Biomechanical evaluation of the pathophysiologic developmental mechanisms of mitral valve prolapse: effect of valvular morphologic alteration

Biomechanical Evaluation of Mitral Valve Repair: Virtual Chordal Transposition to Restore Anterior Leaflet Prolapse

Background

Surgical management of an anterior leaflet prolapse remains comparatively challenging and has led to the lack of any firmly established standard repair techniques, as seen in cases of posterior leaflet prolapse. Chordal transposition repair is widely acknowledged as a remarkably durable technique that utilizes the patient's native chordae. This study aims to evaluate and predict the biomechanical and functional characteristics of a normal mitral valve (MV) model and a pathological MV model featuring anterior ruptured mitral chordae tendineae (RMCT), and to assess the effectiveness of the chordal transposition repair in the pathological MV model.

Methods

There are four stages in the proposed virtual MV repair evaluation protocol: (1) modeling the virtual pathological MV model with an anterior (A2) RMCT; (2) performing chordal transposition as the virtual MV repair procedure; (3) dynamic finite element simulation of the normal (control) MV model, the pre-repair (pathological) MV model, and the post-repair (chorda transposition) MV model; (4) assessment and comparison of the physiological and biomechanical features among the normal, pre-repair, and post-repair cases.

Results

The pathological MV model with anterior RMCT clearly demonstrated a substantial flail, a marked increase in chordal stresses on the two intact chordae adjacent to the ruptured A2 chordae, and severe anterior leaflet prolapse due to the A2 chordal rupture. The virtual chordal transposition demonstrated remarkable efficacy in mitigating the stress concentrations in the leaflet and chordae, restoring leaflet coaptation, and resolving anterior leaflet prolapse.

Conclusions

This virtual MV surgery strategy offers a valuable means to predict, evaluate, and quantify functional and biomechanical improvements before and after MV repair, thereby empowering informed decision-making in the planning of chordal transposition interventions.

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.

Chest pain and palpitations in postmenopausal women with mitral valve prolapse: is there a gastro-oesophageal origin?

BACKGROUND AND AIM

Mitral valve prolapse (MVP) is a common disease in women, causing chest pain and palpitation due to structural and functional valve abnormality, and is sometimes associated with gastro-oesophageal reflux disease (GERD). This is a challenging clinical problem in clinical practice and requires targeted diagnostic assessment to identify the underlying causes of the symptoms, because treatment needs to be tailored, according to the causes themselves, to resolve the symptoms.

AIM

To assess the prevalence of GERD in a population of postmenopausal women affected by MVP and determine if there is any correlation between the two conditions.

METHODS

The MVP diagnosis was performed using echocardiograpy examination, according to American Society Echocardiography criteria. Two hundred and eighty-nine consecutive MVP women, symptomatic for chest pain and palpitation, were included; 250 consecutive women without MVP, symptomatic for chest pain and palpitation, were the control group (CG). The GERD diagnosis was made according to 2013 American College Gastroenterology criteria; women affected by thyroid disorders, all heart disease, including mitral disease with moderate or severe mitral regurgitation, and gastrointestinal diseases assessed using gastroscopy were excluded.

RESULTS

Among 289 women with MVP, 31 (11%) women were affected by GERD, and among 250 in the CG, 11 (4.4%) women were affected by GERD: Chi-squared 8.1; odds ratio 2.7; P < 0.0044. Twenty-six (9%) women affected by GERD, with MVP, presented with mild mitral regurgitation, and 7 (2.8%) women in the CG presented with mild mitral regurgitation as well: Chi-squared 8.95; odds ratio 3.4; 95% CI, P < 0.0028.

DISCUSSION AND CONCLUSIONS

GERD is relatively common in women with MVP. Moreover, women with MVP are approximately three times more likely to be affected by GERD; the two conditions are correlated in a statistically high significant way. GERD assessment needs to be included into routine follow-up strategies in women with MVP to optimise medical therapy, improvinge symptom relief for better quality of life.

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.

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.

EFFECT OF PAPILLARY MUSCLE DISPLACEMENT AND ANNULAR DILATION ON DEVELOPMENT OF FUNCTIONAL MITRAL REGURGITATION

Functional mitral regurgitation (FMR) occurs following left ventricle (LV) dysfunction with normal mitral valve (MV) leaflet. The progress and severity of FMR are closely related to LV dilatation, which often results in displacement of the papillary muscles (PMs) and enlargement of the mitral annulus. We investigated the effect of PM displacement and annular dilation on FMR development to better understand the complex intercorrelation between these pathologic alterations leading to FMR. Virtual MV modeling was performed to create a normal human MV, and several different types of PM displacement, annular dilation, and the combination of PM displacement and annular dilation mimicking the pathology of FMR were modeled. Dynamic finite element evaluation of MV function was performed across the complete cardiac cycle for the normal and FMR MV models. PM displacement to both lateral and apical directions revealed markedly reduced leaflet coaptation and large stress distribution in the P2 scallop. Annular dilation greater than 2% demonstrated the occurrence of leaflet malcoaptation and increased stresses near the anterior saddle-horn region. The pathologic MV model with annular dilation combined with PM displacement provides physiologically realistic biomechanical characteristics as the MVs having FMR. Simulation-based biomechanical evaluation of MV pathology related to LV chamber dilatation provides an excellent tool to better understand the pathophysiologic mechanism of FMR.

