Pacemaker complication

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Paced rhythm with characteristic wide LBBB and pacer spikes
PA Xray with pacemaker
Atrial Sensed Ventricular Paced ECG
Pacer type based on Xray
Generic code for antibradycardia pacing[1]
Chamber(s) paced Chamber(s) sensed Response to sensing Rate modulation Multisite pacing
O = None O = None O = None O = None O = None
A = Atrium A = Atrium T = Triggered R = Rate modulation A = Atrium
V = Ventricle V = Ventricle I = Inhibited V = Ventricle
D = Dual (A+V) D = Dual (A+V) D = Dual (T+I) D = Dual (A+V)


  • Sinus Node Dysfunction-sinus bradycardia/arrest, sinoatrial block, chronotropic incompetence, a-fib.
  • Acquired AV block- 3rd degree block and 2nd degree type II
  • Chronic Bifascicular or Trifascicular block
  • After Acute MI-high mortality with persistent AV block post MI
  • Cardiac Resynchronization Therapy- Conduction delay (>150msec with mortality benefit) in chronic systolic heart failure further decreases EF, increases remodeling and increased MR.
  • Neurocardiogenic Syncope and Carotid Sinus Syndrome

Methods to Identify Manufacturer

  • Patient most often has a pocket card indicating manufacturer
  • Magnet types are specific to each model so use magnets to deactivate pulse generator
  • Manufactuer Hotline has patient database
    • Medtronic Inc. (1-800-328-2518)
    • St. Jude Medical Inc. (1-800-722-3774)
  • Manufactuer code on pulse generator is visible on Chest Xray

Electromagnetic Interference

  • Nonmedical
    • Cell phones: do not interact with device
    • Airport security: may trigger alarm, no alteration of activity
  • Medical Sources
    • MRI: mostly safe, consult cards on device specific recs
    • Cardioversion: Use AP pads >8cm from device to minimize adverse effects

Differential Diagnosis

Pacemaker Malfunction

Problems with pocket

  • Infection
    • Most commonly Staphylococcus aureus or S. epidermidis
    • 2% local wound infection; 1% sepsis/bacteremia
  • Hematoma
    • Typically occurs shortly after placement

Problems with leads

  • Lead separation
  • Lead dislodgment may cause thrombosis or myocardial rupture
  • Lead infection can cause severe sepsis
  • Leads can cause tricuspid regurg, diagnosis with TTE
  • Lead coiling (ie: Twiddler's Syndrome)
    Twiddler Syndrome after large pocket and pacemaker wires spinning on themselves

Failure to Capture

  • Def-delivery of pacing stimulus without depolarization
  • Functional- myocardium in refractory state or tissue reaction around lead insensitive
  • Pathologic- drugs, myocardial disease, lytes
  • Causes-lead dislodgement, fracture, perforation, insulation defect

Failure to Pace

  • Def-failure to deliver a stimulus to the heart (with or with out capture)
  • Oversensing-most common cause-retrograde P’s, T’s, skeletal muscle myopotentials,
  • Crosstalk- type of oversensing-vent lead senses atrial pacing stim, and ventilator output inhibited

Failure to Sense

  • Signal sensed when myocardial depol sent up leads and into pacemaker, if voltage exceeds threshold, pacing inhibited(appropriately)
  • Most commonly break in lead/insulation, battery
  • Voltages of patient's intrinsic QRS complex is too low to be detected
  • New intrinsic arrhythmia, AMI, electrolyte abnormalities, lead separation, battery depletion

Runaway Pacing

  • Physiologic electrical activity (T waves, muscle potentials)
  • External electromagnetic interference
  • Signals generated by interaction of different portions of the pacing system
  • Potentially life-threatening as it can cause V-Fib or (paradoxically) bradycardia due to failure to capture

Pacemaker Mediated Tachycardia

  • Also known as Endless Loop Tachycardia
  • Formation of a re-entrant circuit causing inappropriate tachycardia
  • Tachycardia does not exceed programmed upper limit rate on pacemaker



Expected ECG Patterns

  • Absence of pacer artifact indicates intrinsic depolarization
  • Pacing artifacts preceding depolarizations indicate successful pacing and capture
  • Leads in RV apex produce LBBB pattern with appropriate discordance
  • New RBBB pattern may indicate lead in LV
  • Simultaneous depol of ventricles produces dominant R wave in V1

Plain Film Findings

  • Obtain PA/Lateral Films to confirm pulse generator, manufacturer, lead placement/number/integrity
  • R atrial lead J shaped(tip medially on AP) entering right atrial appendage
  • RV leads point downward with tip between left spine and cardiac apex--lateral XR shows inferior and anterior
  • Coronary sinus lead- courses posteriorly on lateral XR
  • Extra leads may be appropriately abandoned and capped
  • ICD component appears as thickened shock coil


  • Pacemaker Mediated Tachycardia
    • Break with adenosine or magnet.[2]
    • Consider chest wall stimulation techniques[3] - transcutaneous pacing, isometric muscular exercise, precordial thump
  • Use magnet to convert pacemaker to asynchronous mode if oversensing or runaway pacing


  • Infection - admission with MRSA coverage antibiotics, consult to cardiology, with likely replacement of pacemaker after 4-6 weeks of IV antibiotics

See Also


  1. Bernstein AD. et al. The revised NASPE/BPEG generic code for antibradycardia, adaptive-rate, and multisite pacing. North American Society of Pacing and Electrophysiology/British Pacing and Electrophysiology Group. Pacing Clin Electrophysiol 2002 Feb; 25(2) 260-4. lmid:11916002
  2. EB Medicine- Sept 2014- Managing Pacemaker-Related Complications and Malfunctions in the Emergency Department
  3. Barold SS, Falkoff MD, Ong LS, Heinle RA. Pacemaker endless loop tachycardia: termination by simple techniques other than magnet application. Am J Med. 1988;85(6):817-22.