Functional mitral regurgitation: an overview for surgical management framework

Functional mitral regurgitation (FMR) is one the most common complications of myocardial infarction (MI) in adults carrying a significant clinical and economic burden. Despite specific randomized controlled studies to address its treatment have been performed, there are still a number of questions remained unanswered. Outcomes of surgical repair of FMR are still hampered by a significant rate of recurrence of regurgitation and need for reoperation. Mechanisms underlying failure of repairs still need to be completely clarified and questions regarding the indications and optimal timing for intervention as well as the best suitable operative technique to be applied are still debated. This work will review the current knowledge on FMR including its pathogenic mechanisms, the available treatment strategies, the evidences from trials and observational studies and the potential future directions to address the issues related to its treatment.

Transcatheter Technologies for Valvular Replacement: an Update

This report provides a brief overview of the basic principles, recent advances, and recommendations for the treatment of severe aortic stenosis with transcatheter aortic valve replacement (TAVR) in adults. Approaches that avoid neurological, cardiac and peripheral vascular complications have been developed. In addition, TAVR can be performed in intermediate- and low-risk patients. However, these procedures require specialized training and may not allow for complete resolution of the underlying issue. Even if cardiologists learn to perform the procedure and despite advancements in device technology, TAVR is still susceptible to structural valve degeneration, thrombosis and late cerebral embolization. To date, TAVR has shown no consistent advantage over surgical aortic valve replacement (SAVR) in intermediate- and low-risk patients.

Long-term outcome of cryopreserved allograft for aortic valve replacement

OBJECTIVE

The most efficient surgical approach to severe aortic valve disease in the young adult is still debated: cryopreserved aortic allograft offers excellent hemodynamic and avoid anticoagulation, but long-term durability is influenced by structural valve deterioration (SVD). This study aimed to describe long-term results of aortic allografts and to identify factors influencing long-term durability.

METHODS

From January 1993 to August 2010, 210 patients underwent aortic allograft replacement via the free-hand subcoronary implantation technique (N = 55) or root replacement with coronary reimplantation (N = 155). Clinic and echocardiographic follow-up was updated to April 2016.

RESULTS

Overall mortality and cardiac mortality occurred in 80 (38.1%) and 64 (30.5%) patients, respectively. Reoperation was required in 69 cases (32.8%), whereas SVD required reoperation in 57 cases (27.1%). No early endocarditis occurred, whereas late endocarditis occurred in 4 patients. The free-hand technique seems to be associated with improved left ventricular remodeling compared with the root-replacement technique, and smaller allograft size represents a predictor of reoperation independently on the surgical technique used. In the overall population, there were 44 women of childbearing age, and 37 patients remained pregnant during the follow-up of the study. No differences were found in the clinical outcomes among women who had children and who did not.

CONCLUSIONS

Cryopreserved allograft is a valid option, especially in complex infective endocarditis and in women of childbearing age. A careful choice of allograft size and implantation technique can reduce the risk of SVD.

Secondary Open Aortic Procedure Following Thoracic Endovascular Aortic Repair: Meta-Analytic State of the Art

BACKGROUND

Thoracic endovascular aortic repair is characterized by a substantial need for reintervention. Secondary open aortic procedure becomes necessary when further endoluminal options are exhausted. This synopsis and quantitative analysis of available evidence aims to overcome the limitations of institutional cohort reports on secondary open aortic procedure.

METHODS AND RESULTS

Electronic databases were searched from 1994 to the present date with a prospectively registered protocol. Pooled quantification of pre/intraoperative variables, and proportional meta-analysis with random effect model of early and midterm outcomes were performed. Subgroup analysis was conducted for patients who had early mortality. Fifteen studies were elected for final analysis, encompassing 330 patients. The following values are expressed as "pooled mean, 95% confidence interval." Type B dissection was the most common pathology at index thoracic endovascular aortic repair (51.2%, 44.4-57.9). The most frequent indication for secondary open aortic procedure was endoleak (39.7%, 34.6-45.1). More than half of patients had surgery on the descending aorta (51.2%, 45.8-56.6), and one fourth on the arch (25.2%, 20.8-30.1). Operative mortality was 10.6% (7.4-14.9). Neurological morbidity was substantial between stroke (5.1%, 2.8-9.1) and paraplegia (8.3%, 5.2-13.1). At 2-year follow-up, mortality (20.4%, 11.5-33.5) and aortic adverse event (aortic death 7.7%, 4.3-13.3, tertiary aortic open procedure 7.4%, 4.0-13.2) were not negligible.

