Defibrillators, Implantable

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Basics

Description

  • An implantable cardiac device (ICD) is a small battery-powered electrical impulse generator implanted subcutaneously in patients at risk of cardiac arrest from cardiac arrhythmias
  • Positioning of leads via venous return of the heart:
    • Endocardial (RA and RV)
    • Epicardial (LV via coronary sinus)
  • Midaxillary positioning via subcutaneous placement:
    • Eliminates exposure to systemic circulation (S-ICD)
  • The device is able to detect and convert ventricular and atrial arrhythmias to sinus rhythm with electric shocks delivered between the ICD can and coil(s) in the RV (single coil) and the SVC/RA juncture (dual coil)
  • Similar method of implantation as a pacemaker
  • 450,000 individuals experience sudden cardiac death yearly in the U.S.:
    • >100,000 devices implanted in the U.S. each year
    • ICDs have been shown to reduce mortality more effectively than antiarrhythmic drug therapy in patients with left ventricular dysfunction:
      • Absolute risk reduction of mortality of 7% in the first 2 yr
      • Benefit over antiarrhythmic drug therapy is limited to patients with ejection fractions of <35%
    • Effective in reducing mortality in hypertrophic cardiomyopathy
    • Both ischemic and nonischemic dilated cardiomyopathy patients show survival benefit with ICD
  • Immediate postimplant complications:
    • Pneumothorax
    • Vascular perforation
    • Acute lead dislodgement
  • Appropriate shocks:
    • 5% a year for primary prevention
    • 20% a year for secondary prevention
  • Electrical storm:
    • ≥2 appropriate shocks delivered within a 24-hr period
  • Inappropriate shocks:
    • 10–20% of ICD recipients
    • Oversensing
    • Inappropriate classification of rapid supraventricular tachycardia (SVT, afib)
  • Device infection:
    • 1–12% of patients
    • Acute 1–30 d – think staph
    • Subacute >30 d – think Staphylococcus epidermidis or gram negatives
    • 31–66% mortality if the device is left in place
    • Infection may involve the skin, the generator, the defibrillation pocket, or the leads
    • Coagulase-negative staphylococci (42%)
    • Methicillin-sensitive staphylococci (25%)
    • MRSA (4%)
    • Gram-negative bacilli (9%)
  • Pocket hematoma do not aspirate
  • Vascular occlusion

Etiology

  • Electrical storm: (≥2 appropriate shocks delivered within a 24-hr period)
    • Unknown
    • Decompensated heart failure
    • Acute ischemia
    • Metabolic disturbances
    • Drug proarrhythmia
    • Thyrotoxicosis
    • Fever with dilated cardiomyopathy
    • Genetic channelopathies, Brugada syndrome, long QT, catecholaminergic polymorphic VT, arrhythmogenic RV cardiomyopathy
    • Postcardiac surgery
  • Inappropriate shocks:
    • Oversensing:
      • QRS, T-wave, P-wave, myopotential, electromagnetic interference (EMI)
      • Frequent nonsustained ventricular dysrhythmias
      • Lead fracture
      • Loose setscrew
      • Chatter between leads
      • Header (device circuitry) problem
    • Inappropriate classification of rapid SVT:
      • Atrial fibrillation
      • Sinus tachycardia
      • Atrial flutter
      • Other SVTs
  • Device/site-related:
    • Wound infection:
      • Staphylococcus aureus (most aggressive and seen early)
      • S. epidermidis (more indolent and later)
      • Escherichia coli, Pseudomonas species, and Streptococcus species (less common)
    • Pocket hematomas
    • Vascular (venous thrombosis/embolism secondary to impedance of venous flow as a result of the ICD lead[s])

-- To view the remaining sections of this topic, please or --

Basics

Description

  • An implantable cardiac device (ICD) is a small battery-powered electrical impulse generator implanted subcutaneously in patients at risk of cardiac arrest from cardiac arrhythmias
  • Positioning of leads via venous return of the heart:
    • Endocardial (RA and RV)
    • Epicardial (LV via coronary sinus)
  • Midaxillary positioning via subcutaneous placement:
    • Eliminates exposure to systemic circulation (S-ICD)
  • The device is able to detect and convert ventricular and atrial arrhythmias to sinus rhythm with electric shocks delivered between the ICD can and coil(s) in the RV (single coil) and the SVC/RA juncture (dual coil)
  • Similar method of implantation as a pacemaker
  • 450,000 individuals experience sudden cardiac death yearly in the U.S.:
    • >100,000 devices implanted in the U.S. each year
    • ICDs have been shown to reduce mortality more effectively than antiarrhythmic drug therapy in patients with left ventricular dysfunction:
      • Absolute risk reduction of mortality of 7% in the first 2 yr
      • Benefit over antiarrhythmic drug therapy is limited to patients with ejection fractions of <35%
    • Effective in reducing mortality in hypertrophic cardiomyopathy
    • Both ischemic and nonischemic dilated cardiomyopathy patients show survival benefit with ICD
  • Immediate postimplant complications:
    • Pneumothorax
    • Vascular perforation
    • Acute lead dislodgement
  • Appropriate shocks:
    • 5% a year for primary prevention
    • 20% a year for secondary prevention
  • Electrical storm:
    • ≥2 appropriate shocks delivered within a 24-hr period
  • Inappropriate shocks:
    • 10–20% of ICD recipients
    • Oversensing
    • Inappropriate classification of rapid supraventricular tachycardia (SVT, afib)
  • Device infection:
    • 1–12% of patients
    • Acute 1–30 d – think staph
    • Subacute >30 d – think Staphylococcus epidermidis or gram negatives
    • 31–66% mortality if the device is left in place
    • Infection may involve the skin, the generator, the defibrillation pocket, or the leads
    • Coagulase-negative staphylococci (42%)
    • Methicillin-sensitive staphylococci (25%)
    • MRSA (4%)
    • Gram-negative bacilli (9%)
  • Pocket hematoma do not aspirate
  • Vascular occlusion

Etiology

  • Electrical storm: (≥2 appropriate shocks delivered within a 24-hr period)
    • Unknown
    • Decompensated heart failure
    • Acute ischemia
    • Metabolic disturbances
    • Drug proarrhythmia
    • Thyrotoxicosis
    • Fever with dilated cardiomyopathy
    • Genetic channelopathies, Brugada syndrome, long QT, catecholaminergic polymorphic VT, arrhythmogenic RV cardiomyopathy
    • Postcardiac surgery
  • Inappropriate shocks:
    • Oversensing:
      • QRS, T-wave, P-wave, myopotential, electromagnetic interference (EMI)
      • Frequent nonsustained ventricular dysrhythmias
      • Lead fracture
      • Loose setscrew
      • Chatter between leads
      • Header (device circuitry) problem
    • Inappropriate classification of rapid SVT:
      • Atrial fibrillation
      • Sinus tachycardia
      • Atrial flutter
      • Other SVTs
  • Device/site-related:
    • Wound infection:
      • Staphylococcus aureus (most aggressive and seen early)
      • S. epidermidis (more indolent and later)
      • Escherichia coli, Pseudomonas species, and Streptococcus species (less common)
    • Pocket hematomas
    • Vascular (venous thrombosis/embolism secondary to impedance of venous flow as a result of the ICD lead[s])

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