Introduction

Aortic regurgitation (AR), also referred to as aortic insufficiency (AI), is a cardiac valvular disorder distinguished by the abnormal flow of blood from the aortic valve back into the left ventricle during diastole (the relaxation phase of the cardiac cycle). This comprehensive course dives into the various factors responsible for this condition, associated symptoms, and primarily emphasizes the vital role that echocardiography plays in the detection and assessment of AR.

Figure 9.1. Example of severe AR by color flow Doppler

Definition:

Aortic regurgitation is a heart valve disorder where the aortic valve, which separates the left ventricle from the aorta, does not close properly. During diastole, the aortic valve should close tightly to prevent the backflow of blood into the left ventricle. With aortic regurgitation, the valve does not close properly, allowing blood to leak back. This puts extra strain on the heart, which has to try and pump more blood to compensate which can lead to other cardiac problems. In other heart valves, it’s common to see trace to mild degrees of regurgitation, however with AR, any amount is considered abnormal. When any amount of AR is seen, it is important to evaluate the mechanism that’s causing the regurgitation.

Aortic Valve Anatomy:

Starting with the basics, let’s review the structure of the aortic valve, as it will help to understand measurements needed to quantify the severity of aortic regurgitation. The aortic valve (AV) is composed of three cusps (leaflets), which are attached to the root. Each of these leaflets is named according to its position relative to the heart’s center: the right coronary cusp, the left coronary cusp, and the non-coronary cusp. The annulus is a fibrous ring-like structure that forms the base of the aortic valve. It anchors the valve leaflets and serves as a point of attachment. The sinuses of Valsalva consists of three small dilations or pouches that are located just above the aortic valve. They fill with blood during systole (contraction phase) and help to support the valve leaflets. The right and left coronary arteries originate from the sinuses of Valsalva. This anatomical relationship is essential to ensure adequate blood supply to the heart muscle.

Figure 9.2 : Basic anatomy of the Aortic Valve

Causes

Understanding the underlying cause of aortic regurgitation is crucial in not only assessing the severity, but also helps physicians determine the appropriate treatment approach. Some of these causes are:

Aortic Valve Abnormalities:
- Bicuspid aortic valve: A congenital condition where the aortic valve has two leaflets instead of the usual three.

Rheumatic fever: An inflammatory condition that can affect the heart valves.
Age related degeneration: As people age, the aortic valve can become thickened and calcified, which can impair its normal function.

Dilation of the Aorta:
- Conditions like aortic aneurysm can lead to aortic regurgitation.
- Aortic dissection can also cause regurgitation. In this situation, the regurgitation will typically be acute and the patient will have significant symptoms.
Aortitis:
- Aortitis, which can manifest in conditions like Takayasu’s arteritis, granulomatous aortitis, and syphilis, can involve inflammation of the aorta. In these cases, the inflammation can directly damage the aortic valve, resulting in leaflet thickening and impaired closure, causing AR.
Infective Endocarditis:
- Infective endocarditis can lead to acute regurgitation of the aortic valve. The infection produces toxins and enzymes that can break down the tissue and cause damage or holes to the valve leaflets. This type of regurgitation can develop rapidly and is often associated with significant symptoms due to the acute nature of the infection.

Connective Tissue Disorders:
- Connective tissue disorders, including Marfan and Ehlers-Danlos syndrome, are conditions that affect the connective tissues in the body. These disorders can lead to aortic regurgitation due to their impact on the structure of the aortic valve and the aorta.
  - In Marfan syndrome, genetic abnormalities result in elastic fiber issues, causing the aortic valve damage or aortic aneurysms that will stretch the valve annulus, preventing proper closure.
  - In Ehlers-Danlos syndrome, collagen abnormalities weaken the aortic valve leaflets and compromise the resilience of the aortic wall, potentially resulting in valve regurgitation and aortic dilation.

Autoimmune Disease:

Systemic lupus erythematosus, ankylosing spondylitis, and Reiter’s syndrome, among others, are autoimmune diseases that can lead to aortic regurgitation through the common thread of autoimmune-driven inflammation.
- In these disorders, inflammation can damage the aortic valve, which leads to leaflet thickening or stiffness of the valve structure, making it difficult for the valve to close properly allowing blood to flow backwards.

