The value of preoperative 3-dimensional over 2-dimensional valve analysis in predicting recurrent ischemic mitral regurgitation after mitral annuloplasty

Regional geometric differences between regurgitant and non-regurgitant mitral valves in patients with coronary artery disease

OBJECTIVE

Demonstrate that regional geometric differences exist between regurgitant and non-regurgitant mitral valves (MV's) in patients with coronary artery disease and due to the heterogenous and regional nature of ischemic remodeling in patients with coronary artery disease (CAD), that the available anatomical reserve and likelihood of developing mitral regurgitation (MR) is variable in non-regurgitant MV's in patients with CAD.

METHODS

In this retrospective, observational study intraoperative three-dimensional transesophageal echocardiographic data was analyzed in patients undergoing coronary revascularization with MR (IMR group) and without MR (NMR group). Regional geometric differences between both groups were assessed and MV reserve which was defined as the increase in antero-posterior (AP) annular diameter from baseline that would lead to coaptation failure was calculated in three zones of the MV from antero-lateral (zone 1), middle (zone 2), and posteromedial (zone 3).

MEASUREMENTS AND MAIN RESULTS

There were 31 patients in the IMR group and 93 patients in the NMR group. Multiple regional geometric differences existed between both groups. Most significantly patients in the NMR group had significantly larger coaptation length and MV reserve than the IMR group in zones 1 (p-value = .005, .049) and 2 (p-value = .00, .00), comparable between the two groups in zone 3 (p-value = .436, .513). Depletion of the MV reserve was associated with posterior displacement of the coaptation point in zones 2 and 3.

CONCLUSIONS

There are significant regional geometric differences between regurgitant and non-regurgitant MV's in patients with coronary artery disease. Due to regional variations in available anatomical reserve and the risk of coaptation failure in patients with CAD, absence of MR is not synonymous with normal MV function.

Utilization of Engineering Advances for Detailed Biomechanical Characterization of the Mitral-Ventricular Relationship to Optimize Repair Strategies: A Comprehensive Review

The geometrical details and biomechanical relationships of the mitral valve-left ventricular apparatus are very complex and have posed as an area of research interest for decades. These characteristics play a major role in identifying and perfecting the optimal approaches to treat diseases of this system when the restoration of biomechanical and mechano-biological conditions becomes the main target. Over the years, engineering approaches have helped to revolutionize the field in this regard. Furthermore, advanced modelling modalities have contributed greatly to the development of novel devices and less invasive strategies. This article provides an overview and narrative of the evolution of mitral valve therapy with special focus on two diseases frequently encountered by cardiac surgeons and interventional cardiologists: ischemic and degenerative mitral regurgitation.

Visualization and Quantification of the Unrepaired Complete Atrioventricular Canal Valve Using Open-Source Software

BACKGROUND

Repair of complete atrioventricular canal (CAVC) is often complicated by residual left atrioventricular valve regurgitation. The structure of the mitral and tricuspid valves in biventricular hearts has previously been shown to be associated with valve dysfunction. However, the three-dimensional (3D) structure of the entire unrepaired CAVC valve has not been quantified. Understanding the 3D structure of the CAVC may inform optimized repair.

METHODS

Novel open-source work flows were created in SlicerHeart for the modeling and quantification of CAVC valves on the basis of 3D echocardiographic images. These methods were applied to model the annulus, leaflets, and papillary muscle (PM) structure of 35 patients (29 with trisomy 21) with CAVC using transthoracic 3D echocardiography. The mean leaflet and annular shapes were calculated and visualized using shape analysis. Metrics of the complete native CAVC valve structure were compared with those of normal mitral valves using the Mann-Whitney U test. Associations between CAVC structure and atrioventricular valve regurgitation were analyzed.

RESULTS

CAVC leaflet metrics varied throughout systole. Compared with normal mitral valves, the left CAVC PMs were more acutely angled in relation to the annular plane (P < .001). In addition, the anterolateral PM was laterally and inferiorly rotated in CAVC, while the posteromedial PM was more superiorly and laterally rotated, relative to normal mitral valves (P < .001). Lower native CAVC atrioventricular valve annular height and annular height-to-valve width ratio before repair were both associated with moderate or greater left atrioventricular valve regurgitation after repair (P < .01).

