Mitral Regurgitation

Mitral regurgitation may be

Causes of acute mitral regurgitation include

Common causes of chronic mitral regurgitation are intrinsic valve pathology (primary MR) or distortion of a normal valve by dilatation and impairment of the left ventricle and/or the mitral annulus (secondary MR).

Primary MR pathology is most often mitral valve prolapse Mitral Valve Prolapse (MVP) Mitral valve prolapse (MVP) is a billowing of mitral valve leaflets into the left atrium during systole. The most common cause is idiopathic myxomatous degeneration. MVP is usually benign, but... read more or rheumatic heart disease Rheumatic Fever Rheumatic fever is a nonsuppurative, acute inflammatory complication of group A streptococcal pharyngeal infection, causing combinations of arthritis, carditis, subcutaneous nodules, erythema... read more . Less common causes are connective tissue disorders, congenital cleft mitral valve, and radiation heart disease.

Secondary MR occurs when a disease of the left ventricle and atrium impairs valve function. Ventricular impairment and dilation displace the papillary muscles, which tether the otherwise normal leaflets and prevent them from closing fully. The causes are myocardial infarction Overview of Acute Coronary Syndromes (ACS) Acute coronary syndromes result from acute obstruction of a coronary artery. Consequences depend on degree and location of obstruction and range from unstable angina to non–ST-segment elevation... read more (ischemic chronic secondary MR) or intrinsic myocardial disease (nonischemic chronic secondary MR). A less common mechanism is annular dilatation due to chronic atrial fibrillation Atrial Fibrillation Atrial fibrillation is a rapid, irregularly irregular atrial rhythm. Symptoms include palpitations and sometimes weakness, effort intolerance, dyspnea, and presyncope. Atrial thrombi may form... read more with left atrial enlargement. In the presence of cardiomyopathy Overview of Cardiomyopathies A cardiomyopathy is a primary disorder of the heart muscle. It is distinct from structural cardiac disorders such as coronary artery disease, valvular disorders, and congenital heart disorders... read more , any degree of secondary MR worsens prognosis.

In infants, the most likely causes of MR are papillary muscle dysfunction, endocardial fibroelastosis, acute myocarditis, cleft mitral valve with or without an endocardial cushion defect, and myxomatous degeneration of the mitral valve. MR may coexist with mitral stenosis Mitral Stenosis Mitral stenosis is narrowing of the mitral orifice that impedes blood flow from the left atrium to the left ventricle. The usual cause is rheumatic fever. Common complications are pulmonary... read more when thickened valvular leaflets do not close.

Acute mitral regurgitation may cause acute pulmonary edema Pulmonary Edema Pulmonary edema is acute, severe left ventricular failure with pulmonary venous hypertension and alveolar flooding. Findings are severe dyspnea, diaphoresis, wheezing, and sometimes blood-tinged... read more and cardiogenic shock Cardiogenic and obstructive shock Shock is a state of organ hypoperfusion with resultant cellular dysfunction and death. Mechanisms may involve decreased circulating volume, decreased cardiac output, and vasodilation, sometimes... read more or sudden cardiac death.

Complications of chronic MR include gradual enlargement of the left atrium (LA); LV enlargement and eccentric hypertrophy, which initially compensates for regurgitant flow (preserving forward stroke volume) but eventually decompensates (reducing forward stroke volume); atrial fibrillation, which may be further complicated by thromboembolism; and infective endocarditis.

Acute mitral regurgitation causes the same symptoms and signs as acute heart failure Symptoms and Signs Heart failure (HF) is a syndrome of ventricular dysfunction. Left ventricular (LV) failure causes shortness of breath and fatigue, and right ventricular (RV) failure causes peripheral and abdominal... read more (dyspnea, fatigue, weakness, edema) and cardiogenic shock Symptoms and Signs Shock is a state of organ hypoperfusion with resultant cellular dysfunction and death. Mechanisms may involve decreased circulating volume, decreased cardiac output, and vasodilation, sometimes... read more (hypotension with resultant multisystem organ damage). Specific signs of mitral regurgitation may be absent.

