Aortic stenosis and regurgitation

AORTIC STENOSIS AND AORTIC REGURGITATION NOTES

AORTIC STENOSIS

Definition

  • Aortic stenosis is defined as the narrowing of the aortic valve (AOV), which impedes the systolic flow from the left ventricle (LV) through the AOV into the aorta.

  • It is recognized as the most common primary valve disease.

  • The primary diagnostic tool for evaluating aortic stenosis is echocardiography (echo).

  • Distinction between stenosis and sclerosis is based on the peak velocity:

    • Stenosis: Peak velocity >= 2.6 m/s

    • Sclerosis: Peak velocity <= 2.5 m/s

Most Common Etiologies

  1. Calcific Aortic Stenosis of Normal Trileaflet AOV

    • Prevalent in individuals aged 65 and older, characterized as degenerative changes with calcific alterations usually occurring at the central and basal parts of the cusps.

    • Stenosis typically originates at the sinus of Valsalva, extending medial to the AOV cusps.

  2. Congenital Bicuspid AOV

    • This condition may lead to aortic stenosis without calcific changes, particularly during adolescence.

    • Symptoms often manifest between the ages of 20 to 50, with potential outcomes including heart failure, the need for prosthetic valves, or death.

    • The right and left coronary cusps may fuse with the posterior cusp, and 80% of these cases exhibit coronary arteries arising from a common cusp.

    • From the parasternal short axis (PSAX), the opening may appear football-shaped, and a raphe can be present (a ridge-like structure).

    • Considerations include evaluation for associated conditions: aortic aneurysm, aortic dissection, and coarctation (with approximately 50% of coarctations linked to a bicuspid aortic valve).

  3. Rheumatic Aortic Stenosis

    • This is the most prevalent cause of aortic stenosis worldwide.

    • The pathology involves fibrotic changes at the cusp edges, resulting in the fusion of commissures, leading to triangular systolic orifice and calcifications.

    • Unlike calcific AS, stenosis originates at the cusps and extends outward.

    • Rheumatic heart disease (RHD) typically affects both the mitral valve and aortic valve.

  4. Other Types of Aortic Stenosis

    • Supravalvular Aortic Stenosis: Characterized by narrowing of the aorta at the sinotubular junction, often associated with Williams Syndrome.

    • Subvalvular Aortic Stenosis: This includes left ventricular outflow tract (LVOT) obstruction, which can be fixed (either membrane or muscular bands) or dynamic (caused by hypertrophic cardiomyopathy).

Murmur Characteristics

  • The characteristic murmur associated with aortic stenosis is a systolic crescendo-decrescendo sound.

  • This murmur is typically heard at the right upper sternal border and may radiate to the carotid arteries.

Complications

  • The increased left ventricular pressure overload can lead to LV hypertrophy (LVH), LV dilatation, and eventually heart failure (HF).

  • There is an increased risk for infective endocarditis in patients with aortic stenosis.

Signs and Symptoms

  • Patients may present with:

    • Chest pain

    • Depressed cardiac output

    • Signs of heart failure

    • Myocardial infarction

    • Arrhythmias

    • Syncope (either myocardial or cerebral)

    • Pulmonary edema

    • Sudden death

Treatment Options

  1. Serial Echocardiograms

    • Used to track changes in:

      • Aortic stenosis (peak velocity, mean pressure gradient, and aortic valve area)

      • Chamber sizes

      • Left ventricular hypertrophy

      • Systolic and diastolic function

  2. Aortic Valve Replacement (AVR)

    • Indicated if the patient is symptomatic or before heart failure necessitates intervention.

    • Options include surgical AVR and transcatheter aortic valve replacement (TAVR).

Assessment Parameters for Aortic Stenosis

  • Assessment: Condition should be evaluated for:

    1. Level of obstruction

    2. Number of cusps

    3. Cusp mobility and thickening

    4. Calcification status

    5. Degree of commissural fusion

    6. Left ventricle ejection fraction (EF), size, and wall thickness

    7. Peak and mean velocity, and area of the aortic valve (AVA)

2D Echocardiography Findings

  • Bicuspid Aortic Stenosis (BAS) presents as:

    1. Thickened, football-shaped opening

    2. Presence of raphe (ridge)

  • Aortic Stenosis (AS) from echocardiography includes:

    1. Thickened cusps

    2. Doming and decreased excursion

    3. Mitral annular calcification (MAC)

    4. Left atrial enlargement (LAE)

    5. Left ventricular hypertrophy (LVH)

    6. LV dilatation, and decreased ejection fraction (EF)

    7. Post-stenotic dilatation of the aortic root

Doppler Considerations

  • Turbulent systolic flow created by aortic stenosis travels from the left ventricle through the narrowed aortic valve into the aorta.

  • Aortic regurgitation can occur subsequent to aortic stenosis.

    • Doppler Parameters:

    • Peak Velocity: Strongest predictor of outcomes; thresholds over 4 m/s associate with increased symptoms and mortality.

