Pacemaker

See Also

Definition

Thoracic-implanted, self-contained (with battery and circuitry)
Cardiac sensing and pacing device indicated for Symptomatic Bradycardia or Syncope

Indications
Permanent Pacemaker - General

Sinus Node Dysfunction with Symptomatic Bradycardia or Syncope
Advanced second or third degree AV Block (see below)
Chronic bifascicular block
Acute Myocardial Infarction requiring ventricular pacing beyond acute phase
Hypersensitive carotid sinus syndrome and Neurocardiogenic Syncope
Cardiac Transplantation requiring post-operative pacing
Symptomatic recurring SVT
Congenital long QT Interval
Cardiac Resynchronization Therapy with biventricular pacing
Symptomatic Heart Block with Cardiomyopathy or Congenital Heart Disease

Indications
Permanent Pacemaker - AV Block

Class I Indications (helpful)
1. Sick Sinus Syndrome
  1. Symptomatic Bradycardia with frequent sinus pauses (>3 seconds) associated with symptoms
  2. Symptomatic chronotropic incompetence (inadequate Heart Rate response to Exercise or activity)
2. Second Degree AV Block with Symptomatic Bradycardia
3. Third Degree AV Block with one associated condition
  1. Symptomatic Bradycardia
  2. Documented Asystole (3 seconds or greater)
  3. Catheter ablation of the AV junction
  4. Neuromuscular disorder with AV Block
    1. Myotonic muscular disorder
    2. Kearns-Sayre Syndrome
    3. Erb's Dystrophy (limb-girdle)
    4. Peroneal muscular atrophy
Class IIa Indications (probably helpful)
1. Sick Sinus Syndrome
  1. Symptomatic Bradycardia with Heart Rate <40 bpm but symptom association with Bradycardia unclear
  2. Idiopathic Syncope and Sinoatrial Node dysfunction identified on electrophysiologic studies
2. Asymptomatic third degree AV Block
3. Asymptomatic Type II second degree AV Block
4. Asymptomatic Type I AV Block at His level
5. First degree AV Block and Pacemaker syndrome symptoms
Class IIb Indications (Possibly helpful)
1. Sick Sinus Syndrome
  1. Chronic awake rate <40 bpm in minimally symptomatic patients
2. Marked First Degree AV Block (>0.3 seconds) with CHF
3. Hypersensitive carotid sinus syndrome with recurrent Syncope
  1. ACC/AHA recommends if associated with ventricular Asystole for 3 or more seconds
  2. Cochrane review does not find sufficient evidence supporting Pacemakers for Carotid Sinus Syncope
  3. Romme (2011) Cochrane Database Syst Rev (10): CD004194 [PubMed]
Class III Indications (Not helpful, possibly harmful)
1. Asymptomatic Bradycardia due to medication
2. Asymptomatic First Degree AV Block
3. Asymptomatic Type I AV Block limited to supra-His
4. Transient AV Block secondary to resolving condition
  1. Drug toxicity
  2. Lyme Disease

Components

Pulse generator (Electronic device)
Battery (e.g. 5-10 year Lithium ion)
Pacing leads

Description
Pacemaker Codes

Background
1. Most Pacemakers in the U.S. are DDD (dual lead, dual sensed, dual response of trigger and inhibit)
2. Some Pacemakers placed outside the U.S. are VVI (ventricle paced, ventricle sensed, ventricle inhibited)
Position 1 (chamber paced)
1. V - Ventricle
2. A - Atrium
3. D - Dual (A and V)
4. O - None
Position 2 (chamber sensed)
1. V - Ventricle
2. A - Atrium
3. D - Dual (A and V)
4. O - None
Position 3 (response to sensing)
1. V - Triggered
  1. Intrinsic P Wave with no QRS triggers the Pacemaker
2. I - Inhibited
  1. Intrinsic P Wave with a QRS inhibits the Pacemaker
3. D - Dual (T and I)
4. O - None
Position 4 (programmable functions and rate modulation)
1. P - Programmable rate and output
2. M - Muti-programmability of rate, output, sensitivity
3. C - Communicating via telemetry
4. R - Rate modulation
5. O - None
Position 5 (anti-tachyarrhythmia)
1. P - Pacing (anti-tachyarrhythmia)
2. S - Shock
3. D - Dual (P and S)
4. O - None