CONCLUSIONS

It is feasible to model and quantify 3D CAVC structure using 3D echocardiographic images. The results demonstrate significant variation in CAVC structure across the cohort and differences in annular, leaflet, and PM structure compared with the mitral valve. These tools may be used in future studies to catalyze future research intended to identify structural associations of valve dysfunction and to optimize repair in this vulnerable and complex population.

Fully Automated 3D Segmentation and Diffeomorphic Medial Modeling of the Left Ventricle Mitral Valve Complex in Ischemic Mitral Regurgitation

There is an urgent unmet need to develop a fully-automated image-based left ventricle mitral valve analysis tool to support surgical decision making for ischemic mitral regurgitation patients. This requires an automated tool for segmentation and modeling of the left ventricle and mitral valve from immediate pre-operative 3D transesophageal echocardiography. Previous works have presented methods for semi-automatically segmenting and modeling the mitral valve, but do not include the left ventricle and do not avoid self-intersection of the mitral valve leaflets during shape modeling. In this study, we develop and validate a fully automated algorithm for segmentation and shape modeling of the left ventricular mitral valve complex from pre-operative 3D transesophageal echocardiography. We performed a 3-fold nested cross validation study on two datasets from separate institutions to evaluate automated segmentations generated by nnU-net with the expert manual segmentation which yielded average overall Dice scores of 0.82±0.03 (set A), 0.87±0.08 (set B) respectively. A deformable medial template was subsequently fitted to the segmentation to generate shape models. Comparison of shape models to the manual and automatically generated segmentations resulted in an average Dice score of 0.93-0.94 and 0.75-0.81 for the left ventricle and mitral valve, respectively. This is a substantial step towards automatically analyzing the left ventricle mitral valve complex in the operating room.

Segmentation of Tricuspid Valve Leaflets From Transthoracic 3D Echocardiograms of Children With Hypoplastic Left Heart Syndrome Using Deep Learning

Hypoplastic left heart syndrome (HLHS) is a severe congenital heart defect in which the right ventricle and associated tricuspid valve (TV) alone support the circulation. TV failure is thus associated with heart failure, and the outcome of TV valve repair are currently poor. 3D echocardiography (3DE) can generate high-quality images of the valve, but segmentation is necessary for precise modeling and quantification. There is currently no robust methodology for rapid TV segmentation, limiting the clinical application of these technologies to this challenging population. We utilized a Fully Convolutional Network (FCN) to segment tricuspid valves from transthoracic 3DE. We trained on 133 3DE image-segmentation pairs and validated on 28 images. We then assessed the effect of varying inputs to the FCN using Mean Boundary Distance (MBD) and Dice Similarity Coefficient (DSC). The FCN with the input of an annular curve achieved a median DSC of 0.86 [IQR: 0.81-0.88] and MBD of 0.35 [0.23-0.4] mm for the merged segmentation and an average DSC of 0.77 [0.73-0.81] and MBD of 0.6 [0.44-0.74] mm for individual TV leaflet segmentation. The addition of commissural landmarks improved individual leaflet segmentation accuracy to an MBD of 0.38 [0.3-0.46] mm. FCN-based segmentation of the tricuspid valve from transthoracic 3DE is feasible and accurate. The addition of an annular curve and commissural landmarks improved the quality of the segmentations with MBD and DSC within the range of human inter-user variability. Fast and accurate FCN-based segmentation of the tricuspid valve in HLHS may enable rapid modeling and quantification, which in the future may inform surgical planning. We are now working to deploy this network for public use.

Nomogram Predicts Improvement of Ischemic Mitral Regurgitation after Coronary Artery Bypass Grafting

BACKGROUND

Developing a nomogram to predict improvement in moderate ischemic mitral regurgitation (IMR) after coronary artery bypass grafting (CABG) is in need.

