Left atrial geometry in an ovine ischemic mitral regurgitation model: implications for transcatheter mitral valve replacement devices with a left atrial anchoring mechanism

BACKGROUND

Transcatheter mitral valve replacement (TMVR) is a challenging, but promising minimally invasive treatment option for patients with mitral valve disease. Depending on the anchoring mechanism, complications such as mitral leaflet or chordal disruption, aortic valve disruption or left ventricular outflow tract obstruction may occur. Supra-annular devices only anchor at the left atrial (LA) level with a low risk of these complications. For development of transcatheter valves based on LA anchoring, animal feasibility studies are required. In this study we sought to describe LA systolic and diastolic geometry in an ovine ischemic mitral regurgitation (IMR) model using magnetic resonance imaging (MRI) and echocardiography in order to facilitate future research focusing on TMVR device development for (I)MR with LA anchoring mechanisms.

METHODS

A group of 10 adult male Dorsett sheep underwent a left lateral thoracotomy. Posterolateral myocardial infarction was created by ligation of the left circumflex coronary artery, the obtuse marginal and diagonal branches. MRI and echocardiography were performed at baseline and 8 weeks after myocardial infarction (MI).

RESULTS

Six animals survived to 8 weeks follow-up. All animals had grade 2 + or higher IMR 8 weeks post-MI. All LA geometric parameters did not change significantly 8 weeks post-MI compared to baseline. Diastolic and systolic interpapillary muscle distance increased significantly 8 weeks post-MI.

CONCLUSIONS

Systolic and diastolic LA geometry do not change significantly in the presence of grade 2 + or higher IMR 8 weeks post-MI. These findings help facilitate future tailored TMVR device development with LA anchoring mechanisms.

Clinical manifestations, diagnosis, and treatment of ischemic mitral regurgitation: a review

Ischemic mitral regurgitation (IMR) is a frequent complication after acute myocardial infarction (AMI) associated with a worse prognosis. The pathophysiological mechanisms of IMR are not fully understood, but it is known to be a complex process in which ventricular remodelling is the main causal factor. The various imaging techniques in cardiology and echocardiography fundamentally have contributed significantly to clarify the mechanisms that cause and progressively aggravate IMR. At present, different therapeutic options, the most important of which are cardio-surgical, address this problem. Nowadays the improvement in cardiac surgery and transcatheter therapies, have shown a therapeutic advance in IMR management. IMR is a predictor of poor prognosis in patients with heart failure and depressed left ventricular (LV) systolic function. However, it remains controversial whether mitral regurgitation (MR) in these patients is a consequence of dilation and dysfunction of the LV, or whether it contributes to worsening the prognosis of the ventricular dysfunction. Given that echocardiography has a fundamental reference role in the identification, graduation of severity and evaluation of the therapeutics used in the treatment of MR, we are going to focus on it over the rest of the imaging techniques. In contrast to primary MR the benefits of mitral surgery in patients with secondary MR are uncertain. Therefore, we will comment fundamentally on the role of mitral surgery in patients with IMR, with an update of the different surgical interventions available, without forgetting to mention the other therapeutic options currently available.

Mitral valve repair versus replacement in patients with ischemic mitral regurgitation

Background

The optimal management of ischemic mitral regurgitation (IMR) is controversial. The aim of this study was to examine our eight years' experience of surgical treatment in patients with IMR, and to compare outcomes of mitral valve repair versus replacement with concomitant coronary artery bypass grafting (CABG).

Methods

A retrospective, observational, cohort study was undertaken to collect data on consecutive patients with IMR and coronary artery disease who received CABG and mitral valve surgery in our hospital between January 2008 and December 2015. Basic patient characteristics, operative data, and postoperative clinical outcomes were examined.

