Pacemakers and ICDs Flashcards
Medical devices used to generate and deliver electrical impulses to the myocardium to stimulate a normal heartbeat
Artificial pacemakers
Some are external to body and provide temporary treatment, others are permanently implanted in the chest
Temporary pacemakers are ________
Transcutaneous
Delivers electrical impulses through lead wires to electrode pads applied to surface of patient’s chest (UNCOMFORTABLE)
Permanent pacemakers are implanted in ….
A surgically created pocket beneath the skin in the patient’s chest wall just below the clavicle
Components of permanent pacemakers
Generator
Lead wire(s)
Power source (ie lithium battery)
Logic circuits that detect cardiac electrical activity and determine the appropriate response
Conditions in which permanent pacemakers may be used
Symptomatic bradycardia
Sick sinus syndrome
Atrial fibrillation w/ bradycardia
3rd degree AV heart block
Symptomatic 2nd degree AV heart block type II
Sudden combo of AV block or BBB if patient has acute MI
Recurrent tachycardias (ICD only)
Synchronization of the heart beat in HF
What is the Indication Paradigm with regards to permanent pacemakers?
NON-reversible
SYMPTOMATIC
BRADYCARDIA
• Sinus node dysfunction
•2nd/3rd Degree AVB
•AVN ablation
Symptoms of Bradycardia
Syncope or pre-syncope Dizziness CHF Mental confusion Palpitations SOB Exercise intolerance FATIGUE (relentless)
Where are pacemaker electrodes positioned for single-chamber electrodes?
In the atrium or ventricle alone
Where are pacemaker electrodes positioned for duel-chamber pacemakers or AV sequential pacemakers?
In both the atrium and ventricle
How are permanent pacemakers programmed?
To receive and transmit data/programming instructions through the skin using electromagnetic waves
Adjustments can be made to output, sensitivity, refractory period, and rate adaption
What is the pacing mode for single-chamber pacemakers?
One pacing lead is inserted into either the right atrium or right ventricle but not both
What are pacing modes like for dual-chamber pacemakers?
Leads are placed into two chambers one lead paces atrium, other lead paces ventricle
By assisting the heart in coordinating the function between the chambers, it acts similarly to how the heart naturally paces itself
Most can be programmed to a single chamber mode (useful if atrial lead wire fails)
Which pacing mode is this:
Paces the heart at a single, preset rate
Fixed-rate
Which pacing mode is this:
Sensors identify increases or decreases in the patient’s physical activity and automatically adjusts base pacing rate to meet the body’s metabolic needs
Rate-responsive
Can boost HR in response to motion or increased respiration’s - good for those whose body cannot increase the HR during activity
Which pacing mode is this:
Most common type
Demand
Which pacing mode is this:
Fires only when the patient’s intrinsic HR falls below a given threshold level (ie 60 bpm)
Demand
Which pacing mode is this:
Parameters in which device will activate
Lower/Upper Rate Limits
Pacemaker mode and function are described by…
A 5-letter coding system (though in practice, only 3-4 are commonly used)
Pacemaker coding system:
1st letter: _______
2nd letter: _______
3rd letter: _______
4th letter: _______
5th letter: _______
The chamber being PACED
The chamber being SENSED
How the pacemaker generator RESPONDS to sensing
Whether the RATE-RESPONSE FEATURE is activated
Indicates multisite pacing (rarely used)
For the first letter of the pacemaker coding system, what letters are used and what do they mean?
Chamber being paced
O = none A = atrium V = ventricle D = dual (both atrium and ventricle)
For the second letter of the pacemaker coding system, what letters are used and what do they mean?
Chamber being sensed
O = none A = atrium V = ventricle D = dual
For the third letter of the pacemaker coding system, what letters are used and what do they mean?
How the pacemaker generator responds to sensing
O = none T = triggers pacing I = inhibits pacing D = dual (triggers and inhibits)
For the fourth letter of the pacemaker coding system, what letters are used and what do they mean?
Whether the rate-response feature is activated
O = none R = rate responsive
For the fifth letter of the pacemaker coding system, what letters are used and what do they mean?
