1
Q
pacemakers
A
deliver electrical stimulus to cardiac tissue triggering depolarization and contraction
2
Q
categories of pacemakers
A
- temporary or permanent pacemaker
- types of temporary pacemakers
- types of pacing
3
Q
permanent pacemakers
A
- used when pts experience permanent and hemodynamic-compromising bradydysrhythmias
- implanted under the skin and SC tissue in the upper chest area or upper abdomen
4
Q
leadless pacemaker
A
implanted directly into heart with no separate incision under skin
5
Q
temporary pacemakers
A
- used in emergency situations or when the bradydysrhythmias are believed to be transient
- most is external to pt
6
Q
type of temporary pacemakers
A
- transvenous (via lead inserted through large vein into the heart)
- transcutaneous (via electrode pads attached to chest wall)
- epicardial (via temporary, fine wires that are attached to the epicardium placed during open heart surgery)
7
Q
how can pacemakers pace the heart?
A
- single-chamber pacing, where one chamber of the heart is paced (i.e., ventricle or atria)
- dual-chamber pacing, where two chambers of the heart are paced (i.e., ventricle and atria)
8
Q
indications for pacemaker therapy
A
to manage select cardiac dysrhythmias and to enhance cardiac output
9
Q
indications for pacing
A
- sinus brady or arrest
- AV blocks
- MI or ischemia that results in AV blocks or dysrhythmias
- post-cardiac surgery that disrupts conduction
- sick sinus syndrome
- tachydysrhythmias where there is an unnaturally fast rate)
10
Q
what does the pacemaker system comprise of?
A
pulse generator (power source) and one or more pacing leads; with permanent, both are internal; when external pacemakers, a connecting cable is needed
11
Q
what does the pulse generator do?
A
- generate electrical impulses when heart doesn’t generate its own impulse or fires at a low rate
- also capable of sensing the heart’s intrinsic electrical impulses or rhythm
12
Q
the electrical impulse generated by the ____ is transmitted via ______ which are in direct contact with ______
A
pulse generator; the pacing leads; either the atrial or ventricular chambers (single chamber) or both (dual chamber)
13
Q
can dual chamber pulse generator be used for both single or dual chamber pacing?
A
yes
14
Q
components of pulse generators
A
- on/off switch
- pulse generator cover
- sense/pace lights
15
Q
sense light versus pace light
A
sense light is normally orange and lights up when pacemaker senses an intrinsic depolarization
pace light is normally green and is activated when the pacemaker emits an impulse to pace
16
Q
pacemaker settings
A
-HR: set according to pt’s needs to maintain adequate CO; usually 60-80bpm; measured as pulses/min to distinguish between intrinsic HR and artificially generated ones
- output or mA
- sensitivity (mV)
- demand (or synchronous) pacing
17
Q
output or mA
A
- strength of the electrical impulse delivered to the cardiac tissue to initiate a depolarization (measured in mA)
- appropriate mA or output levels are determined by increasing the mA while watching the patient’s ECG, looking for evidence of paced beats
18
Q
pacing threshold
A
Once a paced rhythm is achieved, the output level is noted
19
Q
what is mA usually set at?
A
~2 to 3 times the pacing threshold, allowing for changes in the pacing threshold
20
Q
sensitivity
A
the amount of electrical activity that needs to be generated during a patient’s intrinsic depolarization for the pacemaker to sense it (measured in mV)
21
Q
why is sensitivity an important setting?
A
- it allows the pacemaker to work in sync with the pt’s own electrical activity
- when pacemaker senses the pt’s intrinsic cardiac activity, it will respond in a pre-programmed manner—usually by inhibiting itself from firing, which avoids issues such as firing on a patient’s T wave
22
Q
what if the mV setting is higher?
A
the larger the amount of electrical activity the heart has to generate during its intrinsic depolarization for the pacemaker to recognize it
23
Q
high mV settings indicate?
A
pacemaker is less sensitive to pt’s intrinsic activity
24
Q
low mV settings indicate?
A
pacemaker is more sensitive to pt’s activity
25
sensing threshold
the level of mV at which the pacemaker can sense the patient’s intrinsic activity
26
how do you decide on an appropriate setting for sensitivity?
determine sensing threshold and set it at half of that level
27
demand or synchronous pacing
- when a pacemaker’s sensitivity setting allows it to sense the pt’s intrinsic activity (and respond to that sensed activity by inhibiting itself from firing)
- preferred method
28
fixed or asynchronous pacing
- pacemaker does not respond to any intrinsic heart activity even if it is occurring
- typically used in emergency situations or if the patient is known to have no underlying heart rate
29
pacing lead
- carries “sensed” info from the heart to the pulse generator
- has a positive and a negative electrode
- current flows from negative connector to negative electrode and travels back via positive
30
what is the most common route for temporary pacing?
transvenous
31
which veins is transvenous pacing lead threaded through?
femoral, subclavian, IJ
32
what is important about insertion? what does the nurse do?