METHODS

Between 2010 and 2018, data were retrospectively collected from 112 patients with prior myocardial infarction and moderate IMR undergoing CABG. Patients were divided into two groups based on IMR degree 1 year after CABG as follows: Improved Group with no or mild IMR (n=54) and Failure Group with moderate or severe IMR (n=58). To determine the predictors of postoperative IMR improvement, preoperative clinical and echocardiographic data were compared, and a nomogram was formulated based on all independent predictors. Discriminative ability, calibration, and clinical usefulness of the prediction model were assessed.

RESULTS

Independent predictors of IMR improvement after CABG constructing the nomogram included duration between infarction and operation, poster-inferior to left ventricular volume ratio, maximum difference of the time to reach minimum systolic volume of 16 segments, P3 leaflet tethering angle, and annular Non-planar angle. The nomogram exhibited well-fitted calibration curves and excellent discriminative ability. The area under receiver operating characteristic curve was 0.974. Patients with a score > 236 demonstrated a high probability of IMR improvement (sensitivity, 90.7%; specificity, 93.1%). Patients in the Improved Group demonstrated greater actuarial survival rates than those in the Failure Group.

CONCLUSIONS

The nomogram combining 5 preoperative clinical and echocardiographic predictors provides an accurate preoperative estimation of moderate IMR improvement after surgery, with excellent discriminative ability. Based on this nomogram, patients with a higher score predict higher probabilities of IMR improvement.

Heart Valve Biomechanics: The Frontiers of Modeling Modalities and the Expansive Capabilities of Ex Vivo Heart Simulation

The field of heart valve biomechanics is a rapidly expanding, highly clinically relevant area of research. While most valvular pathologies are rooted in biomechanical changes, the technologies for studying these pathologies and identifying treatments have largely been limited. Nonetheless, significant advancements are underway to better understand the biomechanics of heart valves, pathologies, and interventional therapeutics, and these advancements have largely been driven by crucial in silico, ex vivo, and in vivo modeling technologies. These modalities represent cutting-edge abilities for generating novel insights regarding native, disease, and repair physiologies, and each has unique advantages and limitations for advancing study in this field. In particular, novel ex vivo modeling technologies represent an especially promising class of translatable research that leverages the advantages from both in silico and in vivo modeling to provide deep quantitative and qualitative insights on valvular biomechanics. The frontiers of this work are being discovered by innovative research groups that have used creative, interdisciplinary approaches toward recapitulating in vivo physiology, changing the landscape of clinical understanding and practice for cardiovascular surgery and medicine.

Echocardiographic Assessment of the Mitral Valve for Suitability of Repair: An Intraoperative Approach From a Mitral Center

Intraoperative echocardiography of the mitral valve in the precardiopulmonary bypass period is an integral part of the surgical decision-making process for assessment of suitability for repair. Although there are comprehensive reviews in the literature regarding echocardiographic examination of the mitral valve, the authors present a practical stepwise algorithmic workflow to make objective recommendations. Advances in echocardiography allow for quantitative geometric analyses of the mitral valve, along with precise assessment of the valvular apparatus with three-dimensional echocardiography. In the precardiopulmonary bypass period, echocardiographers are required to diagnose and quantify valvular dysfunction, assess suitability for repair, assist in annuloplasty ring sizing, and determine the success or failure of the surgical procedure. In this manuscript the authors outline an algorithmic approach to intraoperative echocardiography examination using two-dimensional and three-dimensional modalities to objectively analyze mitral valve function and assist in surgical decision-making.

Intraoperative post-annuloplasty three-dimensional valve analysis does not predict recurrent ischemic mitral regurgitation

BACKGROUND

High ischemic mitral regurgitation (IMR) recurrence rates continue to plague IMR repair with undersized ring annuloplasty. We have previously shown that pre-repair three-dimensional echocardiography (3DE) analysis is highly predictive of IMR recurrence. The objective of this study was to determine the quantitative change in 3DE annular and leaflet tethering parameters immediately after repair and to determine if intraoperative post-repair 3DE parameters would be able to predict IMR recurrence 6 months after repair.

METHODS

Intraoperative pre- and post-repair transesophageal real-time 3DE was performed in 35 patients undergoing undersized ring annuloplasty for IMR. An advanced modeling algorhythm was used to assess 3D annular geometry and regional leaflet tethering. IMR recurrence (≥ grade 2) was assessed with transthoracic echocardiography 6 months after repair.