CONCLUSIONS

In the secondary open aortic procedure population, type B dissection was both the most common pathology and the one associated with the lowest early mortality, whereas aortic infection and extra-anatomical bypass were associated with the most ominous prognosis.

Analysing the reasons of failure of surgical mitral repair approaches-do we need to better think in biomechanics?

The failure of mitral valve repair procedures revealed in the outcomes of the recent randomized studies is suggesting the necessity for a better understanding of the biomechanical mechanisms underlying the failure of the surgical approaches. Use of biomechanical modelling and finite element analysis (FEA) in cardiovascular research is an important aid in this context. In our group we developed a biomechanical model taking into account all the component of the mitral valve functional unit including the valve leaflets, the annulus, the papillary muscles, the chordae tendinea and the ventricular geometry. The two-dimensional mathematical model was capable to predict some of the actual geometrical and mechanical features of the valvular and subvalvular apparatuses in physiological and pathological conditions providing the engineering quantitative relations between closing and tethering forces and the mechanisms governing the mitral valve unit function. This model might further become patient-specific by means of 3D reconstruction of clinical imaging. Images are first converted in a standard vector format (DICOM, etc.), then automatically translated in a "structural" finite element model and finally implemented in a finite element code. This allows for in silico simulations to virtually explore the effects of different surgical approaches at an early stage after the procedure, to help the operative decision processes, or to optimize the design of surgical implants.

Papillary muscle approximation in mitral valve repair for secondary MR

Ischemic mitral regurgitation (IMR) is a complex disorder occurring after a myocardial infarction and affecting both the mitral valvular and subvalvular apparati. Several abnormalities can be detected in IMR as annular dilatation, leaflet tethering with impaired coaptation and papillary muscle (PM) displacement along a posterior, apical or lateral vectors. Treatments available include, beside myocardial revascularization, mitral-valve repair or chordal-sparing replacement. Repair is normally achieved downsizing the mitral valve annulus with a rigid or semirigid ring. However, considering the involvement of the subvalvular apparatus, techniques addressing the PM have been developed. The rationale at the basis of this strategy relies in the possibility to reduce the interpapillary muscle distance restoring the geometry of the left ventricle (LV) and ultimately resolving the leaflet tethering at the basis of IMR. Subvalvular apparatus surgical approaches include the papillary muscle approximation (PMA), surgical relocation and PM sling. Improved outcomes in terms of postoperative positive left ventricular remodeling and recurrence of mitral regurgitation have been reported, but more investigations are required to confirm the efficacy of subvalvular apparatus surgery. Application of finite element analysis to improve preoperative and intraoperative planning and achieve a correct and durable repair by means of subvalvular surgery is an exciting new avenue in IMR research.

Biomechanics raises solution to avoid geometric mitral valve configuration abnormalities in ischemic mitral regurgitation

Ischemic mitral regurgitation (IMR) is a form of mitral insufficiency that is characterized by papillary muscle (PM) displacement, leaflet tethering, reduced closing forces, and different degree of annular dilatation. Treatment of this condition includes mitral valve replacement or mitral valve repair with restrictive annuloplasty. Recent evidences in mitral valve repair showed that addressing only the annulus and neglecting the subvalvular apparatus provides a suboptimal operation with poor long-term results. However, the complexity of the geometrical aberrances occurring in IMR demands for more accurate analysis also involving the biomechanics underlying the failing mitral valve and subvalvular apparatus. Finite element analysis (FEA) is a powerful tool in this context and we developed a biomechanical model of mitral valve and subvalvular unit using 3D geometry of the leaflets, annulus, chordae and PM. After the application of structural properties of materials to these elements and simulation of systemic pressure loading, FEA could be used to directly determine biomechanical changes and geometry variations. We believe this approach can provide valuable information to better address the surgical treatment of IMR and answer some of the questions still pending in IMR management.

Pulmonary autograft in aortic position: is everything known?

