Mechanisms Of Ischemic Mitral Regurgitation Research Articles

Surgical intervention for ischemic mitral regurgitation: how can we achieve better outcomes?

Ischemic mitral regurgitation (MR) is a common complication of myocardial infarction. Left ventricular (LV) dysfunction and distortion of the subvalvular apparatus are the main contributors to ischemic MR. Coronary artery bypass grafting alone, mitral valve replacement, and mitral valve repair, with or without subvalvular procedures, have been performed for moderate-to-severe ischemic MR. Several randomized studies on the surgical treatment of ischemic MR have been performed; however, the optimal surgical strategy remains controversial because none have demonstrated a clear survival benefit. Since the mechanisms of ischemic MR are complex and multifactorial, comprehensive preoperative assessment of LV function and geometry (both global and regional), mitral valve configuration, viability testing, and exercise echocardiography are needed. A better understanding of this complicated disease and of the advantages and limitations of each procedure may help us devise more effective patient-specific surgical treatment strategies and achieve better outcomes.

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.

Diagnosis and Management of Ischemic Mitral Regurgitation: Evidence-Based Clinical Decision Making at the Point of Care.

Anatomical, functional, and pathophysiologic mechanisms of ischemic mitral regurgitation (IMR) are markedly different from the primary mitral regurgitation. The older and ubiquitous cutoff of EROA (effective regurgitant orifice area) and Rvol (regurgitant volume) for IMR has been reinstated in the new guideline after a brief hiatus. There had always been a lack of good-quality evidence for its introduction for guiding IMR severity in the previous guideline, and we still do not have quality evidences that could justify its reintroduction. Unlike primary MR, IMR is usually associated with reduced ejection fraction. Therefore, it appears unrealistic to keep the similar cutoff for primary MR and IMR. The cutoff of severity can be modified according to projected values of Rvol normalized to ejection fraction and EROA normalized to Rvol. In addition, the treatment outcome in these patients is determined by factors (left ventricular dyssynchrony, annular dilatation, tenting area, tenting height, tenting volume, and myocardial viability) other than the simple grading. In this review article, a series of graph have been constructed from the numerical data derived from the literatures on IMR to depict the relationship between EROA, Rvol, left ventricular end diastolic volume, and ejection fraction in order to obtain a reasonable projection formula for EROA and Rvol. Furthermore, a management algorithm has been proposed for patients with IMR undergoing coronary artery bypass grafting based on echocardiographic predictors that influence the postoperative outcome.

Ischemic mitral regurgitation.

Ischemic mitral regurgitation (IMR) is a frequent complication of left ventricular (LV) global or regional pathological remodeling due to chronic coronary artery disease. It is not a valve disease but represents the valvular consequences of increased tethering forces and reduced closing forces. IMR is defined as mitral regurgitation caused by chronic changes of LV structure and function due to ischemic heart disease and it worsens the prognosis. In this review, we discuss on etiology, pathophysiology, and mechanisms of IMR, its classification, evaluation, and therapeutic corrective methods of IMR.

Can isolated annular dilatation cause significant ischemic mitral regurgitation? Another look at the causative mechanisms

This study was to investigate the mechanisms of ischemic mitral regurgitation (IMR) by using a finite element (FE) approach. IMR is a common complication of coronary artery disease; and it usually occurs due to myocardial infarction. The pathophysiological mechanisms of IMR have not been fully understood, much debate remains about the exact contribution of each mechanism to IMR. Two patient-specific FE models of normal mitral valves (MV) were reconstructed from multi-slice computed tomography scans. Different grades of IMR during its pathogenesis were created by perturbation of the normal MV geometry. Effects of annular dilatation and papillary muscle (PM) displacement (both isolated and combined) on the severity of IMR were examined. We observed greater increase in IMR (in terms of regurgitant area and coaptation length) in response to isolated annular dilatation than that caused by isolated PM displacement, while a larger PM displacement resulted in higher PM forces. Annular dilation, combined with PM displacement, was able to significantly increase the severity of IMR and PM forces. Our simulations demonstrated that isolated annular dilatation might be a more important determinant of IMR than isolated PM displacement, which could help explain the clinical observation that annular size reduction by restrictive annuloplasty is generally effective in treating IMR.

