Index
This condition is also known as aortic regurgitation.
Aortic regurgitation occurs when blood flows backward, or retrograde, through the aortic valve from the aorta into the left ventricle during diastole.
This abnormal flow of blood flow leads to pathological changes in the heart to compensate for the decrease in effective cardiac output that occurs.
Aortic regurgitation is caused by damage to the aortic valve leaflets or by dilation of the aortic annulus. As the disease progresses, symptoms of congestive heart failure eventually occur.
Definitive treatment is surgical replacement of the aortic valve; However, medical therapy can improve symptoms.
Pathophysiology
The abnormal blood flow that occurs leads to pathological changes that largely depend on the severity of the aortic regurgitation and the rate of development of the disease.
Left ventricular chamber enlargement and hypertrophy occur to help maintain normal cardiac output in chronic aortic insufficiency.
The LV dilates and hypertrophies (eccentrically) slowly over time. These changes help maintain normal LV pressures at a significantly higher LV volume setting.
In fact, patients with severe chronic aortic regurgitation may have the highest LV end diastolic volumes produced by any heart disease , although their LV end diastolic pressures are not significantly elevated.
However, when acute aortic regurgitation occurs, these changes cannot occur. Heart pressures rise rapidly in this setting, and heart failure can occur, as well as cardiogenic shock.
The small increase in left ventricular end diastolic volume, or LVEDV, due to acute RA, would lead to a considerable increase in left ventricular diastolic pressure, or LVEDP.
This increased pressure is automatically transmitted to the pulmonary vasculature, leading to severe symptoms of left heart failure, including rapid pulmonary edema.
As aortic regurgitation worsens, allowing large volumes of blood to regurgitate during diastole, aortic diastolic pressures decrease significantly.
These low diastolic pressures, along with the increased systolic pressures produced by the hypertrophied left ventricle to maintain cardiac output, produce an enlarged pulse pressure and a very large stroke volume.
This large stroke volume leads to a number of unusual findings on peripheral physical examination that are discussed below in peripheral signs.
Low diastolic pressures can significantly affect coronary perfusion pressures, as the coronary arteries fill during diastole.
Afterload is an important factor in the degree of aortic regurgitation. When systemic pressures are high, a greater volume of blood will flow backward into the left ventricle.
Therefore, the mainstay of pharmacotherapy in aortic regurgitation is aimed at reducing afterload.
Causes of aortic regurgitation
Aortic regurgitation may be due to abnormalities of the aortic valve leaflets, dilation of the aortic root, or a severe increase in afterload.
When the aortic leaflets are involved, a destructive process, such as infective endocarditis or rheumatic valve disease, often occurs.
Any disease process that leads to dilation of the aortic root, i.e. Marfan syndrome or aortic dissection, will cause the annulus of the aortic valve to stretch, resulting in the leaflets not adapting properly to diastole and ultimately to aortic regurgitation.
Aortic root and valve repairs are often required in this setting.
Below is a list of the etiologies for aortic regurgitation:
Aortic cusp / leaflet abnormalities
- Infectious: bacterial endocarditis, rheumatic fever.
- Congenital: calcification of the bicuspid aortic valve.
- Inflammatory: systemic lupus erythematosus or SLE, rheumatoid arthritis or RA, Behcet’s syndrome.
- Degenerative: myxomatous (floppy valve), senile calcification.
- Others: Trauma, postaortic valve valvuloplasty, diet drug valve disease, carcinoid valve disease (requires lung metastases or patent foramen ovale or PFO).
Aortic root abnormalities
- Aortic root dilation: Marfan syndrome, syphilitic aortitis, idiopathic aortitis, Ehlers-Danlos syndrome, recurrent polychondritis.
- Loss of commissural support: aortic dissection, trauma, supracrystalline ventricular septal defect or VSD.
Higher rear loading
- Uncontrolled systemic hypertension.
- Supravalvular aortic stenosis (can occur in William syndrome).
- Coarctation of the aorta.
Symptoms of aortic regurgitation
As chronic aortic regurgitation develops slowly over time, the left ventricle compensates slowly and easily, as described above.
