventricular leads
-Atrial leads = 52-53cm
-Ventricular leads = 58-59cm

79
Q

What is special about coronary sinus/left ventricle leads?

A

-They can have multiple poles for pacing
-This is to ensure LV capture

80
Q

Why are leads steroid eluting?

A

-Stops acute threshold rise
-Slow release, suppresses inflammation

Year 3 Cardiac physiology (30 decks)

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