6.5: Aortic Regurgitation

A variety of etiologies can cause aortic regurgitation by preventing proper coaptation of the aortic valve leaflets with a subsequent diastolic reflux of blood from the aorta into the left ventricle. Etiology of aortic regurgitation can be primary valvular, or it can be primarily caused by aortic root or disease.

The origin of primary valve disease may be calcific aortic disease, idiopathic degenerative disease, endocarditis, rheumatic disease, a biscuspid aortic valve, or myxomatous proliferation of valvular tissue. In the majority of patients the disease is caused by rheumatic disease. However, in Western countries the disease is most often of degenerative origin. In the Euro Heart Survey degenerative aortic regurgitation accounted for approximately half of the cases of aortic regurgitation, 15% of cases had a bicuspid aortic valve.[11] Accelerated degeneration of valve leaflets, resulting in regurgitation similar carcinoid syndrome related regurgitation, can be caused by certain anorectic medications, such as fenfluramine and phentermine.[22]

Aortic annulus dilation, without primary involvement of the leaflets may result in aortic regurgitation due to leaflet separation. Aortic regurgitation of primary aortic root or annulus aetiology includes idiopathic aortic root dilatation, aortic dissection, trauma, and chronic severe systemic hypertension. Aortitis represents less than 5% of the aetiologies of aortic regurgitation and may be due to inflammatory disease, such as giant cell, Takayasu and Behcet syndrome. Syphilis and ankylosing spondylitis may affect the aortic valve, but may also be associated with aortic dilatation. Other systemic arteritides and connective tissue disorders such as Marfan syndrome, Reiter disease, Ehlers-Danlos syndrome, osteogenesis imperfecta, and rheumatoid arthritis can lead to annular dilatation and valvular insufficiency. In patients without generalized tissue disease the same pattern of ascending aortic enlargement is known as annuloaortic ectasia. Chronic aortic regurgitation itself may lead to progressive aortic root dilatation.

Aortic valve regurgitation is often accompanied by other valvular abnormalities. Aortic valvular insufficiency is most commonly seen in combination with aortic stenosis. Aortic insufficiency due to rheumatic aetiology is often associated with mitral valve disease. The valve leaflets are retracted by fused commissures and by fibrotic scarring of the leaflets itself.

Aortic cusp prolapse can be isolated, or due to myxomatous degeneration, sometimes with associated mitral or tricuspid valve involvement. In 15% of patients with ventricular septum defect, prolapse of an aortic cusp leads to aortic insufficiency.

Isolated aortic regurgitation is often caused by a primary aortic annular etiology. Rheumatic origin is much less common in patients with pure aortic regurgitation. In approximately 10% of cases, aortic regurgitation results from infective endocarditis, with perforation or erosion of leaflets.

It is of considerable clinical importance to distinguish between acute aortic regurgitation and chronic regurgitation since acute aortic regurgitation can be life-threatening if not treated immediately, in contrast to chronic regurgitation which can be tolerated for years.

Pathophysiology

In patients with aortic insufficiency the regurgitating volume increases the total stroke volume. This volume might equal the effective forward stroke volume in patients with severe aortic regurgitation. In chronic aortic regurgitation, several compensatory mechanisms ensure cardiac output.

Acute aortic regurgitation

Acute aortic regurgitation is a sudden hemodynamically significant aortic incompetence, which can often be catastrophic. An increase in left ventricular end diastolic volume with absence of ventricular remodeling may lead to elevated left atrial and pulmonary artery wedge pressure and decreased effective cardiac output, with compensatory tachycardia to maintain sufficient output.

Acute severe aortic regurgitation typically occurs with infective endocarditis, trauma, and aortic dissection. The left ventricle cannot dilate sufficiently. The patient may present with chest pain due to increased myocardical oxygen consumption combined with decreased coronary blood flow from changes in diastolic perfusion. Coronary blood flow in acute aortic insufficiency occurs during stystolic cardiac phase. Other symptoms of acute aortic regurgitation are tachypnea, tachycardia and rapidly progressive pulmonary edema and/or cardiogenic shock.

Chronic Aortic regurgitation

Aortic root dilatation, annular dilation and congenital bicuspid valve are, in developed countries, the most common causes of severe chronic aortic valve regurgitation.

The slow process of chronic aortic regurgitation allows adaptation of the ventricle to the increased preload and afterload. The left ventricular compensates to the regurgitant flow, the increased volume and pressure by enlargement. The left ventricle end diastolic pressure remains relatively low and does not approach the aortic diastolic pressure. The additional stroke volume is responsible for increased systolic pressure and eventually the wide pulse pressure. The systolic hypertension further increases left ventricle afterload.

In contrast to the compensatory mechanism in mitral valve regurgitation, a modest concentric left ventricular hypertrophy accompanies the eccentric hypertrophy, with a normal mass-to-volume ratio.[38] In a chronic state, progressive left ventricle dilatation leads to pre- and afterload mismatch. With gradually decompensation and deterioration of systolic function, the ventricle is not able to sustain perfusion.

Table 6.5.1: Causes of aortic regurgitation

Causes of Aortic Regurgitation
Aortic root/annular dilation
Congenital bicuspid valve
Previous infective endocarditis
Rheumatic
In association with other diseases

Clinical Presentation

Patients with aortic regurgitation typically present with symptoms of left sided heart failure including dyspnea on exertion, orthopnea, fatigue, and occasionally paroxysmal nocturnal dyspnea. Angina is less common in patients with aortic regurgitation compared to aortic stenosis. The reduced aortic diastolic blood pressure reduces the coronary blood flow, resulting in angina. The same mechanism is presumed to cause syncope.

