Giovanni Esposito (Division of Cardiology, Department of Advanced Biomedical Sciences, Naples, Italy) and others report that, in The American Journal of Cardiology, the results of a meta-analysis support previous findings that preoperative moderate-to-severe mitral regurgitation negatively affects outcomes after transcatheter aortic valve implantation (TAVI). However, the meta-analysis also suggests that there is a trend towards mitral regurgitation improvement after TAVI.
Esposito et al note that the presence of severe mitral regurgitation is not considered to be a contradiction in TAVI patients but “its role on survival is controversial”. They explain: “While some studies have previously reported increased mortality rates in patients with mitral regurgitation undergoing TAVI, some others did not confirm these results.” Furthermore, the authors add that it is “still unclear” whether or not TAVI has a beneficial effect on mitral regurgitation severity. Therefore, the aim of the present meta-analysis was to “define the impact of mitral regurgitation severity on outcomes after TAVI and to assess whether TAVI might improve mitral regurgitation.”
The authors conducted search of articles on Medline, Cochrane, ISI Web of Science and Scopus databases and identified 13 articles (4,839 patients) that met the criteria for their study (had data for TAVI performed in high-risk or inoperable patients, mitral regurgitation severity, and had data for mortality outcomes based mitral regurgitation severity or data for mitral regurgitation outcomes after TAVI). The primary endpoint was the incidence of all-cause mortality in patients with moderate-to-severe mitral regurgitation undergoing TAVI and the secondary endpoint was mitral regurgitation improvement after TAVI.
Compared with patients no or mild mitral regurgitation, moderate-to-severe mitral regurgitation was associated with a significantly increased of all-cause mortality at 30 days, one year, and two years after TAVI. However, when valve types were looked at—Sapien (Edwards Lifesciences) vs. CoreValve (Medtronic)—the risk of all-cause mortality was only increased when the CoreValve device was used. Esposito et al note: “These data were confirmed at short (one month) and long-term follow-up.” They add that the subanalysis of the valve types was only conducted in half of the studies included in the meta-analysis because of the “unavailability of the data in the primary studies”, commenting: “This unexpected and somewhat surprising result should be carefully evaluated, and eventually verified and confirmed in larger future studies.” Therefore, the author suggest exercising caution before performing TAVI in patients with severe mitral regurgitation; nevertheless, they add, whether one valve type is preferable over another is still a matter of concern.
The results of the metal-analysis did indicate that there was non-significant trend towards mitral regurgitation improvement at one month and one year after TAVI, but there was evidence of a significant improvement at the mid-term follow-up point (three to six months). Esposito et al state that the improvement observed in patients with functional mitral regurgitation after surgical aortic valve replacement is “probably due to the decrease in mitral leaflet tethering” and that “the amelioration in mitral regurgitation and the reduction in mitral tethering may occur when left ventricle haemodynamic improves following TAVI.” However, due to lack of data, the authors were not able to identify the impact of TAVI on different aetiologies of mitral regurgitation (ie. degenerative vs. functional).
As the meta-analysis is not “patient-level” and includes “primarily observational studies”, among other factors, Esposito et al conclude that their results should be considered “provisional and hypothesis generating”. “Certainly, new studies aimed at specifically evaluating and comparing the impact of different types of valve in patients with severe aortic stenosis and moderate-to-severe mitral regurgitation should be performed,” they write.