Functional Mitral Regurgitation: Current Understanding and Approach to Management

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.

Functional mitral regurgitation combined with increased early diastolic transmitral velocity to early mitral annulus diastolic velocity ratio is associated with a poor prognosis in patients with shock

BACKGROUND

Functional mitral regurgitation (FMR) is common in critically ill patients and may cause left atrial (LA) pressure elevation. This study aims to explore the prognostic impact of synergistic LA pressure elevation and FMR in patients with shock.

METHODS

We retrospectively screened 130 consecutive patients of 175 patients with shock from April 2016 to June 2017. The incidence and impact of FMR and early diastolic transmitral velocity to early mitral annulus diastolic velocity ratio (E/e') ≥ 4 within 6 h of shock on the prognosis of patients were evaluated. Finally, the synergistic effect of FMR and E/e' were assessed by combination, grouping, and trend analyses.

RESULTS

Forty-four patients (33.8%) had FMR, and 15 patients (11.5%) had E/e' elevation. A multivariate analysis revealed FMR and E/e' as independent correlated factors for 28-day mortality (P = 0.043 and 0.028, respectively). The Kaplan-Meier survival analysis revealed a significant difference in survival between patients with and without FMR (χ2 = 7.672, P = 0.006) and between the E/e' ≥ 14 and E/e' < 14 groups (χ2 = 19.351, P < 0.010). Twenty-eight-day mortality was significantly different among the four groups (χ2 = 30.141, P < 0.010). The risk of 28-day mortality was significantly higher in group 4 (E/e' ≥ 14 with FMR) compared with groups 1 (E/e' < 14 without FMR) and 2 (E/e' < 14 with FMR) (P = 0.001 and 0.046, respectively).

CONCLUSIONS

Patients with shock can be identified by the presence of FMR. FMR and E/e' are independent risk factors for a poor prognosis in these patients, and prognosis is worst when FMR and E/e' ≥ 14 are present. It may be possible to improve prognosis by reducing LA pressure and E/e'.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03082326.

Paroxysmal Severe Mitral Regurgitation

OBJECTIVE

To investigate the clinical presentation, pathophysiology, and treatment for "paroxysmal severe mitral regurgitation" (MR), which is an underappreciated cause of heart failure with preserved left ventricular ejection fraction.

METHODS

We retrospectively reviewed cases of transient severe MR that were evaluated at Mayo Clinic in Rochester, Minnesota, between January 1, 2006, and December 31, 2019. Paroxysmal severe MR was defined as the appearance of transient severe MR in patients with mild MR at rest, normal left ventricle (LV) size, left ventricular ejection fraction greater than 40%, and absence of obstructive coronary artery disease.

RESULTS

We identified 6 patients (5 women) with a median age of 68 years. There were 3 distinct mechanisms of paroxysmal severe MR, which we labeled types 1, 2, and 3. Type 1 MR was caused by LV dyssynchrony from a rate-dependent left bundle branch block, which led to apical leaflet tenting and incomplete coaptation. Type 2 MR occurred from mitral annular dilatation during maneuvers that increased left-sided volume. Type 3 MR was caused by coronary artery vasospasm with apical leaflet tenting. Treatments varied depending on the underlying cause and included cardiac resynchronization therapy for type 1, surgical valve replacement for type 2, and medical therapy for type 3.

CONCLUSION

Paroxysmal severe MR is a rare cause of heart failure in patients with preserved LV function. We have identified 3 distinct mechanisms that can lead to this dynamic process, with treatments varying based on the underlying cause.

Mitral regurgitation in heart failure: insights from CPET combined with exercise echocardiography

Aims

In heart failure patients with reduced ejection fraction (HFrEF), exercise-induced functional mitral regurgitation (MR) may affect functional capacity and outcome. We sought to study functional and cardiac phenotypes of HFrEF patients according to the MR degree.

