Elongation of chordae tendineae as an adaptive process to reduce mitral regurgitation in functional mitral regurgitation

Anatomic, stage-based repair of secondary mitral valve disease

OBJECTIVE

Intervention for repair of secondary mitral valve disease is frequently associated with recurrent regurgitation. We sought to determine if there was sufficient evidence to support inclusion of anatomic indices of leaflet dysfunction in the management of secondary mitral valve disease.

METHODS

We performed a systematic review and meta-analysis of published reports comparing anatomic indices of leaflet dysfunction with the complexity of valve repair and the outcome from intervention. Patients were stratified by the severity of leaflet dysfunction. A secondary analysis was performed comparing outcomes when procedural complexity was optimally matched to severity of leaflet dysfunction and when intervention was not matched to dysfunction.

RESULTS

We identified 6864 publications, of which 65 met inclusion criteria. An association between the severity of leaflet dysfunction and the procedural complexity was highly predictive of satisfactory freedom from recurrent regurgitation. Patients were categorized into 4 groups based on stratification of leaflet dysfunction. Satisfactory results were achieved in 93.7% of patients in whom repair complexity was appropriately matched to severity of leaflet dysfunction and in 68.8% in whom repair was not matched to dysfunction (odds ratio, 0.148; 95% confidence interval, 0.119-0.184; P < .0001).

CONCLUSIONS

For patients with secondary mitral valve disease, satisfactory outcome from valve repair improves when procedural complexity is matched to anatomic indices of leaflet dysfunction. Anatomic indices of leaflet dysfunction should be considered when planning interventions for secondary mitral regurgitation. Routine inclusion of anatomic indices in trial design and reporting should facilitate comparison of results and strengthen guidelines. There are sufficient data to support anatomic staging of secondary mitral valve disease.

Rough-zone suspension with mitral valve replacement for ventricular functional mitral regurgitation

Chordal preservation is recommended in mitral valve replacement for functional mitral regurgitation to preserve left ventricular function. In contrast, papillary muscle suspension toward the anterior mitral annulus can induce left ventricular reverse remodeling after mitral valve replacement for functional mitral regurgitation. However, the extent of suspension depends on the surgeon's experience. Therefore, we developed a new concept of chordal preservation, called rough-zone suspension, which not only spares the subvalvular structure but also suspends the papillary muscles toward the annulus. This procedure is simple and reproducible for determining the extent of suspension, and can increase the probability of left ventricular reverse remodeling after mitral valve replacement for functional mitral regurgitation.

A geometry-based finite element tool for evaluating mitral valve biomechanics

Mitral valve function depends on its complex geometry and tissue health, with alterations in shape and tissue response affecting the long-term restorarion of function. Previous computational frameworks for biomechanical assessment are mostly based on patient-specific geometries; however, these are not flexible enough to yield a variety of models and assess mitral closure for individually tuned morphological parameters or material property representations. This study details the finite element approach implemented in our previously developed toolbox to assess mitral valve biomechanics and showcases its flexibility through the generation and biomechanical evaluation of different models. A healthy valve geometry was generated and its computational predictions for biomechanics validated against data in the literature. Moreover, two mitral valve models including geometric alterations associated with disease were generated and analysed. The healthy mitral valve model yielded biomechanical predictions in terms of valve closure dynamics, leaflet stresses and papillary muscle and chordae forces comparable to previous computational and experimental studies. Mitral valve function was compromised in geometries representing disease, expressed by the presence of regurgitating areas, elevated stress on the leaflets and unbalanced subvalvular apparatus forces. This showcases the flexibility of the toolbox concerning the generation of a range of mitral valve models with varying geometric definitions and material properties and the evaluation of their biomechanics.

