Surgical mitral plasticity for chronic ischemic mitral regurgitation

A morphofunctional analysis of the regurgitant mitral valve as a guide to repair: Another point of view

Based on Carpentier's classification and principles, the techniques for mitral valve repair continue to evolve. We herein report our experience with the morphofunctional echocardiographic analysis of single mitral leaflets, as different anatomic features, even if conflicting, may coexist not only in the two leaflets but in the same leaflet as well. A classification is proposed, based on the length (normal, short, or long) and mobility (normal, restricted, or excessive) of mitral leaflets. The surgical techniques adopted for mitral valve repair are the direct consequence of this analysis.

Cutting the second order chords during mitral valve repair

The chordae tendinae connect the papillary muscles (PMs) to the mitral valve. While the first-order chordae serve to secure the leaflets to maintain valve closure and prevent mitral valve prolapse, the second-order chordae are believed to play a role in maintaining normal left ventricle size and geometry. The PMs, from where the chordae tendinae originate, function as shock absorbers that compensate for the geometric changes of the left ventricular wall. The second-order chordae connect the PMs to both trigons under tension. The tension distributed towards the second-order chordae has been demonstrate to be more than threefold that in their first-order counterpart. Cutting the second-order chordae puts all the tension on the first-order chordae, which are then closer to their rupture point. However, it has been experimentally demonstrated that the tension at which the first-order chordae break is 6.8 newtons (N), by far higher than the maximal tension reached, that is 0.4 N. Even if the clinical reports have been favorable, the importance of cutting the second-order chordae to recover curvature of the anterior leaflet and increase the coaptation length between the mitral valve leaflets has been slowly absorbed by the surgical world. Nevertheless, there are progressive demonstrations that chordal tethering affects the anterior leaflet not only in secondary, but also in primary mitral regurgitation, having a not negligible role in the long-term outcome of mitral repair.

Prognosis for Mitral Valve Repair Surgery in Functional Mitral Regurgitation

Purpose: Our aim was to evaluate the development of new significant mitral regurgitation and long-term survival after mitral repair surgery in functional mitral regurgitation.

Methods: A retrospective observational analysis of the recurrence of functional mitral regurgitation (ischemic and nonischemic) and global mortality during follow-up of 176 patients who underwent mitral repair surgery between 1999 and 2018 in our center was conducted.

Results: The etiology of functional mitral regurgitation was ischemic in 55.7% of cases. After surgery, mitral regurgitation was 0-I in 92.3% of cases. We conducted a long-term clinical follow-up of a mean 42.2 months and an echocardiographic follow-up of a mean 41.8 months. We observed mitral regurgitation of at least grade II in 52 patients (36.9%). Survival at 1, 3, and 5 years was 78.8%, 66.7%, and 52.3%, respectively. Predictive factors for global mortality were age (hazard ratio = 1.038, p = 0.01) and a depressed preoperative ejection fraction. After a competing risk analysis, we found the only predictive factor for the recurrence of mitral regurgitation in our series to be age (sub-hazard ratio = 1.03, 95% confidence interval = 1.01–1.06, p = 0.016).

Conclusion: Repair surgery for functional mitral regurgitation shows age as the only independent predictor of recurrence. Age and depressed ejection fraction were predictors of mortality.

Mitral Plasticity: The Way to Prevent the Burden of Ischemic Mitral Regurgitation?

The ischemic impairment of the left ventricular contractility, followed by an adverse remodeling leading to the displacement of the papillary muscles (PMs), increased tethering forces and loss of valve competence has been the long-term accepted definition of ischemic mitral regurgitation (IMR). Over the years, different approaches of management have attempted to address valve regurgitation, nevertheless failing to achieve satisfactory outcomes. Recent studies have observed some structural and molecular changes of the mitral valve (MV), challenging the concept of a bystander passive to the subvalvular involvement. Indeed, the solely mechanical stretch of the PMs, as in the dilated left ventricle because of the aortic valve regurgitation, is not enough in causing relevant MV regurgitation. This setting triggers a series of structural changes called “mitral plasticity,” leaflets increase in their size among others, ensuring an adequate systolic area closure. In contrast, the ischemic injury not only triggers the mechanical stretch on the subvalvular apparatus but is also a powerful promotor of profibrotic processes, with an upregulation of the transforming growth factor (TGF)-β signaling pathway, leading to a MV with exuberant leaflet thickness and impaired mobility. In this article, we revise the concept of IMR, particularly focusing on the new evidence that supports dynamic changes in the MV apparatus, discussing the consequent clinical insights of “mitral plasticity” and the potential therapeutic implications.

Ischemic Mitral Regurgitation: A Multifaceted Syndrome with Evolving Therapies

Dysfunction of the left ventricle (LV) with impaired contractility following chronic ischemia or acute myocardial infarction (AMI) is the main cause of ischemic mitral regurgitation (IMR), leading to moderate and moderate-to-severe mitral regurgitation (MR). The site of AMI exerts a specific influence determining different patterns of adverse LV remodeling. In general, inferior-posterior AMI is more frequently associated with regional structural changes than the anterolateral one, which is associated with global adverse LV remodeling, ultimately leading to different phenotypes of IMR. In this narrative review, starting from the aforementioned categorization, we proceed to describe current knowledge regarding surgical approaches in the management of IMR.

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.

An observational, prospective study on surgical treatment of secondary mitral regurgitation: The SMR study. Rationale, purposes, and protocol

The natural history of secondary mitral regurgitation (MR) is unfavorable. Nevertheless, there are no evidence that its correction can improve the outcome. If from one side the original cause of secondary MR can be such to limit the possibilities of improvement, from the other side it is possible that the surgical technique widely applied to repair, restrictive mitral annuloplasty, is not adequate to correct the regurgitation. The addition of valvular and/or subvalvular techniques has been considered a possible technical solution. However, we do not know the prevalence of each technique, how many times mitral replacement is used to correct secondary MR. This aspect is of particular importance, as we know that a successful mitral repair causes a better left ventricular systolic remodeling than a unsuccessful repair or replacement. This study is a prospective, observational registry, conceived to understand what is done in the real world. Any surgeon will use the technique he thinks the most suitable for the patient. Every year, for 5 years, patients will have a clinical and echocardiographic follow-up, to evaluate the risk factors for a worse result (death, rehospitalization for heart failure, reoperation for MR return, moderate, or more MR return). This knowledge will give us the possibility to understand which is the technique, or the strategy, more efficient to treat this disease and the real efficacy of the surgical treatment.