Aortic Regurgitation

Aortic regurgitation, also called aortic insufficiency, may be acute (very uncommonly) or chronic.

The primary causes of acute aortic regurgitation, are:

• Dissection of the ascending aorta

• Infective endocarditis

The primary causes of chronic aortic regurgitation in adults are:

• Degeneration of the aortic valve and root (with or without a bicuspid valve)

• Infective endocarditis

• Myxomatous degeneration

• Rheumatic fever

• Thoracic aortic aneurysm

• Trauma

Common causes of chronic aortic regurgitation in children are:

• Ventricular septal defect with aortic valve prolapse

• Bicuspid aortic valve

Aortic regurgitation due to myxomatous degeneration may develop in patients with Marfan syndrome or Ehlers-Danlos syndrome.

Rarely, aortic regurgitation is caused by seronegative spondyloarthropathies (eg, ankylosing spondylitis, reactive arthritis, psoriatic arthritis), rheumatoid arthritis, systemic lupus erythematosus, arthritis associated with ulcerative colitis, luetic (syphilitic) aortitis, osteogenesis imperfecta, supravalvular or discrete membranous subaortic stenosis, Takayasu arteritis, rupture of a sinus of Valsalva, acromegaly, and giant cell arteritis.

In aortic regurgitation, volume overload of the left ventricle (LV) occurs because during diastole the LV receives blood regurgitated from the aorta in addition to blood from the left atrium.

In acute aortic regurgitation, the LV does not have time to dilate to accommodate the increased volume, which can then cause a rapid increase in left ventricular pressure and, subsequently, pulmonary edema and decreased cardiac output.

In chronic aortic regurgitation, LV hypertrophy and dilation can occur gradually, so normal left ventricular pressures and cardiac output are maintained. But decompensation eventually develops, ultimately causing arrhythmias, LV dysfunction, and heart failure (HF).

Acute aortic regurgitation can cause symptoms of heart failure (dyspnea, fatigue, weakness, edema) and cardiogenic shock (hypotension with resultant multisystem organ damage).

Chronic aortic regurgitation is typically asymptomatic for years; progressive exertional dyspnea, orthopnea, paroxysmal nocturnal dyspnea, and palpitations develop insidiously.

Symptoms of heart failure correlate poorly with objective measures of left ventricular function. Chest pain (angina pectoris) affects relatively few patients who do not have coexisting coronary artery disease (CAD) and, when it occurs, is especially common at night. Patients may present with endocarditis (eg, fever, anemia, weight loss, embolic phenomena) because the abnormal aortic valve is predisposed to bacterial seeding.

Signs vary by severity and acuity. Signs in acute aortic regurgitation reflect heart failure and cardiogenic shock and typically include tachycardia, cool extremities, lung crackles, and low blood pressure. The first heart sound (S1) is usually absent (because aortic and LV diastolic pressures equalize), and a third heart sound (S3) is common.

As chronic disease progresses, systolic blood pressure increases while diastolic blood pressure decreases, creating a widened pulse pressure. With time, the LV impulse may become enlarged, increased in amplitude, and displaced downward and laterally, with systolic depression of the entire left parasternal area, giving a rocking motion to the left chest.

The typical heart murmur of aortic regurgitation is a blowing, high-pitched, diastolic decrescendo murmur beginning soon after the first heart sound. It is generally louder in chronic AR, and may be soft or absent in acute AR even if severe. However, a mid-to-late diastolic rumble heard at the apex (Austin Flint murmur) may result from rapid regurgitant flow into the LV, causing mitral valve leaflet vibration at the peak of atrial flow.

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Aortic Regurgitation

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Austin Flint Murmur

A systolic apical or carotid thrill may become palpable in later stages of AR; it is caused by large forward stroke volumes and low aortic diastolic pressure.

Additional auscultatory findings may include a normal S1 and a nonsplit, loud, sharp or slapping second heart sound (S2) caused by increased elastic aortic recoil. The murmur of AR is often unimpressive, beginning soon after the aortic component of S2 (A2); it is loudest at the third or fourth left parasternal intercostal space or at the apex. The murmur is heard best with the diaphragm of the stethoscope when the patient is leaning forward, with breath held at end-expiration. It increases in volume in response to maneuvers that increase afterload (eg, squatting, isometric handgrip). If AR is slight, the murmur may occur only in early diastole. If LV diastolic pressure is very high, the murmur is short because aortic and LV diastolic pressures equalize earlier in diastole.

Other abnormal sounds include a forward ejection and backward regurgitant flow (to-and-fro) murmur, an ejection click soon after the S1, and an aortic ejection flow murmur. A diastolic murmur heard near the axilla or mid left thorax (Cole-Cecil murmur) is caused by fusion of the aortic murmur with the S3, which is due to simultaneous filling of LV from the left atrium and AR. An Austin Flint murmur may mimic the diastolic murmur of mitral stenosis.

