Valvular Stenosis

Aortic Stenosis

Step-by-Step Approach

Step 1: Determine the Etiology of Stenosis

▪ Parasternal two-dimensional (2D) images of the valve in long- and short-axis views (Fig. 11.1)
▪ Number of leaflets, mobility, thickness, and calcification
▪ Level of obstruction: Valvular, subvalvular, or supravalvular
▪ Three-dimensional (3D) transthoracic echocardiography (TTE) or transesophageal echocardiography (TEE) imaging is helpful for better definition of valve anatomy, particularly diagnosis of a unicuspid or bicuspid valve (Fig. 11.2)

Key Points

□ Calcific changes of a trileaflet valve usually start in the central part of the leaflets, resulting in a three-pointed star-shaped orifice.
□ Rheumatic aortic valve disease affects the commissures and leaflet edges, with a triangular-shaped orifice, and is accompanied by rheumatic mitral valve changes.
□ A bicuspid valve may appear trileaflet in diastole due to a raphe in one leaflet; the number of leaflets must be visualized when the valve is open in systole, taking care to identify each commissure, and the points where the leaflets attach to the aortic wall.
□ 3D imaging is recommended when available.
Fig. 11.1 Etiology of aortic valve stenosis.(A) With calcific valve disease, there is increased echogenicity of the leaflets, due to calcification and thickening, with reduced systolic opening of the leaflets. (B) In a patient with a congenitally bicuspid, noncalcified valve, the long-axis view shows thin leaflets with reduced systolic opening due to doming of the leaflets in systole (arrow), as seen by the curve at the tips of the leaflets. Ao, Aorta.
Fig. 11.2 3D TEE imaging of a bicuspid aortic valve.A 3D view of the aortic valve from the aortic side of the valve clearly shows two leaflets, with no raphe, and two commissures in systole.
Fig. 11.3 Aortic jet velocity recorded with CW Doppler.An optimal signal-to-noise ratio is obtained using a small dedicated transducer; the small footprint of this transducer also allows optimal positioning and angulation to align the ultrasound beam parallel to the direction of the stenotic jet. In this example, the scale has been adjusted to show both aortic stenosis (AS) and regurgitation. The aortic jet should show a denser signal around the edge and a smooth velocity curve. The difficulty in identifying the maximum velocity is seen in this example, with fuzzy linear signals at peak velocity that are due to the transit time effect. Maximum velocity is measured at the edge of the denser signal, as shown by the arrow.
□ Subvalvular or supravalvular stenosis is distinguished from valvular stenosis based on the site of the increase in velocity and on the anatomy of the outflow tract.

Step 2: Evaluate Stenosis Severity

Aortic Jet Velocity (Fig. 11.3)

▪ Continuous-wave (CW) Doppler gray-scale spectral recording of aortic jet velocity (Tables 11.1 and 11.2)

TABLE 11.1

Other High-Velocity Systolic Jets That May Be Mistaken for Aortic Stenosis
Subaortic obstruction (fixed or dynamic) Mitral regurgitation Tricuspid regurgitation Ventricular septal defect Pulmonic or branch pulmonary artery stenosis Peripheral vascular stenosis (e.g., subclavian artery)

From Otto CM: Textbook of clinical echocardiography, ed 6, Philadelphia, 2018, Elsevier.

Key Points

□ Use multiple acoustic windows (apical, suprasternal, right parasternal) with careful patient positioning and transducer angulation to avoid underestimation of velocity.
□ A dedicated small CW Doppler transducer provides the optimal signal-to-noise ratio and allows more precise angulation of the transducer.
□ Decrease gain, increase wall filters, and adjust the baseline and scale to optimize identification of the maximum velocity.
□ Use the gray-scale spectral displays, because with some color displays the signal-to-noise ratio is poor and the edge of the spectral envelope may be blurred, leading to overestimation of velocity.
□ A smooth velocity curve with a dense outer edge and clear maximum velocity should be recorded; fine lines at the peak of the curve are due to the transit time effect and are not included in measurements.
□ Color Doppler is usually not helpful for jet direction, because the jet is short with poststenotic turbulence and because the elevational plane is not visualized.