Methods and results

We performed rest and exercise echocardiography (Ex-Echo), simultaneously combined with cardiopulmonary exercise test (CPET), in 102 HFrEF patients, identifying 3 groups: non-severe (ERO <20 mm2) MR (group A), exercise-induced severe (ERO ≥20 mm2) MR (group B), and rest severe MR (group C). Patients were tracked for the composite end point of death and heart failure hospitalization. Group B (ERO: rest= 14 ± 5 mm2, Ex= 28 ± 6 mm2; P = < 0.001) had a functional impairment (workload = 56 ± 21 vs. 50 ± 17 watts, P = 0.42; peak VO2 = 11.8 ± 3.2 vs. 11.5 ± 3.0 mL/Kg/min, P = 0.70) similar to Group C (ERO: rest = 29 ± 7 mm2, Ex = 42 ± 7 mm2, P = < 0.001), associated with comparable advanced left ventricle remodelling (end diastolic indexed volume = 107 ± 34 vs. 115 ± 30 mL/m2, P = 0.27), characterized by exercise-induced pulmonary hypertension (PH) (Ex systolic pulmonary pressures = 63 ± 16 mmHg). Group C showed the worse cardiac phenotype (right ventricle dilatation, dysfunction, and rest PH) with severe ventilatory impairment (VE/VCO2 = 41.2 ± 11) compared with Groups A and B. Moreover, Group C had the higher rate of death and HF hospitalization.

Conclusions

In HFrEF patients, severe dynamic MR produces functional limitation similar to rest severe MR, characterized by dynamic PH. Rest severe MR reflects the most advanced bi-ventricular remodelling associated with rest PH, the most unfavourable ventilatory profile, and the worst mid-term outcome.

Papillary Muscle Free Strain in Patients with Severe Degenerative and Functional Mitral Regurgitation

FUNDAMENTO:

The role of papillary muscle function in severe mitral regurgitation with preserved and reduced left ventricular ejection fraction and the method of choice to evaluate PM have still been the subjects of controversy.

OBJECTIVES:

To evaluate and compare papillary muscle function in and between patients with severe degenerative and functional mitral regurgitation by using the free strain method.

METHODS:

64 patients with severe mitral regurgitation - 39 patients with degenerative mitral regurgitation (DMR group) and 25 patients with severe functional mitral regurgitation (FMR group) - and 30 control subjects (control group) were included in the study. Papillary muscle function was evaluated through the free strain method from apical four chamber images of the anterolateral papillary muscle (APM) and from apical three chamber images of the posteromedial papillary muscle (PPM). Global left ventricular longitudinal and circumferential strains were evaluated by applying 2D speckle tracking imaging.

RESULTS:

Global left ventricular longitudinal strain (DMR group, -17 [-14.2/-20]; FMR group, -9 [-7/-10.7]; control group, -20 [-18/-21] p < 0.001), global left ventricular circumferential strain (DMR group, -20 [-14.5/-22.7]; FMR group, -10 [-7/-12]; control group, -23 [-21/-27.5] p < 0.001) and papillary musle strains (PPMS; DMR group, -30.5 [-24/-46.7]; FMR group, -18 [-12/-30]; control group; -43 [-34.5/-39.5] p < 0.001; APMS; DMR group, (-35 [-23.5/-43]; FMR group, -20 [-13.5/-26]; control group, -40 [-32.5/-48] p < 0.001) were significantly different among all groups. APMS and PPMS were highly correlated with LVEF (p < 0.001, p < 0.001; respectively), GLS (p < 0.001, p < 0.001; respectively) and GCS (p < 0.001, p < 0.00; respectively) of LV among all groups. No correlation was found between papillary muscle strains and effective orifice area (EOA) in both groups of severe mitral regurgitation.

CONCLUSIONS:

Measuring papillary muscle longitudinal strain by the free strain method is practical and applicable. Papillary muscle dysfunction plays a small role in severe MR due to degenerative or functional causes and papillary muscle functions in general seems to follow left ventricular function. PPM is the most affected PM in severe mitral regurgitation in both groups of DMR and FMR.

FUNDAMENTO:

O papel da função do músculo papilar na regurgitação mitral grave com fração de ejeção do ventrículo esquerdo preservada e reduzida e o método de escolha para avaliar PM ainda são objetos de controvérsia.

OBJETIVOS:

Avaliar e comparar a função dos músculos papilares entre pacientes com insuficiência mitral funcional e degenerativa pelo método free strain.