Visible signs include:

• Head bobbing (de Musset sign)

• Pulsation of the fingernail capillaries (Quincke sign, best seen while applying slight pressure)

• Pulsation of the uvula (Müller sign)

Palpable signs include:

• Large-volume pulse with rapid rise and fall (slapping, water-hammer, or collapsing pulse)

• Pulsation of the carotid arteries (Corrigan sign)

• Pulsation of the retinal arteries (Becker sign)

• Pulsation of the liver (Rosenbach sign)

• Pulsation of the spleen (Gerhard sign)

Blood pressure findings may include:

• Popliteal systolic pressure ≥ 60 mm Hg higher than brachial pressure (Hill sign)

• A fall in diastolic blood pressure of > 15 mm Hg with arm elevation (Mayne sign)

Auscultatory signs include a:

• Sharp sound heard over the femoral pulse (pistol-shot sound, or Traube sign)

• Femoral systolic bruit distal and a diastolic bruit proximal to arterial compression (Duroziez sign)

• Echocardiography

Diagnosis of aortic regurgitation is suspected based on history and physical examination findings and confirmed by echocardiography. Doppler echocardiography is the test of choice to detect and quantify the magnitude of regurgitant blood flow and grade overall severity of the AR. Two-dimensional echocardiography can quantify aortic root size and anatomy and LV function. Both two-dimensional and three-dimensional echocardiography can be used to evaluate leaflet morphology.

Severe chronic aortic regurgitation is suggested by any of the following:

• Color Doppler jet width ≥ 65% of the LV outflow tract diameter

• Holodiastolic flow reversal in the abdominal aorta (specific for severe AR)

• Regurgitant volume ≥ 60 mL/beat

• Regurgitation fraction ≥ 50%

• Vena contracta > 6 mm (the narrowest diameter of the fluid stream downstream of the abnormal valve orifice)

Echocardiography can also assess severity of pulmonary hypertension secondary to LV failure, detect vegetations or pericardial effusions (eg, in aortic dissection), and provide information about prognosis. Coarctation is associated with bicuspid valve and is detected echocardiography by placing the ultrasound transducer at the suprasternal notch, as well as evaluating the Doppler pattern in the abdominal aorta. Transesophageal echocardiography and three-dimensional echocardiography provide additional delineation of aortic dilatation and valve anatomy, which is especially useful when surgical repair is being considered. If the aorta is enlarged, gated computed tomography (CT) or magnetic resonance imaging (MRI) is recommended to evaluate the entire thoracic aorta. MRI also can help assess LV function and degree of AR when echocardiographic images are suboptimal.

ECG and chest radiograph should also be performed.

ECG may show repolarization abnormalities with or without QRS voltage criteria of LV hypertrophy, left atrial enlargement, and T-wave inversion with ST-segment depression in precordial leads.

Chest radiograph may show cardiomegaly and a prominent aortic root in patients with chronic progressive AR. If AR is severe, signs of pulmonary edema and HF may also be present. Exercise testing may help assess functional capacity and symptoms in patients with documented AR and equivocal symptoms.

Coronary angiography should be performed before surgery, even if no angina is present because approximately 20% of patients with severe AR have significant coronary artery disease (1), which may need concomitant coronary artery bypass graft surgery.

First-degree relatives of patients with a bicuspid valve should be screened using echocardiography because up to 15% will be similarly affected (2).

Phonocardiographic Characteristics of Heart Murmurs

• Angiotensin II receptor blockers, for aortic root dilation

• Aortic valve replacement or repair

• Pharmacologic treatment of heart failure, if present

When aortic root dilatation is part of the mechanism of aortic regurgitation, angiotensin II receptor blockers may slow progression of root dilation, making them favored medications for patients with concomitant hypertension. These medications do not reduce the severity of aortic regurgitation or alter disease progression.

Intervention is either surgical aortic valve replacement or (less commonly) valve repair . An aortic bioprosthetic valve requires anticoagulation for 3 to 6 months postoperatively, but a mechanical valve requires lifetime anticoagulation using warfarin. Long-term non-vitamin K oral anticoagulants or Intervention is either surgical aortic valve replacement or (less commonly) valve repair . An aortic bioprosthetic valve requires anticoagulation for 3 to 6 months postoperatively, but a mechanical valve requires lifetime anticoagulation using warfarin. Long-term non-vitamin K oral anticoagulants orwarfarin can be considered in patients with a bioprosthetic valve and atrial fibrillation. (See also Anticoagulation for patients with a prosthetic cardiac valve or native valve disease.)

Transcatheter aortic valve implantation (TAVI) is challenging in AR because of the dilated aortic annulus and lack of sufficient leaflet calcification, leading to prosthetic valve migration and/or paravalvular leak (1).

Patients who are not candidates for surgery benefit from pharmacologic treatment of heart failure. Beta-blockers should be used with caution because they block compensatory tachycardia and worsen AR by prolonging diastole. Intra-aortic balloon pump insertion is contraindicated because the diastolic balloon inflation worsens AR.

Patients with severe AR who do not meet the criteria for intervention should be reevaluated by physical examination and echocardiography every 6 to 12 months.

Antibiotic prophylaxis against endocarditis is not recommended for aortic regurgitation except for patients who have had valve replacement (see table Recommended Endocarditis Prophylaxis During Oral-Dental or Respiratory Tract Procedures).

With treatment, the 10-year survival for patients with mild to moderate aortic regurgitation is 80 to 95%. With appropriately timed valve replacement (ie, before heart failure and using accepted criteria for intervention), long-term prognosis for patients with moderate to severe AR is good. However, the prognosis for patients with severe AR and heart failure is considerably poorer.