Diagnostics

Chest Radiography

Chest Radiography in acute aortic regurgitation reveals minimal cardiac enlargement, with normal aortic root and arch. In acute aortic regurgitation, signs of left heart failure are frequent. Cardiomegaly with left ventricular enlargement is the main feature on chest radiography in chronic aorta regurgitation. The ascending aorta may be enlarged in case of an aortic aneurysm or aortic dissection but Chest X-ray is not a sensitive examination to detect ascending aortic aneurysm.

Pulmonary congestion is noted at advanced stages of chronic AR, when heart failure has developed.

Electrocardiography

Electrocardiography in patients with aortic regurgitation may be normal early in the disease. Left ventricular hypertrophy is the main feature of aortic regurgitation, with or without associated repolarization abnormalities. Left axis deviation may be present.

Echocardiography

Echocardiography is used to evaluate the anatomy of the aortic valve and other valves, as well as aortic leaflets and the aortic root. The regurgitation mechanism and etiology can be assessed. Three types of mechanisms can be identified; enlargement of aortic root with normal cusps, cusp prolapse or fenestration and poor cusp tissue quality or quantity. Doppler is used for quantifying the aortic regurgitation by the width of regurgitant jet and its extension into the LV, the rate of decline of aortic regurgitant flow and diastolic flow reversal in the descending aorta.

Severe aortic regurgitation is defined as effective regurgitant orifice (ERO) area of >0.30cm2, regurgitant volume >60mL, or a regurgitant fraction of >50%

Preoperatively transoesophageal echocardiography is performed to more accurately evaluate the anatomy and mechanism of the aortic valve regurgitation.

Treatment

The only direct method to reduce aortic regurgitation is surgical treatment. However, some patients may benefit from medical treatment.

Medical treatment

The relative reduction of myocardial blood supply due to increased demand and/or associated obstructive coronary artery disease may cause angina. Angina may be treated by reducing aortic regurgitation, reduction of myocardial demand of revascularization of the myocardium. Clinical heart failure is treated with traditional therapy, including digitalis, diuretics, and ACEI. In severe heart failure, parenteral inotropic and vasodilator therapy may be needed.

Table 6.5.2: Current guidelines for medical treatment of aortic regurgitation.

Class I	Class IIa	Class IIb	Class III
Vasodilator therapy is indicated for chronic therapy in patients with severe AR who have symptoms or LV dysfunction when surgery is not recommended because of additional cardiac or noncardiac factors. (Level of Evidence: B)	Vasodilator therapy is reasonable for short-term therapy to improve the hemodynamic profile of patients with severe heart failure symptoms and severe LV dysfunction before proceeding with AVR. (Level of Evidence: C)	Vasodilator therapy may be considered for long-term therapy in asymptomatic patients with severe AR who have LV dilatation but normal systolic function. (Level of Evidence: B)	Vasodilator therapy is not indicated for long-term therapy in asymptomatic patients with mild to moderate AR and normal LV systolic function. (Level of Evidence: B) Vasodilator therapy is not indicated for long-term therapy in asymptomatic patients with LV systolic dysfunction who are otherwise candidates for AVR. (Level of Evidence: C) Vasodilator therapy is not indicated for long-term therapy in symptomatic patients with either normal LV function or mild to moderate LV systolic dysfunction who are otherwise candidates for AVR. (Level of Evidence: C)

Surgical treatment

Surgical treatment in case of isolated Aortic valve regurgitation is aortic valve replacement. Aortic valve replacement is indicated in all symptomatic patients with severe Aortic regurgitation and in all asymptomatic patients with severe Aortic regurgitation with left ventricular ejection fraction (LVEF) <50% or left ventricular dilatation (end-diastolic diameter >75 mm or end-systolic diameter >55 mm).

When an aneurysm of the aortic root is associated with severe aortic regurgitation a Bentall procedure can be indicated. The ascending aorta is replacement by a composite graft comprising an aortic prosthesis, with re-implantation of the coronary arteries. When aortic enlargement is localized in the supra-coronary part of ascending aorta, replacing the supra-coronary section of the ascending aorta may be sufficient which is considered technically easier.

Although the prosthetic valve replacement remains the standard for aortic valve regurgitation, aortic valve repair procedures are performed with a combination of different surgical techniques. The quality of the cusps is essential for repair. The annulus and sinotubular junction can be surgically readapted to the cusps, eliminating the regurgitation.

Table 6.5.3: Current guidelines for surgical treatment of aortic regurgitation.

Class I

Class IIb

An adolescent or young adult with chronic severe AR* with onset of symptoms of angina, syncope, or dyspnea on exertion should receive aortic valve repair or replacement. (Level of Evidence: C) Asymptomatic adolescent or young adult patients with chronic severe AR* with LV systolic dysfunction (ejection fraction less than 0.50) on serial studies 1 to 3 months apart should receive aortic valve repair or replacement. (Level of Evidence: C) Asymptomatic adolescent or young adult patients with chronic severe AR* with progressive LV enlargement (end-diastolic dimension greater than 4 standard deviations above normal) should receive aortic valve repair or replacement. (Level of Evidence: C) Coronary angiography is recommended before AVR in adolescent or young adult patients with AR in whom a pulmonary autograft (Ross operation) is contemplated when the origin of the coronary arteries has not been identified by noninvasive techniques. (Level of Evidence: C)

An asymptomatic adolescent with chronic severe AR* with moderate AS (peak LV–to–peak aortic gradient greater than 40 mm Hg at cardiac catheterization) may be considered for aortic valve repair or replacement. (Level of Evidence: C) An asymptomatic adolescent with chronic severe AR* with onset of ST depression or T-wave inversion over the left precordium on ECG at rest may be considered for aortic valve repair or replacement. (Level of Evidence: C)