Implications of the Mitral Leaflet Coaptation Pattern on Clinical Outcomes in Patients With Functional Mitral Regurgitation

The classification of secondary mitral regurgitation (MR) is based on atrial functional MR (AFMR) or ventricular functional MR (VFMR) and volume changes, but the mitral leaflet coaptation angle also contributes to the MR mechanism. The clinical implications of the coaptation angle on cardiovascular (CV) outcomes have not been well evaluated. A total of 469 consecutive patients (265 AFMR vs 204 VFMR) with more than moderate MR were evaluated for the occurrence of heart failure, mitral valve operations, and CV death. The coaptation angle was assessed by measuring the internal angle between both leaflets at mid-systole using the apical 3-chamber view. A coaptation angle ≥130° was classified as leaflet flattening, and an angle <130° was classified as leaflet tethering. AFMR and VFMR were associated with higher frequencies of leaflet flattening and tethering, respectively. AFMR was more likely to be associated with older age, atrial fibrillation, and preserved ejection fraction, all of which were related to leaflet flattening. During a follow-up of 2.3 years, 83 patients had heart failure (17.7%), 21 patients underwent mitral valve operations (4.5%), and 34 patients died (7%). Compared with leaflet tethering, leaflet flattening was more significantly related to CV events, whereas CV event rates were less markedly different in A/VFMR. Irrespective of A/VFMR, leaflet flattening and atrial fibrillation were associated with a higher frequency of CV events. Adjusted analysis showed that leaflet flattening remained an independent predictor of CV events (hazard ratio 3.5, 95% confidence interval 1.11 to 4.88, p = 0.003), whereas A/VFMR did not. In conclusion, the leaflet coaptation angle in patients with functional MR could provide risk stratification superior to that of A/VFMR. Leaflet flattening appears to be associated with unfavorable clinical outcomes.

Assessment of the mechanism of mitral valve prolapse in children: An echocardiography study

BACKGROUND

The high complexity of mitral valve anatomy and function in mitral valve prolapse (MVP) is not yet fully understood.

OBJECTIVE

The purpose of this study was to analyze each part of the mitral valve apparatus in children to determine its impact on the presence of MVP and to assess the interaction between the coaptation length (CL) and mitral regurgitation severity.

METHODS

We prospectively analyzed transthoracic echocardiograms of 60 patients with MVP (mean age 9.8 ± 3.1 years). We compared these patients with 60 control patients without disease. We determined length of leaflets, chordal length, tenting area, coaptation CL, the intrapapillary muscle distance (IPMD) and relation between CL and severity of mitral regurgitation (MR).

RESULTS

For patients with MVP, the posterior mitral leaflet (PML) was significantly enlarged 13.9 ± 4.1 mm versus 10.7 ± 3.5 mm (p < .01), the primary chordal length was significantly decreased 15.4 ± 3.61 mm versus 17.6 ± 3.8 mm (p < .02), and IPMD was significantly greater 18.1 ± 2.7 mm versus 16.6 ± 4.3 mm (p < .03). The difference between CL for both the anterior and posterior mitral leaflets correlated positively with MR (r = .249, p < .05). A greater than 4 mm CL correlated with at least MR (sensitivity 100%, specificity 72%) and greater than 5 mm correlated with at least moderate MR (sensitivity 100%, specificity 60%).

CONCLUSION

The majority of pediatric patients with mitral valve prolapse have structural abnormalities that are defined well by echocardiography. In addition to the presence of prolapse and regurgitation, routine assessment of leaflet length, thickness, chordal length and papillary muscle distance is fundamental for patients with MVP.

Automatic quantitative measurement of left atrial pressure using mitral regurgitation spectrum: clinical study on comparison with floating catheter

Introduction

To explore how to measure LAPEq accurately and quantitatively, that is, the left atrial pressure (LAP) measured and calculated by equation method using mitral regurgitation spectrum.