Therefore, there are no symptoms early in the disease, for a long period of time. Once they occur, the symptoms of aortic regurgitation are primarily from congestive heart failure.
Left heart failure produces symptoms related to low cardiac output. The condition causes dyspnea due to high pressure in the left ventricle that is transmitted to the pulmonary vasculature.
During physical activity, with the heart demanding a performance incapable of being reached in states of heart failure, the increase in the pressure of the left heart causes a transient pulmonary edema.
Since increased pressure in the left heart affects the right ventricle, right heart failure can occur. The most common cause of right heart failure is left heart failure.
Symptoms of right heart failure include dependent lower extremity edema.
When the legs are elevated at night, fluid is redistributed centrally, causing pulmonary edema leading to orthopnea (dyspnea while lying down) or paroxysmal nocturnal dyspnea.
Liver congestion can also occur, causing right upper quadrant abdominal pain.
Palpitations can result from large volumes of strokes and strong LV contractions.
Angina can occur in the absence of atherosclerotic coronary artery disease, as low diastolic pressures in severe aortic regurgitation compromise coronary filling and left ventricular hypertrophy increases oxygen demand.
Other symptoms related to low cardiac output include fatigue, weakness and, in extreme cases, cardiac cachexia.
Unlike chronic aortic regurgitation, almost all patients with significant acute aortic regurgitation are symptomatic. Signs of acute left heart failure develop, including severe dyspnea, including at rest, orthopnea, and PND.
Hypotension, sudden pulmonary edema, and shock can also occur.
Physical exam
In chronic aortic regurgitation, visible heart and arterial pulsations are common due to the large volume of the stroke. The carotid pulse can be seen frequently. The point of maximum impulse, or PMI, moves laterally and caudally due to the dilatation and hypertrophy of the LV that occurs.
On auscultation, the typical murmur of aortic regurgitation is a soft, high-pitched diastolic decrescendo murmur that is best heard in the third intercostal space on the left, known as Erb’s Point, at the end of expiration with the patient seated and inclined. forward.
This murmur is often difficult to distinguish from the Graham-Steele murmur of pulmonary insufficiency. If aortic root disease is the cause of the aortic regurgitation, the murmur will be best heard at the right upper sternal border, not at Erb’s point.
As aortic regurgitation worsens, the murmur shortens in duration, since less time is required for left ventricular and aortic pressure equalization.
In addition to the anterior murmur, there may be a systolic ejection murmur at the right upper sternal border, simply due to the large stroke that passes through the aortic valve with each systolic contraction of the LV.
An early diastolic rumble may also be heard at the apex, as the regurgitant jet strikes the anterior leaflet of the mitral valve and causes it to vibrate; This murmur is called the Austin-Flint murmur.
An enlarged pulse pressure is often present due to the high flow state as described above. When severe heart failure develops, the pulse pressure decreases and the peripheral signs of aortic regurgitation, listed below, decrease.
A fourth heart sound (S4) develops when LVH becomes severe and limits diastolic filling. A third heart sound (S3) is often present, due to increased early diastolic filling in a compatible, dilated left ventricle.
Acute aortic regurgitation will cause a very short early diastolic murmur with rapidly equalizing aortic and left ventricular pressures, as the left ventricle has not had time to dilate or hypertrophy.
Peripheral signs
Peripheral signs of aortic regurgitation are primarily due to the high-flow state, large stroke volume, and wide pulse pressure seen in aortic regurgitation.
Many peripheral signs of aortic regurgitation have been identified and named by the physician who first described it; are listed below.
The sensitivity of these findings is low. While they are intellectually and historically interesting, they are not always clinically useful.
- Corrigan’s pulse : a rapid, forced straining of the arterial pulse with a rapid collapse.
- De Musset’s sign : shake your head with each heartbeat (like a walking bird).
- Muller’s sign: visible pulsations of the uvula.
- Quincke’s sign : capillary pulsations observed in light compression of the nail bed.
- Traube’s sign : systolic and diastolic sounds heard in the femoral artery (“pistol shots”).
- Duroziez’s sign : Gradual pressure on the femoral artery leads to a systolic and diastolic murmur.
