Pacemakers Flashcards
a pacemaker consists of a ___ generator and pacing ___ that deliver electrical current to the heart
Pulse generator and pacing leads
Position 1 pacemaker
chamber paced
position 2 pacemaker
chamber sensed
position 3 pacemaker
response to sensed native cardiac activity
position 4 pacemaker
programability options
position 5 pacemaker
indicates the pacemaker can pace multiple sites
circuit board (“hybrid”)
The pulse generator processes electrical info from the heart, and it responds to these signals based on the programmed settings
Where is the atrial lead positioned?
lodges in the right atrial appendage
Where is the ventricular lead positioned?
lodges in the apex of the right ventricle
What are the indications for pacemaker insertion?
SA node disease
AV node disease
Long QT syndrome
Dilated cardiomyopathy
Hypertrophic obstructive cardiomyopathy
What is the mnemonic that can be memorized to remember the 5 letter code of pacemakers?
PaSeR
Pa= chamber PAced
Se= chamber SEnsed
R= Response
pacemaker position 1 codes
O= none
A= atrium
V= ventricle
D= dual (A+V)
Chamber that is paced
pacemaker position 2 codes
O= none
A= Atrium
V= ventricle
D= dual (A+V)
chamber that is sensed
pacemaker position 3 codes
O= none
T= triggered (sensed activity tells the pacemaker TO fire
I= inhibited (sensed activity tells the pacemaker NOT to fire)
D= dual (T+I) (if native activity is sensed, then pacing is inhibited, if native activity is not sensed, then the pacemaker fires)
- Example: a sensed intrinsic atrial beat will inhibit atrial pacing output and will trigger ventricular pacing
pacemaker position 4 codes
O= none
R= rate modulation
This indicates the programmability of the pacemaker. This describes the ability to adjust heart rate in response to physiologic needs. Sensors can measure respiration, acid-base status vibration ect.
(will increase the pacer’s lower heart rate limit in response to activity that may require an increased myocardial oxygen demand)
pacemaker position 5 codes
O= none
A= atrium
V= ventricle
D= dual (A+V)
This indicates that the pacemaker can pace multiple sites
(pacer may pace BOTH atria and/or BOTH ventricles)
What will you see ok the EKG with atrial pacing?
A pacing spike preceded the P wave, QRS is normal
What will you see ok the EKG with ventricular pacing?
A pacing spike precedes the QRS complex. The QRS is wide
What will you see ok the EKG with atrial + ventricular pacing?
There’s a pacing spike that stimulates the atria and another that stimulates the ventricles.
Examples of Asynchronous pacing
AOO
VOO
DOO
examples of single-chamber demand pacing
AAI
VVI
examples of dual-chamber AV sequential demand pacing
DDD
What does the pacer do in asynchronous pacing?
The pacemaker delivers a constant rate
There is no sense or inhibition
There can be a competitive underlying rhythm
A pacer spike delivered during ventricular Repolarization can result on R on T
What does the pacer do in Single-chamber demand pacing?
Think of this as a backup mode- it only fires when the native heart rate falls below a predetermined rate
What does the pacer do in a dual chamber AV sequential demand pacing?
The most flexible and most common
Makes sure the atrium contracts first, followed by the ventricle
This improves AV synchrony
Failure to capture:
when the pacemaker’s electrical output fails to cause myocardial depolarization
On the EKG you’ll see pacing spikes but they aren’t followed by a QRS complex (ventricular depolarization)
Failure to sense:
the pacemaker fails to recognize intrinsic cardiac electrical activity
Indications for ICD
Ventricular tachycardia
Ventricular fibrillation
Post MI with an EF <30%
Cardiomyopathy with an EF <35%
Hypertrophic
cardiomyopathy
Awaiting a heart transplant
Long QT syndrome
A patient undergoing bunionectomy has a VOO pacemaker with a rate of 80 bpm. During the procedure, there is failure to capture and the heart rate decreases to 50 bpm. Which of the following best explains why this complication occurred
A.) the EtCO2 was 20 mmHg
B.) an ultrasonic harmonic scalpel was used
C.) the patient was hyperthermic
D.) the electrocautery setting was changed from coagulation to cutting
A.) the EtCO2 was 20 mmHg
The pacemaker failed to capture bc hypocarbia (which caused hypokalemia) made the myocardium more resistant to depolarization. The same electrical stimulus from the pacemaker was no longer sufficient to depolarize the heart. You’ll see pacer spikes but will not see capture.
What does placing a magnet over a pacemaker do?
(Usually) converts the pacemaker to asynchronous mode
What does placing a magnet over a ICD do?
Suspends the ICD and prevents shock delivered
What does placing a magnet over a pacemaker + ICD do?
Suspends the ICD and prevents shock delivery. It has no effects on the pacemaker function.
Pacemaker function will be subject to EMI. If EMI is likely, then the pacemaker should be reprogrammed by the manufacturer before the surgical procedure
What conditions can impair pacemaker performance?
EMI (electromagnetic interference)
conditions that make the myocardium more resistant to depolarization:
hyper/hypokalemia
Hypocapnia
hypothermia
If surgical electrocautery is used, the best option for the surgeon to use a ______ device
bipolar device
T/F: MRI is typically contraindicated for a pt with a pacemaker or ICD
TRUE (some newer devices may be compatible)
The most critical information to have preoperatively about a pt with a pacemaker:
The pt’s underlying rhythm - so you know how to prepare for device failure
How is pacemaker failure treated?
Isoproterenol
Epinephrine
Atropine
(all depending on underlying rhythm)