Methods

The mitral regurgitation spectrum, pulmonary arteriolar wedge pressure (PAWP) and invasive arterial systolic pressure of radial artery of 28 patients were collected simultaneously, including 3 patients with rheumatic heart disease, 15 patients with mitral valve prolapse and 10 patients with coronary artery bypass grafting, patients with moderate or above aortic stenosis were excluded. LAPBp (Doppler sphygmomanometer method), LAPEq (Equation method) and LAPC (Catheter method) were measured synchronously, and the measurement results of the three methods were compared and analyzed. A special intelligent Doppler spectrum analysis software was self-designed to accurately measure LAPEq. This study had been approved by the ethics committee of the Northern Theater General Hospital (K-2019-17), and applied for clinical trial (No. Chictr 190023812).

Results

It was found that there was no significant statistical difference between the measurement results of LAPC and LAPEq (t = 0.954, P = 0.348), and significant correlation between the two methods [r = 0.908(0.844, 0.964), P < 0.001]. Although the measurement results of LAPC and LAPBP are consistent in the condition of non-severe eccentric mitral regurgitation, there are significant differences in the overall case and weak correlation between the two methods [r = 0.210, (−0.101, 0.510), P = 0.090]. In MVP patients with P1 or P3 prolapse, the peak pressure difference of MR was underestimated due to the serious eccentricity of MR, which affected the accuracy of LAPBP measurement.

Conclusions

It was shown that there is a good correlation between LAPEq and LAPC, which verifies that the non-invasive and direct quantitative measurement of left atrial pressure based on mitral regurgitation spectrum is feasible and has a good application prospect.

Left atrial reverse remodeling predicts long-term survival after cardiac resynchronization therapy

BACKGROUND

Left ventricular (LV) reverse remodeling has been identified as a strong predictor of long-term survival in patients receiving CRT. Interestingly, CRT induces reverse remodeling in the left atrium (LA) as well. It is currently unknown to what extent LA reverse remodeling is correlated to long-term survival after CRT. This study aims to assess the long-term prognostic value of left atrium (LA) reverse remodeling in patients undergoing cardiac resynchronization therapy (CRT).

METHODS

Baseline and 3-months follow-up echocardiograms after CRT implantation were prospectively assessed to determine changes in left ventricular end-systolic volume (LVESV), left ventricular ejection fraction (LVEF), left atrial volume (LAV), and left atrial reservoir strain (LAS_r). Multivariate Cox regression analysis was performed to identify predictors for long-term survival.

RESULTS

In our study population of 99 patients with a mean follow-up of 6.3 ± 2.1 years, 43 patients (43%) reached the end-point of all-cause mortality. More extensive LA reverse remodeling, as measured by a relative increase in LAS_r, was observed in survivors compared to non-survivors (43 [29-64] % vs. 8 [2-28] %, P < 0.001, respectively). After multivariate analysis, delta LAS_r remained the only significant predictor of mortality [HR per 5%: 0.90 (0.86-0.95); AUC 0.78 (0.68-0.88)].

CONCLUSION

An increase in LAS_r is associated with favorable long-term outcome after CRT. The observed clinical importance of LA reverse remodeling after CRT asks for further validation in larger prospective cohorts.

A toolbox for generating scalable mitral valve morphometric models

The mitral valve is a complex anatomical structure, whose shape is key to several traits of its function and disease, being crucial for the success of surgical repair and implantation of medical devices. The aim of this study was to develop a parametric, scalable, and clinically useful model of the mitral valve, enabling the biomechanical evaluation of mitral repair techniques through finite element simulations. MATLAB was used to parameterize the valve: the annular boundary was sampled from a porcine mitral valve mesh model and landmark points and relevant boundaries were selected for the parameterization of leaflets using polynomial fitting. Several geometric parameters describing the annulus, leaflet shape and papillary muscle position were implemented and used to scale the model according to patient dimensions. The developed model, available as a toolbox, allows for the generation of a population of models using patient-specific dimensions obtained from medical imaging or averaged dimensions evaluated from empirical equations based on the Golden Proportion. The average model developed using this framework accurately represents mitral valve shapes, associated with relative errors reaching less than 10% for annular and leaflet length dimensions, and less than 24% in comparison with clinical data. Moreover, model generation takes less than 5 min of computing time, and the toolbox can account for individual morphological variations and be employed to evaluate mitral valve biomechanics; following further development and validation, it will aid clinicians when choosing the best patient-specific clinical intervention and improve the design process of new medical devices.