RESULTS

Annuloplasty significantly reduced septolateral diameter, commissural width, annular area, and tethering volume and significantly increased all segmental tethering angles (except A2). Intraoperative post-repair annular geometry and leaflet tethering did not differ significantly between patients with recurrent IMR (n = 9) and patients with non-recurrent IMR (n = 26). No intraoperative post-repair predictors of IMR recurrence could be identified.

CONCLUSIONS

Undersized ring annuloplasty changes mitral geometry acutely, exacerbates leaflet tethering, and generally fixes IMR acutely, but it does not always fix the delicate underlying chronic problem of continued left ventricular dilatation and remodeling. This may explain why pre-repair 3D valve geometry (which reflects chronic left ventricular remodeling) is highly predictive of recurrent IMR, whereas immediate post-repair 3D valve geometry (which does not completely reflect chronic left ventricular remodeling anymore) is not.

Operative Results of Mitral Valve Repair and Replacement in Chronic Ischaemic Mitral Valve Regurgitation

BACKGROUND

Ischaemic mitral regurgitation (IMR) carries significant morbidity and mortality. Surgical management includes coronary artery bypass surgery alone or concomitant with mitral valve repair or replacement. There is ongoing debate regarding the appropriate approach to the mitral valve in relation to long-term outcomes. This review examines our early and late follow-up, with operative and echocardiographic outcomes for mitral valve repair and mitral replacement for chronic IMR.

METHODS

A retrospective review was performed on prospectively collected data of 119 consecutive patients who either underwent mitral repair (n=101) or mitral replacement (n=18) for chronic IMR at Prince Henry and The Prince of Wales hospitals in Sydney between 1999-2016. All patients had pre and postoperative transthoracic echocardiograms. Follow-up echocardiographic data was obtained from the most recent clinical appointment. Follow-up mortality outcomes were obtained with ethics approval from the Australian National Death Index (NDI).

RESULTS

There was no statistical difference between cardiopulmonary bypass (CPB) time, cross-clamp time, time spent in intensive care unit (ICU) and time to discharge between cohorts. The replacement cohort was noted to have higher preoperative pulmonary artery (PA) pressures and a higher severity of IMR. Seven (7) deaths were in the mitral valve (MV) repair group within 30 days (6.9%) and three deaths in the MV replacement group within 30 days (16.7%). Echocardiographic follow-up was complete in 78% of the MV repair cohort at an average of 4.06±2.66 years, and 73% complete in the MV replacement cohort at an average of 6.09±4.3 years. Three (3) patients had prior MV repair before MV replacement early at days zero and 17, and late at 8 years respectively. Follow-up echocardiography showed mitral regurgitation (MR) in the mitral valve repair cohort as ≤ mild in 83.5% and ≤ trivial in 35.6%. In the MV replacement cohort MR ≤ mild in 100% and ≤ trivial in 82% with no moderate or severe MR. Preoperative tricuspid regurgitation (TR) and a flexible annuloplasty were predictive of an MR grade > mild in the repair cohort at discharge. Five-year (5-year) survival for the repair cohort was 85% with a mean follow-up time of 7.1±3.83 years. For the replacement cohort, five-year survival was 77.8% with a mean follow-up time of 5.35±1.54 years.

CONCLUSIONS

Mitral valve repair and replacement for chronic IMR has acceptable mortality, reintervention rates and excellent postoperative echocardiographic degrees of IMR in this cohort. Further evaluation is required into quality of life post intervention for IMR and of preoperative predictive factors of significant MR postoperatively to help guide the appropriate choice of treatment. The presence of preoperative tricuspid regurgitation of moderate grade or higher, and the use of a flexible annuloplasty may indicate patients more likely to have a higher grade of MR at follow-up following mitral valve repair in patients with IMR.