Trauma:

Significant trauma, such as blunt force trauma to the chest, can lead to aortic regurgitation by directly damaging the aortic valve or its supporting structures. The force exerted during events like car accidents or sports injuries can cause structural disruptions to the aortic valve leaflets. Trauma may also lead to aortic wall injury, potentially causing aortic dissection or tearing of the aorta, which can result in acute severe aortic regurgitation.

Medications of Radiation Therapy:

Certain cancer treatments, including cancer medications and radiation therapy, can pose a risk of aortic regurgitation through various mechanisms. Radiation therapy, often used for cancer treatment in the chest area, may damage nearby heart tissues, potentially weakening the aortic wall and increasing its susceptibility to dilation, ultimately leading to aortic regurgitation. Certain chemotherapy drugs may also have cardiotoxic effects, potentially harming the heart muscles and valves.

Clinical Symptoms and Symptoms

Figure 9.3 Statistics of life survival in patients that have AR with symptoms

The clinical presentation of aortic regurgitation can vary depending on the severity and duration of the condition. Here are the typical signs and symptoms:

Asymptomatic Phase:
- In the early stages, patients with mild to moderate or less AR, may be entirely asymptomatic. This is particularly common in chronic, slowly progressing cases. If the progression is very slow, patients can even have severe AR without symptoms.
Symptomatic Phase:
- Exertional Dyspnea: As the regurgitation worsens, patients may experience shortness of breath, especially during physical activity. This is due to the increased volume of blood in the left ventricle during diastole, which can lead to elevated pressures in the pulmonary circulation.
- Fatigue: Patients may report feeling tired or fatigued, especially after exertion. This can be a result of the increased demand on the heart.
Orthopnea and Paroxysmal Nocturnal Dyspnea:
- In more advanced cases, patients may experience difficulty breathing while lying flat (orthopnea) or may wake up at night gasping for breath (paroxysmal nocturnal dyspnea).
Palpitations:
- Some patients may feel palpitations or irregular heartbeats, especially if the regurgitation leads to changes in the heart’s rhythm.
Chest Pain:
- While chest pain is not a primary symptom of AR, it may occur in some cases, like acute AR or when there are other associated cardiac conditions.
Pulse Examination:
- Bounding Pulses: Due to the increased stroke volume, patients with severe AR may have strong, bounding pulses. This can be palpated at the radial artery.
- Water-Hammer Pulse (Corrigan’s Pulse): This is a characteristic sign of severe AR where the pulse is forceful and quickly collapses. It’s described as similar to the action of a water hammer.
Physical Examination Findings:
- Diastolic Murmur: A characteristic “decrescendo” blowing diastolic murmur is heard during auscultation. It is best heard at the left lower sternal border and may radiate to the apex. The murmur often starts after the aortic component of the second heart sound.
- Widened Pulse Pressure: The difference between systolic and diastolic blood pressure (pulse pressure) is widened in AR. This can be appreciated during blood pressure measurement.
- Other Associated Signs: Depending on the cause of AR, there may be other findings related to the underlying condition (e.g., signs of connective tissue disorders). This is why having the ability to assess the AV noninvasively with echo is so important.

Figure 9.4: Symptoms of Aortic Regurgitation typically seen by severity stage

Complications

While it’s important to assess the valve itself, it is also important to assess for other complications that can occur within the heart as a result of the aortic regurgitation. These findings could be:

Left Ventricular Enlargement: In order to compensate for the regurgitant flow, the left ventricle may undergo dilation. This is an adaptive response to handle the increased volume of blood being pushed back into the LV.
Heart Failure: Over time, the increased workload on the left ventricle can lead to heart failure. The heart may struggle to pump effectively, leading to symptoms such as fatigue, shortness of breath, and fluid retention.
Mitral Valve Dysfunction: The increased pressure and dilation of the left ventricle can dilate the mitral valve annulus, potentially leading to mitral valve regurgitation.
Myocardial Ischemia: In severe cases, aortic regurgitation can lead to decreased coronary artery perfusion (blood flow to the heart muscle), potentially resulting in angina or heart attack.
Sudden Cardiac Death: Although rare, severe aortic regurgitation can lead to sudden cardiac death, particularly if it is acute and not promptly treated.
Pulmonary Hypertension: In advanced stages, aortic regurgitation can lead to increased pressure in the pulmonary arteries (pulmonary hypertension), which can further strain the right side of the heart.