Aortic strain in bicuspid aortic valve: an analysis

Bicuspid aortic valve (BAV) is monitored by transthoracic echocardiography and computed tomography (CT) angiography. However, it does not have any early marker of disease progression. This study evaluated speckle-tracking echocardiography (STE) aortic and left ventricular (LV) strain prognostic values, their discriminative power, and their correlation with the degree of valvular regurgitation. We conducted a retrospective analysis of a prospectively enrolled cohort of 45 diagnosed with BAV and 20 gender and age matched controls. We performed 2D-STE aortic and LV strain analysis of the selected population. The cohort was followed-up during a median period of 19.9 months (IQR 12.9-25.2), and outcomes (hospital admission for heart failure (HF), aortic valve replacement (AVR), and death) were determined. The mean patient age was 46.6 ± 15.5 years and 80 % were male. LV indexed volumes and aortic diameter were higher in BAV patients. LV global longitudinal strain (GLS) was impaired (p < 0.001) and aortic GLS was significantly augmented (p = 0.027) in BAV patients. Aortic global circumferential strain (GCS) did not vary between groups. Aortic diameter was the best parameter related to BAV (AUC 0.92) and aortic GLS was best correlated with significant AR (AUC 0.76). AVR was the only outcome observed and its only predictor was indexed LV end-diastolic volume. BAV had impaired LV-GLS values. Aortic GLS was abnormally augmented in BAV patients, which might reflect higher aortic diameters that distorted strain calculations. STE aortic strain is related to AR but does not appear to be a reliable predictor of surgery in BAV patients, at 19 months.

The secret life of the mitral valve

In secondary mitral regurgitation, the concept that the mitral valve (MV) is an innocent bystander, has been challenged by many studies in the last decades. The MV is a living structure with intrinsic plasticity that reacts to changes in stretch or in mechanical stress activating biohumoral mechanisms that have, as purpose, the adaptation of the valve to the new environment. If the adaptation is balanced, the leaflets increase both surface and length and the chordae tendineae lengthen: the result is a valve with different characteristics, but able to avoid or to limit the regurgitation. However, if the adaptation is unbalanced, the leaflets and the chords do not change their size, but become stiffer and rigid, with moderate or severe regurgitation. These changes are mediated mainly by a cytokine, the transforming growth factor-β (TGF-β), which is able to promote the changes that the MV needs to adapt to a new hemodynamic environment. In general, mild TGF-β activation facilitates leaflet growth, excessive TGF-β activation, as after myocardial infarction, results in profibrotic changes in the leaflets, with increased thickness and stiffness. The MV is then a plastic organism, that reacts to the external stimuli, trying to maintain its physiologic integrity. This review has the goal to unveil the secret life of the MV, to understand which stimuli can trigger its plasticity, and to explain why the equation "large heart = moderate/severe mitral regurgitation" and "small heart = no/mild mitral regurgitation" does not work into the clinical practice.

Potential mechanism of left ventricular spherical remodeling: association of mitral valve complex-myocardium longitudinal tissue remodeling mismatch