Functional Mitral Regurgitation in Heart Failure

Functional mitral regurgitation (FMR) in the setting of left ventricular (LV) dysfunction and heart failure portends a poor prognosis. Guideline-directed medical therapy remains the cornerstone of initial treatment, with emphasis placed on treatment of the underlying LV dysfunction, as FMR is a secondary phenomenon and a disease due to LV remodeling. Surgical correction of FMR is controversial because it typically does not address the underlying mechanism and etiology of the condition. However, new, minimally invasive transcatheter therapies, in particular the MitraClip system, have shown promise in the treatment of FMR in selected patients. This review will summarize the pathophysiology underlying FMR, the prognosis of patients with heart failure and FMR, and the various medical and procedural treatment options currently available and under investigation.

Semi-automated Image Segmentation of the Midsystolic Left Ventricular Mitral Valve Complex in Ischemic Mitral Regurgitation

Ischemic mitral regurgitation (IMR) is primarily a left ventricular disease in which the mitral valve is dysfunctional due to ventricular remodeling after myocardial infarction. Current automated methods have focused on analyzing the mitral valve and left ventricle independently. While these methods have allowed for valuable insights into mechanisms of IMR, they do not fully integrate pathological features of the left ventricle and mitral valve. Thus, there is an unmet need to develop an automated segmentation algorithm for the left ventricular mitral valve complex, in order to allow for a more comprehensive study of this disease. The objective of this study is to generate and evaluate segmentations of the left ventricular mitral valve complex in pre-operative 3D transesophageal echocardiography using multi-atlas label fusion. These patient-specific segmentations could enable future statistical shape analysis for clinical outcome prediction and surgical risk stratification. In this study, we demonstrate a preliminary segmentation pipeline that achieves an average Dice coefficient of 0.78 ± 0.06.

On the simulation of mitral valve function in health, disease, and treatment

The mitral valve (MV) is the heart valve that regulates blood ?ow between the left atrium and left ventricle (LV). In situations where the MV fails to fully cover the left atrioventricular ori?ce during systole, the resulting regurgitation causes pulmonary congestion, leading to heart failure and/or stroke. The causes of MV insuf?ciency can be either primary (e.g. myxomatous degeneration) where the valvular tissue is organically diseased, or secondary (typically inducded by ischemic cardiomyopathy) termed ischemic mitral regurgitation (IMR), is brought on by adverse LV remodeling. IMR is present in up to 40% of patients and more than doubles the probability of cardiovascular morbidity after 3.5 years. There is now agreement that adjunctive procedures are required to treat IMR caused by lea?et tethering. However, there is no consensus regarding the best procedure. Multicenter registries and randomized trials would be necessary to prove which procedure is superior. Given the number of proposed procedures and the complexity and duration of such studies, it is highly unlikely that IMR procedure optimization will be achieved by prospective clinical trials. There is thus an urgent need for cell and tissue physiologically based quantitative assessments of MV function to better design surgical solutions and associated therapies. Novel computational approaches directed towards optimized surgical repair procedures can substantially reduce the need for such trial-and-error approaches. We present the details of our MV modeling techniques, with an emphasis on what is known and investigated at various length scales.

Application of polymer-mesh device to remodel left ventricular-mitral valve apparatus in ischemic mitral regurgitation

OBJECTIVES

Ischemic mitral regurgitation (IMR) results from ischemic left ventricular (LV) distortion and remodeling, which displaces the papillary muscles and tethers the mitral valve leaflets apically. The aim of this experimental study was to examine efficacy of an adjustable novel polymer filled mesh (poly-mesh) device to reverse LV remodeling and reduce IMR.

METHODS

Acute (N = 8) and chronic (8 weeks; N = 5) sheep models of IMR were studied. IMR was produced by ligation of circumflex branches to create myocardial infarction. An adjustable poly-mesh device was attached to infarcted myocardium in acute and chronic IMR models and compared with untreated sham sheep. Two- and 3-dimensional echocardiography and hemodynamic measurements were performed at baseline, post IMR, and post poly-mesh (humanely killed).