New insights into mitral heart valve prolapse after chordae rupture through fluid-structure interaction computational modeling

Mitral valve (MV) dynamics depends on a force balance across the mitral leaflets, the chordae tendineae, the mitral annulus, the papillary muscles and the adjacent ventricular wall. Chordae rupture disrupts the link between the MV and the left ventricle (LV), causing mitral regurgitation (MR), the most common valvular disease. In this study, a fluid-structure interaction (FSI) modeling framework is implemented to investigate the impact of chordae rupture on the left heart (LH) dynamics and severity of MR. A control and seven chordae rupture LH models were developed to simulate a pathological process in which minimal chordae rupture precedes more extensive chordae rupture. Different non-eccentric and eccentric regurgitant jets were identified during systole. Cardiac efficiency was evaluated by the ratio of external stroke work. MV structural results showed that basal/strut chordae were the major load-bearing chordae. An increased number of ruptured chordae resulted in reduced basal/strut tension, but increased marginal/intermediate load. Chordae rupture in a specific scallop did not necessarily involve an increase in the stress of the entire prolapsed leaflet. This work represents a further step towards patient-specific modeling of pathological LH dynamics, and has the potential to improve our understanding of the biomechanical mechanisms and treatment of primary MR.

Excessive leaflet tissue in mitral valve repair for isolated posterior leaflet prolapse-leaflet resection or shortening neochords? A propensity score adjusted comparison

BACKGROUND

Chordal replacement techniques are progressively used to treat posterior mitral valve leaflet (PMVL) prolapse while leaflet resection remains commonly in use to address excessive leaflet tissue. For excessive tissue in height, shortening neochords can be used alternatively. Use of chordal replacement techniques has been suggested to result in lower diastolic transvalvular gradients, higher freedom from reoperation and improved left ventricular function.

METHODS

From 1/2005 to 12/2016, 150 patients underwent valve repair for isolated PMVL prolapse with excessive tissue. Excessive tissue in height was treated by leaflet resection (N.=99) or shortening neochords (N.=51). Excessive tissue in width was always resected. Logistic regression was used to generate propensity scores for risk-adjusted comparison.

RESULTS

Two patients died postoperatively. In the Neochords group, resection of excessive tissue in width was still needed in 28 (55%) cases. Postoperative echocardiography demonstrated residual (≥2+) mitral regurgitation in 2/150 patients (Resect group). No differences in anuloplasty ring size, postoperative diastolic transvalvular gradients or left ventricular function were observed. Median clinical follow-up duration was 4.4 (IQR 2.0-7.0; 98% complete) years. There was no inter-group difference in overall survival or freedom from reintervention. Mean echocardiographic follow-up was 3.0 (IQR 1.2-5.4; 93% complete) years. In the matched population, the 6-year freedom from recurrent mitral regurgitation rates were 91.3% (95% CI: 81.9-100%) and 97.2% (95% CI: 91.9-100%) for the Resect and Neochords group, respectively (P=0.43).

CONCLUSIONS

Both leaflet resection and shortening neochords provide a valuable tool to address excessive PMVL height. Repair durability is excellent regardless of the technique utilized.

Mitral Prolapse: An Old Mysterious Entity - The Incremental Role of Multimodality Imaging in Sports Eligibility

Mitral valve prolapse is generally a benign condition characterized by fibromyxomatous changes of the mitral leaflet with displacement into the left atrium and late-systolic regurgitation. Although it is an old clinical entity, it still arouses perplexity in diagnosis and clinical management. Complications, such as mitral regurgitation (MR), atrial fibrillation, congestive heart failure, endocarditis, ventricular arrhythmias, and sudden cardiac death (SCD), have been reported. A large proportion of the overall causes of SCD in young competitive athletes is explained by mitral valve prolapse. Recent studies have shown the fibrosis of the papillary muscles and inferobasal left ventricular wall in mitral valve prolapse, suggesting a possible origin of ventricular fatal arrhythmias. Athletes with mitral valve prolapse and MR should undergo annual evaluations including physical examination, echocardiogram, and exercise stress testing to evaluate the cardiovascular risks of competitive sports and obtain the eligibility. In this setting, multimodality imaging techniques – echocardiography, cardiac magnetic resonance, and cardiac computed tomography – should provide a broad spectrum of information, from diagnosis to clinical management of the major clinical profiles of the disease.