263.3 🩺 內科專科考前版

263.3.0.1 1⃣ Inferior MI + AV Block

  • RCA disease → inferior MI + may have AV block
  • Often Mobitz I (AV node ischemia from increased vagal tone)
  • Usually transient — resolves with reperfusion
  • Atropine + temporary pacing if hemodynamically unstable
  • Permanent pacemaker rarely needed (usually resolves)

263.3.0.2 2⃣ Anterior MI + AV Block

  • LAD disease → anterior MI + AV block = block below AV node (His-Purkinje)
  • Mobitz II or complete heart block
  • High mortality
  • Permanent pacemaker often indicated (doesn’t resolve)
  • Worse prognosis than inferior MI + AV block

263.3.0.3 3⃣ Post-Cardiac Surgery AV Block

  • Common (5-10% of cardiac surgery)
  • Often transient
  • Permanent pacemaker if persistent > 7-10 days
  • Especially after aortic valve surgery (proximity to conduction system)

263.3.0.4 4⃣ Bifascicular Block + Syncope

  • RBBB + LAFB (or LPFB) + syncope
  • Risk of intermittent complete AV block (Stokes-Adams attacks)
  • EP study for HV interval > 100 ms → pacemaker indication
  • Alternative: implantable loop recorder if EP negative
  • Pacemaker if intermittent AV block documented

263.3.0.5 5⃣ Carotid Sinus Hypersensitivity

  • Older patients
  • Carotid massage → asystole > 3 sec or BP drop > 50 mmHg
  • Recurrent syncope
  • Pacemaker for cardio-inhibitory type
  • Lifestyle modifications also

263.3.0.6 6⃣ Pacemaker-Induced Cardiomyopathy

  • High RV apex pacing burden → LV dysfunction over time
  • Risk: > 40% ventricular pacing + low baseline LV function
  • Prevention:
    • Minimize pacing if possible (algorithms)
    • Conduction system pacing (HBP, LBBAP) — more physiologic
    • CRT upgrade if LV dysfunction develops

263.3.0.7 7⃣ Drug-Induced Bradycardia

  • β-blockers (esp non-cardioselective)
  • CCB (verapamil, diltiazem)
  • Digoxin
  • Amiodarone
  • Ivabradine (sinus node specific)
  • Lithium
  • Some psychotropics
  • Withdraw before pacemaker decision
  • If drug essential + bradycardia persists → pacemaker

263.3.0.8 8⃣ Sleep + Sinus Bradycardia

  • Sleep-related bradycardia is normal (vagal tone)
  • HR may drop to 30-40 in athletes during sleep
  • Distinguish from sleep apnea + bradyarrhythmia
  • Don’t pace asymptomatic sleep bradycardia

263.3.0.9 9⃣ Athlete’s Heart

  • Resting bradycardia common (sometimes < 40 bpm)
  • 1° AV block + Mobitz I common
  • Improves / normalizes with exercise
  • Distinguish from pathologic SSS
  • Echocardiography + Holter + exercise test

263.3.0.10 10. Pacemaker + MRI (2024)

  • Modern MRI-conditional pacemakers can undergo 1.5T or 3T MRI
  • Coordination with cardiology + pacemaker representative
  • Specific settings + monitoring during scan
  • Old non-MRI-conditional pacemakers may be undergoing scans now in select institutions (carefully)