- CVC must be inserted first
- comfort, supine, meds to help relax, continuous ECG monitoring + VS
- ensure pacing lead and pulse generator secured to prevent dislodgement
33
what is most commonly used in emergency situations and why?
transcutaneous approach b/c its non-invasive, does not require central line access, and can be initiated quickly
34
where do the electrode pads go for transcutaneous pacing?
chest wall; similar to where pads go for defib
35
what is the physiology of transcutaneous pacing?
an electrical impulse is generated by an external pulse generator to depolarize the cardiac cells. This impulse is transmitted through the chest wall to the heart via skin contact pads
36
what is important to ensure with transcutaneous pacing and why?
patient comfort through analgesia or sedation b/c:
- electrical energy or output (mA) required in transcutaneous pacing tends to be larger than with transvenous pacing because it has to travel through the patient’s chest wall before it can depolarize cardiac cells
- larger mA also depolarizes the skeletal chest muscle tissue
- pt will experience skeletal muscle contractions at the set rate of the transcutaneous pacemaker = very painful
37
nursing considerations when initiating transcutaneous pacing
- clipping excess hair for placement of pads
- placing pads on clean, dry skin
- keeping pt in supine
- giving meds to help pt relax and warn them of discomfort
- following doctor's orders for settings based on pt response to therapy
38
what does the rate default the capture to on the monitor?
70mA; can change it by turning dial clockwise (normal range for capture is 40-80mA)
39
what will happen when you obtain capture?
you will overshoot pt's threshold and need to turn down output; decrease output slowly until you just lose capture
40
what is the patient's threshold?
minimum output that obtains capture
41
what do you do with output once pacing is determined?
set output to 10% above that threshold
42
how can mechanical capture be confirmed?
by physically palpating a femoral or R radial brachial pulse (avoid ax carotid/L radial arteries, muscular contractions from pacing pulse may cause misinterpretation)
43
nursing considerations when monitoring transcutaneous pacing are?
- checking pacing pads to ensure they're not drying out and losing contact with the skin surface
- repositioning pt but making sure they do not get up and walk around as this could disrupt lead contact
- ensuring pt comfort, particularly if they are experiencing skeletal muscle contraction with pacing stimulus
- monitoring ECG waveform, VS, and pt’s condition to ensure adequate and effective pacing
44
what does the NBG code convey info about?
the pacemaker’s pacing, sensing, and response functions. It applies to both temporary and permanent pacemakers
44
how many letters are important in temp pacemaking vs permanent?
3 letters in temp; 5 in permanenet
45
what do the first three letters of the NBG code stand for?
1 = heart chamber(s) paced
2 = heart chamber(s) where intrinsic electrical activity is sensed
3 = pacemaker's response when it senses intrinsic electrical activity
46
what does letter four and five stand for?
4 = capacity for rate modulation
5 = multisite pacing
47
1 = chamber paced
2 = chamber sensed
A: atrium
V: ventricle
D: Dual (A or V)
0 = none
48
3 = response to sensing
I: Inhibited
T: Triggered
D: Dual (inhibited & triggered)
0 = none
49
atrial pacing is achieved by? and may be used when?
placing a pacing lead in the right atria; when SA node is diseased or damaged by requires normal conduction through AV node and ventricles
50
why is atrial pacing rarely used in transvenous pacemakers?
- pacing lead is large, risk of perfing the thinner atrial walls = cardiac tamponade
- difficult to keep pacing lead secured situated in the atria
51
what is the common NBG code in atrial pacing?
AAI
- pacemaker pacing atria
- senses intrinsic electrical activity in atria
- will be inhibited from firing when it senses intrinsic activity
52
ventricular pacing in a transvenous pacemaker requires?
placement of a pacing lead in the right ventricle; most common site for transvenous placing
53
common NGB code for ventricular pacing is ?
