Dataset Information

Papillary Muscle Approximation Reduces Systolic Tethering Forces and Improves Mitral Valve Closure in the Repair of Functional Mitral Regurgitation.

ABSTRACT:

Background

Undersizing mitral annuloplasty (UMA) to repair functional mitral regurgitation lacks durability, as it forces leaflet coaptation without relieving the sub-leaflet tethering forces. In this biomechanical study, we demonstrate that papillary muscle approximation (PMA) prior to UMA can drastically relieve tethering forces and improve valve function, without the need for significant annular downsizing.

Methods

An ex vivo model of functional mitral regurgitation (FMR) was used, in which pig mitral valves were geometrically perturbed to induce FMR, and the repairs were performed. Nine pig mitral valves were studied as follows: normal(baseline), functional mitral regurgitation (FMR), true-sized annuloplasty to 30mm (TSR), and undersized annuloplasty to 26mm (DSR); and concomitant papillary muscle approximation (PMA) at both ring sizes. Mitral regurgitation, valve kinematics, and chordal forces were measured and compared between groups.

Results

FMR geometry induced a 16.31±7.33% regurgitant fraction, compared to none at baseline. 30mm/TSR reduced regurgitation to 6.05±5.63% and a 26mm/DSR to 5.06±6.76%. Addition of papillary muscle approximation prior to either rings, reduced regurgitation to 3.87±6.79% with the true sized ring (TSR+PMA), and 3.71±6.25% with the downsized ring (DSR+PMA). Peak anterior and posterior marginal chordal forces were elevated to 0.09±0.1N and 0.12±0.1N respectively with FMR, which were not reduced by annuloplasty of either sizes. Addition of PMA, reduced the forces significantly to 0.23±0.02N and 0.51±0.04N.

Conclusion

This biomechanical study, demonstrates that papillary muscle approximation relieves tethering forces and when added to annuloplasty, and mobilizes the leaflets to achieve a good valve closure. Such a result could be achieved without the need for extensive annular downsizing.

SUBMITTER: Zhan-Moodie S

PROVIDER: S-EPMC8924981 | biostudies-literature | 2021 Sep

REPOSITORIES: biostudies-literature

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Publications

Papillary Muscle Approximation Reduces Systolic Tethering Forces and Improves Mitral Valve Closure in the Repair of Functional Mitral Regurgitation.

Zhan-Moodie Samantha S Xu Dongyang D Suresh Kirthana Sreerangathama KS He Qi Q Onohara Daisuke D Kalra Kanika K Guyton Robert A RA Sarin Eric L EL Padala Muralidhar M

JTCVS open 20210428

<h4>Background</h4>Undersizing mitral annuloplasty (UMA) to repair functional mitral regurgitation lacks durability, as it forces leaflet coaptation without relieving the sub-leaflet tethering forces. In this biomechanical study, we demonstrate that papillary muscle approximation (PMA) prior to UMA can drastically relieve tethering forces and improve valve function, without the need for significant annular downsizing.<h4>Methods</h4>An <i>ex vivo</i> model of functional mitral regurgitation (FMR ...[more]

PMID: 35299626

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Project description:Rationale: Ischemic mitral regurgitation (IMR) is frequently observed following myocardial infarction (MI) and is associated with higher mortality and poor clinical prognosis if left untreated. Accumulating evidence suggests that mitral valve (MV) leaflets actively remodel post-MI, yet the cellular mechanisms underlying these responses and how this affects tissue function remain largely unknown. Objective: We sought to elucidate MV remodeling post-MI at the tissue, cellular, and transcriptomic levels. Methods and Results: The mechanical behavior of ovine MV leaflets pre-MI and 8 weeks post-MI reveal a significant decrease in radial direction extensibility, which essentially eliminated the mechanical anisotropy typically observed in healthy MVs. Quantitative histology and ultrastructural assessment by transmission electron microscopy revealed altered leaflet composition and architecture at 8 weeks post-MI. Assessment of the MV interstitial cell (MVIC) nuclear aspect ratio, a metric of cellular deformation, revealed that MVICs were on average rounder following MI. RNA sequencing (RNA-seq) indicated that YAP-induced genes were elevated at 4 weeks post-MI and genes related to extracellular matrix organization were some of the most downregulated in sheep with IMR compared to sheep without IMR at 4 weeks post-MI. Additionally, RNA-seq revealed the possible recruitment of immune cells in this remodeling process due to the drastic elevation of CXCL9 and CLEC10A. Conclusions: This multiscale assessment revealed significant mechanical and microstructural changes due to MI. RNA-seq provided a baseline for global gene expression changes in response to MI with and without IMR and suggests YAP-induced mechanotransduction, altered expression of ECM-related genes, and recruitment of immune cells as mechanisms contributing to altered MV biomechanics post-MI. Conclusions: This multiscale assessment revealed significant mechanical and microstructural changes due to MI. RNA-seq provided a baseline for global gene expression changes in response to MI with and without IMR and suggests YAP-induced mechanotransduction, altered expression of ECM-related genes, and recruitment of immune cells as mechanisms contributing to altered MV biomechanics post-MI.

Project description:ObjectivesThe Cardiothoracic Surgical Trials Network recently reported no difference in the primary end point of left ventricular end-systolic volume index at 1 year postsurgery in patients randomized to repair (n = 126) or replacement (n = 125) for severe ischemic mitral regurgitation. However, patients undergoing repair experienced significantly more recurrent mitral regurgitation than patients undergoing replacement (32.6% vs 2.3%). We examined whether baseline echocardiographic and clinical characteristics could identify those who will develop moderate/severe recurrent mitral regurgitation or die.MethodsOur analysis includes 116 patients who were randomized to and received mitral valve repair. Logistic regression was used to estimate a model-based probability of recurrence or death from baseline factors. Receiver operating characteristic curves were constructed from these estimated probabilities to determine classification cut-points maximizing accuracy of prediction based on sensitivity and specificity.ResultsOf the 116 patients, 6 received a replacement before leaving the operating room; all other patients had mild or less mitral regurgitation on intraoperative echocardiogram after repair. During the 2-year follow-up period, 76 patients developed moderate/severe mitral regurgitation or died (53 mitral regurgitation recurrences, 13 mitral regurgitation recurrences and death, and 10 deaths). The mechanism for recurrent mitral regurgitation was largely mitral valve leaflet tethering. Our model (including age, body mass index, sex, race, effective regurgitant orifice area, basal aneurysm/dyskinesis, New York Heart Association class, history of coronary artery bypass grafting, percutaneous coronary intervention, or ventricular arrhythmias) yielded an area under the receiver operating characteristic curve of 0.82.ConclusionsThe model demonstrated good discrimination in identifying patients who will survive 2 years without recurrent mitral regurgitation after mitral valve repair. Although our results require validation, they offer a clinically relevant risk score for selection of surgical candidates for this procedure.

Dataset Information

Papillary Muscle Approximation Reduces Systolic Tethering Forces and Improves Mitral Valve Closure in the Repair of Functional Mitral Regurgitation.

Background

Methods

Results

Conclusion

Publications

Papillary Muscle Approximation Reduces Systolic Tethering Forces and Improves Mitral Valve Closure in the Repair of Functional Mitral Regurgitation.

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