Cardiac Devices

Daniela Gomez Zubieta

1. Pacemakers:

A device that maintains or restores a normal heart rhythm by stimulating the myocardium. 

  • Peripheral permanent pacemakers (PPMs)
    • SubQ generator, transvenous leads
      • Single chamber: RV (most common) or RA lead
      • Dual chamber: RV and RA leads
      • BiV (CRT- cardiac resynchronization therapy): RV, RA, and LV (coronary sinus) leads
  • Leadless pacemaker (Micra)
    • Implanted generator in RV; Indication: (class 1 indications below, refer to ACC/AHA guidelines for class 2 and 3)
      • Sinus node dysfunction (sinoatrial exit block, sinus pause, sinus bradycardia, tachy-brady syndrome)
      • AV block (Mobitz II ,3rd degree, 2nd degree of any kind w/ symptomatic bradycardia, chronic bifasicular block
      • Persistent symptomatic 2nd or 3rd degree block after acute MI
      • Neurocardiogenic syncope

2. Implantable Cardioverter/Defibrillators (ICDs):

  • 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 nonischemic
    • Arrhythmogenic syndromes
      • Arrhythmogenic RV cardiomyopathy, Brugada syndrome, HCM and cardiac sarcoid with specific risk factors
    • Secondary prevention
      • Sudden cardiac death
      • Sustained VT/VF (spontaneous sustained, cardiac arrest 2/2 VT/VF)
      • Inducible VT on EP study with history of syncope

3. 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

4. LVADs:

augment cardiac output for end-stage heart failure

Examples of Common Pacing Modes on PPM:

  • 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 pt 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
  • Lead 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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