    • Mean Pressure Gradient: Generally not recommended, but still used in some labs.

    • Mean Gradient: Best correlation with catheter lab findings.

    • AVA Calculation: Determined using the continuity equation.

Continuity Equation Definition

  • The continuity equation states that the flow through a tube must be constant. If the tube's cross-sectional area decreases, velocity must increase to maintain the constant flow.

    • Equation: AVA=(VTI<em>LVOTimesCSA</em>LVOT)/VTIAOVAVA = (VTI<em>{LVOT} imes CSA</em>{LVOT}) / VTI_{AOV} where

      • $VTI_{LVOT}$ = Velocity Time Integral of Left Ventricular Outflow Tract

      • $CSA_{LVOT}$ = Cross-Sectional Area of Left Ventricular Outflow Tract

      • $VTI_{AOV}$ = Velocity Time Integral of Aortic Valve.

Severity Scale of Aortic Stenosis with Normal LVEF

Degree

Peak Velocity (m/s)

Mean PG (mmHg)

AVA (cm²)

Max PG (mmHg)

Aortic sclerosis

<= 2.5

N/A

N/A

N/A

Mild AS

2.6-2.9

< 20

> 1.5

27-34

Moderate AS

3.0-4.0

20-40

1.0-1.5

36-64

Severe AS

> 4.0

> 40

< 1.0

> 64

  • Additional notes regarding aortic stenosis with decreased ejection fraction:

    • AS velocity ratio:

    • Mild AS > 0.5

    • Moderate AS 0.25 - 0.50

    • Severe AS < 0.25

AORTIC REGURGITATION

Definition

  • Aortic regurgitation is defined as an incompetent aortic valve, resulting in backflow of diastolic blood from the aorta through the aortic valve into the left ventricle while the valve is closed.

Causes

  1. Acute Aortic Regurgitation

    • Can arise from:

      • Dissection of the ascending aorta

      • Infective endocarditis

      • Trauma leading to the loss of commissural support.

  2. Chronic Aortic Regurgitation

    • Various causes include:

      • Aortic dilatation due to conditions such as Marfan syndrome, hypertension, syphilis aortitis, or aortic aneurysm.

      • Aortic stenosis.

      • Bicuspid aortic valve.

      • Incomplete closure due to problems such as prolapse or membranous ventricular septal defect (VSD).

      • Congenital factors, including quadricuspid aortic valve.

Murmur Characteristics

  • The murmur of aortic regurgitation is typically described as a high-pitched, blowing, diastolic decrescendo murmur, best heard at the left sternal border.

  • In cases of severe aortic regurgitation, the murmur may present as a low-pitched, mid-diastolic rumble at the apex (Austin Flint murmur).

Complications, Signs & Symptoms

  • Complications associated with aortic regurgitation may lead to:

    • Left ventricular volume overload, leading to left ventricular dilatation and decreased function ultimately resulting in heart failure.

    • Potential for infective endocarditis.

  • Patients may experience the following symptoms:

    • Chest pain

    • Dizziness

    • Exertional dyspnea

    • Syncope (fainting)

    • Decreased cardiac output (CO)

Treatment Options

  • For chronic aortic regurgitation, serial echocardiography is essential to track changes in:

    • The degree of aortic regurgitation

    • Chamber sizes

    • Systolic and diastolic function

  • Aortic valve repair or replacement is indicated, ideally before the left ventricle is compromised.

2D Echocardiography Findings

  • In longstanding aortic regurgitation, decreased LV function can lead to heart failure.

  • The mechanism includes increased preload, resulting in LV volume overload, LV dilatation, higher stroke volume (SV), and left ventricular hypertrophy (LVH).

  • Diastolic flutter of the anterior mitral valve (MV) or interventricular septum (IVS) may be observed during echocardiography.

M-Mode Findings

  • In M-Mode echocardiography, patients may display:

    • Diastolic flutter of the anterior mitral valve (MV).

    • In cases of severe or acute aortic regurgitation, there can be a sudden increase in preload with the heart unable to compensate, causing left ventricular end-diastolic pressure (LVEDP) to exceed left atrial pressure; early closure of the MV and early opening of the AOV may also be noted.

    • Normal AOV flutter during systole (AOV open) may be contrasted with abnormal AOV flutter during diastole (AOV closed).

Doppler Considerations

  • Doppler assessment distinguishes between mild and severe aortic regurgitation:

    • The AR Doppler waveform can resemble that of mitral stenosis (MS), yet, conversely, a flatter waveform may indicate more severity in AR.

  • Measurement of pressure half time (P ½ T) and peak velocity in the context of Doppler analysis is critical:

    • Mild AR: Pressure half-time > 500 ms.

    • Moderate AR: Pressure half-time 200-500 ms.

    • Severe AR: Pressure half-time < 200 ms.

Additional Measurements

  • Flow reversal may occur in the descending aorta in circumstances of severe AR.

  • Color flow jet height assessments can indicate severity, with heights exceeding 60% classifying as severe AR.