Mean Gradient

▪ Transaortic maximum pressure gradient (ΔP) is calculated from velocity (v) using the Bernoulli equation (Fig. 11.4) as:

Δ P = 4 v max 2

(11.1)

Key Points

□ When proximal velocity (V_prox) is greater than 1.0 m/s, it should be included in the Bernoulli equation, so that:

Δ P = 4 ( v max 2 − v prox 2 )

(11.2)

□ Mean gradient is calculated by tracing the velocity curve and averaging instantaneous gradients over the systolic ejection period (Fig. 11.5).
□ Any underestimation of aortic velocity results in an even greater underestimation in gradients.

TABLE 11.2

Categories of Stenosis Severity
Aortic Stenosis Severity	Valve Anatomy and Hemodynamics	LV Geometry and Function
At risk of AS	Bicuspid valve or aortic sclerosis, V_max <2 m/s	Normal
Progressive AS	Mild AS: V_max 2.0-2.9 m/s or mean ΔP <20 mm HgModerate AS: V_max 3.0-3.9 m/s or mean ΔP 20-39 mm Hg	Mild LVH and diastolic dysfunction may be present.
Severe AS	Severe leaflet calcification with reduced systolic motion or congenital ASV_max ≥ 4 m/s, orMean ΔP ≥ 40 mm HgTypically AVA ≤ 1.0 cm²	LVH, diastolic dysfunction, systolic function usually normal.Patient may be asymptomatic or symptomatic.
Low-output low-gradient severe AS with low EF	Severely calcified aortic valveV_max <4 m/s (rest)AVA ≤1.0 cm²	LV EF <50%DSE − V_max ≥ 4 m/s with AVA ≤1.0 cm²
Low-output low-gradient severe AS with normal EF	Severely calcified aortic valve.V_max <4 m/s (rest) AVA ≤1.0 cm²Indexed AVA ≤0.6 cm²/m²SV index <35 mL/m²Measured with normal BP	Small LV chamber with increased relative wall thickness.Normal EFRestrictive diastolic filling

Categories of Stenosis Severity
Mitral Stenosis Severity	Hemodynamics	Associated Findings
At risk of MS	Rheumatic leaflet changes without stenosis
Progressive MS	Rheumatic valve diseasePressure half time <150 msMVA >1.5 cm²	PA systolic pressure <30 mm HgMild LA enlargement
Severe MS	MVA ≤1.5 cm²	PA systolic pressure >30 mm HgModerate LA enlargement
Very severe MS	MVA ≤1.0 cm²	PA systolic pressure >30 mm HgModerate-severe LA enlargement

Continuity Equation Valve Area (Fig. 11.6)

□ Aortic valve area (AVA) is calculated as:

AVA = ( CSA LVOT × VTI LVOT ) / VTI Ao

(11.3)

▪ The simplified continuity equation, which uses maximum velocities instead of velocity-time integrals (VTIs), also can be used:

AVA = CSA LVOT × ( V LVOT ) / V Ao

(11.4)

Key Points

□ Left ventricular outflow tract (LVOT) diameter is measured in the parasternal long-axis view in mid-systole using zoom mode and adjusting gain setting to optimize the blood-tissue interface (Fig. 11.7).
□ Diameter (D) is measured at the basal insertion of the aortic leaflets from inner edge to inner edge of the aortic annulus. Calculate the circular cross-sectional area:

CSA = π ( D 2 ) 2

(11.5)

