Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
All-cause mortality
[86] Systematic review	3203 people 8 RCTs in this analysis	Rate of mortality with cardiac resynchronisation therapy (CRT) with usual care Absolute results not reported	RR 0.79 95% CI 0.66 to 0.96 Some RCTs included in the analysis compared CRT plus implantable cardiac defibrillators (ICDs) versus ICDs alone	Small effect size	CRT
[87] Systematic review	3380 people 8 RCTs in this analysis	Rate of mortality 264/1847 (14%) with CRT 260/1533 (17%) with control (not further defined)	OR 0.72 95% CI 0.59 to 0.88 The review included RCTs in which ICDs were used in all people randomised	Small effect size	CRT
[88] Systematic review	2249 people 4 RCTs in this analysis	Rate of mortality 245/1283 (19%) with CRT 247/966 (26%) with usual care (medical treatment)	OR 0.67 95% CI 0.50 to 0.90 This analysis included those RCTs in which neither arm was treated with an ICD	Small effect size	CRT
[89] Systematic review	3164 people with heart failure 5 RCTs in this analysis	All-cause mortality 224/1664 (14%) with CRT 244/1364 (18%) with usual care	RR 0.70 95% CI 0.60 to 0.83	Small effect size	CRT
Cardiac mortality
[86] Systematic review	1647 people 7 RCTs in this analysis	Rate of death from progressive heart failure with CRT with usual care Absolute results not reported	RR 0.60 95% CI 0.36 to 1.01 Some RCTs included in the analysis compared CRT plus ICDs versus ICDs alone		Not significant
[89] Systematic review	1716 people with heart failure 2 RCTs in this analysis	Death from congestive heart failure 98/1004 (9%) with CRT 92/712 (13%) with usual care	RR 0.79 95% CI 0.60 to 1.03		Not significant
[89] Systematic review	2085 people with heart failure 3 RCTs in this analysis	Sudden cardiac death 49/1191 (4%) with CRT 59/894 (7%) with usual care	RR 0.67 95% CI 0.46 to 0.96 P = 0.03	Small effect size	CRT