Adding implantable cardioverter-defibrillator to cardiac resynchronization therapy in patients with non-ischemic cardiomyopathy: a systematic review and meta-analysis with focus on elderly subpopulation

BACKGROUND  Cardiac resynchronization therapy (CRT) has been a major therapeutic advancement for patients with heart failure and electrical dyssynchrony. While CRT improves symptoms, reduces hospitalizations, and enhances survival, the role of implantable cardioverter-defibrillators (ICDs) alongside CRT in patients with non-ischemic cardiomyopathy (NICM) remains controversial. To evaluate and compare the outcomes of CRT with ICD (CRT-D) versus CRT with pacemaker-only (CRT-P) in individuals diagnosed with NICM, with a specific focus on the elderly.

METHODS  A comprehensive search of PubMed, Embase, and the Cochrane Central Register of Controlled Trials was conducted in January 2024. Studies comparing CRT-D and CRT-P in patients with NICM were included, with subgroup analyses focusing on patients aged 75 years and older.

RESULTS  Twelve studies, including two randomized clinical trials, with a total of 62,145 patients and 16,754 pooled death events (9,171 in CRT-D and 7,583 in CRT-P), were analyzed. CRT-D was associated with a significantly lower risk of all-cause mortality compared to CRT-P (pooled OR = 0.72; 95% CI: 0.61–0.85; P < 0.01), with significant heterogeneity (I² = 83%). RCT subgroup analysis, was not statistically significant (pooled OR = 0.82; 95% CI: 0.64-1.06; P = 0.41; I² = 0%). In patients older than 75 years, no significant difference in mortality risk was observed (pooled OR 0.96; 95% CI: 0.81–1.15; I²=39%).

CONCLUSION  Our meta-analysis suggests that the addition of ICD therapy to CRT in patients with NICM significantly reduces all-cause mortality. However, this benefit does not extend to cardiovascular mortality, likely due to the primary role of ICDs in preventing sudden cardiac death rather than other causes such as progressive heart failure. The survival advantage of CRT-D is most pronounced in younger patients, with those over 75 years of age deriving less benefit. This highlights the importance of careful patient selection, considering age and comorbidities, when deciding on ICD implantation in NICM patients.