Pacemakers Flashcards
(108 cards)
1
Q
Methods for temporary cardiac pacing
A
- Transcutaneous
- Transesophageal
- Transvenous
- Epicardial
2
Q
Preferred pacing method in an emergency
A
Transcutaneous
3
Q
Disadvantages to transcutaneous pacing
A
- It’s painful
- Least effective capture (40-80 mA)
- Ventricular only pacing
4
Q
Placement options for transesophageal pacing
A
- Have pt swallow pill electrode that is connected to a pacing wire
- Insert a flexible catheter connected to a pacing wire
5
Q
Disadvantages to transesophageal pacing
A
- Only paces the atria
- Requires relatively high current for capture (>20mA)
- Is uncomfortable and requires sedation if possible
6
Q
Advantage of transesophageal pacing
A
No need for x-rays or cath lab
7
Q
When is temporary transvenous pacing indicated?
A
If a patient is stable or if transcutaneous pacing isn’t working
8
Q
How is the pacing function of the temporary transvenous pacing controlled?
A
Through an external pacemaker box
9
Q
Why does temporary transvenous pacing take longer?
A
It requires central line placement and leads to be placed through the central line
10
Q
Advantages to temporary transvenous placement
A
- A provider can place atrial and ventricular leads
- Provides more effective capture
- Does not require as much energy for capture (1.5-3mA)
11
Q
Disadvantages to temporary transvenous placement
A
- More time consuming
2. Requires expert placement
12
Q
What is epicardial pacing?
A
- Leads are sewn into myocardium when chest is open during cardiac surgery
- Pacing is controlled through external pacemaker box
13
Q
Permanent pacemaker consisting of a pulse generator that is connected to pacing wires that have been inserted into the heart via the subclavian vein
A
Cardiovascular implantable electronic device (CIED)
14
Q
3 types of CIEDs
A
- Pacemakers
- Automated implantable cardioverter defibrillators (ICDs)
- Chronic resynchronization therapy (CRT or biventricular pacemakers)
15
Q
2 primary reasons for a patient to receive a pacemaker
A
- To pace patients with slow heart rates
2. To improve the timing of atrial and ventricular beats in patients with complete heart block
16
Q
Can provide pacing, synchronized cardioversion and antitachycardia pacing in addition to defibrillation
A
Intravascular ICDs
17
Q
Indicated only for defibrillation
A
Subcutaneous ICDs
18
Q
Improves ventricular synchrony in pts with HF with 2 ventricular leads
A
Biventricular pacemakers (CRT)
19
Q
What should you do when they test the ICD?
A
Give a small propofol bolus prior to shock
20
Q
Refers to cardiac cells responding to pacemaker stimulation
A
Capture
21
Q
Refers to minimum current level at which capture is observed
A
Pacing threshold
22
Q
Normal capture for transvenous/epicardial approach
A
1.5-3mA
23
Q
Normal capture for transcutaneous approach
A
40-80 mA
24
Q
Current at which the pacemaker maintains capture
A
Maintenance threshold
25
How do you determine the maintenance threshold?
At least 10% higher than the pacing threshold
26
How sensitive the pacemaker is to sensing electrical activity within the heart
Sensitivity threshold
27
If pacemaker sensitivity is too high,
it may not pace as much as it should
28
If pacemaker sensitivity is too low,
it may pace when it is not supposed to
29
Pace at which the pacemaker is typically programmed
60 bpm
30
How can you tell if a heart beat comes from a pacemaker?
If there is a pacer spike prior to a P wave or QRS complex
31
True/false. If a patient has a pacemaker, the SA node can still initiate heart beats
True
32
Why is it dangerous to have 2 potential sources of heart beats?
If the R wave occurs during the time that a T wave should occur (R on T phenomenon), it can lead to vfib/vtach
33
Pacing mode that ensures only one source is providing current to the heart at a given time through sensing
Demand mode
34
When does the pacemaker initiate heart beats in demand mode?
If the HR is too low
35
What happens to a demand pacemaker during cautery?
It will stop pacing as it senses surgical cautery to be electrical activity of the heart
36
When is a patient pacemaker dependent?
