Transcatheter Edge-to-Edge Repair in Proportionate Versus Disproportionate Functional Mitral Regurgitation

The Evolving Concept of Secondary Mitral Regurgitation Phenotypes: Lessons From the M-TEER Trials

Conflicting results from 2 randomized clinical trials of transcatheter mitral valve edge-to-edge repair in secondary mitral regurgitation (SMR) have led to the recognition that SMR is a heterogeneous disease entity presenting with different functional and morphological phenotypes. This review summarizes the current knowledge on SMR caused primarily by atrial secondary mitral regurgitation (aSMR) and ventricular SMR pathology. Although aSMR is generally characterized by severe left atrial enlargement in the setting of preserved left ventricular anatomy and function, different patterns of mitral annular distortion cause different phenotypes of aSMR. In ventricular SMR, the relation of SMR severity to left ventricular dilation as well as the degree of pulmonary hypertension and right ventricular dysfunction are important phenotypic characteristics, which are key for a better understanding of prognosis and treatment response.

Mitral Regurgitation "Proportionality" in Functional Mitral Regurgitation and Outcomes After Mitral Valve Transcatheter Edge-to-Edge Repair: A Systematic Review and Meta-Analysis

Background

Certain patients with functional mitral regurgitation survive longer with fewer heart failure hospitalizations after undergoing transcatheter edge-to-edge repair (TEER); however, clinical markers identifying who will benefit have not been established. The 'proportionality' of mitral regurgitation (MR) severity compared to left ventricular size has been hypothesized to predict clinical outcome.

Methods

We sought to combine existing studies to compare outcomes between 'proportionate' MR and 'disproportionate' MR in patients undergoing TEER. PubMed and Medline were searched from January 2018 until May 2023. Data was extracted and synthesized by 2 independent authors using random effects models with risk ratios (RRs) for binary outcomes. The primary outcome was a combined endpoint of all-cause mortality or heart failure hospitalization (ACM/HFH). Other outcomes of interest included ACM and residual >2+ MR after TEER.

Results

Six trials with a total of 1594 patients (mean age 71 years, 66% male) were included, which assessed MR proportionality using either a ratio of estimated regurgitant orifice area to left ventricular end-diastolic volume (EROA:LVEDV) or regurgitant fraction. Seven hundred and five (mean age 70 years, 75% male) were classified as proportionate MR, and 889 (mean age 72 years, 60% male) had disproportionate MR. There was no significant association between MR proportionality (by EROA:LVEDV) and ACM (RR 0.79, 95% confidence interval [CI] 0.44-1.42). Proportionality did not significantly associate with ACM/HFH, though there were divergent effect signals when proportionality was measured by EROA:LVEDV (RR 0.80, 95% CI 0.45-1.44) or regurgitant fraction (RR 1.48, 95% CI 0.53-4.11). Disproportionate MR showed a greater association with residual MR > 2+ post-TEER that did not meet statistical significance (RR 1.86, 95% CI 0.77-4.49).

Conclusions

In patients undergoing TEER for functional mitral regurgitation, MR proportionality was not significantly associated with ACM/HFH, all-cause mortality, or residual MR.

Regurgitant volume to LA volume ratio in patients with secondary MR: the COAPT trial

AIMS

The conceptual framework of proportionate vs. disproportionate mitral regurgitation (MR) translates poorly to individual patients with heart failure (HF) and secondary MR. A novel index, the ratio of MR severity to left atrial volume (LAV), may identify patients with 'disproportionate' MR and a higher risk of events. The objectives, therefore, were to investigate the prognostic impact of MR severity to LAV ratio on outcomes among HF patients with severe secondary MR randomized to transcatheter edge-to-edge repair (TEER) with the MitraClip™ device plus guideline-directed medical therapy (GDMT) vs. GDMT alone in the COAPT trial.

METHODS AND RESULTS

The ratio of pre-procedural regurgitant volume (RVol) to LAV was calculated from baseline transthoracic echocardiograms. The primary endpoint was 2-year covariate-adjusted rate of HF hospitalization (HFH). Among 567 patients, the median RVol/LAV was 0.67 (interquartile range 0.48-0.91). In patients randomized to GDMT alone, lower RVol/LAV was independently associated with an increased 2-year risk of HFH (adjHR: 1.77; 95% CI: 1.20-2.63). RVol/LAV was a stronger predictor of adverse outcomes than RVol or LAV alone. Treatment with TEER plus GDMT compared with GDMT alone was associated with lower 2-year rates of HFH both in patients with low and high RVol/LAV (Pinteraction = 0.28). Baseline RVol/LAV ratio was unrelated to 2-year mortality, health status, or functional capacity in either treatment group.

CONCLUSION

Low RVol/LAV ratio was an independent predictor of 2-year HFH in HF patients with severe MR treated with GDMT alone in the COAPT trial. TEER improved outcomes regardless of baseline RVol/LAV ratio.

