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Aortic Regurgitation

by Guy P. Armstrong, MD

Aortic regurgitation (AR) is incompetency of the aortic valve causing backflow from the aorta into the left ventricle during diastole. Causes include valvular degeneration and aortic root dilation (with or without a bicuspid valve), rheumatic fever, endocarditis, myxomatous degeneration, aortic root dissection, and connective tissue (eg, Marfan syndrome) or rheumatologic disorders. Symptoms include exertional dyspnea, orthopnea, paroxysmal nocturnal dyspnea, palpitations, and chest pain. Signs include widened pulse pressure and an early diastolic murmur. Diagnosis is by physical examination and echocardiography. Treatment is surgical aortic valve replacement or repair. Percutaneous valve replacement is being evaluated.

Etiology

AR may be acute (very uncommonly) or chronic.

The primary causes of acute AR are

  • Infective endocarditis

  • Dissection of the ascending aorta

Chronic AR in adults is most often caused by

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

  • Rheumatic fever

  • Infective endocarditis

  • Myxomatous degeneration

  • Trauma

In children, the most common cause is a ventricular septal defect with aortic valve prolapse.

Rarely, AR is caused by seronegative spondyloarthropathies (ankylosing spondylitis, reactive arthritis, psoriatic arthritis), RA, SLE, arthritis associated with ulcerative colitis, luetic (syphilitic) aortitis, osteogenesis imperfecta, thoracic aortic aneurysm, aortic dissection, supravalvular or discrete membranous subaortic stenosis, Takayasu arteritis, rupture of a sinus of Valsalva, acromegaly, and giant cell (temporal) arteritis. AR due to myxomatous degeneration may develop in patients with Marfan syndrome or Ehlers-Danlos syndrome.

Pathophysiology

In chronic AR, left ventricular (LV) volume and stroke volume gradually increase because the LV receives aortic blood regurgitated during diastole in addition to blood from the pulmonary veins and left atrium. LV hypertrophy and chamber enlargement compensate for the increase in LV volume over years, but decompensation eventually develops. These changes may ultimately cause arrhythmias, LV impairment, and heart failure (HF).

Symptoms and Signs

Acute AR causes symptoms of HF and cardiogenic shock.

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

Symptoms of HF correlate poorly with objective measures of LV function. Chest pain (angina pectoris) affects only about 5% of 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 AR reflect HF and cardiogenic shock and typically include tachycardia, cool extremities, lung crackles, and low BP. The 1st heart sound (S 1 ) is usually absent (because aortic and LV diastolic pressures equalize), and a third heart sound (S 3 ) is common. An AR murmur may be absent even if AR is severe, although an Austin Flint murmur (see below) is common.

As chronic disease progresses, systolic BP increases while diastolic BP decreases, creating a widened pulse pressure. With time, the LV impulse may become enlarged, sustained, 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.

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.

Auscultatory findings include a normal S 1 and a nonsplit, loud, sharp or slapping 2nd heart sound (S 2 ) caused by increased elastic aortic recoil. The murmur of AR is often unimpressive. The murmur is blowing, high-pitched, diastolic, and decrescendo, beginning soon after the aortic component of S 2 (A 2 ); it is loudest at the 3rd or 4th left parasternal intercostal space. 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.

Sound is that of a normal S 1 followed by a sharp or slapping S 2 and a blowing, high-pitched, decrescendo diastolic murmur.

Aortic Regurgitation

Other abnormal sounds include a forward ejection and backward regurgitant flow (to-and-fro) murmur, an ejection click soon after the S 1 , 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 S 3 , which is due to simultaneous filling of LV from the left atrium and AR. 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; this murmur mimics the diastolic murmur of mitral stenosis.

S 1 is soft; S 2 is obscured by a soft regurgitant murmur and a louder, low-pitched, late-diastolic murmur. The diastolic murmur mimics mitral stenosis and is attributed to mitral valve leaflet vibration or mild obstruction caused by rapid regurgitant flow.

