Mitral regurgitation

Mitral regurgitation (MR) is the leakage of blood from the left ventricle into the left atrium due to incomplete closure of the mitral valve during systole. It is a common form of valvular disease and categorized according to onset (into acute and chronic forms) and etiology. Primary MR involves the structure of the mitral valve whereas secondary MR is a result of different pathologies that lead to valvular incompetence (e.g., cardiomyopathy). Ischemic MR can be acute (e.g., papillary muscle rupture in myocardial infarction) or chronic (in coronary artery disease). Symptoms vary from cardiogenic shock and flash pulmonary edema in acute manifestations to mild symptoms such as cough and dyspnea in chronic cases. Echocardiography is the diagnostic modality of choice; further imaging and treatment options are determined by the etiology. The definitive treatment in primary MR is surgical repair or valve replacement, while therapy of an underlying condition, e.g., percutaneous coronary intervention (PCI) in coronary artery disease, is the mainstay of therapy in secondary MR. Pharmacological treatment aims to reduce the degree of heart failure.

• Primary MR (organic): mitral regurgitation caused by direct involvement of the valve leaflets or chordae tendinae ^[1]
  • Degenerative mitral valve disease (mitral valve prolapse, mitral annular calcification, ruptured chordae tendinae)
  • Rheumatic fever
  • Infective endocarditis
  • Ischemic MR (e.g., papillary muscle rupture following acute MI)
• Secondary MR (functional): caused by changes of the left ventricle that lead to valvular incompetence
  • Coronary artery disease or prior myocardial infarction causing papillary muscle involvement
  • Dilated cardiomyopathy (e.g., peripartum cardiomyopathy) and left-sided heart failure
• Acute MR: Acute dysfunction of the mitral valve leads to volume overload and symptoms of acute heart failure. ^[2]
• Chronic MR
  • To preserve cardiac output, valve dysfunction is initially compensated for by cardiac remodeling.
  • Over time, remodeling affects LVEF, leading to heart failure. ^[2]

• Acute MR: ↑ left atrial volume with normal left atrial compliance and ↑ LV end-diastolic volume → rapid ↑ in LA and pulmonary pressures → pulmonary venous congestion → pulmonary edema ^[3]
• Chronic (compensated) MR: progressive dilation of the LV (via eccentric hypertrophy) → ↑ volume capacity of the LV (preload and afterload return to normal values) → ↑ end-diastolic volume → maintains ↑ stroke volume (normal EF)
• Chronic (decompensated) MR: progressive LV enlargement and myocardial dysfunction → ↓ stroke volume → ↑ end-systolic and end-diastolic volume → ↑ LV and LA pressure → pulmonary congestion, possible acute pulmonary edema, pulmonary hypertension, and right heart strain

References:^[4][5]

Acute mitral regurgitation ^[6]

• Signs and symptoms
  • Dyspnea
  • Symptoms of left-sided heart failure
  • Signs and symptoms of pulmonary edema (e.g., bibasilar, fine, late inspiratory crackles)
  • Cardiogenic shock: poor peripheral perfusion, tachycardia, tachypnea, and hypotension
  • Palpitations ^[7]
• Auscultation ^[6]
  • Soft, decrescendo murmur
  • No murmur in severe regurgitation with LV systolic dysfunction or hypotension ^[8]
  • Potentially: S₃ heart sound

Chronic mitral regurgitation

• Signs and symptoms
  • Dyspnea (including exertional dyspnea), dry cough
  • Fatigue ^[7]
  • Palpitations ^[9]
  • Symptoms of left-sided heart failure (potentially also symptoms of right-sided heart failure)
• Auscultation ^[7]
  • Lateral displacement of the apical impulse
  • Quiet S₁ heart sound
  • S₃ heart sound in advanced stages of disease
  • Holosystolic murmur (high-pitched, blowing)
    • Radiates to the left axilla and heard best over the apex (5^th intercostal space at the left midclavicular line)
    • Intensity can be increased by increasing preload (e.g., leg raise) or afterload (e.g., handgrip) due to increased regurgitation.
  • See also auscultation in valvular defects

American Heart Association (AHA) staging for MR ^[3]

• Used to monitor intervals and determine the need for interventions
• Based on echocardiographic criteria of valve anatomy, hemodynamics, and associated cardiac findings (e.g., LV dilation)
• Criteria vary between primary and secondary MR.