CLINICAL TRIAL REGISTRATION

Trial Name: Cardiovascular Outcomes Assessment of the MitraClip Percutaneous Therapy for Heart Failure Patients With Functional Mitral Regurgitation (The COAPT Trial) (COAPT) ClinicalTrial.gov Identifier NCT01626079URL https://clinicaltrials.gov/ct2/show/NCT01626079.

Mortality Associated With Proportionality of Secondary Mitral Regurgitation After Transcatheter Mitral Valve Repair: North American Mitraclip for Functional Mitral Regurgitation Registry

The association, if any, between the effective regurgitant orifice area (EROA) to left ventricular end-diastolic volume (LVEDV) ratio and 1-year mortality is controversial in patients who undergo mitral transcatheter edge-to-edge repair (m-TEER) with the MitraClip system (Abbott Vascular, Santa Clara, CA). This study's objective was to determine the association between EROA/LVEDV and 1-year mortality in patients who undergo m-TEER with MitraClip. In patients with severe secondary (functional) mitral regurgitation (MR), we analyzed registry data from 11 centers using generalized linear models with the generalized estimating equations approach. We studied 525 patients with secondary MR who underwent m-TEER. Most patients were male (63%) and were New York Heart Association class III (61%) or IV (21%). Mitral regurgitation was caused by ischemic cardiomyopathy in 51% of patients. EROA/LVEDV values varied widely, with median = 0.19 mm2/ml, interquartile range [0.12,0.28] mm2/ml, and 187 patients (36%) had values <0.15 mm2/ml. Postprocedural mitral regurgitation severity was substantially alleviated, being 1+ or less in 74%, 2+ in 20%, 3+ in 4%, and 4+ in 2%; 1-year mortality was 22%. After adjustment for confounders, the logarithmic transformation (Ln) of EROA/LVEDV was associated with 1-year mortality (odds ratio 0.600, 95% confidence interval 0.386 to 0.933, p = 0.023). A higher Society of Thoracic Surgeons risk score was also associated with increased mortality. In conclusion, lower values of Ln(EROA/LVEDV) were associated with increased 1-year mortality in this multicenter registry. The slope of the association is steep at low values but gradually flattens as Ln(EROA/LVEDV) increases.

Valvular heart disease and cardiomyopathy: reappraisal of their interplay

Cardiomyopathies and valvular heart diseases are typically considered distinct diagnostic categories with dedicated guidelines for their management. However, the interplay between these conditions is increasingly being recognized and they frequently coexist, as in the paradigmatic examples of dilated cardiomyopathy and hypertrophic cardiomyopathy, which are often complicated by the occurrence of mitral regurgitation. Moreover, cardiomyopathies and valvular heart diseases can have a shared aetiology because several genetic or acquired diseases can affect both the cardiac valves and the myocardium. In addition, the association between cardiomyopathies and valvular heart diseases has important prognostic and therapeutic implications. Therefore, a better understanding of their shared pathophysiological mechanisms, as well as of the prevalence and predisposing factors to their association, might lead to a different approach in the risk stratification and management of these diseases. In this Review, we discuss the different scenarios in which valvular heart diseases and cardiomyopathies coexist, highlighting the need for an improved classification and clustering of these diseases with potential repercussions in the clinical management and, particularly, personalized therapeutic approaches.

Challenges and pitfalls in classification of disproportionate mitral regurgitation

The concept of disproportionate mitral regurgitation (dispropMR) has been introduced to identify patients with functional mitral regurgitation (MR) who benefit from percutaneous treatment. We aimed to examine echocardiographic characteristics behind this entity. We retrospectively included 172 consecutive patients with reduced left ventricular ejection fraction (LVEF), and more than mild MR referred to clinically indicated echocardiography. According to the proportionality ratio (effective regurgitant orifice area (EROA)/left ventricular end-diastolic volume (LVEDV)) patients were divided into dispropMR and proportionate MR (propMR) group. Potential factors which might affect proportionality definition were analyzed. 55 patients (32%) had dispropMR. Discrepant grading of MR severity was observed when using regurgitant volume (RegVol) by proximal isovelocity surface area (PISA) method or volumetric method, with significant discordance only in dispropMR (p < 0.001). Patients with dispropMR had more frequently left ventricular foreshortened images for LVEDV calculation than patients with propMR (p = 0.003), resulting in smaller LVEDV in dispropMR group. DispropMR group had more substantial dynamic variation of regurgitant flow compared to propMR. Accordingly, EROA was consistently overestimated by standard single-point PISA method compared to serial PISA method. This was more pronounced in dispropMR (bias:10.5 ± 28.3 mm2) compared to propMR group (bias:6.4 ± 12.8 mm2). DispropMR may be found in roughly one third of clinically indicated echocardiographic studies in patients with reduced LVEF and more than mild MR. EROA overestimation due to dynamic variation of regurgitant flow and LVEDV underestimation due to LV foreshortening were more frequently found in dispropMR. Our results indicate that methodological limitations of echocardiographic MR grading could not be neglected in classifying the proportionality of MR.

