NICE guidance has stated which patients should be considered for the use of implantable cardioverter defibrillators (ICD) include (1):
Implantable cardioverter defibrillators (ICDs) are recommended as options for:
- treating people with previous serious ventricular arrhythmia, that is, people who, without a treatable cause:
 
 - have survived a cardiac arrest caused by either ventricular tachycardia (VT) or ventricular fibrillation or
 
 
- have spontaneous sustained VT causing syncope or significant haemodynamic compromise or
 
 
- have sustained VT without syncope or cardiac arrest, and also have an associated reduction in left ventricular ejection fraction (LVEF) of 35% or less but their symptoms are no worse than class III of the New York Heart Association (NYHA) functional classification of heart failure
 
 
 
- treating people who:
 
 - have a familial cardiac condition with a high risk of sudden death, such as long QT syndrome, hypertrophic cardiomyopathy, Brugada syndrome or arrhythmogenic right ventricular dysplasia or
 
 
- have undergone surgical repair of congenital heart disease
 
Implantable cardioverter defibrillators (ICDs), cardiac resynchronisation therapy (CRT) with defibrillator (CRT-D) or CRT with pacing (CRT-P) are recommended as treatment options for people with heart failure who have left ventricular dysfunction with a left ventricular ejection fraction (LVEF) of 35% or less as specified in table below:
- Treatment options with ICD or CRT for people with heart failure who have left ventricular dysfunction with an LVEF of 35% or less (according to NYHA class, QRS duration and presence of LBBB)
|  |  |  |  |  | 
|  | ICD if there is a high risk of sudden cardiac death | ICD if there is a high risk of sudden cardiac death | ICD if there is a high risk of sudden cardiac death | ICD and CRT not clinically indicated | 
| 120- 149 milliseconds without LBBB |  |  |  |  | 
| 120-149 milliseconds with LBBB |  |  |  |  | 
| >=150 milliseconds with or without LBBB |  |  |  |  | 
LBBB, left bundle branch block; NYHA, New York Heart Association
The NICE guidance does not cover the use of implantable defibrillators for non-ischaemic dilated cardiomyopathy.
Notes:
- subcutaneous implantable cardioverter defibrillator (2) - current evidence on the efficacy of the insertion of a subcutaneous implantable cardioverter defibrillator (ICD) for the prevention of sudden cardiac death in the short and medium term is adequate
 
 
- an entirely subcutaneous ICD differs from a conventional ICD in that the lead is placed subcutaneously, rather than transvenously - the lead comprises 2 sensing electrodes and a shocking coil
- the ICD senses cardiac signals, but the lead is not directly attached to the heart
- unlike a conventional ICD, the subcutaneous device is not designed to provide long-term pacing
 
 
Reference:
- NICE (June 2014). Implantable cardioverter defibrillators and cardiac resynchronisation therapy for arrhythmias and heart failure
- NICE (April 2013). Insertion of a subcutaneous implantable cardioverter defibrillator for prevention of sudden cardiac death.