□ LVOT diameter is useful for valve area calculation but should not be used for sizing of transcatheter valves because of the complex anatomy of the outflow tract and valve. CT imaging of the aortic annulus is preferred for this indication.
Fig. 11.5 Mean transaortic pressure gradient.For accurate measurement of aortic velocity and mean gradient, the baseline is moved and the scale is adjusted so that the stenotic signal fills the vertical range of the display. The horizontal axis or “sweep speed” is adjusted to 100 mm/s to allow accurate measurement. The Doppler curve is traced along the outer edge of the dark signal to obtain the velocity-time integral (VTI). The instantaneous pressure gradients over the systolic ejection period are averaged by the analysis package to provide the mean systolic gradient. Note that the mean gradient is not calculated by using the mean velocity in the Bernoulli equation.
Fig. 11.6 Continuity equation.The basic principle is that the volume of flow proximal to and in the narrowed valve must be equal. Flow for one cardiac cycle in the left ventricular outflow tract (LVOT) is shown as a cylinder with a diameter equal to LVOT diameter. Length is equal to the velocity-time integral (VTI) of LVOT flow (because the integral of velocity over time is distance, like traveling in a car). The flow through the orifice is shown as a cylinder with the cross-section equal to aortic valve area (AVA) and length equal to the VTI of the aortic stenosis (AS) jet. Because the volume of both cylinders is the same, the equation is solved for AVA as shown.
Fig. 11.7 Transaortic volume flow rate.(A) Left ventricular outflow tract diameter (LVOTd) is measured in a parasternal long-axis view in mid-systole from the inner edge of the septum to the inner edge of the anterior mitral leaflet, immediately adjacent to the aortic valve leaflets (markers). A magnified image allows more accurate measurement, and typically several beats are measured to ensure a reproducible value. A typical outflow tract diameter is 2.2 to 2.6 cm in adult men and 2.0 to 2.4 cm in adult women. (B) Although LVOTd is measured from the parasternal window, to provide axial resolution of the tissue-blood interfaces, with ultrasound imaging, LVOT velocity is recorded from the apical window to allow parallel alignment between the ultrasound beam and flow direction. Pulsed Doppler is used to measure the velocity signal on the ventricular side of the aortic valve, in an anteriorly angulated 4-chamber view (as shown here) or in a long-axis view. The sample volume length or gate is adjusted to 2 to 3 mm and the sample volume is positioned as close to the valve as possible (often the closing click is seen), avoiding the small area of flow acceleration immediately adjacent to the stenotic orifice. The sample volume position should correspond to the site where LVOT diameter was measured. The velocity range and baseline are adjusted so the signal fits but fills the scale, using a fast (100 to 150 mm/s) horizontal axis scale. A smooth curve with a dense band of velocities (“envelope of flow”) with a well-defined peak velocity should be seen. The midpoint of the spectral broadening at peak velocity is measured. Ao, Aorta.
□ LVOT velocity is recorded with pulsed Doppler from the apical window with the sample volume positioned just apically from the flow acceleration into the valve. An aortic closing click on the spectral tracing indicates correct sample volume positioning.
□ Move the baseline, adjust the velocity scale, and use an expanded time scale for accurate measurements.
□ Trace the modal systolic velocity (VTI_LVOT) and measure peak velocity (V_LVOT).
□ If LVOT diameter cannot be accurately measured, calculate the aortic valve index, which is the ratio of LVOT to aortic jet velocity:

Aortic valve ratio = V Lvot / V Ao

(11.6)

Planimetry of Aortic Valve Area

▪ Planimetry of the valve area can be helpful in selected cases with excellent images, but caution is needed due to reverberations and shadowing from leaflet calcification.
▪ With calcific aortic stenosis (AS), the systolic orifice is not planar, so measurement from 2D or 3D images is not recommended.
▪ The orifice of a unicuspid, bicuspid, or rheumatic valve may be identified using 3D TEE imaging, allowing direct measurement of valve opening (Fig. 11.8).

Key Points

□ A full-volume 3D image is acquired, focused on aortic valve anatomy.
□ The valve area measurement is made by adjusting the three image planes to show the valve orifice in systole.
□ With congenital valve disease, the leaflets “dome” is systole with the valve orifice at the tip of the leaflets; valve area will be overestimated if the tomographic plane is not optimally adjusted.
□ Gains are adjusted to show the white–black interface to trace the valve area.
□ Accuracy may be limited with extensive calcification due to shadowing and reverberation artifacts.