MÉTODOS:

64 pacientes com insuficiência mitral grave - 39 pacientes com insuficiência mitral degenerativa grave (grupo IMD) e 25 com insuficiência mitral funcional grave (grupo IMF) - e 30 indivíduos controle (grupo controle) foram incluídos no estudo. A função dos músculos papilares foi avaliada pelo método free strain a partir de imagens apicais quatro-câmaras do músculo papilar anterolateral (MPA) e imagens apicais três-câmaras do músculo papilar posteromedial (MPP). Strains circunferenciais e longitudinais globais do ventrículo esquerdo foram avaliados por meio de imagens bidimensionais a partir do rastreamento de conjunto de pontos de cinza (speckle tracking).

RESULTADOS:

O strain longitudinal global do ventrículo esquerdo (grupo IMD, -17 [-14,2/-20]; grupo IMF, -9 [-7/-10,7]; grupo controle, -20 [-18/-21] p < 0,001); strain circunferencial global do ventrículo esquerdo (grupo IMD, -20 [-14,5/-22,7]; grupo IMF, -10 [-7/-12]; grupo controle, -23 [-21/-27,5] p < 0,001) e strains de músculos papilares (MPP; grupo IMD, -30,5 [-24/-46,7]; grupo IMF, -18 [-12/-30]; grupo controle; -43 [-34,5/-39,5] p < 0,001; MPA; grupo IMD, (-35 [-23,5/-43]; grupo IMF, -20 [-13,5/-26]; grupo controle, -40 [-32,5/-48] p < 0,001) mostraram-se significativamente diferentes nos grupos. MPA e MPP mostraram-se altamente correlacionados com a FEVE (p < 0,001, p < 0,00; respectivamente), SLG (p < 0,001, p < 0,001; respectivamente) e SCG (p < 0,001, p < 0,001; respectivamente) do VE entre todos os grupos. Não foi encontrada correlação entre os strains de músculos papilares e área eficaz do orifício (AEO) nos grupos de insuficiência mitral grave.

CONCLUSÕES:

A medição do strain longitudinal de músculos papilares pelo método free strain é prática e aplicável. A disfunção dos músculos papilares tem um papel pequeno em IM grave devido a causas degenerativas e funcionais, e a função dos músculos papilares, em general, parece seguir a função ventricular esquerda. O MPP é o MP mais afetado na insuficiência mitral em ambos os grupos, IMD e IMF.

Functional and Biomechanical Effects of the Edge-to-Edge Repair in the Setting of Mitral Regurgitation: Consolidated Knowledge and Novel Tools to Gain Insight into Its Percutaneous Implementation

Mitral regurgitation is the most prevalent heart valve disease in the western population. When severe, it requires surgical treatment, repair being the preferred option. The edge-to-edge repair technique treats mitral regurgitation by suturing the leaflets together and creating a double-orifice valve. Due to its relative simplicity and versatility, it has become progressively more widespread. Recently, its percutaneous version has become feasible, and has raised interest thanks to the positive results of the Mitraclip(®) device. Edge-to-edge features and evolution have stimulated debate and multidisciplinary research by both clinicians and engineers. After providing an overview of representative studies in the field, here we propose a novel computational approach to the most recent percutaneous evolution of the edge-to-edge technique. Image-based structural finite element models of three mitral valves affected by posterior prolapse were derived from cine-cardiac magnetic resonance imaging. The models accounted for the patient-specific 3D geometry of the valve, including leaflet compound curvature pattern, patient-specific motion of annulus and papillary muscles, and hyperelastic and anisotropic mechanical properties of tissues. The biomechanics of the three valves throughout the entire cardiac cycle was simulated before and after Mitraclip(®) implantation, assessing the biomechanical impact of the procedure. For all three simulated MVs, Mitraclip(®) implantation significantly improved systolic leaflets coaptation, without inducing major alterations in systolic peak stresses. Diastolic orifice area was decreased, by up to 58.9%, and leaflets diastolic stresses became comparable, although lower, to systolic ones. Despite established knowledge on the edge-to-edge surgical repair, latest technological advances make its percutanoues implementation a challenging field of research. The modeling approach herein proposed may be expanded to analyze clinical scenarios that are currently critical for Mitraclip(®) implantation, helping the search for possible solutions.