Table 1.

NICE Guidance for device therapy according to NYHA class and QRS duration. Reproduced with permission.³⁷

	NYHA Class
QRS Interval	I	II	III	IV
<120 msec	ICD if there is a high risk of sudden cardiac death			ICD and CRT not clinically indicated
120–149 msec without LBBB	ICD	ICD	ICD	CRT-P
120–149 msec with LBBB	ICD	CRT-D	CRT-P or CRT-D	CRT-P
>150 msec with or without LBBB	CRT-D	CRT-D	CRT-P or CRT-D	CRT- P

CRT = cardiac resynchronisation therapy; CRT-D = defibrillator; CRT-P = pacemaker; ICD = implanted cardioverter defibrillator; LBBB = left bundle branch block; NYHA = New York Heart Association.