Step 3: Evaluate Aortic Regurgitation and Ascending Aorta

▪ If regurgitation is significant (vena contracta ≥3 mm), evaluate as detailed in Chapter 12.
▪ Dilation of the ascending aorta may accompany AS, particularly with a bicuspid valve.

Key Points

□ Most patients with AS have some degree (usually mild) of regurgitation.
□ With combined moderate stenosis and regurgitation, quantitation of both lesions is needed.
□ The end-diastolic diameter of the aorta is measured at the sinuses, sinotubular junction, and mid-ascending aorta when aortic valve disease is present (see Chapter 16).

Step 4: Evaluate the Consequences of Chronic LV Pressure Overload

▪ Measure LV size and wall thickness and calculate ejection fraction as detailed in Chapter 6.
▪ Evaluate LV diastolic function as detailed in Chapter 7.
▪ Evaluate coexisting mitral regurgitation (if vena contracta ≥3 mm) as detailed in Chapter 12.
▪ Estimate pulmonary pressures as detailed in Chapter 6.

TABLE 11.3

Possible Causes of Discrepancies in Measures of Aortic Stenosis Severity
Severe AS by Velocity or Gradient but Not by Valve Area (AS Velocity >4 m/s and AVA >1.0 cm²)
LVOT diameter overestimated
LVOT velocity recorded too close to valve
High transaortic flow rate due to: • Moderate to severe aortic regurgitation • High output state • Large body size
Severe AS by Valve Area But Not by Velocity or Gradient (AS Velocity ≤4 m/s and AVA ≤1.0 cm²)
LVOT diameter underestimated
LVOT velocity recorded too far from valve
Small body size
Low transaortic flow volume due to: • Low ejection fraction • Small ventricular chamber • Moderate to severe mitral regurgitation • Moderate to severe mitral stenosis

From Otto CM: Textbook of clinical echocardiography, ed 6, Philadelphia, 2018, Elsevier.

Key Points

□ AS typically results in concentric LV hypertrophy.
□ Systolic function and ejection fraction remain normal in most patients but, occasionally, systolic dysfunction is identified in an asymptomatic patient.
□ Diastolic dysfunction, usually impaired relaxation, is common.
□ Pulmonary pressures may be elevated with longstanding severe AS.

Step 5: Additional Evaluation for Low-Output Low-Gradient Aortic Stenosis

▪ Additional evaluation may be needed when clinical evaluation suggests AS may be more severe than indicated by standard measures of stenosis severity (Table 11.3).
▪ With a calcified aortic valve and a valve area ≤1.0 cm² but a velocity <4 m/s in conjunction with an LV ejection fraction less than 50%, dobutamine stress echo should be considered.
▪ With a calcified aortic valve and a valve area ≤1.0 cm² but a velocity <4 m/s and a normal ejection fraction, an integrative approach to evaluation is needed.

Key Points

□ The degree of valve calcification (mild, moderate, severe) is a simple, important parameter that is predictive of clinical outcome.
□ The aortic valve index (the dimensionless ratio of outflow tract to aortic jet velocity) provides a simple index of stenosis severity (normal, 1.0; mild, 0.5; severe, 0.25).
Fig. 11.9 Effect of variable heart rate on aortic velocity.When the cardiac rhythm is irregular, the velocity (and pressure gradient) across a stenotic valve varies with the length of the R-R interval because of an increased stroke volume (SV) with a longer diastolic filling period. This example shows the variation in aortic jet velocity (at a slow sweep speed to include multiple beats) in a patient in atrial fibrillation. Ideally, heart rate should be controlled before evaluation of stenosis severity is performed. Several beats are then averaged for each measurement. Signal quality in this example is suboptimal so additional efforts to improve patient and/or transducer positioning are needed.
□ Blood pressure should be recorded at the time of the velocity data acquisition; stenosis severity may be underestimated in hypertensive patients, so measurement should be repeated after effective treatment of hypertension.
□ With atrial fibrillation, several beats should be averaged for each measurement (Fig. 11.9).
□ With low output AS and a low LV ejection fraction, a velocity ≥4 m/s with an AVA ≤1.0 cm² on dobutamine stress echocardiography is consistent with severe AS (Fig. 11.10).

