Mechanism of Mitral Regurgitation in Dilated Cardiomyopathy

Dilated cardiomyopathy is a condition characterized by chamber dilatation and impaired systolic function, resulting in the clinical manifestations of congestive heart failure. Mitral regurgitation occurs with varying frequency in dilated cardiomyopathy, and its detection depends on the diagnostic modality utilized. The presence of mitral regurgitation imposes an additional burden on the failing ventricle, and appears to be an independent prognostic indicator of mortality. The mechanism of mitral regurgitation in dilated cardiomyopathy is complex, controversial, and incompletely understood. The mitral apparatus consists of the left atrial wall, mitral annulus, mitral leaflets, chordae tendineae, papillary muscles, and left ventricular wall, and each of these components and the intimate interrelationship between these structures may contribute to the development of mitral regurgitation. Left atrial enlargement, reduced left atrial contractility, mitral leaflet retraction, abnormal vector of chordal tendineae pull, papillary muscle dysfunction (either asynergic contraction or malalignment), mitral annular dilatation, and changes in the size, shape, and function of the left ventricle have been suggested as possible mechanisms for the development of mitral regurgitation in dilated cardiomyopathy. The primary event in the development of mitral regurgitation appears to be left ventricular dilatation and dysfunction. Controversy persists as to whether the associated mechanism is annular dilatation, papillary muscle or free left ventricular wall dysfunction, or a combination of all, but recent echo-Doppler studies reviewed in this article support the notion that annular dilatation is the predominant mechanism. Improved understanding of the mechanism of mitral regurgitation in dilated cardiomyopathy may lead to a more aggressive approach with regard to pharmacological therapy, thus impacting on survival in this group of patients. (ECHOCARDIOGRAPHY, Volume 8, March 1991)     

Severe Mitral Regurgitation after Radiotherapy

We present the case of a 69‐year‐old patient with a history of gynecological neoplasia and a pulmonary metastasis, who in 1996 underwent chemotherapy and mediastinal radiotherapy followed by cancer remission. Ten years later she presented with heart failure and her Doppler echocardiogram showed severe mitral regurgitation with pulmonary hypertension. In 2011, she underwent a mitral valve replacement with a biological prosthesis and the pathology exam revealed valve damage consistent with radiotherapy‐induced changes. This unusual mechanism of mitral regurgitation can be demonstrated clearly by echocardiography and should be disseminated among cardiology physicians and in patients who have survived for long periods after radiotherapy, it is important to remember that cardiac complications may indeed occur, and the treating physician is responsible for detecting them.     

Diastolic Mitral Regurgitation

An 89-year-old female with a history of hypertension presented to the hospital with symptoms of fatigue. Her electrocardiogram (ECG) showed high-grade atrioventricular (AV) block, so a transthoracic echocardiogram was obtained to assess for structural heart abnormalities (Figure 1). Color Doppler showed mild mitral regurgitation (MR) extending into diastole. Temporal interrogation of the MR jet using continuous wave Doppler confirmed the diastolic component.Open in a separate windowFigure 1The hemodynamic elements of this mitral regurgitation (MR) are dissected and explained. MR: mitral regurgitation; LA: left atrial; LV: left ventricle; LVEDP: left ventricular end-diastolic pressure.Diastolic MR is generally described in the setting of AV dissociation. In patients with high-degree AV block and underlying sinus rhythm, the prolonged diastolic time with accompanying superimposed left atrial (LA) contractions will lead to a significant elevation in left ventricular end-diastolic pressure (LVEDP), creating a reverse gradient favoring flow from the left ventricle back into the LA during diastole. Diastolic MR also can occur with substantial elevations in LVEDP in restrictive cardiomyopathies and acute severe aortic regurgitation.     

