ICD Indications (Guidelines)

    • Indications for ICD (CCS Guidelines 2005)
        Landmark Trials: (MADIT I & II)
      • Class 1: VF or VT arrest not due to a reversible cause
      • Class 1: Sustained VT in ptsw/o treatment options
      Inherited conditions
      • Long QT
      • Brugada
      Systolic Dysfunction (HF)  
      • Class 1: LVEF ≤ 30% (>1mo post-MI, and >3mo post-CABG)
      • Class 1: LVEF ≤ 30% (non-ischemic CMP x9mo)
      • Class 2a/b: LVEF 31-35% (ischemic heart disease)
      • Class 2a/b: LVEF 31-35% + NYHA class II-III HF (non-ischemic CMP)
      • NOTE: LVEF measurements must be made:
        • Ischemic CMP: ≥1 month post MI, and ≥3mo post-PCI/CABG
        • Non-Ischemic CMP: ≥9mo of optimal medical therapy


    CRT Indications (Guidelines)

    • Canadian Guidelines - CCS - Indications for CRT

      Landmark: RAFT & MADIT-CRT Trials


      • Optimal medical therapy prior to CRT
      • Must Meet All (STRONG recommendation, high quality data)
        • Sinus Rhythm
        • NYHA class II or III (or ambulatory IV)
        • LVEF ≤ 35%
        • QRS Duration ≥ 130ms because of LBBB (RBBB = no benefit, 5 trials)
          • (Can be considered for ≥ 150ms with NO LBBB)
      • Atrial Fibrillation
        • Can be considered (Weak recommendation, low-quality data)
      • Chronic Pacing
        • Can be considered for pts with chronic RV pacing, who have:
          • Signs/symptoms of HF AND
          • LVEF ≤ 35%
      • Echo not recommended for "dyssynchrony" assessment, use QRS


    • US Guidelines - AHA 2012 ACCF/AHA/HRS - Indications for CRT


      • Class I Indications: (ALL OF following:)
        • LVEF ≤ 35%
        • Sinus Rhythm
        • QRS ≥ 150ms
        • NYHA II, III, Ambulatory IV


      • Class IIa Indications: (Class I indication modifications:)
        • QRS 120 - 149ms, LBBB pattern
        • Non-LBBB pattern, QRS ≥ 150ms, NYHA III or ambulatory IV
        • AFib + requires ventricular pacing (+meets above criteria)
        • AFib + AV ablation or rate control will allow near 100% ventricular pacing with CRT
        • Undergoing device placement with anticipated requirement for significant (>40%) ventricular pacing.


      • Class IIb Indications: (Class I indication modifications:)
        • NYHA class I, LVEF ≤ 30% (ischemic etiology of heart failure), QRS ≥ 150ms
        • QRS 120-149ms,  Non-LBBB pattern, NYHA class III/ambulatory IV
        • Non-LBBB, QRS ≥ 150ms, NYHA class II
      • No Benefit: (Class III)
        • comorbidities and/or frailty limit survival with good functional capacity to < 1 year.

    Permanent Pacemaker Guidelines


      AV Block SA Node Dysfunction
    Class I 


    3rd Degree AV Block

    - Symptoms presumed due to AV Block

    - Symptomatic bradycardia due to required drugs

    - Asystole > 3.0s or any escape < 40bpm 

       (in awake asymptomatic pts)


    2nd Degree AV Block With symptomatic

      bradycardia! (regardless of type or level of block)


    - AV ablation

    - Post-op AV Block (not expected to resolve

    - Neuromuscular disease w/ AB block

      (myotonic dystrophy, Kears-Sayre, Erb's,peroneal atrophy)

    1. SA Dysfunction, documented

       symptomatic bradycardia

    (i.e. sinus pauses producing symptoms)

    (some will be due to therapeutic drugs

     with no alternatives)


    2. Symptomatic chronotropic



    Class IIA

    3rd Degree AV Block (any anatomic site)

    - Awake Rate ≥ 40bpm 


    2nd Degree AV Block

    - Asymptomatic Type II AV Block

    - Asymptomatic Type I AV Block (intra- or infra-His

      levels found incidentally at EP study for other reason


    1st Degree AV Block

    - Symptoms of pacemaker syndrome and documented

      symptom imrpovement w/ temporary AV pacing.

    Spontaneous (or d/t essential drug therapy

    w/ symptomatic sinus node dysfunction

    with heart rate <40 bpm

    BUT no clear documentation of

    symptom-rhythm correlation.

    Class IIB

    1st Degree AV Block 

    - Marked block > 0.30s in pts with LV dysfunction

      HF symptoms, if shorter AV interval can result in

      hemodynamic improvement. (decr. LA filling pressure)

    Minimally symptomatic patients, w/

    chronic heart rate <30 bpm while awake.