Surgical management of ischemic mitral regurgitation: indications, procedures, and future prospects

Ischemic mitral regurgitation (IMR) is one of the most important risk factors affecting prognosis of patients who suffer from myocardial infarction. The mechanisms of IMR, the indications for surgical intervention, the operative procedures, and the limitations of surgical procedures are discussed in this review article.

Multiplane Two‐Dimensional versus Real Time Three‐Dimensional Transesophageal Echocardiography in Ischemic Mitral Regurgitation

Intraoperative three-dimensional (3D) transesophageal echocardiography (TEE) has been suggested to be a valuable technique for the evaluation of the mechanisms of ischemic mitral regurgitation (IMR). Studies comparing multiplane two-dimensional (2D) with 3D TEE reconstruction of the mitral valve using the new mitral valve quantification (MVQ) software are lacking. We undertook a prospective comparison between multiplane 2D and 3D TEE for the assessment of IMR. We evaluated echocardiographically 45 patients with IMR who underwent mitral valve surgery in our institution. 2D and 3D TEE examinations followed by a 3D offline assessment of the mitral valve apparatus were performed in all patients. Offline analysis of mitral valve apparatus was conducted with QLAB-MVQ. 3D TEE image acquisitions were performed in a short period of time and were feasible in all patients. Real time 3D TEE imaging was superior to 2D in identifying specific mitral scallops (A1, A3, P1, P3) and commissures. When compared with 2D TEE, 3D offline reconstruction of the mitral valve allows an accurate quantification of the shape and diameters of the mitral annulus. Both approaches provide almost similar values for the tenting area and the coaptation depth. The 3D approach gave the advantage of direct calculation of the leaflets angles, tenting volume, and surface of the leaflets. The interpapillary muscles distance at the level of the papillary muscle head was greater in 2D than in 3D. 3D TEE imaging provides valuable and complementary information to multiplane 2D TEE for the assessment of patients with IMR.

Abstract 2832: Papillary Muscle Infarction is a Predictor of Ischemic Mitral Regurgitation: Novel Insights from Cardiac Magnetic Resonance Study

Introduction Ischemic mitral regurgitation (MR) bodes worsened prognosis and increased mortality in patients with ischemic cardiomyopathy. Various mechanisms of ischemic MR have been purposed, resulting in a spectrum of surgical strategies with varying success rates. Papillary muscle infarction may contribute to ischemic MR, but could not be identified non-invasively until the recent development of chronic infarction specific imaging (delayed-enhancement, or DE-MRI). Hypothesis We hypothesized that papillary muscle infarction, determined by DE-MRI, was correlated with the presence of ischemic MR. Methods Contrast-enhanced cardiac MRI for viability assessment was performed in 100 patients with ischemic cardiomyopathy (67 male, mean age 65 years). Papillary muscle infarction was determined from DE-MRI, and left ventricular (LV) functional parameters were calculated from contiguous short-axis cine-MRI images using the disc-summation technique. Results MR by echocardiography was present in 67%: 30% with mild MR (1+), 27% moderate MR (2+), and 10% severe MR (3– 4+). In patients with no, mild, moderate, and severe MR, there was a positive correlation with the prevalence of posterior papillary muscle infarction (15%, 40%, 52%, and 70%, respectively), but there was no association with anterior papillary muscle infarction (p=NS). There was a significant inverse relationship with LV ejection fraction (LVEF) (29%, 26%, 24%, and 20%, respectively). Both LVEF (p=0.013) and posterior papillary muscle infarction (p=0.006) were significantly associated with ischemic MR on univariate analysis. Using multiple logistic regression analysis, both posterior papillary muscle infarction and LVEF remained independent determinants of MR presence and severity (p<0.001 for both). Conclusions Patients with ischemic cardiomyopathy demonstrate a significant and positive correlation between the severity of MR and prevalence of posterior, but not anterior papillary muscle infarction identified by DE-MRI, and an inverse relationship with LVEF. The identification of papillary muscle infarction may provide insights into alternative approaches for repair of ischemic MR.

