Aortic valve disease





Aortic valve anatomy


CASE 3-1a


Normal trileaflet aortic valve



Fig 3.1


Intraoperative TEE in a short-axis view (left) shows the closed aortic valve and the orientation of the three cusps: noncoronary cusp (NCC), left coronary cusp (LCC), and right coronary cusp (RCC). The long-axis view (middle) shows the RCC and NCC; these are the cusps most often seen in the long-axis orientation, although occasionally the LCC is seen instead of the NCC. A 3D TEE image of an aortic valve (right) is demonstrated, and in real time, artifactual dropout is seen in the NCC. LA = left atrium, RA = right atrium, RV = right ventricle, RVOT = right ventricular outflow tract.



Fig 3.2


At surgery, in an image taken from the head of the operating table, a normal aortic valve is seen. The leaflets are thin and noncalcified. The commissural attachments to the sinotubular junction are visible.



Fig 3.3


This illustration shows the relationship between the normal aortic valve and associated structures as seen on TEE, and as seen in the OR from the patient’s head.



Fig 3.4


The deep transgastric (right top panel) and transgastric long-axis (left top panel) views of the aortic valve. These may be used for assessment of LVOT and transvalvular gradients. The bottom left panel shows a pulse wave Doppler tracing from the LVOT, and the bottom right panel shows a continuous wave Doppler through the aortic valve. There is little pressure gradient in this patient with a normal aortic valve. The two diastolic waves seen in the bottom right panel are the velocities of transmitral LV filling picked up by continuous wave Doppler.




CASE 3-1b


Bicuspid aortic valve


This 47-year-old male presented to the OR for mitral valve repair. Incidentally, a bicuspid aortic valve was detected; however, the systolic opening was normal with a normal antegrade flow velocity, and only mild aortic regurgitation was present.



Fig 3.5


Bicuspid aortic valve leaflet morphology. Schematic of BAV phenotypes, with this figure modified to correspond to a TEE midesophageal short-axis view. Small inset at top left depicts a normal aortic valve in the same orientation with right coronary cusp (RC), left coronary cusp (LC), noncoronary cusp (NC), right coronary artery (RCA), and left coronary artery (LCA). Valve phenotypes and their frequencies are shown: type 1, “fusion” between right and left coronary cusp; type 2, “fusion” between right and noncoronary cusp; type 3, “fusion” between left and noncoronary cusp. Top row, without a raphe; bottom row, with raphe. Type 3 with without a raphe was not seen in the study group. Numbers indicate the observed frequency in the authors’ cohort.

(Adapted with permission from Schaefer BM, Lewin MB, et al. The bicuspid aortic valve: An integrated phenotypic classification of leaflet morphology and aortic root shape. Heart 2008; 94:1634–1638.)



Fig 3.6


The left panel is a midesophageal short-axis view demonstrating a raphe at the fusion of the right and left coronary cusps. The asterisk indicates the left main coronary artery. The right panel is a midesophageal long-axis view demonstrating doming of the fused cusp (arrow) .



Fig 3.7


A 3D image of the bicuspid aortic valve from the ascending aortic perspective. The arrow indicates the raphe. In real time, Dropout is noted in the region of the anterior cusp.




CASE 3-1c


Unicuspid aortic valve


This 22-year-old male with a known unicuspid valve had mild and slightly progressive dyspnea on exertion, but was otherwise well. Serial echocardiographic imaging showed only mild regurgitation and moderate stenosis; however, because of progressive aortic root dilation (7 cm), he was referred for aortic valve and aortic root replacement.



Fig 3.8


The left panel is a midesophageal short-axis image of a unicuspid aortic valve with only a single postero-lateral attachment. The right panel midesophageal long-axis image of the unicuspid aortic valve reveals doming (arrow) in the anterior portion of the leaflet.



Fig 3.9


Intraoperative exposure of the unicuspid aortic valve demonstrates a thick leaflet. There is posterior attachment (white arrow) but no anterior attachment (black arrow) , which distinguishes it from a bicuspid valve.




CASE 3-1d


Quadricuspid aortic valve


This 39-year-old female had a repair of tetralogy of Fallot as an infant and was also known to have a quadricuspid aortic valve. She developed increasing dyspnea on exertion and fatigue. Noninvasive imaging showed severe pulmonic and aortic regurgitation with increasing right and left ventricular volumes so she was referred for aortic and pulmonic valve replacements.



Fig 3.10


3D TEE images from the aortic perspective show four aortic leaflets in systole (left) and diastole (center) . The addition of color Doppler (right) during diastole shows central regurgitation (arrow) .