    Class III 



    1st Degree AV Block - If Asymptomatic


    2nd Degree AV Block - Type I

    - Asymptomatic, at the supra-His (AV node) level or

      not known to be intra- or infra-Hisian.


    AV block expected to resolve and unlikely to recur

    (eg, drug toxicity, Lyme disease). 

    SA dysfunction in asymptomatic patients,

    (including sinus bradycardia <40 bpm 

    due to long-term drug treatment.


    Symptomatic bradycardia due to

    nonessential drug therapy.







    •   Description Possiblities
      Letter #1 Chamber that is paced V (ventricle) A (atrium), O (none), D (dual)
      Letter #2 Chamber being sensed V (ventricle) A (atrium), O (none), D (dual)
      Letter #3 Response to event (what will make it discharge)

      I (Inhibited) - Device will pulse to chamber unless intrisic activity

      O (None)

      T (Triggered) - Generally used for testing device

      D (Dual) - Inhibited and triggered

      Letter #4

      Rate modulation (if any) - i.e. rate increases

      based on physical demands (exercise). 

      Programmable or using accelerometers

      i.e. DDDR & VVIR (increases rate during exercise)

      Letter #5 Anti-Tachycardia Action (if any)  

      Indicates rate of pacing,

      or in VVI - threshold for pacing

      I.e. VVI 60 (will pace if intrinsic rate goes below 60)



    • Conditions and preferred modes:  (example only!!!)
      AAI Uncomplicated sinus node dysfunction

      Sinus-node dysfunction with AV-node disease

      - AV Block

      - Cardiomyopathy

      - Neurogenic Syncope

      VVI - AV block with no organized atrial activity
      DDI - Neurogenic Syncope


    • paceMakerAlgorithm.png

      Source: Bayes de Luna (2014) ECGs for Beginners (1st ed)


    Device Notes

    • NOTE: Surgical electrocautery can generate interference that is sensed by ICD -->inappropriate discharge (should have ICD turned off during OR by using magnet).
    • Magnet on ICD --> turns off shock delivery, but pacing unaffected (will pace if hits low treshold)
    • Magnet on Pacemaker --> inhibit sensing, goes into asynchronous mode that delivers constant pacing (magnet turns off sensing, can can assess sensing).
    • Pacemaker
      • Nomenclature
        • 1st Letter - chamber being paced
        • 2nd Letter - chamber being sensed
        • 3rd Letter - Response - 
        • 4rth Letter - Respond to increased metabolic activity
        • "VVIR" (ventricle pacing, ventricle sensing, natural conduction inhibits pacemaker, has accelerometer to modulate rate based on movement)
          • Tested CO2 and accelerometer for movement, but accelerometer was better.
        • AAIR (atrium paced, atrium sensed [same lead], Inhibited, Rate modulating).
          • Sick sinus syndrome.  But high risk of developing AV block 5%/year, so now put in DDDR devices.
          • Risk of infection opening  (3-5% each time)
          • DDDR device (dual [two leads - atrium + vent], dual sensing, Dual [inhibit and trigger], rate modulating.
        • (intrinsic conduction is always better, paced conduction desynchronizes the heart).
        • DDD MODE, can have 4 modes of operation:
          • AP-VP
          • AS-VP (if intrinsic heart rate picks up artrial activity, Atrial sensing, ventricular pacing)
          • AP-VS (preferred for sick sinus, senses ventricles to see if conducted, but if AV block will pace both).
          • AS-VP (atrial sensing to generate ventricular beat when atria contract).
            • In AV block.
            • Sometimes atrial tachycardia, device pacest fast.  Set upper tracking limit to 130 or so (to prevent overdrive, which looks like VTach).
            • NEW: 2:1 pacing (smooth changes in heart rate)
    • In ER: if signs of infection of pocket, DO NOT stick a needle in the pacemaker pocket.  Just start broad spectrum abx.
    • QT interval in paced QRS is associated with depolarization abnormality we generated (abnormal repolarization).
    • Beeping device:
      • Typically ICD beeping requires a call to the Arrhythmia Sevice, can mean several things:
        • Battery dead (rare - patients get very close follow-up)
        • Lead impedance (most likely cause) - issue with connection of device with lead, lead itself, or lead connection to heart (erosion)
    • ASSERT Paper...?
    • For a long time DDD thought to be better for AV block, but VVI shown to be similar.
      • No hemodynamic changes, VVI (one lead)
      • One lead - less complications than two lead.
    • In sick sinus: why not put AAI pacemaker (atrially paced, atrially sensed, Inhibited)
      • Can develop AV block, (1 in 2 developed AV block?)
      • 1:2 % progression to complete AV block with AAI. (used to check if AV conduction present at 120bpm).
    • Troubleshooting:
      • Dislodgement.
        • (even milimeters change, not seen on CXR, can be dislodged).
      • Perforation  <1% with new leads, extremely rare. (Sudden change of impedance, i.e. increase in conduction b/c perforated).
      • Sensing (under/over)
        • Ignores underlying rhythm, paces anyways.
        • Threshold to detect P-wave can change, have autosensitivity modes, but consume battery. 
        • 1. Inappropriately programmed sensitivity (above)
        • 2. Lead dislodgement.
        • 3. Lead Failure (insulation break, conductor fracture) - some devices recalled, and need to be replaced either immediately or at time of battery change).
        • 4. Lead maturation - OLD 25-35y leads.
        • 5. Change in native signal.
          • Change in signal when electrolyte changes, or infarcted area of capture.
        • Oversensing:
          • asystole when using microwave etc... (patients drop)
          • (Poor connection todevice, change in ecg... i.e hyperkalemia makes tall T, sensed as QRS).
          • Intereference very rare nowadays with new algorithms.  In the old days microwaves could do that, but some case reports of electric water heaters in shower, etc..  MRI is common for interference. 
      • non-capture
      • no output
      • Pseudomalfunction.
    • 5% risk of infection when opening a pocket, so minimize!
    • Putting leads no longer in apex, but going against gravity into the outflow tract.
    • Paper: SELECT approach (Circ arrhythmia 2012, JC arrhythmia 2011)
      • Randomized 
      • Clinical outcome better, (BNP, etc..) 
    • Pacemaker Syndrome
      • Put pacemaker, and come back short of breathe. 
      • Several possibilities (unknown reason).  Initially thought V-A conduction (depol of atrum against closed AV valve?)
        • But later thought to be due to desynchronization of ventricles.
        • So started putting leads --> screwing them into the RV outflow tract to increase intrinsic conduction.
    • Airport:
      • Usually do not trigger, but sometimes triggers hand-held metal detectors.
      • Usually they get a card to carry
      • Arc welding --> ok, but do not put cord around neck.
      • Exercise is OK! 