Values for Mitral Valve Annulus Dimensions in Normals and Patients with Mitral Regurgitation

Objectives. The present study was designed to investigate the dimensions of mitral valve annulus in the presence of mitral regurgitation. Method. Fifty-four patients were examined. On transthoracic echocardiographic images, we performed linear measurements in the parasternal plane in order to define the size of the left ventricle, left atrium, and mitral valve annulus. We compared these findings with those obtained in 16 control subjects. Results. Twenty-one patients with mild or moderate mitral regurgitation demonstrated no significant change of the mitral valve annulus compared with the control group (P > 0.05). Seventeen patients with severe mitral regurgitation (grade of 4) had a significant increase of the dimensions of the mitral valve annulus, left ventricle, and left atrium (P < 0.05). The etiology of mitral regurgitation was degenerative in 32 patients, rheumatic in 2 patients, and mitral valve prolapse in 4 patients. All patients had normal left ventricular systolic function. Thirty-one patients were in normal sinus rhythm, and seven were in atrial fibrillation. Conclusions. The measurement of the diameter of the mitral valve annulus is feasible with transthoracic echo-cardiography. In addition to the evaluation of mitral valve leaflets and subvalvular apparatus, the measurement of the mitral valve annulus is important in the evaluation of mitral regurgitation, as its enlargement is indicative for severe mitral regurgitation .     

Dynamic Ischaemic Mitral Regurgitation and the Role of Stress Echocardiography

Objective:

This paper aims to explain the main mechanisms that cause ischaemic mitral regurgitation (MR), the pathophysiology, and the role played by stress echocardiography in the evaluation of the dynamic component of MR.

Introduction:

Chronic ischaemic MR is a frequent complication of myocardial infarction (MI), and is associated with a poor prognosis and outcome. The more the severity of ischaemic MR, the lower is the survival rate. In recent times, improvements in the management of the acute phase of MI, has increased the survival rate after MI. This, combined with an increase in the incidence of MI, will probably lead to a higher prevalence of ischemic MR in the next decades. As a consequence, ischaemic MR should be thoroughly understood and promptly identified. Furthermore, it is well recognized that ischaemic MR is dynamic. The best way to explore the dynamic nature of ischaemic MR is exercise stress echocardiography, and this test should probably be integrated in the evaluation and the management of patients with chronic ischaemic MR.

Conclusion:

Based on our experience, exercise stress echocardiography might be of interest in the following subsets of patients: 1) in patients with left ventricular (LV) dysfunction who present exertional dyspnea out of proportion to the severity of resting LV dysfunction or MR severity, 2) in patients in whom acute pulmonary oedema occurs without any obvious cause; 3) to unmask patients at high risk of mortality and heart failure 4) before surgical revascularization in patients with moderate ischaemic MR and, 5) following surgery, to identify persistence of pulmonary hypertension and explain the absence of functional class improvement.     

经食道超声心动图在二尖瓣关闭不全瓣膜修补术中的应用

对严重的二尖瓣关闭不全病人进行二尖瓣修补术与置换相比，有着明显的利益，然而，部分病例修补术后可能持续存在二尖瓣返流，且传统的术中评价二尖瓣修补术效果的方法往往不可靠。本组术中经食道超声心动图（TEE）发现二尖瓣修补术后仍有22％（2／9）的病例存在严重的二失瓣返流，根据这一信息．这2例病人当即进行了二尖瓣置换术。随访16～24个月，7例二尖瓣修补术的病人心功能一级，无需再次手术。因此，术中TEE技术是快速准确的评价瓣膜修补术效果的方法，保证了手术的成功，能使更多更复杂的病例进行二尖瓣修补术。     

二尖瓣反流经导管介入微创治疗新进展

随着微创及介入治疗技术在心脏瓣膜病的治疗中不断发展,心脏瓣膜病治疗的适应证逐渐扩大,尤其在二尖瓣反流的介入治疗领域,各项实验技术成果在动物及临床实验当中取得显著效果。现介绍二尖瓣反流经导管介入治疗的新进展,并针对当前研究热点,重点对有关技术的临床研究进展做一综述。     

Atrial Functional Mitral Regurgitation: A JACC: Cardiovascular Imaging Expert Panel Viewpoint