Types
Pacemaker modes

Synchronous mode
1. Synchronous with heart beat
Asynchronous mode (fixed mode)
1. Asynchronous in regards to heart beat (no response to sensing)
2. Pacemakers revert to asynchronous mode when exposed to a magnet

Types
Pacemaker Selection for Sinus Node Dysfunction

No signs or future risks for impaired AV conduction
1. Rate response: Rate-responsive atrial pacer (AAIR)
2. No rate response: Atrial Pacemaker (AAI)
Impaired AV Conduction and no AV synchrony needed
1. Rate response: Rate-responsive dual chamber (DDDR)
2. No rate response: Ventricular Pacemaker (DDD)
Impaired AV Conduction and AV synchrony needed
1. Tachyarrhythmia (e.g. PSVT)
  1. Rate response: Rate-responsive dual chamber (DDDR)
  2. No rate response: Dual chamber Pacemaker (DDD)
2. No Tachyarrhythmia
  1. Rate response: Rate-responsive dual and mode switch
  2. No rate response: Dual chamber with mode switching

Precautions

Magnetic field exposure
1. Pacemakers typically switch to asynchronous pacing at a set rate on exposure to magnetic field
2. Cell phones should be held on the opposite side of body, away from Pacemaker
  1. Had been theoretical risk only in the past
  2. More powerful magnets are as of 2022 installed in phones for wireless charging (e.g. IPhone 12 MagSafe)
    1. Case reports of magnet triggered Syncope and other pacer adverse events are now more common
    2. Nadeem (2021) J Am Heart Assoc
      1. https://www.ahajournals.org/doi/10.1161/JAHA.121.020818
3. Other wearable and personal use devices (e.g. Electronic Cigarettes) may interfere with Pacemaker function
  1. Shea (2020) HeartRhythm Case Rep 6(3): 121-3 [PubMed]
  2. Asher (2020) HeartRhythm Case Rep 7(3): 167-9 [PubMed]
4. Magnets may be helpful in some emergency settings (e.g. applied to AICD that is delivering inappropriate shocks)
5. MRI scans have been historically contraindicated
  1. Devices manufactured after 2000 are considered safe for non-thoracic MRI (after first 6 weeks)
  2. Avoid MRI with 6 weeks of placement due to device dislodgement
  3. Set Pacemaker to asynchronous mode (reset after scan), and turn AICD devices off
  4. Pacemaker may distort images
  5. Typically performed at tertiary centers with emergency backup and temporary Pacemaker reprogramming
  6. Russo (2017) N Engl J Med 376(8): 755-64 +PMID:28225684 [PubMed]
  7. Nazarian (2013) Circ Arrhythm Electrophysiol 6(2): 419-28 [PubMed]
Battery life remaining in Pacemaker
1. Pacers are interrogated to determine remaining battery life
2. When battery life drops below ERI (Elective replacement indicator), Heart Rate will be be fixed at a manufacturer-set rate
3. When battery life drops below EOL (End of life), Heart Rate will be fixed at a different fixed manufacturer-set rate
External Defibrillation, cardioversion and external pacing
1. Electrical shock may theoretically damage Pacemaker
2. Emergency Defibrillation may be performed without regard to Pacemaker
3. Avoid applying elective cardioversion pads directly over Pacemaker
  1. Try to apply pads at least 10-15 cm away from the device

Imaging
Chest XRay

Indications
1. May identify misplaced or damaged lead
2. Identifies the Pacemaker type via a radiodense device stamp (requires a high penetration Chest XRay)
Interpretation - Normal Pacemaker wire configuration
1. Most newer Pacemakers are dual lead (but some may have only a single lead to either atrium or ventricle)
2. Pacemaker tip positioning - PA View (or AP View)
  1. Pacemaker leads should coss the midline (from the left chest wall implantation site to the right heart)
  2. Atrial leads should be directed slightly upwards
  3. Ventricular leads should be directed slightly downwards
3. Pacemaker tip positioning - Lateral View (or Lateral View)
  1. Pacemaker leads should be directed towards the Sternum (anteriorly)
  2. As with PA view, atrial leads are directed upward and ventricular leads downward

