Jean-Nicolas Corvisart first discovered mitral regurgitation in 1808, which he found associated with heart failure. Mitral regurgitation was later associated with rheumatic heart disease by Graham Steell. Mitral valve replacements were introduced in 1948.1 The epidemiology and risk factors for the two types of chronic mitral regurgitation—primary and secondary—are quite different, but their presentation, diagnosis, and treatment are essentially the same.2 Acute mitral regurgitation, however, is unique in its epidemiology, presentation, and treatment, and will be discussed later.
Primary, or degenerative, mitral regurgitation is most commonly caused by mitral valve prolapse.3 Other causes include rheumatic heart disease, radiation, chronic annular calcification, and congenital causes such as a valve cleft.3
Secondary mitral regurgitation also is known as functional mitral regurgitation, and is caused by ischemic heart disease or heart failure. Whether mitral disease is primary or secondary, all of these underlying conditions can lead to increased intracardiac pressure, left ventricular (LV) dysfunction, and the inability for the mitral valve leaflets to coapt.2
As the most common valvular disorder in the United States, mitral regurgitation increases in prevalence with age: fewer than 1% of patients under age 55 years are affected, compared with 9% of patients age 75 years and older.4 Of those who are younger (under age 55 years), most are women, and their disease is a result of mitral valve prolapse. Other factors or characteristics highly associated with the condition are older men, lower body mass index, renal dysfunction, previous myocardial infarction, and previous mitral stenosis. Mitral regurgitation is not related to other cardiovascular risk factors such as dyslipidemia or diabetes.5
Most patients with chronic mitral regurgitation are asymptomatic but may exhibit fatigue, exercise intolerance, and dyspnea upon exertion as the disease progresses (Table 1).2 Dyspnea and fatigue are early signs; pulmonary hypertension indicates disease progression and leads to LV failure, orthopnea, and peripheral edema.3
In patients with acute mitral regurgitation, sudden onset of dyspnea as a result of increased regurgitation is commonly caused by a myocardial infarction and/or ruptured chordae tendineae.6 Proper assessment of these patients is critical because acute mitral regurgitation is a medical emergency. Patients also may present with signs and symptoms of shock such as hypotension, tachycardia, weakness, dizziness, and altered mental status.7
ASSESSMENT AND DIFFERENTIAL DIAGNOSES
Mitral regurgitation is initially diagnosed based on careful auscultation. Often, the regurgitation is detected as a murmur, most typically heard at the apex as systolic, blowing, high pitched, and radiating toward the axilla; however, the intensity of this murmur does not indicate the severity of the disorder.8,9
Mitral regurgitation sometimes is difficult to distinguish from aortic stenosis on auscultation, as both are systolic, but aortic stenosis has a crescendo-decrescendo sound, radiates to the neck, is more commonly associated with an S4, and is heard better at the base.9 In mild mitral regurgitation, an S1 may be diminished due to failed leaflet closure; however, a holosystolic murmur that radiates in the direction of the regurgitant jet indicates a flail leaflet—a condition in which one of the leaflets becomes detached from the chordae tendineae.6 Associated pulmonary hypertension produces a split S2 and more attenuated P2 on chest auscultation.8
In patients with severe mitral regurgitation, regurgitant blood flowing back into the left ventricle produces an S3, indicative of LV failure, with a brisk dropoff of arterial pulse palpation, lateral placement of the apical pulse, and a palpable thrill.3
Once the clinical presentation and examination findings lead to a suspicion of mitral regurgitation, other diagnostic tools are used to confirm the diagnosis. Transthoracic echocardiogram (TTE) is diagnostic in quality and also provides information about the size and function of the left and right ventricles, as well as pulmonary artery pressure.2 TTE also evaluates the mechanism and severity of mitral regurgitation. If the patient's symptoms are not consistent with the severity of his or her mitral regurgitation, exercise hemodynamics are warranted, either with Doppler echocardiography or cardiac catheterization, and treadmill testing can determine symptoms and exercise tolerance. Transesophageal echocardiogram (TEE) also may be used to provide a more detailed picture of the severity and mechanism of mitral regurgitation but is not typically done diagnostically, unless TTE is nondiagnostic or endocarditis is suspected.2
TREATMENT AND FOLLOW-UP
The treatment of both types of mitral regurgitation is patient-specific, with pharmacologic and surgical options. Patients with an LV ejection fraction of less than 60% should be prescribed beta-blockers and drugs that block the renin-angiotensin-aldosterone system, such as angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs). In particular, carvedilol, which is primarily a beta-blocker, has been shown to not only preserve LV function and decrease LV remodeling but also decrease the amount of regurgitant volume.10,11 Bisoprolol or sustained-release metoprolol also are specifically indicated for patients with New York Heart Association (NYHA) Class II or greater heart failure, which correlates to a slight limitation in activities and symptoms with activity.12 In addition to reducing the risk of death and hospitalization in patients with heart failure, one clinical review showed that ACE inhibitors and ARBs modestly decreased the regurgitant volume and LV size in patients with chronic mitral regurgitation.12,13 Patients with symptoms of volume overload should also have a loop diuretic as part of their medication regimen. Other potential add-on therapies for patients with NYHA Class II heart failure and reduced ejection fraction include a combination of hydralazine/nitrates for black patients and an aldosterone antagonist such as spironolactone for patients with adequate renal function and normal serum potassium concentrations.12