Chronic mitral regurgitation in most patients is initially asymptomatic. Symptoms develop insidiously as the LA enlarges, pulmonary artery pressure and venous pressure increase, and LV compensation fails. Symptoms include dyspnea, fatigue (due to heart failure), orthopnea, and palpitations (often due to atrial fibrillation Atrial Fibrillation Atrial fibrillation is a rapid, irregularly irregular atrial rhythm. Symptoms include palpitations and sometimes weakness, effort intolerance, dyspnea, and presyncope. Atrial thrombi may form... read more ). Rarely, patients present with endocarditis Infective Endocarditis Infective endocarditis is infection of the endocardium, usually with bacteria (commonly, streptococci or staphylococci) or fungi. It may cause fever, heart murmurs, petechiae, anemia, embolic... read more (eg, with fever, weight loss, embolic phenomena).

Signs develop only when mitral regurgitation becomes moderate to severe (see table Grading of Mitral Regurgitation Grading of Mitral Regurgitation ). Inspection and palpation may detect a brisk apical impulse and sustained left parasternal movement due to systolic expansion of an enlarged LA. An LV impulse that is sustained, enlarged, and displaced downward and to the left suggests LV hypertrophy and dilation. A diffuse precordial lift occurs with severe MR because the LA enlarges, causing anterior cardiac displacement, and pulmonary hypertension Pulmonary Hypertension Pulmonary hypertension is increased pressure in the pulmonary circulation. It has many secondary causes; some cases are idiopathic. In pulmonary hypertension, pulmonary vessels may become constricted... read more causes right ventricular hypertrophy. A regurgitant murmur (or thrill) may also be palpable in severe cases.

On auscultation, the 1st heart sound (S1) may be soft (or occasionally loud). A 3rd heart sound (S3) at the apex reflects a dilated LV and severe MR.

The cardinal sign of mitral regurgitation is a holosystolic (pansystolic) murmur, heard best at the apex with the diaphragm of the stethoscope when the patient is in the left lateral decubitus position. In mild MR, the systolic murmur may be abbreviated or occur late in systole.

The murmur begins with S1 in conditions causing leaflet incompetency throughout systole, but it often begins after S1 (eg, when chamber dilation during systole distorts the valve apparatus or when myocardial ischemia or fibrosis alters dynamics). When the murmur begins after S1, it always continues to the 2nd heart sound (S2). The murmur radiates toward the left axilla; intensity may remain the same or vary. If intensity varies, the murmur tends to crescendo in volume up to S2.

MR murmurs increase in intensity with handgrip or squatting because peripheral vascular resistance to ventricular ejection increases, augmenting regurgitation into the LA; murmurs decrease in intensity with standing or the Valsalva maneuver. A short rumbling mid-diastolic inflow murmur due to torrential mitral diastolic flow may be heard following an S3. In patients with posterior leaflet prolapse, the murmur may be coarse and radiate to the upper sternum, mimicking aortic stenosis.

MR murmurs may be confused with those of tricuspid regurgitation Tricuspid Regurgitation Tricuspid regurgitation (TR) is insufficiency of the tricuspid valve causing blood flow from the right ventricle to the right atrium during systole. The most common cause is dilation of the... read more , which can be distinguished because tricuspid regurgitation murmur is augmented during inspiration.

Diagnosis of mitral regurgitation is suspected clinically and confirmed by echocardiography Echocardiography This photo shows a patient having echocardiography. This image shows all 4 cardiac chambers and the tricuspid and mitral valves. Echocardiography uses ultrasound waves to produce an image of... read more . Doppler echocardiography is used to detect regurgitant flow and pulmonary hypertension. Two-dimensional or 3-dimensional echocardiography is used to determine the cause and severity of MR (see table Grading of Mitral Regurgitation Grading of Mitral Regurgitation ), the presence and extent of annular calcification, and the size and function of the LV and LA and to detect pulmonary hypertension.