VVI
- pacemaker is pacing ventricle
- senses intrinsic electrical activity in ventricle
- inhibited from firing when it senses intrinsic activity
54
what is important to recognize in VVI pacing about the pacemaker?
it does not communicate with the atria as lead is in the ventricle = pacemaker is unaware of atrial depolarization and has no way of coordinating or synchronizing paced ventricular activity with the pt’s intrinsic atrial activity = asynchronous contraction of the atria and ventricles = decrease in atrial kick, preload and CO
55
what does electrical discharge from a cardiac pacemaker produce on an ECG strip?
spike or artifact
56
a pacemaker with a lead placed in the atria shows what on an ECG?
spike followed by a P wave
57
a pacemaker with a lead placed in the ventricle shows what on an ECG?
spike followed by a QRS complex that is wide and bizarre b/c ventricular depolarization from pacing does not follow the normal conduction pathway
58
common pacemaker malfunctions
- failure to pace
- failure to capture
- inappropriate sensing
59
what is failure to pace and how would it look on an ECG strip?
failure of the pulse generator to emit an electrical impulse; would see no pacer spikes on ECG strip
60
causes of failure to pace
- low battery power in pulse generator
- circuitry failure
- overall malfunction in pacemaker
- broken pacing lead *light will still flash
- disconnection in system *light will still flash
61
troubleshooting failure to pace
1. assess battery strength and fx of pulse generator
2. check connections between pulse generator, connecting cable and pacing wire
3. consider # in pacer wire
4. notify doctor, if pt symptomatic = emergency
62
what is failure to capture and how does it show on an ECG strip?
- occurs when the electrical impulse is emitted from the pulse generator but fails to depolarize the myocardium
- will see a spike alone/without a waveform (not follow by P or QRS)
63
causes of failure to capture
can be caused by anything that increases the difficulty of the electrical impulse delivered from the pulse generator to induce depolarization of the cardiac cells
- acidosis, electrolyte imbalance, and myocardial ischemia, or can be pacer-related issues, such as a mispositioned pacer leading to poor contact with the chamber tissue or inadequate mA (output) setting
64
troubleshooting failure to capture
1. reposition pt in attempt to float pacing lead closer to interior chamber walls
2. increase output setting on pulse gen until capture is achieved.
3. review pt info for evidence of pt-related issues and intervene accordingly
4. notify doctor
65
inappropriate sensing or failure to sense
consists of oversensing and undersensing
66
oversensing
- occurs when the pacemaker senses extraneous, non-cardiac electrical signals ie) muscle tremors cause pacemaker to be inappropriately inhibited or triggered
- pacemaker is too sensitive
67
oversensing on an ECG strip
- may be present where pacing should have occurred (will see long pauses)
- can look like failure to pace
68
how to differentiate oversensing from failure to pace?
alter the sensitivity setting and watch the response on the patient’s ECG. To decrease the sensitivity setting, increase the mV. This means that a larger amount of electrical activity is required for the pacemaker to become aware of intrinsic electrical activity. If normal pacer function is restored, then the issue was oversensing
69
undersensing
- pacemaker is too insensitive
- sensitivity setting requires larger intrinsic electrical activity for the pacemaker to recognize it
- high possibility of pt's intrinsic activity not being sensed
- puts pt at risk of R-on-T phenomenon
70
R-on-T phenomenon
- occurs when a pacing stimulus is delivered during the downslope of the T wave, when the heart is in the relative refractory period and is not fully repolarized but is capable of responding to a stimulus
- can precipitate life-threatening dysrhythmias
71
how will undersensing show on ECG?
pacer spikes are out of place; may occur in middle of QRS complex or immediately after an intrinsic beat
72
causes of undersensing
- inappropriate sensitivity settings *troubleshoot by adjusting sensitivity setting
- lead displacement
- loose cable connections
73
what's different about a paced QRS and regular QRS?
paced QRS is wide and bizarre
74
how do you name a paced rhythm?
examples:
- ventricular pacing with failure to capture (sixth beat)
- ventricular pacing with failure to sense
- atrial pacing with six-second period of failure to pace
- sinus rhythm with occasional ventricular-paced beats
- ventricular-paced rhythm with occasional intrinsic beats
75
failure to pace interventions
- Check pt (ABC)
- Change pulse generator battery
- Check all connections.
- Check the integrity of pacing leads
- Call doctor
76
failure to capture interventions
- Check pt (ABC)
- Check cable connections.
- Reposition pt to ensure pacing lead has contact with the heart.
- Increase output (mA) if in line with agency’s policy.
- Call the doctor if needed
77
failure to sense interventions
- Check pt (ABC).
- Adjust sensitivity (mV).
- Eliminate electrical interference
- Reposition pt to ensure pacing lead is in contact with heart