RESULTS

In acute models, moderate IMR developed in all sheep and decreased to trace/mild (vena contracta: 0.50 ± 0.09 cm to 0.26 ± 0.12 cm; P < .01) after poly-mesh. In chronic models, IMR decreased in all sheep after poly-mesh, and this reduction persisted over 8 weeks (vena contracta: 0.42 ± 0.09 cm to 0.08 ± 0.12 cm; P < .01) with significant increase in the slope of end-systolic pressure-volume relationship (1.1 ± 0.5 mm Hg/mL to 2.9 ± 0.7 mm Hg/mL; P < .05). There was a significant reduction in LV volumes from chronic IMR to euthanasia stage with poly-mesh compared with sham group (%end-diastolic volume change -20 ± 11 vs 15% ± 16%, P < .01; %end-systolic volume change -14% ± 19% vs 22% ± 22%, P < .05; poly-mesh vs sham group) consistent with reverse remodeling.

CONCLUSIONS

An adjustable polymer filled mesh device reduces IMR and prevents continued LV remodeling during chronic follow-up.

Artificial intelligence in mitral valve analysis

Background:

Echocardiographic analysis of mitral valve (MV) has become essential for diagnosis and management of patients with MV disease. Currently, the various software used for MV analysis require manual input and are prone to interobserver variability in the measurements.

Aim:

The aim of this study is to determine the interobserver variability in an automated software that uses artificial intelligence for MV analysis.

Settings and Design:

Retrospective analysis of intraoperative three-dimensional transesophageal echocardiography data acquired from four patients with normal MV undergoing coronary artery bypass graft surgery in a tertiary hospital.

Materials and Methods:

Echocardiographic data were analyzed using the eSie Valve Software (Siemens Healthcare, Mountain View, CA, USA). Three examiners analyzed three end-systolic (ES) frames from each of the four patients. A total of 36 ES frames were analyzed and included in the study.

Statistical Analysis:

A multiple mixed-effects ANOVA model was constructed to determine if the examiner, the patient, and the loop had a significant effect on the average value of each parameter. A Bonferroni correction was used to correct for multiple comparisons, and P = 0.0083 was considered to be significant.

Results:

Examiners did not have an effect on any of the six parameters tested. Patient and loop had an effect on the average parameter value for each of the six parameters as expected (P < 0.0083 for both).

Conclusion:

We were able to conclude that using automated analysis, it is possible to obtain results with good reproducibility, which only requires minimal user intervention.

Multi-Modality Imaging in the Evaluation and Treatment of Mitral Regurgitation

OPINION STATEMENT

Mitral regurgitation (MR) is frequent and associated with increased mortality and morbidity when severe. It may be caused by intrinsic valvular disease (primary MR) or ventricular deformation (secondary MR). Imaging has a critical role to document the severity, mechanism, and impact of MR on heart function as selected patients with MR may benefit from surgery whereas other will not. In patients planned for a surgical intervention, imaging is also important to select candidates for mitral valve (MV) repair over replacement and to predict surgical success. Although standard transthoracic echocardiography is the first-line modality to evaluate MR, newer imaging modalities like three-dimensional (3D) transesophageal echocardiography, stress echocardiography, cardiac magnetic resonance (CMR), and computed tomography (CT) are emerging and complementary tools for MR assessment. While some of these modalities can provide insight into MR severity, others will help to determine its mechanism. Understanding the advantages and limitations of each imaging modality is important to appreciate their respective role for MR assessment and help to resolve eventual discrepancies between different diagnostic methods. With the increasing use of transcatheter mitral procedures (repair or replacement) for high-surgical-risk patients, multimodality imaging has now become even more important to determine eligibility, preinterventional planning, and periprocedural guidance.

Multimodality imaging assessment of mitral valve anatomy in planning for mitral valve repair in secondary mitral regurgitation

Secondary mitral regurgitation (MR) is frequent valvular heart disease and conveys worse prognostic. Therapeutic surgical or percutaneous options are available in the context of severe symptomatic secondary MR, but the best approach to treat these patients remains unclear, given the lack of clear clinical evidence of benefit. A comprehensive evaluation of the mitral valve apparatus and the left ventricle (LV) has the ability to clearly define and characterize the disease, and thus determine the best option for the patient to improve its clinical outcomes, as well as quality of life and symptoms. The current report reviews the mitral valve (MV) anatomy, the underlying mechanisms associated with secondary MR, the related therapeutic options available, and finally the usefulness of a multimodality imaging approach for the planning of surgical or percutaneous mitral valve intervention.