Ischemic cardiomyopathy: possibilities of surgical treatment

The high morbidity and mortality in patients with serious heart failure is a therapeutic challenge for current medicine. The leading cause of left ventricular dysfunction remains ischemic heart disease. Coronary artery bypass surgery is a treatment of choice in moderate-to-severe ischemic cardiomyopathy. The scarcity of completed prospective randomized clinical trials and high surgical risks create significant uncertainty concerning the optimal current treatment strategy. The role of imaging techniques of assessment for myocardial viability based on current guidelines may be very important in clinical decision-making. Present paper reviews some of the relevant literature concerning surgical treatment of ischemic cardiomyopathy and current evidence-based recommendations on this method of treatment. In advanced heart failure, coronary revascularization alone is an insufficient treatment modality. In the presence of moderate-to-severe ischemic mitral regurgitation, mitral valve repair or replacement should be considered at coronary artery bypass grafting surgery. One of the most common mechanisms of ischemic mitral regurgitation is Carpentier's type IIIb dysfunction, in which an undersized mitral anuloplasty might be helpful. Surgery of left ventricular shape and volume restoration leads to improvement of left ventricular function in patients with ischemic cardiomyopathy. When the results from three ongoing prospective randomized studies--the Surgical Treatment for Ischemic Heart Disease trial, Heart Failure Revascularization trial, the PET and Recovery Following Revascularization-2 trial--determining outcome of revascularization versus medical therapy are available, clinicians will have reliable data for making decisions concerning the optimum treatment strategy. At present, the choice of management still remains based on the data obtained from available retrospective trials or the state of art in the field.

Ischemic mitral valve repair: Correlations between the mechanisms of mitral regurgitation and left ventricular function prior to and following surgery

Objective. To define the mechanisms of ischemic mitral regurgitation (MR) and its correlation with left ventricular (LV) function prior to and 1 year following mitral valve (MV) repair. Design. Fifty-three patients (pts) underwent echocardiographic evaluation of the MR mechanism according to Carpentier's classification; quantification of MR and LV function. Results. Forty-one, 5% of pts had Type I (annulus dilation), 20, 5% had Type II (commissural prolapse) and 38% had Type IIIb MR (predominant posterior leaflet restriction). Preoperative LV function was slightly better preserved in pts with Type II and IIIb MR. Despite similar MV repair efficiency intraoperatively, after 1 year Type I MR progressed vs the remaining types. LV function, including dimensions, ejection fraction and pulmonary artery pressure had a tendency to worsen in pts with Type I and markedly improved in Type II and IIIb MR. Conclusions. Ischemic MR of Type I is associated with more marked LV dysfunction preoperatively, its further deterioration and MR progression after MV repair. Type II and IIIb MR correlates with better preserved LV function preoperatively and its incremental improvement late after surgery.

Suture Relocation of the Posterior Papillary Muscle in Ischemic Mitral Regurgitation

Despite advances in our understanding of the pathophysiology of ischemic mitral regurgitation as well as advances in surgical technique and perioperative care, surgical treatment of ischemic mitral regurgitation is associated with mortality rates as high as 20% in some series. It is generally agreed that in the majority of cases, mitral valve repair results in superior short- and mid-term outcomes when compared with mitral valve replacement. In our own series of patients withischemicmitralregurgitation,thehospitalmortalityrate for patients undergoing concomitant coronary artery bypass grafting and mitral valve repair was significantly less (1.9%) than patients undergoing coronary artery bypass grafting/ mitral valve replacement (10.7%). 1 There is some debate remaining as to whether repair or replacement is best suited for the sickest patients. Given the fact that ischemic mitral regurgitationoccursinthesubstrateofanoftenpoorlyfunctioning ventricle, it is not surprising that surgical mortality rates are higher for this lesion than for other causes of mitral regurgitation. However, in many cases, failure of the mitral valve repair technique to adequately treat the mechanism of the individual patient’s ischemic mitral regurgitation may significantly impact the clinical outcome. Observational studies in both experimental animals and clinical patients reveal that the mechanisms of ischemic mitral regurgitation are varied. Carpentier’s classification of leaflet motion reveals 2 plausible mechanisms. In patients with Carpentier’s type I dysfunction (Fig. 1), leaflet motion is unrestricted and ischemic mitral regurgitation occurs on the basis of annular dilation, with resultant failure of leaflet coaptation. This is ordinarily treated adequately by ring annuloplasty. In the case of Carpentier’s type IIIb dysfunction (Fig. 2), there is tethering of A3 and P3 segments to the anterior and posterior leaflets, respectively. This results from posterior displacement of the posterior papillary muscle and subjacent left ventricle as a product of myocardial infarction. This mechanism is poorly treated by simple mitral annuloplasty as abundant clinical experience has shown. Ring annuloplasty fails to restore adequate leaflet coaptation as the leaflet edges remain tethered below the annular level. Adequate treatment will only result if the leaflet edges can be allowed to return to the annular level. In addition, the combination of annular dilation as well as leaflet tethering may be at play with individual patients. These patients are also inadequately treated by ring annuloplasty alone. These latter 2 mechanisms are likely the mechanisms responsible for reports of up to 20% residual and/or progressive mitral regurgitation after annuloplasty alone. A number of procedures have been developed to try to improve results of mitral repair in these cases. Asymmetric mitral rings have been developed which attempt to deal with themoreeccentricmitralleak.TheAlfierirepair,inwhichthe anterior and posterior leaflets are sewn together, has been used by us and others with mixed results. In our hands, long-term improvement in mitral regurgitation has been poor. Kon’s method of patch anterior leaflet augmentation attempts to let the level of leaflet coaptation fall more posteriorly toward the level of the displaced papillary muscles. 2 Various types of ventricular modeling procedures also have been tried to restore papillary muscle geometry. We developed a method of suture relocation of the posterior papillary muscle that relieves A3 and P3 leaflet restriction. The procedure is simple and quick, which is of benefit in these generally unhealthy patients. In cases where the left ventricle is markedly enlarged, a Dor procedure is added to both stabilize the position of the papillary muscles and prevent late apical migration of the subvavular apparatus.