Indicates multisite pacing
O = none A = atrium V = ventricle D = dual
What does this code mean:
VOO
Asynchronous ventricular pacing
• Ventricular pacing
• Ø sensing
• Ø response to sensing
Do to surgery where bovine used causes interference or applied magnet
DO NOT LEAVE PATIENT LIKE THIS
What does this code mean:
VVIR
Ventricular inhibitory pacing with rate modulation
• Ventricular pacing
• Ventricular sensing
• Inhibits ventricular pacing if activity sensed
• Rate-response active
Used for chronic afib patients, or those needing resynchronization (BIV)
What does this code mean:
AAI
Atrial inhibitory pacing, no rate modulation
• Atrial pacing
• Atrial sensing
• Inhibits atrial pacing if atrial activity sensed
Used for SA node dysfunction, normal AV conduction (not a common mode)
What does this code mean:
DDDR
Dual-chamber pacing • Dual pacing • Dual sensing • Dual response (inhibitors and triggers) • Rate modulating
AV sensed/AV pace/inhibited and triggered
What does this code mean:
DDI
Dual chamber pacing without atrial-synchronous ventricular-pacing
• Dual-paced
• Dual-sensed
• Inhibits ventricular pacing if ventricular activity sensed
Indicates pacemaker unable to “track” atrial rate to direct ventricular pacing (mode switch)
Avoids ventricular tracking of abnormally high atrial rates
What does this code mean:
ODO
Pacemaker is OFF
Most pacemakers perform these four functions…
Stimulate cardiac depolarization
Sense intrinsic cardiac function
Respond to increased metabolic demand by providing rate responsive pacing
Provide diagnostic info stored by the device (may dx atrial or ventricular arrhythmias)
What is Cardiac Resynchronization Therapy (CRT)?
Resynchronize biventricular contraction, a common problem in patients with heart failure
Employs three leads (one in atrium, one in right ventricle, one inserted through coronary sinus to pace the free wall of the left ventricle)
Where are the three leads located in CRT?
Right atrium
Right ventricle
Through the coronary sinus to the free wall of the left ventricle
Name the system:
Positive electrode is positioned in the heart tissue and the negative electrode is connected to the pulse generator
Unipolar system
Unipolar systems produce __________ spikes on the ECG
Tall pacing spikes
Name the system:
Electrodes are only millimeters apart in the cardiac tissue
Bipolar system
Bipolar systems produce _______ spikes on ECG
Short pacemaker spikes
ECG features of a pacemaker depend on…
How many chambers are paced
The firing of a pacemaker produces one or two narrow pacemaker spikes
What are the two features of a paced ECG complex?
Narrow “pacing spikes” which reflect the impulse depolarizing the paced chamber
P wave or QRS complex that immediately follows the pacing spike
Reasons why your granddaddy’s pacemaker might not work right…
Failure to capture
Failure to sense
Failure to pace (oversensing)
Pacemaker-mediated tachycardia
Presence of pacemaker spikes that are not followed by a P wave or broad QRS complex
Failure to capture
How do you recognize failure to capture?
Presence of pacemaker spikes that are not followed by a P wave or broad QRS complex
Presence of ECG pacemaker spikes that fall where they should have been inhibited
Failure to sense
How do you recognize failure to sense?
Presence of ECG pacemaker spikes that fall where they should have been inhibited
Absence of pacemaker spikes in the presence of a heart rate that is slower than the rate set for the pacemaker
Failure to pace (oversensing)
How do you recognize failure to pace on ECG?
Absence of pacemaker spikes in the presence of a HR that is slower than the rate set for the pacemaker
Fast HR with a pacemaker spike preceding each QRS complex on ECG
Pacemaker-mediated tachycardia
How do you recognize pacemaker-mediated tachycardia?
Fast HR with a pacemaker spike preceding each QRS complex on ECG
Implanted Cardioverter-Defibrillators (ICD) are implanted in patients who…
Are at risk of sudden cardiac death due to ventricular fibrillation and ventricular tachycardia
Implantable Cardioverter-Defibrillators are programmed to detect ________ and correct them by _______
Cardiac dysrhythmias
Delivering paced beats, cardioversion, or defibrillation
What are the different types of therapies provided by ICD
Antibradycardia pacing
Antitachydysrhythmia pacing
Cardioversion
Defibrillation
Which ICD therapy:
Electrical pacing is used to increase the HR when it is too slow.
Antibradycardia pacing
Most ICDs can pace one chamber at a preset rate. Some can sense and pace both chambers.
Which ICD therapy:
Mode that generates a series of small, rapid electrical pacing pulses to interrupt ventricular tachycardia (by “capturing” the ventricle and breaking the reentry circuit) and return the heart to its normal rhythm
Antitachydysrhythmia pacing
Which ICD therapy:
Mode that uses a low- or high-energy shock (up to 35 joules), which is timed to the R wave (which is detected by the right ventricular electrode) to terminate VT and return the heart to its normal rhythm
Cardioversion
Which ICD therapy:
Mode that delivers a high-energy shock (up to 35 joules) to the heart to terminate ventricular fibrillation and return the heart to its normal rhythm
Defibrillation
Electromagnetic fields that may affect pacemakers are ______
Radio-frequency waves
50-60 Hz are most frequently associated with pacemaker interference
Few sources of EMI are found in the home or office but several exist in hospitals
Sources of EMI that interfere with pacemaker operation include…
Electrocautery (if within 6 in of heart)
Transthoracic defibrillation (if req’d do not withhold)
Extracorporeal shock-wave lithotripsy (if abd device)
Therapeutic radiation (requires device shielding)
RF ablation (defer to EP doing case)
TENS units (fine if bipolar system, avoid if unipolar)
MRI (may compatible systems now)