Austin Flint Murmur

Other signs are unusual; sensitivity and specificity are low or unknown. Visible signs include head bobbing (Musset sign) and pulsation of the fingernail capillaries (Quincke sign, best seen while applying slight pressure) or uvula (Müller sign). Palpable signs include a large-volume pulse with rapid rise and fall (slapping, water-hammer, or collapsing pulse) and pulsation of the carotid arteries (Corrigan sign), retinal arteries (Becker sign), liver (Rosenbach sign), or spleen (Gerhard sign). BP findings may include popliteal systolic pressure 60 mm Hg higher than brachial pressure (Hill sign) and a fall in diastolic BP 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) and a femoral systolic bruit distal and a diastolic bruit proximal to arterial compression (Duroziez sign).

Diagnosis

  • Echocardiography

Diagnosis 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.

Severe AR is suggested by any of the following:

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

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

  • Holodiastolic flow reversal in the abdominal aorta

  • Regurgitant volume > 60 mL/beat

  • Regurgitation fraction > 50%

In the presence of severe AR, decompensation of the left ventricle (and thus need for surgery) is suggested by any of the following:

  • End-systolic LV volume > 60 mL/m 2

  • End-systolic LV diameter > 50 mm

  • LV ejection fraction (LVEF) <50%

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 by placing the ultrasound transducer at the suprasternal notch. Transesophageal echocardiography provides additional delineation of aortic dilatation and valve anatomy, which is especially useful when surgical repair is being considered. If the aorta is enlarged, CT or 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.

Radionuclide imaging may be used to determine LVEF if echocardiographic results are borderline abnormal or if echocardiography is technically difficult.

ECG and chest x-ray should be done. 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 x-ray 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 done before surgery, even if no angina is present because about 20% of patients with severe AR have significant CAD, which may need concomitant coronary artery bypass graft surgery.

First-degree relatives of patients with a bicuspid valve should be screened using echocardiography because 20 to 30% will be similarly affected.

Prognosis

With treatment, the 10-yr survival for patients with mild to moderate AR is 80 to 95%. With appropriately timed valve replacement (ie, before HF and using criteria below), long-term prognosis for patients with moderate to severe AR is good. However, the prognosis for those with severe AR and HF is considerably poorer.

Treatment

  • Aortic valve replacement or repair

  • Sometimes vasodilators, diuretics, and nitrates

When aortic root dilatation is part of the mechanism of AR, angiotensin-receptor blockers may slow progression, making them favored drugs for patients with concomitant hypertension.

Intervention is indicated when AR is severe and is causing symptoms or LV dysfunction (EF < 50%, LV end-systolic dimension > 50 to 55 mm, or LV end-diastolic dimension > 65 to 75 mm). Sometimes, intervention is done earlier if the ascending aorta is dilated > 55 mm (> 50 mm in patients with Marfan syndrome and a bicuspid aortic valve). When cardiac surgery is done for other indications, concomitant aortic valve intervention is indicated if the AR is moderate or severe.

Intervention is either surgical aortic valve replacement or (less commonly) repair. Percutaneous options are being developed.

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

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

Antibiotic prophylaxis against endocarditis is no longer recommended for AR except for patients who have had valve replacement (see Table: Recommended Endocarditis Prophylaxis During Oral-Dental or Respiratory Tract Procedures*).

Key Points

  • The primary causes of acute AR are infective endocarditis and dissection of the ascending aorta; chronic AR in adults is most often caused by degeneration of the aortic valve or root.

  • Acute AR causes symptoms of HF and cardiogenic shock, but signs of AR may be absent.

  • Chronic AR is typically asymptomatic for years followed by progressive exertional dyspnea, orthopnea, and paroxysmal nocturnal dyspnea.

  • Typical heart sounds include a normal S 1 followed by a sharp or slapping S 2 and a blowing, high-pitched, decrescendo diastolic murmur.

  • Acute AR requires prompt aortic valve replacement or repair.

  • Chronic AR requires aortic valve replacement or repair when symptoms or LV dysfunction develops; patients who meet criteria but are not candidates for surgery benefit from HF treatment.

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