The role of surgery for secondary mitral regurgitation and heart failure in the era of transcatheter mitral valve therapies

Long-term outcomes comparison of mitral valve repair or replacement for secondary mitral valve regurgitation. An updated systematic review and reconstructed time-to-event study-level meta-analysis

BACKGROUND AND AIM

The ideal surgical intervention for secondary mitral regurgitation (SMR), a disease of the left ventricle not the mitral valve itself, is still debated. We performed an updated systematic review and study-level meta-analysis investigating mitral valve repair (MVr) versus mitral valve replacement (MVR) for adult patients with SMR, with or without coronary artery disease (CAD).

METHODS

PubMed, CENTRAL and EMBASE were searched for studies comparing MVr versus MVR. Randomized trial or observational studies were considered eligible. Primary endpoint was long-term mortality for any cause. Kaplan-Meier survival curves were reconstructed and compared with Cox linear regression. Landmark analysis and time-varying hazard ratio (HR) were analyzed. Sensitivity analyses included meta-regression and separate sub-analysis. A random effects model was used.

RESULTS

Twenty-three studies (MVr=3,727 and MVR=2,839) were included. One study was a randomized trial, and 19 studies were adjusted. The mean weighted follow-up was 3.7±2.8 years. MVR was associated with significative greater late mortality (HR=1.26; 95 % CI, 1.14-1.39; P<0.0001) at 10-year follow-up. There was a time-varying trend showing an increased risk of mortality in the first 2 years after MVR (HR=1.38; 95 % CI, 1.21-1.56; P<0.0001), after which this difference dissipated (HR=0.94; 95 % CI, 0.81-1.09; P=0.41). Separate sub-analyses showed comparable long-term mortality in patients with concomitant coronary surgery ≥90 %, left ventricle ejection fraction ≤40 %, and sub-valvular apparatus preservation rate of 100 %.

CONCLUSIONS

Compared to repair, MVR is associated with higher probability of mortality in the first 2 years following surgery, after which the two procedures showed comparable late mortality rate.

Updated pathophysiological overview of functional MR (ventricular and atrial)

Basic mechanism of ventricular functional mitral regurgitation (FMR) is subvalvular tethering. Left ventricular (LV) dilatation, in association with mitral valve (MV) annular dilatation, causes outward displacement of papillary muscles (PMs), which abnormally pulls or tethers MV leaflets, resulting in MV tenting, reduction in leaflets coaptation and MR. Because surgical annuloplasty does shorten distance between anterior and posterior MV annuli to improve coaptation but does not address this subvalvular tethering, ventricular FMR frequently persists or recurs in the chronic stage after surgical annuloplasty. This high incidence of persistent/recurrent MR requires additional procedures to reduce subvalvular tethering. Although patients occasionally show marked improvements after annuloplasty with surgical tethering reduction procedures such as PM approximation, evidence to support benefits of such surgery is limited, requiring further trials. Recently, MV adaptation or MV leaflets tissue growth associated with LV dilatation attracts attention. Patients with larger MV leaflets with significant LV dilatation/dysfunction show less MV tethering and MR compared to those with smaller MV leaflets but with similar LV remodeling, suggesting the protective or beneficial role of MV leaflets tissue growth against LV remodeling. The MV leaflets tissue growth has the potential to lead to novel strategies of treatment for ventricular FMR. It is well known that atrial FMR is frequent in patients with left atrial dilatation, typically in those with isolated atrial fibrillation. The degree of atrial FMR is usually mild, even when it is present, and occasionally moderate, and severe atrial FMR is really rare. It is known that only severe regurgitation causes heart failure in primary MR, resulting in description on indications of surgery or intervention for only severe MR in current guidelines. Therefore, this atrial FMR up to moderate degree did not attract attention for a long time. However, recent studies have shown that patients with only moderate atrial FMR develop severe heart failure, suggesting more aggressive indication of MV surgery or intervention for "moderate" regurgitation in patients with atrial FMR. Therefore, atrial FMR is now recognized highly important. The unveiled malignant nature of atrial FMR arises many questions, including (1) why patients with only moderate atrial FMR develop heart failure? (2) do patients with mild atrial FMR develop heart failure or not?, and many others. Atrial FMR seems even more mysterious after the unveiling of its significance.

Parameters of the mitral apparatus in patients with ischemic and nonischemic dilated cardiomyopathy

The mitral valve apparatus is a complex structure consisting of several coordinating components: the annulus, two leaflets, the chordae tendineae, and the papillary muscles. Due to the intricate interplay between the mitral valve and the left ventricle, a disease of the latter may influence the normal function of the former. As a consequence, valve insufficiency may arise despite the absence of organic valve disease. This is designated as functional or secondary mitral regurgitation, and it arises from a series of distortions to the valve components. This narrative review describes the normal anatomy and the pathophysiology behind the mitral valve changes in ischemic and non-ischemic dilated cardiomyopathies. It also explains the value of a complete multiparametric assessment of this structure. Not only must an assessment include quantitative measures of regurgitation, but also various anatomical parameters from the mitral apparatus and left ventricle, since they carry prognostic value and are predictors of mitral valve repair success and durability.

Moderate Ischemic Mitral Regurgitation with Ejection Fraction <40% Undergoing Concomitant Mitral Valve Repair during Revascularization: A Single-Center Observational Study

Background

Numerous studies have examined the therapeutic effects of mitral valve repair during revascularization on moderate ischemic mitral regurgitation (IMR), as well as the incremental benefit of subvalvular repair alongside an annuloplasty ring. However, the impact of depressed left ventricular (LV) function on the surgical outcome of patients with moderate IMR has been rarely investigated. The aims of this single-center, retrospective, observational study were firstly to evaluate short- and medium-term outcomes in this patient group after undergoing mitral valve repair during revascularization, and secondly to assess the impact of depressed LV function on surgical outcomes.

