Elsevier

The Lancet

Volume 373, Issue 9672, 18–24 April 2009, Pages 1382-1394
The Lancet

Review
Mitral regurgitation

https://doi.org/10.1016/S0140-6736(09)60692-9Get rights and content

Summary

Mitral regurgitation affects more than 2 million people in the USA. The main causes are classified as degenerative (with valve prolapse) and ischaemic (ie, due to consequences of coronary disease) in developed countries, or rheumatic (in developing countries). This disorder generally progresses insidiously, because the heart compensates for increasing regurgitant volume by left-atrial enlargement, causes left-ventricular overload and dysfunction, and yields poor outcome when it becomes severe. Doppler-echocardiographic methods can be used to quantify the severity of mitral regurgitation. Yearly mortality rates with medical treatment in patients aged 50 years or older are about 3% for moderate organic regurgitation and about 6% for severe organic regurgitation. Surgery is the only treatment proven to improve symptoms and prevent heart failure. Valve repair improves outcome compared with valve replacement and reduces mortality of patient with severe organic mitral regurgitation by about 70%. The best short-term and long-term results are obtained in asymptomatic patients operated on in advanced repair centres with low operative mortality (<1%) and high repair rates (≥80–90%). These results emphasise the importance of early detection and assessment of mitral regurgitation.

Introduction

Mitral regurgitation is defined as systolic retrograde flow from the left ventricle into the left atrium. Although a trivial form of this valve disease is often seen in healthy people,1 epidemiological data show that moderate or severe regurgitation is the most frequent valve disease in the USA2 and is the second most common form of valvular heart disease needing surgery in Europe.3 Despite substantial reduction in the incidence of rheumatic heart disease, mitral regurgitation is a growing public health problem.2 Moderate or severe regurgitation is frequent, its prevalence increases with age, and it was estimated to affect 2·0–2·5 million people in the USA in 2000—a number expected to almost double by 2030 because of population ageing and growth.2 Although no large epidemiological studies are available, mitral regurgitation is prevalent in young adults in countries with endemic rheumatic fever.4 Substantial progress has been achieved to improve its diagnosis, quantification,5 and surgical treatment. Improved knowledge of clinical outcome of patients with mitral regurgitation resulted in refined surgical indications.6, 7 Hence, mitral regurgitation is a disease in which restoration of life expectancy can often be achieved,8, 9 an encouraging outcome that emphasises the importance of early detection, assessment, and prompt consideration for treatment of patients with this condition.6, 7 Challenges in management of patients with mitral regurgitation remain—elderly patients and those with disease due to ischaemic heart disease are often not offered surgery; valve repair—the preferred surgical method—is insufficiently done;3 new interventional techniques—minimally invasive or percutaneous—are under investigation.10 However, the general absence of clinical trials means evidence to guide treatment is weak.

Section snippets

Causes and mechanisms

All lesions that cause mitral regurgitation do so by reduction or elimination of the normal systolic coaptation between anterior and posterior mitral leaflets, which normally ensures mitral competence. Consistent anatomical and functional descriptors of mitral lesions are essential to assess surgical reparability but overlapping and poorly defined terminology has caused confusion. Causes and mechanisms are not synonymous and a particular cause might produce regurgitation by different mechanisms

Pathophysiology and progression

The degree of mitral regurgitation is defined by lesion severity (measured as effective regurgitant orifice [ERO] area)35 and the yielding volume overload (measured as regurgitant volume[RVol]), but it is also affected by the driving force (left-ventricular systolic pressure) and left-atrial compliance.5 Thus, in acute disease, the large regurgitant orifice converts ventricular energy mostly into potential energy (left-atrial pressure V-wave) due to non-compliant left atrium.36 In chronic

Assessment

Initial clinical assessment looks for symptoms, signs of heart failure, and physical signs of severe mitral regurgitation—ie, displaced apical impulse, systolic thrill, loud systolic murmur, S3, early diastolic rumble, and cardiomegaly with left-atrial enlargement on chest radiography and atrial fibrillation. These signs are important but not specific enough to rely solely on them to suggest surgery.6

Doppler echocardiography is the main method for assessment of patients with mitral

Natural history and clinical outcome

Although a few prospective studies are available,9, 80, 81 most data for mitral regurgitation outcome are extracted from observational series. Clinical outcome under medical management and after surgery is different in organic and functional disease.

Natural history of organic regurgitation has been poorly defined, largely because of limitations in severity assessment. Old studies, before echocardiography, showed a wide range in 5-year survival rates from 27% to 97%, probably related to

Treatment

The natural history of untreated organic and functional mitral regurgitation emphasises the importance of treatment of patients with severe regurgitation. Because the effects of various treatments on survival have not been tested in randomised clinical trials, the value of any approach is estimated on the basis of outcome studies.6, 7

Medical treatment aims to prevent progression of organic disease. Prevention of endocarditis is directed at forestalling catastrophic infectious complications and

Controversies and guidelines for treatment

In view of the experimental nature of medical and interventional treatments for mitral regurgitation, surgery is the only treatment recommended by management guidelines.6, 7 Because surgery is associated with small but definite risks, those patients with a higher risk of spontaneous complications than of surgery-related complications are selected. Guidelines should, in our opinion, be interpreted as a minimum to be applied by all physicians but should not deter centres with better results than

Search strategy and selection criteria

We searched PubMed, Medline, and Embase with the terms “mitral regurgitation”, “mitral valve”, and “heart valve surgery” for papers up to 2007. There were no language restirictions. We also searched the reference lists in articles identified by this strategy. Reviews were included as references if they represented practice guidelines or provided a comprehensive overview of specific topics.

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