Fig 3.11


In the left panel, a deep transgastric image shows thickened and poorly coapting leaflets (arrow) . In the right panel, a deep transgastric image with the addition of color Doppler shows aortic regurgitation.



Fig 3.12


Magnetic resonance imaging (MRI) of the aortic valve in a short-axis plane demonstrates the four leaflets. The explanted aortic valve leaflets are arranged to show the anatomic positions.




TABLE 3-1

Optimal TEE Views for Assessing the Aortic Valve

































Midesophageal short-axis aortic valve view Relative to the heart, the aortic valve plane is oblique. A 30- to 60-degree transducer angle is necessary to show symmetrical imaging of all valve cusps ( Fig 3.1 ).
During systole, cusp opening is normally unrestricted with the orifice shape identifying the number of cusps and planimetry of the edges determining the anatomic valve area.
During diastole, the three cusps of the normal valve close and color Doppler may be added to show AR.
Withdrawing the probe slightly in the esophagus reveals the left and right coronary ostia, whereas advancing the probe yields a short-axis view of the LV outflow tract.
Midesophageal long-axis aortic valve view Rotating the transducer angle to 120 to 140 degrees from the short-axis view with slight probe advancement shows a long-axis view of the LV outflow tract, aortic valve, and ascending aorta (see Fig 3.1 ).
The normal aortic valve leaflets appear as thin, parallel lines within the sinuses of Valsalva, the RCC is always anterior adjacent to the RV outflow tract, and the posterior cusp is either the LCC or, more often, the NCC.
Aortic annular dimensions are measured during systole, whereas color Doppler demonstrates the presence and site of disturbed flow related to obstruction or AR.
Transgastric view of aortic valve In the transgastric long-axis view at 90 to 120 degrees, the aortic valve is displayed on the right side of the screen. From a deep transgastric view at 0 degrees the image plane is angled anteriorly from the foreshortened four-chamber view to display the aortic valve ( Fig 3.4 ).
Although assessment of aortic valve anatomy may be imprecise in transgastric views, they may be useful for spectral Doppler alignment to measure optimal transvalvular velocity.
3D echocardiographic aortic valve imaging 3D TEE can assess valvular morphology in more detail compared with 2D TTE. In some cases, 3D planimetry of the anatomic aortic valve orifice may be helpful.

AR, aortic regurgitation; LCC, left coronary cusp; LV, left ventricular; NCC, noncoronary cusp; RCC, right coronary cusp; RV, right ventricular; TEE, transesophageal echocardiography; TTE, transthoracic echocardiography; 2D, two-dimensional. (From Oxorn D. Intraoperative Echocardiography, Practical Echocardiography Series, Elsevier, 2012.)




Aortic stenosis


CASE 3-2


Severe calcific aortic stenosis


A 71-year-old man presented to a local ED with shortness of breath and dyspnea on exertion. His symptoms had progressed over the past 6 months and now were consistent with NYHA class III. TTE revealed severe aortic stenosis (AS) with an aortic velocity of 4.1 m/s, valve area of 0.9 cm 2 by continuity equation, a significantly dilated LV, and an ejection fraction of 35%. He was sent for surgical consultation for potential aortic valve replacement.



Fig 3.13


Intraoperative TEE in a midesophageal short-axis view, obtained with rotation of the image plane to 71 degrees and slight flexion of the probe, shows a heavily calcified trileaflet aortic valve with reduced systolic opening. Although this short-axis image is correctly aligned, planimetry of the valve area is not possible because of shadowing and reverberations from the valve calcium and the irregular shape of the orifice. In addition, the stenotic valve often has a complex 3D shape with a nonplanar orifice that may not be visualized in a single 2D-image plane. With rotation of the image plane to 150 degrees and leftward turning of the probe, a long-axis view of the aortic valve, aortic root, and left ventricular outflow tract is obtained. This long-axis view shows severe leaflet calcification with reduced systolic motion.



Fig 3.14


Color Doppler flow imaging in the long and short axis views shows a small amount of aortic regurgitation (arrows) .



Fig 3.15


In this 3D image of the aortic valve, from the ascending aortic perspective, the leaflets are noted to be extremely thick, with minimal opening in systole and an irregular-shaped orifice but no commissural fusion.



Fig 3.16


Multiplanar reconstruction of the aortic valve allows measurement of the LVOT diameter at 2.3 cm, area at 3.71 cm 2 , and circumference at 7.18 cm.



Fig 3.17


Continuous wave Doppler obtained in the deep transgastric position of the LVOT (left panel) and the aortic valve (right panel) . The maximum velocity is 3.9 m/sec. The mean gradient (40 mm Hg) is calculated by tracing the velocity curve with averaging of the instantaneous pressure gradients over the systolic ejection period. Although this velocity and mean gradient might be underestimated because of a nonparallel intercept angle, both are consistent with severe aortic stenosis.