If the rely on their pacemaker to have normal cardiac output
37
When the pacemaker cannot sense anything, and is therefore constantly pacing
Asynchronous mode
38
Advantage of asynchronous mode
The pacemaker will not stop pacing during cautery, preventing cautery induced bradycardia
39
Disadvantage of asynchronous mode
Can lead to R on T phenomenon if the paced rate is slower than the intrinsic rate
40
How to prevent R on T phenomenon with asynchronous mode
Ensure the paced rate is greater than the intrinsic rate
41
How can the anesthetist ensure the pt's intrinsic rate is slower than what the asynchronous rate would be?
Give beta blockers
42
When should the pacemaker be converted to asynchronous mode?
If the pt was experiencing clinically significant and prolonged cautery induced bradycardia
43
How does the pacemaker get converted to asynchronous mode?
The anesthetist can place a magnet over it or the pacemaker rep can reprogram it prior to surgery
44
Programmed to increase the paced HR whenever it senses increases in movement and/or minute ventilation
Rate modulation
45
Terminates tachycardia by pacing faster than the intrinsic rate
Antitachycardia pacing
46
When is antitachycardia pacing effective?
For afib, aflutter, SVT and monomorphic vtach
47
When does the pacemaker shock the heart with antitachycardia pacing?
If several attempts at ATP prove ineffective
48
Indications for a pacemaker
1. Sinus bradycardia
2. Sick sinus syndrome (malfunctioning SA node where SA node speeds up and slows down)
3. 3rd degree AV block
4. Mobitz Type II heart block
5. Afib with slow ventricular response
49
What type of pacemaker should be used for a patient with chronic bradycardia and/or sick sinus syndrome?
Atrial
50
What type of pacemaker should be used for a patient with afib with slow ventricular response?
Ventricular
51
What type of pacemaker should be used for a patient with complete heart block?
Dual chamber
52
A dual chamber pacemaker can fix complete heart block if:
1. The atrial lead senses when the atria contracts
| 2. The ventricular lead is programmed to pace 120-200 msec after the atria contracts
53
Significance of single chamber pacemaker for complete heart block
Sensing portion in R atrium and pacing portion in ventricle
| -No atrial pacing spikes because there is no atrial lead
54
Where is the L ventricular lead inserted for the biventricular pacemaker?
Via the coronary sinus with the aid of fluoroscopy
55
Why is an additional lead in the L ventricle helpful?
In advanced HF, RBBB, LBBB, the R and L ventricles can be out of sync when they contract, leading to decreased CO
- Improves SV and CO
- Decreased myocardial oxygen demand
56
Why are ICDs dangerous?
They can be inappropriately triggered to shock whenever cautery is used
57
Energy used to shock arrhythmias with ICDs
15-35J
58
How to prevent accidental shock from an ICD during surgery
1. Disable the shock function of the ICD, either with pacemaker rep or place a magnet over it in the OR
2. Keep electrical current away from the ICD (use harmonic scalpel or bipolar cautery)
59
Advantages to harmonic scalpel
1. Cuts thicker tissue than bovie
2. Less smoke
3. Less thermal damage
60
Disadvantages to harmonic scalpel
1. Takes longer to cut and coagulate tissue
| 2. Can only coagulate as it cuts
61
How does a magnet affect ICDs
1. It disables the shock function only
| 2. Does not convert to asynchronous mode
62
Can cautery induced bradycardia still occur in pacemaker dependent patients despite magnet placement?
Yes, if they have an ICD
63
When does the shock function NOT have to be disabled?
If the surgical site is below the umbilicus
64
Advantages to subcutaneous ICD
- Less risk compared to intravascular leads
| - Effective as standard transvenous devices
65
Disadvantages to subcutaneous ICD
1. Not indicated in pts who require anti-bradycardia pacing, cardiac resynchronization therapy or antitachycardia pacing
2. Increased energy requirements
3. Not designed to treat ventricular arrhythmias at rates lower than 170 bpm
66
15 minute procedure that checks the function and battery life of a pacemaker
Pacemaker interrogation
67
How often should pacemakers be checked?
Every year
68
How often should ICDs be checked?
Every 6 months
69
What should you know preop about pacemakers?