Patients with primary mitral regurgitation who are symptomatic with an LV ejection fraction less than 30% should be considered for valve repair or replacement.2 Those who are asymptomatic with an LV ejection fraction of 30% to 60% and an LV end systolic diameter of more than 40 mm also are good candidates for surgery. Although surgery is not curative in patients with secondary mitral regurgitation, it can be considered in patients with severe heart failure, especially when other cardiac surgeries, such as coronary artery bypass grafting or aortic valve repair, also are being performed.2 The American Heart Association and American College of Cardiology recommend valve repair over replacement in most cases.2 This is supported by a recent literature review that reported no difference in mortality between the two procedures, but increased rates of mitral regurgitation recurrence after replacement.14
Patients with sudden exacerbations of mitral regurgitation and symptoms of heart failure need rapid evaluation and a cardiology consultation. Acute, symptomatic mitral regurgitation is a medical emergency, usually necessitating surgical intervention. The specific surgical treatment depends upon hemodynamic changes and the underlying cause.7 Pharmacologic treatment should always include the addition of an IV loop diuretic to decrease afterload and regurgitant volume.2,12 Once the patient is stabilized, the cause of the acute episode should be investigated and treated promptly. If the underlying cause of the acute regurgitation is an event that damages the valve, such as chordal or papillary muscle rupture or endocarditis, surgical repair or replacement is necessary.7 However, if the cause is functional (for example, myocardial ischemia or infarction), coronary artery bypass grafting is warranted. Valve repair also may be needed, and is assessed on a case-by-case basis.
PROGNOSIS AND COMPLICATIONS
Because mitral regurgitation is strongly associated with eventual heart failure regardless of initial LV function, patients must be carefully monitored for this outcome. A 2011 study of patients with secondary mitral regurgitation showed that severity and other comorbidities highly influence prognosis and possible complications.15 Patients with low-to-moderate asymptomatic mitral regurgitation have a very good prognosis, although outcomes vary with severity and patient-specific factors such as increased LV or atrial dimensions, or the development of atrial fibrillation (AF), pulmonary hypertension, or LV dysfunction.3,16 Patients who underwent treatment, whether pharmacologic or surgical, were shown to have much better prognoses, especially in the case of severe disease. AF and stroke are common complications of worsening mitral regurgitation but happen less frequently in patients undergoing treatment.3 (Note that patients who had AF before surgery or who have other risk factors for postoperative dysrhythmia, such as ischemia, hemodynamic shifts, and electrolyte disorders, are more at risk for continued AF after repair or replacement procedures.17)
Endocarditis is a potential complication of valve repair or replacement. The indication for antibiotic prophylaxis has been greatly reduced according to appropriate guidelines, but remains essential in patients with mitral valve repair or replacement. Proper dental hygiene in conjunction with sterile technique during invasive procedures remains imperative in the prevention of endocarditis.2
PREVENTION AND PATIENT EDUCATION
In general, primary mitral regurgitation is not considered preventable, as it is most often associated with aging. However, appropriate treatment of ischemic heart disease and heart failure can help prevent the advancement of secondary mitral regurgitation due to these causes; prevention of heart disease can prevent secondary mitral regurgitation completely. Providers should treat patients with sore throats quickly, especially patients who test positive for Streptococcus species and need antibiotics to prevent rheumatic fever, a rare cause of mitral regurgitation.2
Because patients with primary mitral regurgitation often are asymptomatic until the disease is severe, they should be told to seek immediate medical attention if they develop sudden onset of new symptoms such as chest pain, shortness of breath, rapid weight gain, or palpitations.6
Tell patients that they may need anticoagulant therapy after valve repair or replacement to prevent formation of dangerous thrombi.2 The necessity, type, and extent of anticoagulation following valve surgery varies depending on the type of valve received. Educate patients about the risks, benefits, and appropriate monitoring of anticoagulation therapy.
The provider also can reassure patients after surgery. At 10 years postoperatively from valve repair, the requirement for reoperation falls below a 5% chance; therefore, fear of recurrence is usually unfounded.
Mitral regurgitation is a moderately prevalent disorder within our population, specifically in older adults, and when left untreated, typically leads to heart failure.18 Many patients would be shocked to hear that their 5-year survival rate is greater with stage 3 colon cancer than with heart failure.19 This knowledge should greatly motivate providers to educate their patients about mitral regurgitation as they would any other serious condition. This can be challenging because most of the early symptoms are largely considered benign. Sometimes the murmur is difficult to auscultate, and unfortunately once heart failure ensues, the survival rate rapidly declines to 50% at 5 years.18
A study by Lindekleiv and colleagues found no benefit in echocardiogram screening the general population.20 Outcomes between the control group and the screening group showed no differences in all-cause mortality, mortality from heart disease, nor incidence of stroke or myocardial infarction. Therefore, early recognition of symptoms is key to improving morbidity and mortality. Further development of repair and replacement devices also should be encouraged; current procedures and treatment decrease complications significantly, but are far from facilitating optimal outcomes at this time.
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