Since mitral valve (MV) complex (MVC) longitudinally bridges left ventricular (LV) base end and its middle, insufficient MVC longitudinal tissue length (TL) elongation relative to whole LV myocardial longitudinal TL elongation could limit LV-base-longitudinal-TL elongation, leading to predominant LV-base-transverse-TL elongation, constituting LV spherical remodeling. In 30 patients with dilated cardiomyopathy (DCM), 30 with aortic regurgitation (AR), and 30 controls, LV sphericity, LV-apex- or base-transverse- and longitudinal-TL, MVC-longitudinal-TL, and whole-LV-longitudinal-TL were measured by three-dimensional (3D) echocardiography. Ratio of each measure versus mean normal value (i.e., LV-apex-transverse-TL ratio) was considered to express the directional and regional tissue elongation. [LV-base-longitudinal-TL ratio/global-LV-TL ratio] and [MVC-longitudinal-TL ratio/whole-LV-longitudinal-TL ratio] were obtained as the degree of LV-base-longitudinal-TL or MVC-longitudinal-TL elongation relative to the whole LV elongation. LV-apex-transverse-, LV-apex-longitudinal-, and LV-base-transverse-TL ratios were significantly increased (1.27 to 1.42, P < 0.01) in both DCM and AR, while the LV-base-longitudinal-TL ratio was not increased in DCM [1.04 ± 0.19, not significant (ns)] and only modestly increased in AR (1.12 ± 0.21, P < 0.01). Whole-LV-longitudinal-TL ratio was significantly increased in both DCM and AR (1.22 ± 0.18 and 1.20 ± 0.16, P < 0.01), while MVC-longitudinal-TL ratio was not or only modestly increased in both groups (1.07 ± 0.15, ns, and 1.12 ± 0.17, P = 0.02, respectively). Multivariable analysis revealed that LV sphericity was independently related to a reduced [LV-base-longitudinal-TL ratio/global-LV-TL ratio] (standard β = -0.42, P < 0.01), which was further related to a reduced [MVC-longitudinal-TL ratio/whole-LV-longitudinal-TL ratio] (standard β = 0.72, P < 0.01). These are consistent with the hypothesis that relatively less MVC-longitudinal-TL elongation in the process of primary LV myocardial tissue elongation may limit LV-base-longitudinal-TL elongation, contributing to LV spherical remodeling.NEW & NOTEWORTHY Left ventricular (LV) spherical remodeling is associated with poor prognosis and less-effective cardiac performance, which commonly develops in dilated cardiomyopathy. However, its mechanism remains unclear. We hypothesized and subsequently clarified that less mitral valve complex (MVC) tissue longitudinal elongation relative to whole LV myocardial tissue longitudinal elongation is related to disproportionately less LV base longitudinal versus transverse myocardial tissue elongation, constituting spherical remodeling. This study suggests modification of MVC tissue elongation could be potential therapeutic targets.

Geometric description for the anatomy of the mitral valve: A review

The mitral valve is a complex anatomical structure whose physiological functioning relies on the biomechanical properties and structural integrity of its components. Their compromise can lead to mitral valve dysfunction, associated with morbidity and mortality. Therefore, a review on the morphometry of the mitral valve is crucial, more specifically on the importance of valve dimensions and shape for its function. This review initially provides a brief background on the anatomy and physiology of the mitral valve, followed by an analysis of the morphological information available. A characterisation of mathematical descriptions of several parts of the valve is performed and the impact of different dimensions and shape changes in disease is then outlined. Finally, a section regarding future directions and recommendations for the use of morphometric information in clinical analysis of the mitral valve is presented.

Surgical mitral plasticity for chronic ischemic mitral regurgitation

BACKGROUND AND AIM OF THE STUDY

The outcome of mitral valve (MV) repair for chronic ischemic mitral regurgitation (IMR) is suboptimal, due to the high recurrence rate of moderate or severe mitral regurgitation (MR) during follow-up. The MV adapts to new MR increasing its area to cover the enlarged annular area (mitral plasticity). As this process is often incomplete, we aimed to evaluate if augmenting the anterior leaflet (AL) and cutting the second-order chords (CC) together with restrictive mitral annuloplasty, a strategy we call "surgical mitral plasticity," could improve the midterm results of MV repair for IMR.

MATERIALS AND METHODS

From November 2017 to October 2019, 22 patients with chronic IMR underwent surgical mitral plasticity. Mean age was 73 ± 7 years and six were female. Mean ejection fraction was 32% ± 11%, IMR grade was moderate in 10 and severe in 12. Mean clinical and echocardiographic follow-up was 12 ± 6 months.