Methods

A total of 272 eligible patients who had moderate IMR and underwent concomitant mitral valve repair and revascularization from January 2010 to December 2017 were included in the study. These patients were categorized into different groups based on their ejection fraction (EF) levels: an EF < 40% group (n = 90) and an EF ≥ 40% group (n = 182). The median time course of follow-up was 42 months and the shortest follow-up time was 30 months. This study compared in-hospital outcomes (major postoperative morbidity and surgical mortality) as well as midterm outcomes (moderate or more mitral regurgitation, all-cause mortality, and reoperation) of the two groups before and after propensity score (PS) matching (1:1).

Results

No significant difference was observed in surgical mortality between groups (8.9% vs. 3.3%, p = 0.076). More patients in the EF < 40% group developed low cardiac output (8.9% vs. 2.7%, p = 0.034) and prolonged ventilation (13.3% vs. 5.5%, p = 0.026) compared to the EF ≥ 40% group. Propensity score (PS) matching successfully established 82 patient pairs in a 1:1 ratio. No significance was discovered between the matched cohorts in terms of major postoperative morbidity and surgical mortality, except for prolonged ventilation. Conditional mixed-effects logistic regression analysis revealed that EF < 40% had an independent impact on prolonged ventilation (odds ratio (OR) = 2.814, 95% CI 1.321-6.151, p = 0.031), but was not an independent risk factor for surgical mortality (OR = 2.967, 95% CI 0.712-7.245, p = 0.138) or other major postoperative morbidity. Furthermore, the two groups showed similar cumulative survival before (log-rank p = 0.278) and after (stratified log-rank p = 0.832) PS matching. Cox regression analysis suggested that EF < 40% was not related to mortality compared with EF ≥ 40% (PS-adjusted hazard ratio (HR) = 1.151, 95% CI 0.763-1.952, p = 0.281).

Conclusions

Patients with moderate IMR and EF < 40% shared similar midterm outcomes and surgical mortality to patients with moderate IMR and EF ≥ 40%, but received prolonged ventilation more often. Depressed LV function may be not associated with surgical or midterm mortality.

Usefulness of Vena Contracta for Identifying Severe Secondary Mitral Regurgitation: A Three-Dimensional Transesophageal Echocardiography Study

Background

In secondary mitral regurgitation (SMR), effective regurgitant orifice area by the proximal isovelocity surface area method ( EROA PISA ) evaluation might cause an underestimation of regurgitant orifice area because of its ellipticity compared with vena contracta area (VCA). We aimed to reassess the SMR severity using VCA-related parameters and EROA PISA .

Methods

The three-dimensional transesophageal echocardiography data of 128 patients with SMR were retrospectively analyzed; the following parameters were evaluated: EROA PISA , anteroposterior and mediolateral vena contracta widths (VCWs) of VCA (i.e., VCW AP and VCW ML ), VCW Average calculated as ( VCW AP + VCW ML )/2, and VCA Ellipse calculated as π × ( VCW AP /2) × ( VCW ML /2). Severe SMR was defined as ≥ 0.39 cm 2 .

Results

The mean age of the patients was 77.0 ± 8.9 years, and 78 (60.9%) were males. Compared with EROA PISA (r = 0.801), VCW Average (r = 0.940) and VCA Ellipse (r = 0.980) were strongly correlated with VCA. On receiver-operating characteristic curve analysis, VCW Average and VCA Ellipse had C-statistics of 0.981 (95% confidence interval [CI], 0.963-1.000) and 0.985 (95% CI, 0.970-1.000), respectively; these were significantly higher than 0.910 (95% CI, 0.859-0.961) in EROA PISA (p = 0.007 and p = 0.003, respectively). The best cutoff values for severe SMR of VCW Average and VCA Ellipse were 0.78 cm and 0.42 cm 2 , respectively. The prevalence of severe SMR significantly increased with an increase in EROA PISA (38 of 88 [43.2%] patients with EROA PISA < 0.30 cm 2 , 21 of 24 [87.5%] patients with EROA PISA = 0.30-0.40 cm 2 , and 16 of 16 [100%] patients with EROA PISA ≥ 0.40 cm 2 [Cochran-Armitage test; p < 0.001]). Among patients with EROA PISA < 0.30 cm 2 , SMR severity based on VCA was accurately reclassified using VCW Average (McNemar's test; p = 0.505) and VCA Ellipse (p = 0.182).

Conclusions

Among patients who had SMR with EROA PISA of < 0.30 cm 2 , suggestive of moderate or less SMR according to current guidelines, > 40% had discordantly severe SMR based on VCA. VCW Average and VCA Ellipse values were useful for identifying severe SMR based on VCA in these patients.

Structural Interventions in Heart Failure: Mending a Broken Heart

Advanced heart failure is often accompanied by perturbations in cardiac chamber or valve geometries which result in worsening cardiac function and hemodynamics. Once limited to surgical procedures, recent developments in minimally invasive percutaneous techniques have demonstrated efficacy in patients with both reduced and preserved ejection fraction who are at an elevated surgical risk for perioperative events. This review highlights a subset of the interventions available in clinical practice or in development for the treatment of these valvular and structural alterations.