Our study was the first meta-analysis to assess TEER on the early outcomes in high-risk surgical patients with DMR compared with surgery. The main findings are as follows. First, there was no significant difference in early all-cause mortality, survival at 1-year and SF-36 physical score at 1-year between TEER and surgery. Second, TEER was associated with a higher risk of acute postprocedural residual MR > 2 + and recurrent MR > 2 + at 1-year. The quality of evidence of our outcomes was moderate or low.
TEER has been proven a viable alternative option in the management of severe functional or secondary MR (FMR) at high surgical risk, with less procedure-related complications and satisfactory early survival benefit, compared with medical therapy or surgery [23–25]. However, distinct MR etiologies between DMR and FMR may obviously influence the clinical efficacy of TEER. According to current guidelines, surgical mitral valve repair is still the gold standard for treating DMR originated from its good durability and excellent long-term outcomes [5, 6]. Currently, the experience of TEER for DMR patients mainly comes from the EVERST Ⅱ trial. Unfortunately, the short- and mid-term TEER outcomes, including restoring left ventricular function, need for reoperation, and recurrent severe MR, are really inferior to surgery [12, 26]. To date, the effectiveness and safety of TEER for high or prohibitive surgical risk DMR remains controversial.
Our meta-analysis showed that there was no significant difference in early all-cause mortality and survival at 1-year between TEER and surgery. This was similar with TEER in treating FMR and indicated that the safety of TEER was trustworthy. With regard to mid- (≥ 5 years) and long-term (≥ 10 years) survival, no data was reported in pure DMR cohort. The EVERST Ⅱ trial published its 5-year follow-up outcomes in 2015 [26]. Five-year mortality rates were 20.8% for TEER and 26.8% for surgery (P = 0.4), and the result did not alter significantly even if in multivariable analysis. However, this result is just for reference, as its cohort included not only DMR but also FMR.
Acute postprocedural residual and recurrent MR during follow-up is a major concern regarding TEER in treating DMR. Previous studies have demonstrated that acute postprocedural residual MR > 2 + is more prone to emerge mitral valve (MV) reoperation, worsening cardiac function, and rehospitalization for heart failure (HF), with a poor long-term survival [27–30]. As for recurrent MR, previous studies have also shown that it was associated a bad prognosis if the grade > 2+. Our meta-analysis showed that TEER occurred a higher incidence of acute postprocedural residual MR > 2 + and recurrent MR > 2 + at 1-year compared with surgery. For this issue, future studies with a long-term follow-up are warranted.
Compared with surgery, the main advantage of TEER is minimally invasive [12]. Because sternotomy and cardiopulmonary bypass are not required, postoperative major adverse events (MAEs) such as stroke, acute kidney injury, low cardiac output syndrome, and new-onset atrial fibrillation are low apparently in TEER treated patients. However, since the definition of MAEs was not inconsistent in different studies, we did not conduct a data pooling for this result. However, we believe that TEER favors a lower risk of MAEs compared with surgery.
It is still too early to draw a conclusion as to whether TEER is suitable for treating high-risk patients with DMR. At present, TEER can be performed using PASCAL (Edwards Lifesciences, USA) or MitraClip devices (Abbott Vascular, USA). Compared to the widely used MitraClip device, the PASCAL device exhibited high procedural success, durable MR reduction, and high survival at 2-year in patients with clinically severe MR [31, 32]. In 2022, the CLASP ⅡD randomized trial was published [33]. It randomly assigned DMR patients at prohibitive surgical risk to receive MitraClip or PASCAL in a 2:1 ratio and demonstrated a better outcome of the PASCAL device. Future trials can compare the effectiveness and safety of PASCAL device and surgery on DMR patients.
Our study has the following limitations. First, the pooled raw data derives from 1 DMR cohort of the EVERST Ⅱ trial and 3 observational cohort studies. This affects the credibility of evidence in our results due to unadjusted confounders such as age, gender and comorbidities. Second, the sample sizes of the included studies were relatively small; thus, our findings may be biased. Third, owing to limited included studies, we could not compare the occurrence of MV reoperation and rehospitalization for HF between both groups. Finally, our study only evaluated the early outcomes; therefore, future studies are required to assess TEER on the mid-and long-term results.