AICD (Automatic Implantable Cardioverter Defibrillator)

 

Indication: (For more in depth review of indications/contraindications view North American Society of Pacing and EP consensus).

  1. Symptomatic VT and VF
     
  2. Unexplained syncope
     
  3. Sustained VT and VF during or > 48 hours after MI
     
  4. VT and VF despite antiarrhythmics

Types:

  1. All consist of power supply, lead that senses the activity and the analyzer of the rhythm.
     
  2. Most recent ones consist of the lead that is introduced via L subclavian into R ventricle. The lead is divided in two electrodes for defibrillation: one in RV and the second in junction of RA and SVC. Some advanced AICDs have also PM capability.
     
  3. Most of ICDs deliver 30 J when defibrillate. It takes about 5-15 seconds to recharge and deliver following shock. Usually 3-6 shocks are delivered. Note! Newer ICDs are available that can be programmed for patient's needs.
     
  4. Longevity is 5-8 years.

Complications:

  1. Although overall rate of Sudden Death has decreased due to prevention of VT/VF other causes of death in patients with ICD are still present and these could be due to:
    1. ICD malfunction  with consequent failure to sense and/or treat
    2. Frequent shocks that can depress myocardium and induce heart failure
    3. Inability to read and interpret  bradycardia or EMT/PEA. Note! Newer ICDs are available to bypass these inconveniences
       
  2. Frequent AICD activation can be 2ry to:
    1. New ischemia
    2. Change in cardiac medications
    3. Lead dislodgment
    4. SVT that is sensed as VT/VF
    5. Pericarditis

Diagnosis of  Malfunction:

  1. In AICDs of  latest design it is possible to interrogate  the unit and to see if there was a proper or improper response of the AICD.
     
  2. If one is certain that there are improperly delivered shocks, the unit can be deactivated by applying a magnet.

Do's and Dont's  with AICD:

  • MRI is contraindicated. Cxray and CT are safe.
  • Any device that contains electrocautery such as endoscopy can activate ICD, thus AICD must be disactvated.
  • Cell phones can interfere. Microwaves are safe.

S & S:

  • Patient that was properly shocked will experience presyncopal episode. If this is not the case, one must investigate further.  (see diagnosis)

DX:

  • If above S&S are not described get CXray to document lead placement.
  • Check blood level of cardiac medications.
  • Check serum electrolytes.
  • Have cardiologist to interrogate the device.

Treatment:

  1. For improperly delivered shocks see above
     
  2. Correct electrolyte abnormalities
     
  3. 3. In case of VT/VF standard ACLS is applied.

 

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