The Ross operation provides several advantages compared to other valve substitutes to manage aortic valve disease, such as growth potential, excellent hemodynamics, freedom from oral anticoagulation and hemolysis, and better durability. However, progressive dilatation of the pulmonary autografts after Ross operation reflects the inadequate remodeling of the native pulmonary root in the systemic circulation, which results in impaired adaptability to systemic pressure and risk of reoperation after the first decade. A recently published article showed that remodeling increased wall thickness and decreased stiffness in the failed specimens after Ross operation, and the increased compliance might play a key role in determining the progressive long-term autograft root dilatation. Late dilatation can be counteracted by an external barrier which prevents failure. Therefore, an inclusion cylinder technique with a native aorta or a synthetic external support, such as Dacron, might stabilize the autograft root and improve long-term outcomes. In this article, we offer a prospective about the importance of biomechanical features in future developments of the Ross operation. Pre-clinical and clinical evaluations of the biomechanical properties of these reinforced pulmonary autografts might shed new light on the current debate about the long-term fate of the pulmonary autograft after Ross procedure.

Ischemic mitral valve prolapse

Ischemic mitral prolapse (IMP) is a pathologic entity encountered in about one-third among the patients undergoing surgery for ischemic mitral regurgitation (IMR). IMP is generally the result of a papillary muscle injury consequent to myocardial, but the recent literature is progressively unveiling a more complex pathogenesis. The mechanisms underlying its development regards the impairment of one or more components of the mitral apparatus, which comprises the annulus, the chordae tendineae, the papillary muscle and the left ventricular wall. IMP is not only a disorder of valvular function, but also entails coexistent aspects of a geometric disturbance of the mitral valve configuration and of the left ventricular function and dimension and a correct understanding of all these aspects is crucial to guide and tailor the correct therapeutic strategy to be adopted. Localization of prolapse, anatomic features of the prolapsed leaflets and the subvalvular apparatus should be carefully evaluated as also constituting the major determinants defining patient's outcomes. This review will summarize our current understanding of the pathophysiology and clinical evidence on IMP with a particular focus on the surgical treatment.

Basic and Clinical Research Against Advanced Glycation End Products (AGEs): New Compounds to Tackle Cardiovascular Disease and Diabetic Complications

Diabetes is a major risk factor for cardiovascular disease, and recent advances in research indicate that a detailed understanding of the pathophysiology of its effects is mandatory to reduce diabetes-related mortality and morbidity. Advanced Glycation End Products (AGEs) play a central role in the genesis and progression of complications of both type 1 and type 2 diabetes mellitus, and have been found to be important even in non-diabetic patients as a marker of cardiovascular disease. AGEs have a profound impact on patient's prognosis regardless of the glycemic control, and therefore pharmacologic approaches against AGEs accumulation have been proposed over the years to treat cardiovascular diseases, parallel to a more detailed understanding of AGEs pathophysiology. Compounds with anti-AGEs effects are currently under investigation in both pre-clinical and clinical scenarios, and many of the drugs previously used to treat specific diseases have been found to have AGE-inhibitory effects. Some products are still in "bench evaluation", whereas others have been already investigated in clinical trials with conflicting evidences. This review aims at summarizing the mechanisms of AGEs formation and accumulation, and the most relevant issues in pre-clinical and clinical experiences in anti-AGEs treatment in cardiovascular research.

Is subvalvular repair worthwhile in severe ischemic mitral regurgitation? Subanalysis of the Papillary Muscle Approximation trial

OBJECTIVE

The symmetry of mitral valve tethering and regional left ventricle wall dysfunction are reported to play a fundamental role in the outcomes and long-term durability of surgical repair in ischemic mitral regurgitation (IMR). We recently demonstrated in a randomized clinical trial (the Papillary Muscle Approximation trial) the superiority of papillary muscle approximation (PMA) in combination with standard restrictive annuloplasty (RA) in severe IMR over annuloplasty alone in terms of adverse left ventricular remodeling and mitral regurgitation (MR) recurrence. This approach, however, failed to produce a survival advantage and was still plagued by a high incidence of reoperation. We therefore performed a subanalysis of the PMA trial on the basis of preoperative parameters to elucidate the value of subvalvular surgery in certain subcategories of patients with the aim of creating a decisional algorithm on the best operative strategy.

METHODS

We performed a subanalysis of PMA trial, evaluating 96 patients with severe IMR and eligible for myocardial revascularization randomized to PMA + RA (n = 48) versus RA alone (n = 48) in association with coronary artery bypass grafting. Endpoints included left ventricular remodeling, MR recurrence, overall mortality, reoperation, and a composite cardiac endpoint (cardiac death, stroke, reintervention, hospitalization for heart failure, or New York Heart Association class worsening). Stratification variables were preoperative symmetry of mitral valve tethering and regional wall motion abnormality.