Results

The series included 22 consecutive patients (21 male; 1 female). The mean age was 62.1±11.4 years old. The mean preoperative left ventricular ejection fraction (LVEF) was 33.4%±15.4%. The mean cardiopulmonary bypass (CPB) time was 165.4±38.4 minutes, and the mean aortic cross clamp time was 113.8±33.6 minutes. Eighteen patients underwent CABG plus mitral valve repair, and four patients underwent CABG plus mitral valve replacement (MVR). There were three early in-hospital mortalities: two in the mitral valve repair group, and one in the replacement group. The follow-up was complete in all patients, with a mean follow-up duration of 3.1±2.3 years. The mean last LVEF was 35.3%±17.7%. There were 2 late mortalities. Both were from the repair group. The overall late survival rate was 81.6%, with 83.0% in the repair group and 75.0% in the replacement group. In patients with echocardiography follow-up of more than or equal to 1 year duration, the residual or recurrent mitral regurgitation rates were 0.0% in the replacement group and 57.1% in the repair group. One patient in the repair group later underwent MVR due to severe regurgitation postoperatively.

Conclusions

Our preliminary findings showed that the surgical outcome of mitral valve repair might be comparable to that of MVR in terms of early mortality and long-term survival. However, mitral valve repair was associated with a higher residual or recurrent mitral regurgitation rate. According to the latest literature, the role of MVR can justifiably be indicated for severe IMR. As for moderate IMR, CABG alone without mitral valve intervention may provide similar clinical outcomes.

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.

A Comparison of 2 Mitral Annuloplasty Rings for Severe Ischemic Mitral Regurgitation: Clinical and Echocardiographic Outcomes

Controversies regarding the choice of annuloplasty rings for treatment of ischemic mitral regurgitation still exist. Aim of the study is to compare early performance of 2 different rings in terms of rest and exercise echocardiographic parameters (transmitral gradient, systolic pulmonary artery pressure, and mitral valve area), clinical outcomes, and recurrence of mitral regurgitation. From January 2008 till December 2013, prospectively collected data of patients who underwent coronary artery bypass grafting and undersizing mitral valve annuloplasty for severe chronic ischemic mitral regurgitation at our Institution were reviewed. A total of 93 patients were identified; among them 44 had semirigid Memo 3D ring implanted (group A) whereas 49 had a rigid profile 3D ring (group B). At 6 months, recurrent ischemic mitral regurgitation, equal or more than moderate, was observed in 4 and 6 patients in the group A and B, respectively (P = 0.74). Group A showed certain improved valve geometric parameters such as posterior leaflet angle, tenting area, and coaptation depth. Transmitral gradient was significantly higher at rest in the group B (P < 0.0001). During exercise, significant increase of transmitral gradient and systolic pulmonary artery pressure was observed in group B (P < 0.0001). Mitral valve area was not statistically significantly smaller at rest in between groups (P = 0.09); however, it significantly decreased with exercise in group B (P = 0.01). At midterm follow-up, patients in group B were more symptomatic. In patients with chronic ischemic mitral regurgitation, use of semirigid Memo 3D ring when compared to the rigid Profile 3D may be associated with early improved mitral valve geometrical conformation and hemodynamic profile, particularly during exercise. No difference was observed between both groups in recurrent mitral regurgitation.

A novel approach to ischemic mitral regurgitation (IMR)

Ischemic mitral regurgitation (IMR) is a complicated medical condition with varying degrees of coronary artery disease and mitral regurgitation (MR). The traditional surgical treatment option for those with indications for intervention is coronary artery bypass grafting (CABG) plus or minus mitral valve repair or replacement (MVR). Percutaneous coronary intervention, hybrid coronary revascularization (HCR), and conventional CABG are three techniques available to address coronary artery disease (CAD). Percutaneous edge-to-edge repair, minimally invasive, and traditional sternotomy are accepted approaches for the treatment of MR. When taken in combination, there are nine methods available to revascularize the myocardium and restore competency to the mitral valve. While most of these treatment options have not been studied in detail, they may offer novel solutions to a widely variable and complex IMR patient population. Thus, a comparative analysis including an examination of potential benefits and risks will be helpful and potentially allow for more patient-specific treatment strategies.