Carpentier classification

• Uses echocardiography findings to classify leaflet motion (Carpentier types I–III). ^[1][10]
• Used in the planning of surgical repair

Approach

• Rule out myocardial infarction and consider other causes of AHF.
• Perform transthoracic echocardiography (TTE).
• For suspected acute MR, obtain emergency preoperative diagnostics.
• Consider additional diagnostics (e.g. coronary angiography) based on the suspected etiology.

Acute MR is a medical and surgical emergency, as patients can decompensate rapidly. ^[3][8]

Echocardiography

• Indications: to assess the valve apparatus, size and function of left ventricle and atrium, and grade the severity of MR ^[7]
  • TTE: modality of choice for the initial assessment of all patients with suspected valvular abnormality ^[6][7]
  • Transesophageal echocardiography (TEE): indicated prior to surgery and during the diagnostic workup of MR if TTE is inadequate ^[1][7]

Findings ^[6][11][12]

• Findings in secondary mitral regurgitation may include: ^[3]
  • Normal valve anatomy but abnormal function
  • Signs of an underlying condition may be present (e.g., apical left ventricular ballooning in takotsubo cardiomyopathy)

Laboratory studies

• Troponin: Elevation may indicate myocardial ischemia.
• BNP
  • Acute MR: typically normal because of the acute onset of symptoms ^[20]
  • Chronic MR: normal or elevated as regurgitation severity increases and the left ventricle is remodeled ^[7][21]
• Blood cultures: in suspected infective endocarditis (at least three sets) ^[22]

Myocardial infarction must be ruled out in patients presenting with acute mitral regurgitation!

ECG

• Acute MR: Findings are often nonspecific.
  • Normal sinus rhythm
  • Sinus tachycardia with nonspecific ST and T-wave abnormalities ^[6]
  • Atrial fibrillation ^[7]
  • Signs of acute ischemia in ischemic MR (see acute coronary syndrome)
• Chronic MR: ECG changes usually reflect cardiac remodeling.
  • Left ventricular hypertrophy (50% of patients) ^[7]
  • P mitrale
  • Atrial fibrillation ^[9]
  • Signs of right heart strain with P pulmonale in later stages ^[7]

Chest x-ray

• Indications: assess for pulmonary edema, rule out other causes of acute dyspnea
• Supportive findings
  • Decompensated MR and acute MR: signs of pulmonary congestion (see x-ray findings in pulmonary congestion) ^[6][8]
  • Acute MR: normal-sized cardiac silhouette ^[6]
  • Chronic MR: Changes related to cardiac remodeling and associated heart failure may be visible.
    • LV enlargement: laterally displaced left cardiac border
    • LA enlargement: straightening of the left cardiac border and double density sign ^[23]
    • Annular calcification may be visible as a C-shaped density. ^[7]

Additional evaluation

In primary MR, additional diagnostics should be considered if echocardiography does not allow for the adequate assessment of mitral valve function. In secondary MR, consider advanced diagnostics to determine the underlying condition (e.g., coronary artery disease).

• Cardiac MRI (CMR): if both TTE and TEE findings are inconclusive, and for suspected cardiomyopathy or ischemic MR ^[24]
• Stress echo: in ischemic MR and to help assess the need for surgery ^[25]
• CT angiography: in suspected ischemic cardiomyopathy
• Coronary angiography: in suspected ischemic MR, prior to surgical intervention

Acute mitral regurgitation ^[1][3]

General principles

• Management of acute MR is complex and cardiology and cardiothoracic surgery should be consulted as early as possible.
• All patients with acute primary MR should undergo urgent surgical repair or valve replacement.
• Arrange early interfacility transfer if cardiothoracic surgery is not available locally.
• While awaiting surgery, any symptoms of heart failure should be managed with medical therapy (e.g., diuretics, nitrates, antihypertensive drugs).
• If secondary MR is suspected, identify and treat the underlying cause (e.g., revascularization therapy for ischemic MR) ^[10]

Initial stabilization

For acute primary MR, medical treatment is usually only a temporizing measure while surgery is planned. The aim is to reduce the symptoms of heart failure and improve forward flow.