3 ISCHEMIC MITRAL VALVE REPAIR: THE IMPACT OF THE MECHANISM OF MITRAL REGURGITATION ON LATE POSTOPERATIVE RESULTS

Aim: The aim of our study was to establish the anatomical‐functional mechanisms of ischemic mitral regurgitation (MR) and to analyse its impact on late results after mitral valve (MV) reconstructive surgery. Methods: The study included 53 patients with ischemic MR, who underwent CABG and MV repair. MV surgery consisted of subvalvular apparatus repair and/or annuloplasty. 2D Doppler investigations performed pre‐, 10–14 days, and 12 months after surgery included evaluation of MV and left ventricular (LV) geometry and function. Results: Analysis of the mechanisms of ischemic MR permitted dividing patients into two groups: group 1—29 patients with inferobasal scar and posterior papillary muscle (PM) displacement, including 22 patients with PM infarction and 7 patients without it, and group 2—24 patients with isolated mitral annulus (MA) dilation. In the case of PM infarction two different mechanisms of MR were stated: (a) P3 restriction and A3 prolapse due to chordal tethering, (b) A3 P3 (commissural) prolapse due to chordal papillary elongation. Preoperatively LV geometry and function were better preserved in group 1 and late MV repair results were better versus (vs.) group 2: LV end‐systolic diameter index decreased from 22.9 ± 3.1 mm/m2 to 20.9 ± 3.6 mm/m2 at 1 year, p < 0.05, LV ejection fraction increased from 34.9 ± 8.4 to 41.8 ± 8.1%, respectively, p < 0.05. No significant changes in LV geometry and function were noted in group 2. Conclusions: The underlying mechanism of ischemic MR has an impact on MV repair results. In patients with MR due to posterobasal infarction MV repair resulted in more favorable postoperative effect‐marked improvement in LV geometry and function late after surgery versus MR due to isolated MA dilation.

Trends in the surgical management of ischemic mitral regurgitation.

The surgical approach to ischemic mitral regurgitation (IMR) remains a topic of considerable controversy. Will coronary artery bypass alone suffice, or should the valve be intervened upon? The poor late survival of patients with IMR is well recognized, but it remains unknown if this can be altered by addressing the valve directly. And if surgery is undertaken, should the valve be repaired or replaced? The underlying mechanisms of IMR remain incompletely understood, and although current theory focuses on the role of alterations in ventricular geometry in its pathogenesis, IMR is most often addressed by annuloplasty alone. Is this sufficient, or does the ventricle itself require "remodeling?" The debate is confounded by imprecise terminology that fails to distinguish between acute and chronic disease, and active ischemia from completed infarction. Available clinical information is from retrospective studies with all of their inherent limitations and potential for bias. Still, progress is being made as increasing attention is focused on this clinically important entity.