Pacemaker complication

Background

Nomenclature

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

I	II	III	IV	V
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)

Indications

• 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

Evaluation

Work-Up

• BMP and Mg
• CXR
• ECG
• Troponin
• Interrogation

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
• Simulataneous 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

Management

• Pacemaker Mediated Tachycardia- dual chamber devices-PAC or PVC trigger with pacemaker in loop. Break with adenosine or magnet.
• Use magnet to convert pacemaker to asynchronous mode if oversensing or runaway pacing

Disposition

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

See Also

• Medical device complications

References

Authors

Ross Donaldson, Neil Young