- Hill’s sign: popliteal systolic blood pressure that exceeds the brachial systolic blood pressure of 60 mm Hg or more (the most sensitive sign for aortic regurgitation).
- Shelly’s sign : pulsation of the cervix.
- Rosenbach’s sign : liver pulsations.
- Becker’s sign: visible pulsation of the retinal arterioles.
- Gerhardt’s sign (also known as Sailer’s sign) : pulsation of the spleen in the presence of splenomegaly.
- Mayne’s sign: a decrease in diastolic blood pressure of 15 mm Hg when the arm is held above the head (very nonspecific).
- Landolfi’s sign: systolic contraction and diastolic dilation of the pupil.
In acute aortic regurgitation, the peripheral signs listed above are absent, as the heart does not have time to compensate for the increased LV volume.
In addition, the murmur of aortic regurgitation is short-lived and may be difficult to hear with aortic pressure and LV pressure (elevated in acute RA) rapidly equalizing in diastole.
There may be a soft first sound of the heart, due to the early closure of the mitral valve.
Diagnosis of aortic regurgitation
Aortic regurgitation is best diagnosed by echocardiography, as the murmur can be missed on physical examination in many cases. Almost 100% sensitive and specific for detecting aortic regurgitation, echocardiography is also crucial in determining etiology and estimating severity.
The actual regurgitant jet can be directly visualized using color flow Doppler; this is extremely important in patients with acute RA, as the physical examination may not reveal any valvular abnormalities.
Regarding the etiology, structural abnormalities can be observed, such as a bicuspid aortic valve or a prolapse of the VA.
Vegetations in the aortic valve can also be identified, indicating that endocarditis is the cause, although transesophageal echocardiography is more sensitive. In addition, the size of the aortic root can be measured and aortic dissections can be identified.
The severity of aortic regurgitation can be estimated using three parameters on echocardiography:
- Regurgitant jet size.
- Half time pressure.
- Regurgitant fraction.
Regurgitant jet size represents the relationship between the diameter of the aortic regurgitant jet just below the aortic valve leaflets and the size of the LV outlet diameter.
Ideally, the ratio should be zero because there should be no regurgitant jet. A proportion less than 24 is mild, between 25 and 45 moderate, between 46 and 64 moderately severe and greater than 65 severe.
The pressure half-time index is the time it takes for the initial maximum pressure gradient in diastole to drop by 50%. In patients with mild aortic regurgitation, this pressure drop is gradual.
In the setting of severe aortic regurgitation, there is a rapid drop in the pressure gradient.
A mean pressure of more than 500 milliseconds is considered mild aortic regurgitation, 500 to 349 ms is moderate, 349 to 200 ms is moderately severe, and less than 200 ms is severe.
The severity of aortic regurgitation assessed using half-time pressure is overestimated in patients with significantly higher LVEDP.
The regurgitant fraction is perhaps a more direct means of assessing the severity of aortic regurgitation. The regurgitant fraction is the percentage of stroke volume that returns to the left ventricle from the aorta during diastole.
For example, a regurgitant fraction of 33% would indicate that one-third of the total stroke volume returns to the LV retrograde through the aortic valve during diastole.
A regurgitant fraction of less than 20% indicates mild aortic regurgitation, 20% to 35% moderate aortic regurgitation, 36% to 50% moderately severe aortic regurgitation, and more than 50% severe aortic regurgitation.
It is important to note that the severity of aortic regurgitation assessed by echocardiography depends on the hemodynamic status of the patient at the time of assessment, most importantly afterload.
Cardiac catheterization with aortography and hemodynamic measurements is not necessary in most patients with aortic regurgitation due to the precision of echocardiography.
During cardiac catheterization, aortic regurgitation can be detected by injecting contrast into the aortic root and visualizing the appearance of contrast in the left ventricle.
Catheterization can also evaluate for aortic root disease. Several factors affect the classification of the severity of aortic regurgitation during the procedure.
If the catheter is placed too close to the aortic valve, the amount of aortic regurgitation will be overestimated. The volume and speed of the contrast injection into the aortic root affect the amount of aortic regurgitation visualized.
