Harvey's Garden

Cardiac implantable electronic devices

3 min read

  • Epidemiology & Risk Factors
    • Categories: Includes Permanent Pacemakers (PPM), Implantable Cardioverter-Defibrillators (ICD), and Cardiac Resynchronization Therapy (CRT / Biventricular pacemakers).
    • Population: Primarily older adults w/ advanced structural heart disease, conduction abnormalities, or inherited channelopathies (e.g., Long QT, Brugada).
    • Risk Factors for CIED Complications:
      • Infections: DM, ESRD, corticosteroid use, early pocket re-exploration, pocket hematoma.
      • Lead dislodgement: Advanced age, cognitive impairment (Twiddler’s syndrome).
  • Clinical Features
    • Presentations Requiring CIEDs: Syncope (due to AV block/VT/VF), symptomatic bradycardia, chronotropic incompetence, severe HF symptoms (NYHA II-IV) despite guideline-directed medical therapy (GDMT).
    • Symptoms of Device Malfunction/Complication:
      • Inappropriate shocks: Sudden, painful jolt in the chest without preceding lightheadedness (often due to AFib w/ RVR).
      • Pocket infection: Localized erythema, swelling, tenderness, purulent drainage.
      • CIED Endocarditis: Fever, chills, systemic toxicity, new tricuspid murmur.
      • Pacemaker Syndrome: Fatigue, dizziness, palpitations, and visible neck vein pulsations (cannon A waves) due to AV dyssynchrony.
  • Diagnosis
    • Initial/Screening:
      • EKG: Assesses pacing spikes (atrial vs. ventricular), underlying rhythm, capture failure, or oversensing.
      • CXR: Evaluates lead position, lead fracture, or post-op complications (pneumothorax).
    • Confirmatory/Gold Standard: Device Interrogation (identifies battery life, lead impedance, sensing thresholds, and logs of arrhythmias/shocks).
    • Key Labs/Imaging (Infection Suspicion): Blood cultures (always draw before Abx), TEE (superior to TTE for evaluating lead vegetations/tricuspid valve).
  • Differential Diagnostics (Differentiating Device Indications)
    • PPM vs. ICD vs. CRT:
      • PPM: Treats bradyarrhythmias (e.g., symptomatic sinus node dysfunction, Mobitz II 2nd-degree AV block, 3rd-degree AV block). Does not shock.
      • ICD: Prevents sudden cardiac death (SCD) from tachyarrhythmias (VT/VF). Incorporates pacing functions.
      • CRT: Treats HF by resynchronizing LV/RV contraction (biventricular pacing). Usually combined with an ICD (CRT-D).
    • Appropriate vs. Inappropriate Shock:
      • Appropriate: Device triggered by life-threatening VT/VF.
      • Inappropriate: Device triggered by T-wave oversensing, SVT, or AFib w/ RVR. Diff by interrogation.
  • Management
    1. Primary Prevention ICD Criteria:
      • LVEF 35% + NYHA II-III HF symptoms + expected survival > 1 yr.
      • LVEF 30% + post-MI (> 40 days) + NYHA I.
    2. Secondary Prevention ICD Criteria: Prior hemodynamically unstable VT or VF arrest.
    3. CRT Criteria: LVEF 35% + NYHA II-IV HF symptoms + LBBB with QRS 150 ms.
    4. Infection Management:
      • Pocket infection or Endocarditis: Complete system extraction (leads + generator) + prolonged IV Abx (often covering S. aureus and S. epidermidis). Do not salvage the device.
    5. Perioperative/Procedural Management:
      • Electrocautery can cause electromagnetic interference (EMI), leading to inappropriate shocks.
      • Place a clinical magnet over the ICD during surgery above the umbilicus: temporarily suspends tachy-therapies (shocks) but leaves pacing intact (reverts to asynchronous pacing mode).
  • Complications
    • Acute (Peri-procedural): Pneumothorax, hemothorax, myocardial perforation (causing pericardial effusion/tamponade), pocket hematoma.
    • Mechanical: Lead dislodgement, lead fracture, Twiddler’s syndrome (patient subconsciously rotates the generator in the pocket, wrapping/dislodging the leads).
    • Infectious: CIED endocarditis (predominantly right-sided/tricuspid valve), pocket infection.
    • Vascular: Subclavian vein thrombosis (presents w/ ipsilateral upper extremity swelling), tricuspid regurgitation c

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