Implantable defibrillators and cardiac resynchronisation therapy
How ICDs detect and treat arrhythmias, transvenous versus subcutaneous devices, CRT indications by QRS width and morphology, reading a device check, managing shocks, deactivation at the end of life, and driving.
Tier 2Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- An ICD senses ventricular rate and morphology, and treats VT or VF with anti-tachycardia pacing (ATP) or a shock. Every transvenous ICD also paces for bradycardia.
- CRT paces both ventricles (an RV lead plus a coronary sinus lead on the LV lateral wall) to resynchronise a heart with LBBB. It comes as CRT-P (pacemaker) or CRT-D (with a defibrillator).
- Who needs an ICD is set out in ventricular tachycardia (secondary prevention) and heart failure (primary prevention). Inherited conditions are in HCM, ARVC, long QT and Brugada.
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Sources
- 2022 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac deathEuropean Society of Cardiology (Eur Heart J 2022, doi:10.1093/eurheartj/ehac262), 2022
- 2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapyEuropean Society of Cardiology (European Heart Journal, doi:10.1093/eurheartj/ehab364), 2021
- Køber L, Adamo M et al. 2026 ESC Guidelines for the management of heart failure. Eur Heart J 2026. doi:10.1093/eurheartj/ehag100European Society of Cardiology, 2026
- ESC clinical consensus statement on indications for conduction system pacingEuropean Society of Cardiology and European Heart Rhythm Association (EP Europace), 2025
- Cardiac Society of Australia and New Zealand (CSANZ) Position Statement on the Follow-Up of Cardiovascular Implantable Electronic Devices 2022AU/NZCardiac Society of Australia and New Zealand (Heart, Lung and Circulation 2022;31(8):1054-63, doi:10.1016/j.hlc.2022.05.001), 2022
- Knops RE et al. Subcutaneous or transvenous defibrillator therapy (PRAETORIAN). N Engl J Med 2020;383:526-36New England Journal of Medicine, 2020
- Moss AJ et al. Reduction in inappropriate therapy and mortality through ICD programming (MADIT-RIT). N Engl J Med 2012;367:2275-83New England Journal of Medicine, 2012
- HRS expert consensus statement on the management of cardiovascular implantable electronic devices in patients nearing end of life or requesting withdrawal of therapyHeart Rhythm Society (Heart Rhythm 2010;7:1008-26), 2010
- Assessing Fitness to Drive for commercial and private vehicle drivers (2022 edition; ICD criteria for commercial drivers revised 22 June 2022)AU/NZAustroads and the National Transport Commission, 2022
- Last updated
- 14 November 2026
What changed
- 14 November 2026 Personal emails, About story and Australian-style copy