Diagnostic Evaluation by Echocardiography:

Echo is a crucial tool for diagnosing and assessing the severity of aortic regurgitation. Accurate and detailed echocardiographic assessment is vital for guiding clinical decision-making and determining the most appropriate treatment timing. Evaluation by echo includes:

2D echocardiographic findings:
- Always try to identify the etiology/mechanism of the AR when scanning.
  - Look at the valve structure and motion of leaflets such as prolapse, flail, restriction, valve coaptation, calcification, or vegetations.
- Image and measure the aortic root and ascending aorta to assess for dilatation
- Assess Left Ventricular Function:
  - Evaluate left ventricular size, shape, and function (ejection fraction). Note any signs of chamber dilation or hypertrophy, which may be secondary to chronic regurgitation.
M-mode findings:
- Fine diastolic flutter of anterior mitral valve leaflet
- Fine to coarse diastolic closure line flutter of aortic valve
- Color m-mode can show severity by seeing how much of the jet is taking up the outflow tract. (see figure 9.5)

Figure 9.5: Color M-Mode from PSAX demonstrating different severities in AR

Color Doppler Imaging:
- Color Doppler is used to visualize blood flow direction and velocity. Regurgitant flow through the aortic valve will appear as a mosaic of colors, indicating the direction and turbulence of the regurgitant jet.
  - From PLAX, show a color image of how far back the AR goes into the LV
  - Quantification using color can be done for vena contracta and PISA radius measurements
  - Assess the jet width and area vs. the LVOT diameter from parasternal views
  - Use color in the abdominal, ascending and descending aorta to assess for diastolic flow reversal

Continuous Wave (CW) Doppler:
- CW will provide information about the velocity and pressure gradient of the regurgitant jet.
- Severe AR CW signal will be a dense signal with a short pressure half-time (PHT)
  - PHT of <200 msec = severe AR
  - It’s important to note that PHT is very subjective and can be inaccurate, therefore it should always be correlated to other measurements.
Pulsed Wave (PW) Doppler:
- Use PW Doppler to measure the velocity of blood flow in the left ventricular outflow tract (LVOT) and across the aortic valve.
  - LVOT velocity and VTI trace can both be increased with significant AR
  - Shortened MV deceleration times with increased E/A ratio
  - These findings are usually associated with acute severe AR
- Diastolic mitral regurgitation:
  - May indicate severe AR with increased LVEDP

Figure 9.6: Diastolic MR occurs when the LV pressure exceeds the LA pressure during diastole, producing a reverse atrioventricular gradient.

Diastolic flow reversal in descending thoracic aorta
- Trace if you see holodiastolic flow
  - A VTI of >20cm = severe

Figure 9.7: Severe AR holodiastolic flow reversal in the descending aorta

Diastolic flow reversal in abdominal aorta
- Holodiastolic flow indicates significant regurgitation

Figure 9.8: Example of holodiastolic flow in the abdominal aorta with PW Doppler

Quantification:

Aortic regurgitation can be very difficult to assess correctly. There are many different ways to quantify the amount of AR, and multiple methods should be correlated together to ensure correct assessment of regurgitation severity. These can include:

Vena Contracta Width: From the PLAX zoomed view of the AV, measure the narrowest portion of the regurgitant jet using color Doppler (see figure 9.9). A wider vena contracta indicates more severe regurgitation
- Severe AR measurement is >0.6 cm
- This method is not as reliable when there is an eccentric jet

Figure 9.9. Example of Vena Contracta measurement

Jet height vs. outflow tract height:
- From a PLAX view with color, assess the broadening in the jet as it moves into the LVOT.
- A jet height vs.LVOT diameter ratio greater >60% is considered severe. Most often this is a visual estimation.

Figure 9.10: Drawing demonstrating AR jet height vs. LVOT height assessment method

Jet area vs. LVOT area:
- This is similar to jet vs. LVOT height, but done from the PSAX view with color at the AV level. A image with color over the AV assesses the area of regurgitation compared to the LVOT area.

Figure 9.11: Drawing demonstrating AR jet area vs. LVOT area assessment method

Pressure Half-Time:
- A steeper pressure half-time suggests more regurgitation (see figure 9.12).
- This measurement is blood pressure dependent and can be inaccurate.