1. What type of device (pacemaker vs ICD)
2. What is the programmability of the device?
3. Underlying rhythm?
4. Pacemaker dependent?
5. Rate modulation?
6. Capture effectively?
7. Magnet response?
8. Adequate battery life? (>3-6 months)
9. Manufacturer's perioperative recommendations
70
Supplies to be readily available if a patient has a pacemaker or ICD
1. External pacemaker with pacing pads
2. Magnet
3. Anti-bradycardia drugs
71
True/false. Devices should be interrogated and/or reprogrammed to original function after surgery
True, pts should not be discharged without their devices being interrogated
72
First letter of pacemaker classification
Which chambers have pacing leads
| A, V, D
73
Second letter of pacemaker classification
Which chambers can "sense" electrical activity
| A, V, D, O (O= none)
74
Third letter of pacemaker classification
How a pacemaker responds after it senses electrical activity
| I, D, T, O
75
Fourth letter of pacemaker classification
Programmability
76
Fifth letter of pacemaker classification
Antitachyarrhythmia function
77
What does the "I" mean in the third letter
The pacemaker will inhibit itself from pacing whenever it senses intrinsic/electrical activity in the heart (it is in demand mode)
78
What does the "T" mean in the 3rd letter?
The ventricular lead will be triggered to pace when it senses intrinsic/electrical activity (good in complete heart block or with biventricular pacemaker)
79
When the 2nd pacemaker letter is "O", the 3rd letter will always be:
O
80
3 letter pacemaker code for sinus bradycardia
AAI
81
3 letter pacemaker code for slow afib/a flutter
VVI
82
3 letter pacemaker code for AV block, normal sinus node
DDD or VDD
83
3 letter pacemaker code for AV block and sinus bradycardia
DDD
84
3 letter pacemaker code for sinus bradycardia with a magnet placed
AOO
85
What is contraindicated with CIED patients?
MRI
86
How do you avoid damage to the CIED during radiation?
Shield it as much as possible
87
Are ICDs or pacemakers more sensitive to radiation therapy interference?
ICDs
88
Precautions with radiofrequency ablation?
May be acceptable under direction of the attending physician
89
Precautions with emergency defibrillation
Place pads away from pacemaker
90
Precautions with transcutaneous electrical nerve stimulation
Can interfere with ICD resulting in inappropriate shock
91
Cardiovascular effects of ECT
After/during the shock, there is an initial parasympathetic discharge (10-15 sec) followed by a sympathetic response (3-5 min) where HR, BP and myocardial oxygen consumption all increase
92
Cerebral effects of ECT
Cerebral oxygen consumption, blood flow, and ICP increase
93
Anesthetics used for ECT
- Etomidate or Brevital
- Methohexital (not used commonly)
- Propofol
- Ketamine
94
Significance of etomidate for ECT
Longer seizure duration, but does not blunt the sympathetic response
95
Significance of propofol for ECT
Decreases seizure duration but does blunt the sympathetic response
96
Significance of ketamine for ECT
Long seizure duration when compared to barbiturates and propofol. ICP increases and can be concerning
97
Airway management for ECT
- Intubation is not required unless risk for reflux
- Ventilation can be assisted with face mask
- Hyperventilation lowers seizure threshold and prolongs seizure duration
98
Significance of NMBs for ECT
They reduce muscle convulsions and decrease risk of serious injury (succs is commonly used)
99
CIED implications for ECT
- Can be triggered by skeletal muscle potentials during seizures (low risk)
- Regular demand pacemakers should be converted to asynchronous mode if pt is pacemaker dependent
- Shock function of ICDs should be deactivated prior to therapy
100
Synchronized litho shock delivery
Triggered by R wave on EKG, delivered in refractory period
101
Advantage of synchronized litho shocks
Lower risk of causing PVCs/arrhythmias
102
Disadvantage of synchronized litho shocks
Procedure goes slower because it can only shock as fast as the heart rate
103
Advantage of non-synchronized litho shocks
Procedure goes faster
104
Disadvantage of non-synchronized litho shocks
More likely to cause PVCs/arrhythmias
105
Implications of CIEDs with lithotripsy
1. Can interpret shock same way as cautery is interpreted
2. In atrial paced patients with synchronized shocks, litho can perceive an atrial pacing spike as an R wave and deliver a shock prior to the R wave, causing arrhythmias
106
Management of lithotripsy in atrial paced patients
Avoid synchronized shocks
107
Management of lithotripsy in regular demand pacemakers
Place pacemaker in asynchronous mode
108
Management of lithotripsy in ICDs
Disable the shock function at minimum, but AHA recommends ESWL be avoided in these patients