Patient-Specific Quantitative In-Vivo Assessment of Human Mitral Valve Leaflet Strain Before and After MitraClip Repair

PURPOSE

Mitral regurgitation (MR) is a highly prevalent and deadly cardiac disease characterized by improper mitral valve (MV) leaflet coaptation. Among the plethora of available treatment strategies, the MitraClip is an especially safe option, but optimizing its long-term efficacy remains an urgent challenge.

METHODS

We applied our noninvasive image-based strain computation pipeline [1] to intraoperative transesophageal echocardiography datasets taken from ten patients undergoing MitraClip repair, spanning a range of MR etiologies and MitraClip configurations. We then analyzed MV leaflet strains before and after MitraClip implementation to develop a better understanding of (1) the pre-operative state of human regurgitant MV, and (2) the MitraClip's impact on the MV leaflet deformations.

RESULTS

The MV pre-operative strain fields were highly variable, underscoring both the heterogeneity of the MR in the patient population and the need for patient-specific treatment approaches. Similarly, there were no consistent overall post-operative strain patterns, although the average A2 segment radial strain difference between pre- and post-operative states was consistently positive. In contrast, the post-operative strain fields were better correlated to their respective pre-operative strain fields than to the inter-patient post-operative strain fields. This quantitative result implies that the patient specific pre-operative state of the MV guides its post-operative deformation, which suggests that the post-operative state can be predicted using pre-operative data-derived modelling alone.

CONCLUSIONS

The pre-operative MV leaflet strain patterns varied considerably across the range of MR disease states and after MitraClip repair. Despite large inter-patient heterogeneity, the post-operative deformation appears principally dictated by the pre-operative deformation state. This novel finding suggests that though the variation in MR functional state and MitraClip-induced deformation were substantial, the post-operative state can be predicted from the pre-operative data alone. This study suggests that, with use of larger patient cohort and corresponding long-term outcomes, quantitative predictive factors of MitraClip durability can be identified.

Mitral Interventions in Heart Failure

Patients with heart failure with reduced ejection fraction who have secondary mitral regurgitation (SMR) have poorer outcomes and quality of life than those without SMR. Guideline-directed medical therapy is the cornerstone of SMR treatment. Careful evaluation of landmark trials using mitral transcatheter edge-to-edge repair in SMR has led to an improved understanding of who will benefit from percutaneous interventions with emphasis on a multidisciplinary approach. The success with mitral transcatheter edge-to-edge repair in SMR has also spurred the evaluation of its role in populations that were not initially studied, such as end-stage heart failure and cardiogenic shock. A spectrum of transcatheter devices in development and clinical trials promise to further provide a growing array of management options for heart failure with reduced ejection fraction patients with symptomatic SMR.

Epiphenomenon or Prognostically Relevant Interventional Target? A Novel Proportionality Framework for Severe Tricuspid Regurgitation

Background Tricuspid regurgitation (TR) frequently develops in patients with long-standing pulmonary hypertension, and both pathologies are associated with increased morbidity and mortality. This study aimed to improve prognostic assessment in patients with severe TR undergoing transcatheter tricuspid valve intervention (TTVI) by relating the extent of TR to pulmonary artery pressures. Methods and Results In this multicenter study, we included 533 patients undergoing TTVI for moderate-to-severe or severe TR. The proportionality framework was based on the ratio of tricuspid valve effective regurgitant orifice area to mean pulmonary artery pressure. An optimal threshold for tricuspid valve effective regurgitant orifice area/mean pulmonary artery pressure ratio was derived on 353 patients with regard to 2-year all-cause mortality and externally validated on 180 patients. Patients with a tricuspid valve effective regurgitant orifice area/mean pulmonary artery pressure ratio ≤1.25 mm²/mm Hg (defining proportionate TR) featured significantly lower 2-year survival rates after TTVI than patients with disproportionate TR (56.6% versus 69.6%; P=0.005). In contrast with patients with disproportionate TR (n=398), patients with proportionate TR (n=135) showed more pronounced mPAP levels (37.9±9.06 mm Hg versus 27.9±8.17 mm Hg; P<2.2×10^-16) and more severely impaired right ventricular function (tricuspid annular plane systolic excursion: 16.0±4.11 versus 17.0±4.64 mm; P=0.012). Moreover, tricuspid valve effective regurgitant orifice area was smaller in patients with proportionate TR when compared with disproportionate TR (0.350±0.105 cm² versus 0.770±0.432 cm²; P<2.2×10^-16). Importantly, proportionate TR remained a significant predictor for 2-year mortality after adjusting for demographic and clinical variables (hazard ratio, 1.7; P=0.006). Conclusions The proposed proportionality framework promises to improve future risk stratification and clinical decision-making by identifying patients who benefit the most from TTVI (disproportionate TR). As a next step, randomized controlled studies with a conservative treatment arm are needed to quantify the net benefit of TTVI in patients with proportionate TR.