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More than 75% implantable cardiac defibrillators (ICDs) are placed as a prophylactic measure for risk of sudden cardiac death (SCD) from specific disease states (e.g., HCM).
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Many patients who receive a pacemaker for specific causes (see chapter 18) will have dual-function devices, also capable of defibrillation.
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All implanted devices, ICD as well as pacemakers, are contraindicated in the MRI suite.
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- Prior cardiac arrest
- NYHA class II or III nonischemic dilated CM, EF <30%
- Prior MI (>40 days), EF <30%
- Structural heart disease or inherited arrhythmia syndromes (long QT, Brugada):
- Genetic disorder that is characterized by right bundle branch block, ST segment elevation in V1 to V3, and sudden death in patients with a structurally normal heart. EKG pattern with J point elevation
- Syncope of unknown origin
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- Larger than pacemakers; therefore, often implanted under pectoralis muscle under GA (VF induction for testing)
- Functions:
- Overdrive pacing if monomorphic VT
- Cardioversion or defibrillation if polymorphic VT or VF
- Pacing function if pause (especially after cardioversion or defibrillation)
- Four-letter code
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- Rarely absence of response to VT/VF
- Most often inappropriate electric shock
- Causes:
- Electrocautery (Bovie) essentially
- RF ablation
- Lithotripsy
- ECT
- Electrolyte/acid–base abnormalities
- Medications:
- Succinylcholine (fasciculations can inhibit PM or trigger ICD; not an absolute contraindication)
- Other (rare): orthopedic saw, telemetric devices, mechanical ventilators, nerve stimulator (anesthesia or SSEP/MEP)
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- Determine type of ICD functions through manufacturer’s identification card and/or ID bracelet
- Determine battery function and when the device was last interrogated
- Turn ICD functions off:
- Interrogation and disabling of device by company representative or qualified personnel
- If not possible, magnet application to be kept on for duration of procedure (usually done in OR):
- ICDs manufactured by CPI are deactivated after 30 seconds of magnet application (beeping sound) but magnet reapplication can reactivate device; therefore, do not use magnet (except in emergency) if type/brand of device not known
- Reevaluation of device postmagnet therapy
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- Need to monitor HR by another device than EKG: pulse oximeter and/or A-line
- Deactivate device (if not done preoperatively in holding area):
- Defibrillator function
- Antitachycardia function
- Place external defibrillator pads connected to defibrillator:
- Anterior/posterior position, not apex/right upper thorax
- Not overlying implanted device
- Place cautery return pad as far from ICD as possible:
- Advise surgeon to use short <1 second bursts of electrocautery
- Use bipolar cautery if possible, regardless of device deactivation, to minimize risk of device damage from EMI
- Avoid/correct any cause of dysrhythmia: electrolyte imbalance, ischemia, hypovolemia
- If malfunction:
- Turn off all electrical devices
- If VT/VF without ICD response, use external defibrillator
- If inappropriate shocks, evaluate clinical tolerance: