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Cardiac Devices

Matt Gayoso

Pacemakers:

  • Provide anti-bradycardia pacing by stimulating myocardium

  • Peripheral permanent pacemakers (PPMs)

    • SubQ generator, transvenous leads
      • Single chamber RV or RA lead
      • Dual chamber RV and RA leads (most common)
      • BiV (CRT- cardiac resynchronization therapy): RV, RA, and LV (coronary sinus) leads

  • Leadless pacemaker (Micra)

    • Implanted generator in RV

  • Indications

    • Symptomatic sinus node dysfunction: sinoatrial exit block, sinus pause, sinus bradycardia, tachy-brady syndrome
    • Degenerative AV block: 2nd degree type II (Mobitz II) or 3rd degree
    • Neurocardiogenic syncope

Implantable Cardioverter/Defibrillators (ICDs)

  • Types:

  • Transvenous: defibrillation coil ± pacing lead

    • Detect and treat VT/VF
    • Anti-tachycardic pacing (ATP)- attempts to pace out of VT to prevent a shock
    • Defibrillation if ATP unsuccessful

  • Subcutaneous: defibrillation only, all extravascular

  • Indications:
    • Primary prevention
      • HFrEF
        • EF \<35% and NYHA II-III or EF \<30% and NYHA I
        • Must be >90d from revasc, >40d from MI, and on GDMT >90d if non-ischemic
      • Arrhythmogenic syndromes
        • Arrhythmogenic RV cardiomyopathy, Brugada syndrome, HCM and cardiac sarcoid with specific risk factors
    • Secondary prevention
      • Sudden cardiac death
      • Sustained VT/VF
      • Inducible VT on EP study with history of syncope

Cardiac Resynchronization Therapy (CRT)

  • BiV pacer that coordinates LV/RV contraction through synchronized activation of each ventricle following atrial contraction.
  • -P: CRT pacing only
  • -D: ICD function
  • Class I indications: LBBB and QRS≥150 with EF90d, NSR

Loop Recorders

  • implantable devices for monitoring arrhythmias (most often Afib)

LVADs

  • augment cardiac output for end-stage heart failure

Interpreting Pacemaker Codes

1st Letter 2nd Letter 3rd Letter 4th Letter
A: atrial, V: ventricular, D: dual, O: none, I: inhibition, R: rate-adaptive Chamber Paced Chamber Sensed Response to Sensed Beat Program Features

Examples of Common Pacing Modes

  • VVI: Single RV lead that delivers a beat if no beat sensed. Often used with chronic AF with bradycardia
  • DDDR: Senses and paces both the atria and ventricle. If beat not sensed within a predefined interval, beat delivered. R indicates rate responsivity (changes rate based on changes in patient activity)
  • Magnet: Paces at a fixed rate without respect to native electrical activity (AOO,VOO,DOO). Deactivates ICD shock. Often used in surgery or at end of life to avoid ICD shocks

Peri-Procedural Anticoagulation:

  • NOAC: hold 24-72h before procedure and 24-72h following procedure
  • Warfarin: continue through procedure
  • Antiplatelet: continue through procedure
  • Heparin and heparin related products to be avoided peri-implantation due to higher rates of pocket hematoma

Placement Complications

  • Pocket hematoma - Cardiac Tamponade
  • Pneumothorax - Infection
  • Myocardial Perforation - Lead Displacement or Disconnection

Long term Complications

  • Secondary device Infection
  • Lead fracture (lead lifetime 10-15 years)

  • Insulation failure

    The Pacemaker ID app is free and is useful for identifying device brand for interrogation

    When differentiating PPM vs. ICD, look for a coil and charge generator to identify the ICD.

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