RESULTS

PMA improved ventricular remodeling and recurrence of MR in both preoperative symmetric and asymmetric tethering and in case of inferior wall dyskinesia but did not produce an additional benefit in anterolateral wall dysfunction.

CONCLUSIONS

Preoperative symmetric and asymmetric tethering and isolated inferior wall dyskinesia are an indication for subvalvular apparatus surgery in IMR.

Is it time to change how we think about incomplete coronary revascularization?

The optimal degree of revascularization for patients with chronic multivessel coronary artery disease remains an unsolved issue. Intuitively, complete revascularization decreases cardiovascular events and improves outcomes compared to incomplete procedures, but in recent years the concept of incomplete revascularization moved from a sub-optimal or a defective treatment towards the most appropriate revascularization technique in some categories of patients. A reasonable level of incomplete anatomic revascularization has been shown to be safe and achievable with both percutaneous (PCI) and surgical procedures (CABG), despite with different long-term outcomes. What are the mechanisms underlying the clinical benefits of an incomplete revascularization and what are the factors explaining the discrepancy in the long-term clinical outcomes between the two modes of revascularization PCI and CABG? The biological consequences of coronary reperfusion might provide valuable hints in this context and at the same time cast new light on the way we think about incomplete revascularization.

Biomechanics drive histological wall remodeling of neoaortic root: A mathematical model to study the expression levels of ki 67, metalloprotease, and apoptosis transition

The pulmonary artery autograft (PA) is the ideal substitute for aortic valve disease in children and young adult. However, it is harnessed by the issue of long-term dilation and regurgitation, often requiring surgery. PA implanted in aortic position during the growth phase in children undergoes a process of mechanical remodeling. We previously developed a semiresorbable armored prosthesis able to mechanically sustain the neoaorta preventing dilation and to gradually integrate with the PA wall inducing a progressive arterial-like tissue positive remodeling. We also described the mechanisms of growth, remodeling and stress shielding of the reinforced PA through a mathematical model. We sought to demonstrate the biological counterpart and the potential molecular mechanisms underlying this histological and mechanical remodeling. A specific mathematical model was developed to describe mechanical behavior of the PA. Mallory trichrome red staining and immunohistochemistry for MMP-9 were performed to elucidate extracellular matrix remodeling phenomena. Apoptosis and cell proliferation were determined by TUNEL assay and immunohistochemistry for Ki67, respectively. An histological remodeling phenomenon sustained by increased level of MMP-9, augmented cell proliferation and reduced apoptosis in the reinforced PA was demonstrated. The mathematical model predicted the biomechanical behavior subtended by the histological changes of the PA in these settings. Changes in metalloproteinases (MMP-9), cell proliferation and apoptosis are the main actors in the remodeling process occurring after transposition of the PA into systemic regimens. Use of semiresorbable reinforcements might induce a positive remodeling of the PA in the context of Ross operation. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2785-2793, 2016.

Compliance mismatch and compressive wall stresses drive anomalous remodelling of pulmonary trunks reinforced with Dacron grafts

Synthetic grafts are often satisfactory employed in cardiac and vascular surgery, including expanded poly(ethylene terephthalate) or expanded poly(tetrafluoroethylene). However, accumulating evidences suggest the emergence of worrisome issues concerning the long-term fate of prosthetic grafts as large vessel replacement. Disadvantages related to the use of synthetic grafts can be traced in their inability of mimicking the elasto-mechanical characteristics of the native vascular tissue, local suture overstress leading to several prosthesis-related complications and retrograde deleterious effects on valve competence, cardiac function and perfusion. Motivated by this, in the present work it is analyzed - by means of both elemental biomechanical paradigms and more accurate in silico Finite Element simulations - the physical interaction among aorta, autograft and widely adopted synthetic (Dacron) prostheses utilized in transposition of pulmonary artery, highlighting the crucial role played by somehow unexpected stress fields kindled in the vessel walls and around suture regions, which could be traced as prodromal to the triggering of anomalous remodelling processes and alterations of needed surgical outcomes. Theoretical results are finally compared with histological and surgical data related to a significant experimental animal campaign conducted by performing pulmonary artery transpositions in 30 two-month old growing lambs, followed up during growth for six months. The in vivo observations demonstrate the effectiveness of the proposed biomechanical hypothesis and open the way for possible engineering-guided strategies to support and optimize surgical procedures.