Fig 3.18


At surgery, the valve was heavily calcified and stenotic. The leaflets were nonpliable as demonstrated by the surgeon, who is grasping the noncoronary cusp. The valve was replaced with a 23-mm tissue valve.




Comments


In current clinical practice, aortic stenosis is best evaluated by transthoracic echocardiography. The standard evaluation of stenosis severity is based on:



  • 1.

    2D or 3D imaging of valve anatomy, the extent of calcification, and leaflet motion.


  • 2.

    Continuous wave Doppler measurement of the antegrade velocity across the valve (the aortic “jet”) with calculation of maximum and mean pressure gradients.


  • 3.

    Calculation of valve area using the continuity equation.



On 2D imaging the number of valve leaflets is identified, although severe calcification of a bicuspid valve may be indistinguishable from a severely calcified trileaflet valve. TEE 3D imaging may provide better visualization of the number of valve leaflets and degree of valve opening when TTE imaging is suboptimal. Accurate planimetry of valve area is possible on 3D TEE imaging in many cases.


The aortic jet velocity is recorded from the acoustic window that shows the highest velocity signal. This is especially important, as accurate velocity data (and calculated pressure gradients) depend on a parallel intercept angle between the ultrasound beam and the high-velocity jet. Because the 3D direction of the jet is unpredictable, in practice the jet velocity is recorded from multiple windows with careful patient positioning to ensure that a parallel intercept angle is obtained. The most useful windows are apical and suprasternal, but in some cases the highest velocity is recorded from a subcostal or high right parasternal position. The most common error in assessment of aortic stenosis severity is failure to obtain a parallel intercept angle, which results in underestimation of stenosis severity. TEE transgastric views may allow measurement of aortic velocity but the possibility of underestimation resulting from a nonparallel intercept angle always should be considered.


Transaortic pressure gradients (∆P in mmHg) are calculated with the simplified Bernoulli equation using the aortic jet velocity (V AS ) as:


<SPAN role=presentation tabIndex=0 id=MathJax-Element-1-Frame class=MathJax style="POSITION: relative" data-mathml='∆P = 4(V)2′>∆P = 4(V)2∆P = 4(V)2
∆P = 4(V )2


The simplified Bernoulli equation assumes that the proximal velocity can be ignored, a reasonable assumption when velocity is <1 m/s because squaring a number <1 makes it even smaller. The maximum instantaneous gradient is calculated from the maximum velocity; the mean gradient is calculated by averaging the instantaneous gradients over the ejection period, or can be approximated by the formula:


<SPAN role=presentation tabIndex=0 id=MathJax-Element-2-Frame class=MathJax style="POSITION: relative" data-mathml='∆Pmean= 2.4(V)2′>∆Pmean= 2.4(V)2∆Pmean= 2.4(V)2
∆Pmean = 2.4(V )2


The physiologic cross-sectional area of flow across the stenotic valve is calculated using the continuity equation, based on the principle that the stroke volume (SV) proximal to and in the orifice must be equal. Volume flow rate at any site equals the 2D cross-sectional area × the velocity time integral of flow (mean velocity × ejection period) through that site.


Stroke volume in the left ventricular outflow tract (LVOT) and in the narrowed aortic stenotic (AS) orifice are equal:


<SPAN role=presentation tabIndex=0 id=MathJax-Element-3-Frame class=MathJax style="POSITION: relative" data-mathml='SV= SV’>SV= SVSV= SV
SV = SV


Thus,


<SPAN role=presentation tabIndex=0 id=MathJax-Element-4-Frame class=MathJax style="POSITION: relative" data-mathml='CSA× VTI= AVA × VTI’>CSA× VTI= AVA × VTICSA× VTI= AVA × VTI
CSA × VTI = AVA × VTI


Solving for aortic valve area (AVA):


<SPAN role=presentation tabIndex=0 id=MathJax-Element-5-Frame class=MathJax style="POSITION: relative" data-mathml='AVA = (CSA× VTI)/VTI’>AVA = (CSA× VTI)/VTIAVA = (CSA× VTI)/VTI
AVA = (CSA × VTI )/VTI


In clinical practice, this equation is often simplified by using maximum velocities, instead of velocity time integrals:


<SPAN role=presentation tabIndex=0 id=MathJax-Element-6-Frame class=MathJax style="POSITION: relative" data-mathml='AVA = (CSA× V)/V’>AVA = (CSA× V)/VAVA = (CSA× V)/V
AVA = (CSA × V )/V

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Jan 2, 2020 | Posted by in CARDIOLOGY | Comments Off on Aortic valve disease

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