Diagnostics
Electrocardiogram

Pacer spike
1. Long, very narrow signal preceding a complex
ST and T Waves
1. Should always be discordant or opposite to the major QRS Complex (similar to a Left Bundle Branch Block)
  1. Discordance (or QRS Complex in the opposite direction as the ST Segment and T Wave) is normal
  2. Concordance (QRS and ST/T Wave in same direction) may suggest acute Myocardial Infarction
2. Sgarbossa Criteria may distinguish Pacemaker altered ST-T morphology versus an acute Myocardial Infarction
  1. Applies to Left Bundle Branch Block induced with a right ventricular Pacemaker lead
  2. No guidelines directing Sgarbossa use in Pacemaker patients
    1. However original Sgarbossa study included a subset of Pacemaker patients
QRS Complex
1. Typically Left Bundle Branch Block (Pacemaker leads are typically placed in the right ventricle)

Diagnostics
Magnet placed over Pacemaker

Indicated if Pacemaker malfunction is suspected
Perform an Electrocardiogram before and after applying magnet
Before magnet application (synchronous mode)
1. Pacing is typically rate responsive via Pacemaker sensing functionality
After magnet application (asynchronous mode, fixed mode)
1. Turns off Pacemaker sensing functionality
2. Pacemaker will now pace at an intrinsic rate (80-100 depending on manufacturer)
  1. QRS Complexes present after magnet application suggests a failure of Pacemaker sensing
  2. No QRS Complexes after magnet applications may suggest a failure of Pacemaker capture

Diagnostics
Pacemaker Interrogation

All Pacemakers can perform Electrocardiograms (may be turned off to conserve battery life)
1. Electrocardiogram functionality is enabled during interrogation
Pacemaker programming head is placed directly over Pacemaker and push interrogate button
Identify the patient's underlying rhythm
1. Are the pacer spikes atrial or ventricular?
2. Is the rhythm Pacemaker dependent?
  1. If uncertain, Pacemaker rate can be slowed to see if patient's rate also drops
Can the Pacemaker sense the heart rhythm?
Can the Pacemaker pace the heart?
Are there other rhythm problems?
1. Some Pacemakers can store abnormal rhythm events (e.g. VT runs) with a date-time stamp
Is the Pacemaker programmed correctly?
ERI (Elective replacement indicator)
1. Battery life remaining before replacement is needed

