Seven RCTs (4,536 participants) were included. Study size ranged from 126 to 1,520 participants. Thee studies (CRT-D to ICDs) scored 5 for quality, three scored 3 and one scored 2 on the Jadad scale.
Compared to controls, CRT-D therapy was associated with a statistically significant reduction in all-cause mortality (OR 0.55, 95% CI 0.40 to 0.76, I2=60%; seven studies). Sensitivity analysis suggested that one study was responsible for heterogeneity; results that excluded this study were not reported.
In subgroup analyses, CRT-D was associated with a statistically significant reduction in all-cause mortality when compared to CRT (OR 0.48, 95% CI 0.31 to 0.75, I2=79%; four studies) and medical therapy (OR 0.64, 95% CI 0.46 to 0.90; one study). There was no statistically significant difference in mortality between CRT-D and ICD therapy (I2=0%, three trials).