    Device Complications


    • Present as:
      • Localized pocket erosion or abscess
      • Vegetation on a lead.
      • Unexplained bacteremia.
    • DO NOT aspirate device site (can damage leads).
    • Management:
      • Blood cultures
      • Transthoracic echo
      • (If blood cultures positive, TEE for lead and valve examination).
    • Treatment:
      • Extraction of entire system (including leads) followed by antibiotics.
      • Decision ti re-implant depends on risks/benefits.



    • If not tense, and well-healed incision --> conservative management. 
    • Do not put needle into pocket. 


    Device Erosion

    • Infected by definition


    What to do after a shock?

    • If one shock:
      • Call pacemaker clinic to inform them.
      • Interrogate in 1-2 days.  (i.e. next day in pacemaker clinic)
    • If multiple (≥2) shocks:  EMERGENCY!
      • Instruct to go to ER
      • Need 12 Lead ECG
      • History, ischemia r/o
      • Interrogate quickly
    • Approach in ER
      • Was there a shock?
        • (If "little shock" -> unlikely real shock)
      • Was it appropriate?
        • i.e. Sometimes overseses T-Waves as QRS (i.e. sinus tach)
        • i.e. AFib -> misinterpreted as VT (most common)
        • External Noise: Electromagnetic interference, Electrocautery, TENS, etc..
        • Internal Noise: Muscle  potentials, lead kinked by clavicle. 
      • Management
        • Determine if appropriate
        • Place a magnet (will disable shock - if end of life, inappropriate shock, perioperative)
          • Can tape on the magnet. 
        • 12-Lead ECG, Investigate any ischemia, etc. 
        • Admit for monitoring


    Beta Blocker Toxicity

    • See ICU > Toxins > Therapeutic Drug Overdoses




    • Extracorporeal vs Implantable
    • Pulsatile vs. Rotational pumps
    • Cannula in the apex
    • Pulsatile
      • Sucks, fills the chamber to top, then ejects.
      • Ensures blood doesn't flow back using valves.  However, valves are not durable. 
      • Preload dependent (cannot fill, cannot suck form chamber)
      • Aortic valve should be working on echo. 
    • Rotational (i.e. HeartMate II)
      • Continuous flow
      • Sucks blood continuously from apex
    • Predictors
      • RV function (tapse)
      • Position of septum (if RV is full, may push septum)
      • AO valve opening (if closed, can cause some AI?)
    • Problems:
      • Cannula occlusion (fibrin deposition)
      • Pump thrombosis (8-12%)  [alarm will turn on, pulsatility index will rise.  hemolysis occurs [LDH, etc..], worsening HF on echo]
      • Ramp study
        • Ramp up the speed, until: 
          • Suction events occur (if sucks in septum, free wall, or sucks in aortic valve into regurgitation)
          • VEDD decreases <3.0cm
        • First, ensure no clot, and ensure INR >1.8, aPTT > 60 (otherwise can suck in a thrombus)
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