Mitral Stenosis

Step-by-Step Approach

Step 1: Evaluate Mitral Valve Morphology

▪ Use long- and short-axis views of the mitral valve to demonstrate the typical findings of rheumatic valve disease (Fig. 11.11):
1. ▪ Commissural fusion resulting in diastolic doming
2. ▪ Chordal shortening and fusion
▪ Evaluate mitral valve leaflet mobility, thickening, calcification, and subvalvular disease.
▪ Use 3D imaging for better evaluation of the symmetry of commissural fusion (Fig. 11.12).

Key Points

□ Rheumatic valve disease is the most common cause of mitral stenosis.
□ Rarely, severe mitral annular calcification encroaches on the mitral orifice, but calcific stenosis is rarely severe.
Fig. 11.10 Low-output low-gradient aortic stenosis (AS).Changes in aortic valve opening and Doppler flows with dobutamine stress echocardiography for low-output low-gradient AS. The baseline data show a hypothetical patient with an ejection fraction (EF) of 35% and limited aortic valve systolic opening, an aortic jet velocity (AS-jet) of 3.5 m/s, and aortic valve area (AVA) of 0.9 cm². If true, severe AS is present (middle panel), as EF increases from 35% to 45%, transaortic flow rate increases but aortic opening is fixed, resulting in a marked increase in aortic velocity (and pressure gradient) with no change in valve area. In a patient with the same baseline data but “pseudo-severe AS,” the increase in EF and transaortic stroke volume (SV) “push” the aortic leaflets to open more so there is a smaller increase in aortic velocity in association with an increase in AVA. Current diagnostic testing relies on Doppler data with dobutamine stress testing, because direct imaging of valve anatomy is not adequate for visualization of the exact systolic orifice. VTI, Velocity-time integral.
From Otto CM, Owens DS: Stress testing for structural heart disease. In Gillam LD, Otto CM: Advanced approaches in echocardiography: practical echocardiography series, Philadelphia, 2013, Elsevier.

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Apr 23, 2020 | Posted by admin in CARDIOLOGY | Comments Off

Key Points

Aortic Jet Velocity (Fig. 11.3)

Key Points

Key Points

Key Points

Key Points

Key Points

Key Points

Key Points

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Thoracic Key

Fastest Thoracic Insight Engine

Valvular Stenosis

Valvular Stenosis

Aortic Stenosis

Step-by-Step Approach

Step 1: Determine the Etiology of Stenosis

Step 2: Evaluate Stenosis Severity

Mean Gradient

Continuity Equation Valve Area (Fig. 11.6)

Key Points

Planimetry of Aortic Valve Area

Step 3: Evaluate Aortic Regurgitation and Ascending Aorta

Step 4: Evaluate the Consequences of Chronic LV Pressure Overload

Step 5: Additional Evaluation for Low-Output Low-Gradient Aortic Stenosis

Mitral Stenosis

Step-by-Step Approach

Step 1: Evaluate Mitral Valve Morphology

Full access? Get Clinical Tree

Thoracic Key

Fastest Thoracic Insight Engine

Valvular Stenosis

Aortic Stenosis

Step-by-Step Approach

Step 1: Determine the Etiology of Stenosis

Key Points

Step 2: Evaluate Stenosis Severity

Aortic Jet Velocity (Fig. 11.3)

Key Points

Mean Gradient

Key Points

Continuity Equation Valve Area (Fig. 11.6)

Key Points

Planimetry of Aortic Valve Area

Key Points

Step 3: Evaluate Aortic Regurgitation and Ascending Aorta

Key Points

Step 4: Evaluate the Consequences of Chronic LV Pressure Overload

Key Points

Step 5: Additional Evaluation for Low-Output Low-Gradient Aortic Stenosis

Key Points

Mitral Stenosis

Step-by-Step Approach

Step 1: Evaluate Mitral Valve Morphology

Key Points

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