22. Implantable cardioverter-defibrillators (ICD)

Background

  • ICDs address ventricular arrhythmia by sensing abnormal rhythm and delivering overdrive pacing (also known as antitachycardia pacing (ATP)) or a shock (cardioversion or defibrillation).
  • Most ICDs have transvenous leads allowing for pacing (for bradycardia or VT termination), but subcutaneous ICDs may be considered if these are unable to be placed (infection risk, no vascular access) or if pacing is not felt to be necessary.
  • For interrogation and EP consultation it is important to ask patient which device company they have.
  • Compared to pacemakers, ICDs are much larger (have a large battery) and can be distinguished from pacemakers on exam or CXR.
  • MRI compatibility: devices typically labeled, with MRI compatible or MRI conditional status noted.

Indications

Primary prevention: increased risk of ventricular arrhythmia causing sudden cardiac death.

Class I indications:

  • Ischemic or nonischemic cardiomyopathy with a left ventricular ejection fraction ≤35% despite guideline directed medical therapy.
  • NSVT in a patient with prior MI and left ventricular ejection fraction ≤40% (at discretion of cardiologist).

NOTE: ICD is NOT recommended in NYHA Class IV patients with medication-refractory HF who are not candidates for LVAD or transplant or who otherwise have life expectancy <1 year.

Secondary prevention: following an episode of sustained VT, ventricular arrhythmia causing syncope, or cardiac arrest.

Class I Indications: must not be a reversible cause and “meaningful” survival must be >1 year.

  • History of cardiac arrest due to VT/VF.
  • Unstable VT (hemodynamically significant).
  • Stable sustained VT.
  • Ischemic heart disease and unexplained syncope with inducible sustained monomorphic VT on EP study.

Specific conditions to consider:

  • Arrhythmogenic RV cardiomyopathy with syncope.
  • Hypertrophic cardiomyopathy with risk factors.
  • Giant cell myocarditis.
  • Cardiac sarcoidosis.
  • Neuromuscular disorders with progressive cardiac involvement or PPM indication.
  • Cardiac channelopathies (long QT syndrome, catecholaminergic polymorphic VT, Brugada).

Complications/Adverse Events

Device shocks: consider whether appropriate (due to VT/VF) or inappropriate (e.g. shocking due to afib with RVR).

  • If appropriate: address underlying etiology of VT/VF.
  • If inappropriate: consider non-ventricular arrhythmia (e.g. SVT or sinus tachycardia), abnormal/inappropriate sensing, or lead fracture.
  • Consider whether device programing might address inappropriate shocks (i.e. changing shock threshold).

Structural complications: infection (of lead or pocket), lead failure, tricuspid valve injury, circuit or generator failure.

Implantation-related: pneumothorax, tamponade, and myocardial perforation.

References:

Al-khatib SM, Stevenson WG, Ackerman MJ, et al. 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. Circulation. 2018;138(13):e272-e391.

Atwater BD, Daubert JP. Implantable cardioverter defibrillators: risks accompany the life-saving benefits. Heart. 2012;98(10):764-72.

Cesario D, Dec GW. Implantable Cardioverter-Defibrillator Therapy in Clinical Practice. JACC. 47;2006;47:1507-1517.

Van Reese, J, de Bie M, Thijssen J, et al. Implantation-related Complications of Implantable Cardioverter-defbrillators and Cardiac Resynchronization Therapy Devices: a systemic review of randomized clinical trials. JACC. 2011; 58; 995-1000.

Daubert JP, Zareba W, Cannom DS, et al. Inappropriate implantable cardioverter-defibrillator shocks in MADIT II: frequency, mechanisms, predictors, and survival impact. J Am Coll Cardiol. 2008;51(14):1357-65.