When it is acute, severe MR may not be apparent on color Doppler echocardiography, but suspicion is raised when acute heart failure is accompanied by hyperdynamic LV systolic function.

If endocarditis or valvular thrombi are suspected, transesophageal echocardiography Echocardiography This photo shows a patient having echocardiography. This image shows all 4 cardiac chambers and the tricuspid and mitral valves. Echocardiography uses ultrasound waves to produce an image of... read more (TEE) can provide a more detailed view of the mitral valve and LA. TEE is also indicated when mitral valve repair instead of replacement is being considered to evaluate the mechanism of MR in more detail.

An ECG and chest x-ray are usually obtained initially.

ECG may show LA enlargement and LV hypertrophy with or without ischemia. Sinus rhythm is usually present when MR is acute because the atria have not had time to stretch and remodel.

Chest x-ray in acute MR may show pulmonary edema; abnormalities in cardiac silhouette are not evident unless an underlying chronic disorder is also present. Chest x-ray in chronic MR may show LA and LV enlargement. It may also show pulmonary vascular congestion and pulmonary edema with heart failure.

Cardiac catheterization Cardiac Catheterization Cardiac catheterization is the passage of a catheter through peripheral arteries or veins into cardiac chambers, the pulmonary artery, and coronary arteries and veins. Cardiac catheterization... read more is done before surgery, mainly to determine whether coronary artery disease (CAD) is present. A prominent systolic c-v wave is seen on pulmonary artery occlusion pressure (pulmonary capillary wedge pressure) tracings during ventricular systole. Ventriculography can be used to quantify MR. Cardiac MRI can accurately measure regurgitant fraction and determine the cause of dilated myopathy with MR.

Periodic exercise testing Stress Testing In stress testing, the heart is monitored by electrocardiography (ECG) and often imaging studies during an induced episode of increased cardiac demand so that ischemic areas potentially at risk... read more (stress ECG ) is often done to detect any decrease in effort tolerance, which would prompt consideration of surgical intervention. Periodic echocardiography is done to detect progression of MR.

Prognosis of mitral regurgitation varies by duration, severity, and cause. Some MR worsens and eventually becomes severe. Once MR becomes severe, about 10% of asymptomatic patients become symptomatic each year thereafter. About 10% of patients with chronic MR caused by mitral valve prolapse require surgical intervention.

Angiotensin-converting enzyme (ACE) inhibitors and other vasodilators do not delay LV dilation or MR progression and so have no role in asymptomatic MR with preserved LV function. However, if LV dilation or dysfunction is present, drug therapy using an angiotensin receptor blocker, neprilysin inhibitor (eg, sacubitril), aldosterone antagonist, and/or vasodilating beta-blocker (eg, carvedilol) is indicated. In secondary MR, these drugs can reduce the severity of MR and probably improve prognosis.

If the ECG shows left bundle branch block, then biventricular pacing may be beneficial for secondary MR.

Loop diuretics such as furosemide are helpful in patients with exertional or nocturnal dyspnea. Digoxin may reduce symptoms in patients with atrial fibrillation or those in whom valve surgery is not appropriate.

Antibiotic prophylaxis is no longer recommended except for patients who have had valve replacement or repair utilizing prosthetic materials (see table Recommended Endocarditis Prophylaxis During Oral-Dental or Respiratory Tract Procedures Recommended Endocarditis Prophylaxis During Oral-Dental or Respiratory Tract Procedures* ).

Anticoagulants are used to prevent thromboemboli Prevention Pulmonary embolism (PE) is the occlusion of pulmonary arteries by thrombi that originate elsewhere, typically in the large veins of the legs or pelvis. Risk factors for pulmonary embolism are... read more in patients with atrial fibrillation.