Moderate-to-Severe Mitral Regurgitation Signals Elevated Mortality Risk After TAVR

Among patients undergoing TAVR, concomitant moderate-to-severe mitral regurgitation (MR) at baseline is tied to a heightened mortality risk at 30 days and 1 year, according to a study published online June 9, 2015, ahead of print in Heart. The severity of MR improved in about half of these patients after TAVR, with greater gains observed in those who received balloon-expandable valves.

“The effects of and changes in MR in [TAVR] candidates should be taken into account in the clinical decision-making, procedural, and follow-up process of such a challenging group of patients,” write Josep Rodés-Cabau, MD, of the Quebec Heart & Lung Institute (Quebec City, Canada), and colleagues. “Also, the possibility of a double-valve procedure should be considered in such cases, especially in the presence of severe MR in those patients at moderate or high but not prohibitive surgical risk.”

The researchers performed a meta-analysis that included 8 studies (2 RCTs and 6 national registries) with a total of 8,015 patients to assess the relationship between significant MR—defined as moderate or severe—and mortality. Also included were 9 observational studies, with a total of 1,278 patients, to evaluate changes in MR after TAVR.

Significant MR at baseline was associated with an increase in mortality at 30 days (OR 1.49; 95% CI 1.16-1.92) and 1 year (HR 1.32; 95% CI 1.12-1.55) after TAVR, although there was significant heterogeneity across studies (P < .05). The relationship between MR and mortality did not differ between self-expanding and balloon-expandable valves at either time point.

At baseline, MR severity was graded as none in 18.7%, mild in 40.5%, moderate in 30.2%, and severe in 10.6%. At a median follow-up of 180 days, MR severity improved in 22.5% of patients, remained unchanged in 70.0%, and worsened in 7.6%.

Roughly half of the patients with moderate-to-severe MR at baseline (50.5%) showed lessened severity over time; however, that rate was higher among the patients who received a balloon-expandable vs a self-expanding valve (66.7% vs 40.8%; P = .001).

Substantial Heterogeneity in Effect of MR on Mortality

The impact of concomitant MR on clinical outcomes following TAVR has not been examined in a systematic way, according to the authors, and prior studies have provided mixed results. Also, wide variation has been reported regarding the improvement in MR severity after the procedure.

The heterogeneity in the effect of significant MR on 30-day mortality seen in the meta-analysis “was mainly driven by differences between BEV [balloon-expandable valve] and  SEV [self-expanding valve] studies, with SEV data being more homogenous in the global effect of significant MR on early mortality,” Dr. Rodés-Cabau and colleagues write. “This heterogeneity between studies might partially be explained by higher proportion of severe MR in some studies (about 6%–9%) compared with others (about 2%) and the incremental risk associated with increasing grades of MR severity.”

With longer-term follow-up out to 1 year, the authors add, “this discrepancy across studies may be related in part to the challenge of MR quantification and the lack of a core laboratory for the assessment of MR severity.”

Between-Valve Comparisons Not Definitive

The authors suggest that several factors could be behind the increased likelihood of improvement in moderate-to-severe MR among patients receiving BEVs.

“It has been suggested that the longer frame of the SEV may physically interfere with the anterior leaflet of the mitral apparatus, although this was not confirmed in a recent large CoreValve series,” they write. “The CoreValve system is associated with a higher degree of post-TAVR paravalvular aortic regurgitation and may maintain volume overload and contribute to a [smaller] MR improvement in such patients. In addition, SEV implantation is associated with a higher rate of both left bundle branch block and the need for pacemaker implantation, which indeed may lead to LV asynchrony and a negative effect on LV remodeling and MR improvement.”

However, the authors note, “the comparison between the 2 types of prostheses should be interpreted with caution due to observational nature of the studies included in the meta-analysis and the lack of randomized data.”

Indeed, the meta-analysis was limited in that it included mostly observational studies, there was significant heterogeneity in the mortality findings across studies, multiple grading methods to assess MR severity were used, no centralized echo core lab data were available, and there was no information on the etiology of MR (functional vs organic), according to the researchers.

“Despite these limitations, the large sample size and the robustness of our results clearly show the need for ongoing critical evaluation of this problem when evaluating candidates for TAVR,” they write.

Note: Study coauthor Martin B. Leon, MD, is a faculty member of the Cardiovascular Research Foundation, which owns and operates TCTMD.

Nombela-Franco L, Eltchaninoff H, Zahn R, et al. Clinical impact and evolution of mitral regurgitation following transcatheter aortic valve replacement: a meta-analysis. Heart. 2015;Epub ahead of print.

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