• Management of acute heart failure
  • Vasodilators: to reduce afterload and improve cardiac output
    • Nitroprusside ^[7][26]
    • Nitrates (e.g., nitroglycerin ) ^[7][27]
    • Nicardipine ^[3]
  • Diuretics (e.g., furosemide ) and noninvasive positive-pressure ventilation: for acute pulmonary edema ^[28][29]
• Management of cardiogenic shock ^[29][30]
  • Vasopressors (e.g., norepinephrine ) ^[31]
  • Inotropes (e.g., dobutamine )
• Management of atrial fibrillation: Consider rhythm control to improve hemodynamics. ^[1]

Heart failure treatment may worsen hypotension; use caution in hemodynamically unstable patients.

Bridging devices

• Indications
  • Patients whose symptoms continue to deteriorate despite medical therapy ^[32]
  • Unstable patients prior to surgery
• Procedures
  • Intra-aortic balloon pump (IABP) ^[6][32]
    • Reduces afterload and preload and improves cardiac output ^[32]
    • Improves coronary blood flow ^[32]
    • Particularly useful in patients with acute MR driven by ischemia or cardiomyopathy ^[32]
    • Contraindicated in acute aortic regurgitation
  • Consider left ventricular assist device (LVAD) or ECMO in patients who are deteriorating despite pharmacological therapy and IABP. ^[8]

Surgical management ^[3][6]

• Indications
  • Acute primary MR: emergency/urgent surgery
  • Acute secondary MR that does not adequately respond to medical therapy
• Procedures
  • Valve repair: preferred option because of the reduced risk of mortality and complications ^[33]
  • Valve replacement: may be necessary if there is severe destruction of the mitral valve ^[8]
  • Revascularization therapy: e.g., CABG; may be helpful in ischemic MR ^[3]

All patients with acute primary MR should undergo urgent surgical repair or valve replacement.

Chronic mitral regurgitation ^[1][3]

Management of chronic MR is guided by the symptoms and extent of heart failure and the cause of MR. Medical therapy should be initiated in all patients to optimize cardiac function but surgery is the definitive treatment option.

Medical management

• Identify and treat any underlying cause (particularly in secondary MR). ^[7]
• Heart failure management ^[7]
  • Diuretics (e.g., furosemide )
  • ACE inhibitors (e.g., lisinopril ) ^[7]
  • Beta blockers (e.g., metoprolol tartrate ) ^[7]
• Cardiology consult for further treatment options
  • Ischemic MR: consideration and timing of revascularization therapy ^[11]
  • Atrial fibrillation: evaluation for cardiac resynchronization therapy ^[7]

Surgical management and transcatheter mitral repair

• Chronic primary MR ^[3]
  • Indications: severe primary MR with any of the following
    • Asymptomatic patients with LV systolic dysfunction; (LVEF ≤ 60% and/or LVESD ≥ 40 mm, stage C2)
    • Symptomatic patients irrespective of LV systolic function (stage D) ^[3][34]
  • Procedure
    • Valve repair is preferred to replacement because it is associated with reduced mortality and fewer complications. ^[33]
    • Transcatheter mitral valve procedures, such as a clip device, can be considered in patients who are considered to be unsuitable for surgical repair and severely symptomatic. ^[1]
• Chronic secondary MR ^[3][7]
  • Indications: Consider for patients with severe MR (stage D) and persistent symptomatic heart failure (NYHA classes III–IV) despite optimal medical management. ^[3]
  • Procedure:
    • Transcatheter mitral valve procedures: consider on an individual basis in specialized centers ^[1]
    • LVAD and cardiac transplant: consider for patients whose heart failure is driven by severe LV remodeling. ^[1]

• Heart failure, pulmonary edema
• Cardiogenic shock
• Atrial fibrillation
  • Increases risk of stroke and other thromboembolic complications
  • Can result in acute decompensation of heart failure in chronic MR
• Endocarditis
• Pulmonary artery hypertension

We list the most important complications. The selection is not exhaustive.

• Perform ABCDE assessment.
• Initiate cardiac monitoring and pulse oximetry.
• Rule out myocardial infarction.
• Treat complications of MR.
  • Inotropic support (e.g., dobutamine) for hypotension
  • Vasodilators for acute heart failure if BP permits
  • Rhythm control for Afib if needed.
  • Consider IABP as a temporizing measure.
• Obtain emergency preoperative diagnostics.
• Obtain TTE to confirm the diagnosis.
• Consult cardiology and cardiothoracic surgery.
• Consider early interfacility transfer if required.
• Pursue definitive management, e.g., surgical valve repair or replacement, PCI, or operative revascularization for MI.
• Initiate input/output monitoring.
• Transfer to operating room or ICU.