Functional or secondary mitral regurgitation (MR) is associated with increased cardiovascular morbidity and mortality. Mechanistically, secondary MR is attributable to an imbalance between mitral leaflet tethering and closure forces, leading to poor coaptation. The pathophysiology of functional MR is most often the result of abnormalities in left ventricular function and remodeling, seen in ischemic or nonischemic conditions. Less commonly and more recently recognized is the scenario in which left ventricular geometry and function are preserved, the culprit being mitral annular enlargement associated with left atrial dilatation, termed atrial functional mitral regurgitation (AFMR). This most commonly occurs in the setting of chronic atrial fibrillation or heart failure with preserved ejection fraction. There is variability in the published reports and in current investigations as to the definition of AFMR. This paper reviews the pathophysiology of AFMR and focus on the need for a collective definition of AFMR to facilitate consistency in reported data and enhance much-needed research into outcomes and treatment strategies in AFMR.     

Severe Mitral and Aortic Regurgitation in Association with Ankylosing Spondylitis

Aortic disease and aortic valve regurgitation are well documented in association with ankylosing spondylitis, although involvement of the mitral valve occurs more rarely. We report a case of severe mitral and aortic regurgitation in association with ankylosing spondylitis. We then discuss the characteristic cardiac manifestations that may occur in association with ankylosing spondylitis and the associated echocardiographic features.     

Relation of Mitral Annular Dilation with Dynamic Mitral Regurgitation in Patients with Rheumatic Mitral Regurgitation

Introduction: Dynamic mitral regurgitation (MR) is frequently investigated in patients with left ventricular systolic dysfunction (LVSD). Data about the dynamic MR in patients with organic valve disease are limited. The aim of this study was to evaluate the alteration of MR by exercise in patients with rheumatic valve disease (RVD). Methods: Asymptomatic patients with rheumatic MR and normal left ventricular function had been included in our study. Transthoracic echocardiography and Doppler measurements were performed at rest and just after submaximal exercise test performed with treadmill. Severity of MR was evaluated quantitatively by measuring effective regurgitant orifice area (EROA) with flow convergence method. Results: A total of 34 patients with rheumatic MR had been included. Severity of MR increased in 10 patients with exercise (Group 1) and decreased in 24 of them (Group 2). When the variables of two groups were compared; diastolic blood pressure after exercise, EROA, left atrial volume, left ventricular diastolic volume and mitral annular area values were significantly higher in Group 1 patients. A linear regression model was constructed by considering change of EROA by exercise the dependent, and the variables showing significant differences as the independents. Mitral annular area was found to be independently associated with EROA increase with exercise (R²= 0.499; P < 0.001). Conclusion: Mitral annular dilation is independently associated with increase of MR with submaximal exercise in asymptomatic patients with MR due to RVD with normal left ventricular function.     

缺血性二尖瓣关闭不全的外科治疗

目的：本文旨在回顾性研究单中心外科治疗缺血性二尖瓣关闭不全的临床经验。 方法：回顾性分析279例缺血性二尖瓣关闭不全患者的临床资料。平均年龄59.2±7.4岁。心功能分级II级141例，III级117例，IV级21例。左室舒末内径57~91mm ，左室射血分数20%~59%。二尖瓣反流程度：中度156例，中-重度75例，重度48例。冠脉造影结果三支病变240例，两支病变30例，单支病变9例。 结果：二尖瓣成形术224例，术后即刻TEE示无返流152例，微量返流43例，微量-轻度21例，轻度8例。二尖瓣置换术75例，IABP辅助37例。冠状动脉旁路移植远端吻合口3.6±0.5个。手术死亡13例，死亡率4.7%（13/279）。出院时左室舒末内径46~86mm，左室射血分数20%~62% 。二尖瓣无反流232例，微量26例，轻度12例，轻-中度7例，中度2例。 结论：外科治疗冠心病合并缺血性二尖瓣关闭不全可获得满意的治疗效果，尤其是对于射血分数降低、左心增大、心力衰竭的患者，获益更大。