Management
Troubleshooting a malfunctioning Pacemaker

See Cardiac Pacemaker Infection
Evaluation
1. See Chest XRay (above) for Pacemaker lead positioning and device stamp
2. See Magnet Application (above)
3. See Electrocardiogram (above) for Pacemaker-related findings
4. See Pacemaker Interrogation (above)
Pacemaker device malfunction categories
1. Failure to capture (despite pacer spike)
  1. Pacemaker spike present without ensuing QRS Complex
  2. May indicate lead Fracture or dislodgement, or malfunction central to the device
  3. Lead displacement is the most common cause and typically occurs in first month
2. Failure to output (without pacer spike, includes oversensing, exit block)
  1. Pacer spikes are absent
  2. May indicate lead Fracture or dislodgement, battery depletion
  3. May indicate device oversensing
    1. Pacemaker inhibited by a Hyperacute T Wave, muscle Fasciculation, cell phone within 10 cm
    2. Misinterpreted as an intrinsic beat
    3. Applying a magnet over the Pacemaker is diagnostic and therapeutic
  4. May indicate exit block
    1. Altered interface between Pacemaker lead and endocardium
    2. Causes include MI, fibrosis, Hyperkalemia, Antiarrhythmics
3. Failure to sense (undersensing)
  1. Pacemaker fails to sense intrinsic cardiac activity and paces as if intrinsic activity is absent
  2. Pacer spike appear regardless of intrinsic rhythm
  3. May indicate lead dislodgement, altered position, acute right ventricular infarction
  4. Risk of R on T phenomenon
  5. Response depends on Pacemaker mode and programmed sensing parameters
  6. Placing a magnet over the Pacemaker will disable the aberrant functionality until it may be repaired
Specific Pacemaker problems
1. Dislodged/displaced or Fractured Pacemaker lead
  1. Pacemaker lead displacement is most common
  2. Pacemaker leads are most prone to Fracture at the lead insertion site and under the clavicle or first rib
2. Pacemaker syndrome (up to 20% of cases)
  1. Loss of atrial capture with only ventricle paced (atria contracts against a closed AV valve)
  2. Presents with retrograde pulsations into the neck
  3. Atrial distention results in diuresis and Hypotension
  4. Loss of Preload may result in secondary Heart Failure
  5. Symptoms include weakness, Fatigue, Dizziness, Orthostasis, Dyspnea and Chest Pain
3. Runaway Pacemaker syndrome
  1. A damaged Pacemaker theoretically could sporadically increase paced rates at well above 100
  2. Pacemaker mediated Tachycardia (endless loop Tachycardia) is a reentrant variant
  3. Rare, but life threatening
  4. Typically due to battery failure or Pacemaker damage
  5. Apply magnet to deactivate sensing and terminate reentrant Dysrhythmia
    1. Typically requires emergent removal of the device
4. Inadequate pacer energy
5. Twiddler's Syndrome
  1. Pacemaker patients may manipulate the Pacemaker site (subconsciously)
  2. Results in lead retraction and displacement
  3. Presentations
    1. Pacemaker failure (e.g. Syncope)
    2. Symptoms specific to new lead location (e.g. Hiccups, diaphragmatic spasm, arm twitching)
  4. Risk factors
    1. Elderly or obese (loose subcutaneous Pacemaker pocket)
    2. Dementia, Obsessive Compulsive Disorder or Developmental Delay
  5. Diagnosis
    1. Electrocardiogram (evaluate for appropriate sensing)
    2. See Chest XRay below regarding lead positioning (also observe for Fractured leads)
  6. References
    1. Jhun and Shoenberger in Herbert (2015) EM:Rap 15(7): 17
Data to have available when communicating with Cardiology about a patient with possible Pacemaker-related problem
1. Pacemaker information
  1. Most patients will have a card with Pacemaker information (device type, interrogation phone numbers)
  2. Pacemaker type can also be read from a high penetration Chest XRay
2. Is the device a Pacemaker or Defibrillator?
3. How many wires to heart are present?
4. When and where was the device implanted?

Precautions
Magnetic Resonance Imaging (MRI)

Most Pacemakers can not undergo MRI
1. Risk of Arrhythmia or capture loss
2. Certain tertiary centers perform MRI on non-MRI conditional devices with electrophysiologist present
  1. (2017) Am J Neuroradiol 38:2222 [PubMed]
Abandoned leads can not typically undergo MRI
1. Lead super-heating and local myocardial wall ablation
MR Conditional Devices and leads may undergo MRI under certain conditions
1. Most manufacturers as of 2018 produce MR conditional devices
2. Obtain Chest XRay in advance of MRI
3. Requires Pacemaker temporary reprogramming (off or asynchronous mode with higher rates and outputs)
4. Expect scatter on imaging from the device (for targets near the device)
References
1. Abresch (2018) Cardiac Arrhythmia Conference, UMN, Minneapolis

Complications
Acute complications associated with placement

Pneumothorax or Hemothorax (complicates 1-3% of Pacemaker placements)
Myocardial perforation (with associated Cardiac Tamponade risk)
Brachial nerve injury
Pacemaker Infection (1-7% risk)
Acute lead dislodgment (2-4% risk)

Complications
Chronic complications

Atrial Fibrillation
1. Increased risk with ventricular pacing (e.g. RV pacing)

References

Jones and Orman in Majoewsky (2012) EM:Rap 12(5): 4-6
Mallemat, Swaminathan and Egan in Herbert (2014) EM:Rap 14(10): 5-7
Vanlandingham (2015) Crit Dec Emerg Med 29(10): 2-14
Bernstein (1987) Pacing Clin Electrophysiol 10:794-9 [PubMed]
Denay (2014) Am Fam Physician 89(4): 279-82 [PubMed]
Epstein (2008) J Am Coll Cardiol 51(21):e1-62 [PubMed]
Gregoratos (1998) J Am Coll Cardiol 31:1175-209 [PubMed]
Gregoratos (2005) Am Fam Physician 71:1563-70 [PubMed]