As mentioned above, hemodynamic parameters at the time of evaluation also affect the severity of aortic regurgitation, again, mostly after loading.
The rating scale for aortic regurgitation used during catheterization is below. Cardiac catheterization can also measure LVEDV and LVEDP, which can be helpful in determining aortic regurgitation.
Cardiac catheterization with coronary angiography is indicated if aortic valve replacement is planned, so images of the coronary arteries can be obtained.
If there is significant coronary atherosclerosis, a coronary artery bypass graft, or CABG, may be performed at the same time as the valve replacement.
The ECG in patients with aortic regurgitation is nonspecific and may show left ventricular hypertrophy and left atrial enlargement.
In acute aortic regurgitation, sinus tachycardia due to increased sympathetic nerve tone may be the only abnormality on the ECG.
The chest radiograph is also not specific for aortic regurgitation. Cardiomegaly is present in patients with chronic RA. In acute RA, pulmonary edema is almost universally present. If the AR is due to an aortic dissection, the mediastinum may appear widened.
Treatment
In patients with mild to moderate aortic regurgitation, no specific treatment is required. These patients should be monitored annually to assess disease progression. Antibiotic prophylaxis is recommended to prevent bacterial endocarditis.
Patients with moderate to severe aortic regurgitation who are symptomatic should undergo AVR if they fall into New York Heart Association class III-IV functional heart failure.
Those in NYHA class II should receive a stress test to assess endurance and exercise capacity and are treated with diuretics and afterload reducers (commonly angiotensin-converting enzyme inhibitors) until AVR is indicated.
If there is moderate to severe aortic regurgitation but the patient is asymptomatic, AVR is not clearly indicated. Afterload reducers are administered, and frequent echocardiographic evaluation is recommended to monitor for left ventricular dysfunction.
The ideal time for AVR is late enough in the course of the disease to justify the risk-benefit ratio of surgery, but early enough to prevent possible irreversible myocardial damage from occurring.
LV ejection fraction has been shown to better correlate with surgical outcome.
Although reducing afterload with medications can decrease RA and improve symptoms, there is no evidence that this approach delays the need for a surgical AVR.
Medications most commonly used for this purpose include ACE inhibitors, such as lisinopril or ramipril, and dihydropyridine calcium channel blockers, such as amlodipine and nifedipine.
The definitive replacement of the aortic valve is surgical therapy.
Indications, according to the American College of Cardiology / American Heart Association guidelines, include the following:
- Symptomatic heart failure (class I).
- Misleading symptoms and poor performance in a treadmill stress test (class I).
- No symptoms, but left ventricular ejection fraction <50% (class I).
- No symptoms, normal left ventricular ejection fraction, but left ventricular enlargement with a final systolic dimension of 55 mm and a final diastolic dimension of 75 mm (class IIa).
- Severe aortic regurgitation without symptoms, a normal left ventricular ejection fraction, but left ventricular end systolic dimension between 50-55 mm or end diastolic dimension between 70-75 mm (class IIb).
Indications for aortic valve replacement, when endocarditis is the etiology, include the following:
- Congestive heart failure due to valve failure.
- Failure of antibiotic therapy to successfully suppress infection, or infection with difficult-to-treat organisms (fungi, Pseudomonas, Brucella, drug-resistant organisms).
- Annular valve abscess.
- Peripheral embolism of vegetation.
- Vegetation size> 1.0 cm.
Acute aortic regurgitation carries a very high mortality if rapid surgical intervention in the form of aortic valve replacement (AVR) is not performed.
Treating pulmonary edema and reducing afterload can help alleviate symptoms, buying the patient some time before surgery is done.
Nitroprusside is the treatment of choice, since it reduces preload and afterload very effectively. Dobutamine may be necessary if the patient remains hypotensive with low cardiac output.
The use of intra-aortic balloon counterpulsation is contraindicated in severe aortic regurgitation.
Furthermore, the approach is not commonly used in acute aortic regurgitation as it is in acute mitral regurgitation.
If acute aortic regurgitation is due to infective endocarditis, antibiotics are often given intravenously at least 7 days before valve replacement.