Figure 9.12: Physiology of PHT

PISA (Proximal Isovelocity Surface Area) Calculation:

PISA calculation requires multiple measurements that are based on flow convergence and is used to estimate the area of the orifice in which the AR blood flows. PISA calculation will give you an EROA, regurgitant volume and regurgitant fraction. Below is a basic overview of the measurements needed:

Measuring the PISA radius
- ZOOM on the AV with color and pan through the valve to find the largest radius. This can be done from an apical 3 or 5 chamber and on eccentric jets, PLAX can sometimes be the best option.

Turn color baseline up (or in direction of color flow) and measure the radius seen as demonstrated in figure 9.13.

Figure 9.13: PISA radius measurement from apical window

Using continuous wave Doppler, align the cursor parallel with the regurgitant flow to get the best signal to trace.

Figure 9.14: CW signal trace of AR

Don’t be afraid to think outside the box and try different windows to assess both CW and color, as eccentric jets can sometimes be best assessed from the PLAX view or even subcostal window.

Figure 9.15 Severity chart from ASE guidelines

Other Testing Available

Transesophageal echocardiogram (TEE): A TEE exam is performed if the TTE images are not adequate or the cardiologist needs to see the AV structure in more detail. Since it’s more invasive than a TTE, it is typically not the first choice of testing ordered.

Cardiac catheterization is performed if other studies are inconclusive about the severity or cause of AR. A cath can also be ordered to differentiate the diagnosis of acute coronary syndrome vs AR.
Computerized Tomography (CT): Can provide detailed information about the structure and function of the heart. Is often done when aortic dissection is suspected. If the patient is unable to do a CT, a TEE is also an option.
Cardiac MRI is rarely used in acute settings unless TTE images are very suboptimal. In chronic settings, it can be useful to view the entire heart without lung interference as well as being able to change imaging planes in multiple angles.

Treatment Options

Medical Management:
- Blood Pressure Control: Maintaining optimal blood pressure is crucial for managing aortic regurgitation. Medications like angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) may be prescribed to help regulate blood pressure.
- Heart Failure Management: If aortic regurgitation has led to heart failure, medications such as diuretics, beta-blockers, and inotropes may be used to alleviate symptoms and improve cardiac function.
- Monitoring and Follow-Up: Regular check-ups and echocardiograms are essential to monitor the progression of the condition and assess the timing and need for intervention.
Surgical Intervention:
Deciding the timing of surgery with chronic aortic regurgitation can be difficult for physicians to decide. Most physicians go by the guidelines set by the American College of Cardiology and the American Heart Association.
- Aortic Valve Repair: In cases where the valve structure can be preserved, aortic valve repair may be performed. This involves techniques to correct or reconstruct the valve.
- Aortic Valve Replacement: If the valve is severely damaged or repair is not feasible, aortic valve replacement with a mechanical or bioprosthetic valve is considered.
- Transcatheter Aortic Valve Replacement (TAVR): This is a less invasive procedure that involves replacing the aortic valve with a catheter inserted through a blood vessel, typically in the groin.
- Ross Procedure (congenital): This is a specialized surgical technique in which the patient’s own pulmonary valve is used to replace the damaged aortic valve, and a homograft (donor pulmonary valve) is used to replace the pulmonary valve.

Figure 9.16 : Guidelines for surgical intervention

Watchful Waiting:
- In cases of mild or moderate aortic regurgitation without symptoms, particularly if the heart function is normal, a conservative approach with regular monitoring may be recommended.
Lifestyle Modifications:
- Encourage the patient to have a heart-healthy lifestyle, including a balanced diet, regular exercise, smoking cessation, and limited alcohol consumption.
Education and Support:
- Provide education about the condition, its management, and the importance of compliance with medications and follow-up exams. Make sure the patient knows the signs and symptoms that can occur with AR.

Conclusion

In aortic regurgitation, the assessment of the severity is based mainly on symptoms and echo findings and calculations.
It is helpful to review the patient’s history and symptoms prior to starting an echo scan. Physicians will order an echo based on symptoms and physical exam, so knowing what these are will give the sonographer an idea of what they could expect to find during the exam.
Current guidelines suggest that surgery be performed in patients with severe AR and symptoms, however newer findings are suggesting that if there is severe AR without significant symptoms, it might be more beneficial for the patient to have a repair or AVR before there is damage to the heart such as LV dilation or decreased EF.

Aortic Regurgitation: Part 1

Aortic Regurgitation: Part 1