Persistence of significant secondary mitral regurgitation post-cardiac resynchronization therapy and survival: a systematic review and meta-analysis

Cardiac resynchronization therapy (CRT) significantly reduces secondary mitral regurgitation (MR) in patients with severe left ventricular systolic dysfunction. However, uncertainty remains as to whether improvement in secondary MR correlates with improvement with mortality seen in CRT. We conducted a meta-analysis to determine the association of persistent unimproved significant secondary MR (defined as moderate or moderate-to-severe or severe MR) compared to improved MR (no MR or mild MR) post-CRT with all-cause mortality, cardiovascular mortality, and heart failure hospitalization. A systematic search of PubMed, EMBASE, and Cochrane Library databases till July 31, 2022 identified studies reporting clinical outcomes by post-CRT secondary MR status. In 12 prospective studies of 4954 patients (weighted mean age 66.8 years, men 77.8%), the median duration of follow-up post-CRT at which patients were re-evaluated for significant secondary MR was 6 months and showed significant relative risk reduction of 30% compared to pre-CRT. The median duration of follow-up post-CRT for ascertainment of main clinical outcomes was 38 months. The random effects pooled hazard ratio (95% confidence interval) of all-cause mortality in patients with unimproved secondary MR compared to improved secondary MR was 2.00 (1.57–2.55); p