RESULTS

There was no early death, and one patient died 6 months after surgery. Ejection fraction improved from 32% ± 15% to 40% ± 6% (P = .031). IMR was absent or mild in all patients, and none showed recurrent moderate or more IMR. Tenting area decreased significantly from 2.5 ± 0.5 to 0.5 ± 0.3 cm² and coaptation length increased from 1.9 ± 0.7 to 7.8 ± 1.6 mm. All patients were in New York Heart Association class I or II.

CONCLUSIONS

Mitral plasticity, if uncomplete, is ineffective in preventing IMR to become significant. Surgical mitral plasticity, by completing incomplete process of MV adaptation, has a strong rationale, which however needs to be validated with longer follow-up.

Functional anatomy and pathophysiologic principles in mitral regurgitation: Non-invasive assessment

Mitral regurgitation (MR) is the most prevalent cause of valvular heart disease (VHD) in western countries. In the Euro Heart Survey on VHD, MR was the second most common heart VHD requiring surgery. It is also the most common form of VHD in community and population-based studies from the United States. The categorization of MR based on causes and mechanisms is a major determinant of clinical outcome, of possible therapies for the MR and of the effectiveness of these therapies. Surgical mitral valve (MV) repair has been shown to improve survival in patients with severe primary MR compared with MV replacement. In addition, new percutaneous repair and replacement procedures have been recently developed. Hence, accurate understanding of the functional anatomy of the MV and the pathophysiologic principles underlying MR is needed to appropriately target valve lesions. Recent advances in cardiac imaging have allowed to deeply strengthen the knowledge of the function of the MV. The present review aims at describing the functional anatomy and pathophysiology of MR through different cardiac imaging modalities.

Effect of Losartan on Mitral Valve Changes After Myocardial Infarction

BACKGROUND

After myocardial infarction (MI), mitral valve (MV) tethering stimulates adaptive leaflet growth, but counterproductive leaflet thickening and fibrosis augment mitral regurgitation (MR), doubling heart failure and mortality. MV fibrosis post-MI is associated with excessive endothelial-to-mesenchymal transition (EMT), driven by transforming growth factor (TGF)-β overexpression. In vitro, losartan-mediated TGF-β inhibition reduces EMT of MV endothelial cells.

OBJECTIVES

This study tested the hypothesis that profibrotic MV changes post-MI are therapeutically accessible, specifically by losartan-mediated TGF-β inhibition.

METHODS

The study assessed 17 sheep, including 6 sham-operated control animals and 11 with apical MI and papillary muscle retraction short of producing MR; 6 of the 11 were treated with daily losartan, and 5 were untreated, with flexible epicardial mesh comparably limiting left ventricular (LV) remodeling. LV volumes, tethering, and MV area were quantified by using three-dimensional echocardiography at baseline and at 60 ± 6 days, and excised leaflets were analyzed by histopathology and flow cytometry.

RESULTS

Post-MI LV dilation and tethering were comparable in the losartan-treated and untreated LV constraint sheep. Telemetered sensors (n = 6) showed no significant losartan-induced changes in arterial pressure. Losartan strongly reduced leaflet thickness (0.9 ± 0.2 mm vs. 1.6 ± 0.2 mm; p < 0.05; 0.4 ± 0.1 mm sham animals), TGF-β, and downstream phosphorylated extracellular-signal-regulated kinase and EMT (27.2 ± 12.0% vs. 51.6 ± 11.7% α-smooth muscle actin-positive endothelial cells, p < 0.05; 7.2 ± 3.5% sham animals), cellular proliferation, collagen deposition, endothelial cell activation (vascular cell adhesion molecule-1 expression), neovascularization, and cells positive for cluster of differentiation (CD) 45, a hematopoietic marker associated with post-MI valve fibrosis. Leaflet area increased comparably (17%) in constrained and losartan-treated sheep.

CONCLUSIONS

Profibrotic changes of tethered MV leaflets post-MI can be modulated by losartan without eliminating adaptive growth. Understanding the cellular and molecular mechanisms could provide new opportunities to reduce ischemic MR.