Comprehensive assessment of the aortic valve in critically ill patients for the non-cardiologist. Part I: Aortic stenosis of the native valve

Figures

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  FIGURE 1. Normal aortic valve anatomy on echocardiography. Diastolic (a) and a systolic (B) frame of a normal aortic valve (AV) from a transthoracic echocardiography short axis view (57°). The AV consists of the valve annulus and 3 leaflets. The left main coronary artery and right coronary artery originate from the aorta above the left coronary cusp (LCC) and the right coronary cusp (RCC), respectively. The interatrial septum (IAS) is adjacent to the non-coronary cusp (NCC). LA – left atrium, RA – right atrium, RV – right ventricle, TV – tricuspid valve, PV – pulmonary valve, PA – pulmonary artery

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  FIGURE 2. Rheumatic left-sided valve disease. Example of rheumatic valve disease with involvement of the aortic valve (AV) and mitral valve (MV). Panel a shows a systolic frame. Note the commissural fusion from the annulus of the AV. Panel B demonstrates involvement of both left sided heart valves. The anterior mitral valve leaflet has the typical hockey morphology. Panel C shows diastolic atrial convergent flow before the narrowed mitral valve area. Note the post-stenotic turbulence in the LV. This panel shows a typical flow colour flow mapping (CFM) pattern of mitral stenosis. Panel d demonstrates the continuous wave (CW) Doppler signal across the AV, with a peak velocity of 405 cm s-1, demonstrating severe aortic stenosis. Panel e shows mild aortic regurgitation. Panel f shows a 3D echo image of the MV. Note the typical fish mouth opening of the MV. Panel g shows the transmitral CW signal, consistent with moderate MS (mean gradient 7.5 mm Hg)

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  FIGURE 3. Bicuspid aortic valve. Systolic transthoracic echocardiography frame of a sclerotic bicuspid aortic valve. Note the commissural fusion of left and right coronary cusp

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  FIGURE 4. Simplified Bernoulli equation. Description of the simplification of the Bernoulli equation to the equation that is used in clinical medicine. See text

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  FIGURE 5. Continuous wave (CW) measurement of mean and peak gradient across the aortic valve. CW Doppler measurement across the aortic valve. The peak velocity is 466 cm. According to the simplified Bernoulli equation: peak pressure = 4 × (peak velocity m s-1)2 = 4 × (4.66)2 = 86.86 mm Hg. By contouring the aortic regurgitation CW signal, the velocity time integral across the aortic valve is determined, allowing the software to calculate the mean pressure gradient. In this case the aortic stenosis mean gradient is 52.75 mm Hg

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  FIGURE 6. Echocardiographic assessment of stroke volume (SV). Required echocardiography measurements to calculate SV. Flow is the product of velocity and area. Panel a shows the pulsed wave echo Doppler measurement of the velocity time integral in the LVOT (VTILVOT). Panel B shows the measurement of LVOT diameter. LVOT surface area = π (LVOTd/2)2. SV = π (LVOTd/2)2 × VTILVOT = 0.785 × (LVOTd)2 × VTILVOT

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  FIGURE 7. Calculation of aortic valve area (AVA), using the continuity equation. Assessment of AVA by the continuity equation. The left ventricular outflow tract (LVOT) flow equals the flow through the AVA. Flow is the product of velocity (VTI – velocity time integral) times surface area (CSA – circumferential surface area). To calculate AVA, measurement of LVOT diameter, VTILVOT and VTIAVA is needed. D – diameter

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  FIGURE 8. M-mode through the left ventricle (LV) from the parasternal long axis view. M-mode from the parasternal long axis view. Note the concentric hypertrophy (left ventricular end-diastolic wall thickness [LVIDd] of 1.6 mm) of the left ventricle and the preserved LV systolic function

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  FIGURE 9. M-mode through the aortic root and left atrium. M-mode through the aortic root, obtained from the parasternal long axis vies. Note the reduced aortic valve opening box in aortic stenosis and the pronounced aortic valve sclerosis on the scout view

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  FIGURE 10. Grading of diastolic function. Transmitral echo Doppler signal (row a) and medial mitral valve annular tissue Doppler e’ (row B). Column 1 shows an example of a normal diastolic flow pattern. Column 2: diastolic disfunction grade I (delayed relaxation). Column 3: pseudonormal diastolic flow pattern (diastolic disfunction grade II). Column 4: restrictive diastolic filling (diastolic disfunction grade III–IV). Notably, e’ decreases with increasing diastolic disfunction, while E/A ratio is decreased in diastolic disfunction grade I. From diastolic disfunction grade II, E/A increases with increasing diastolic disfunction

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  FIGURE 11. Grading of diastolic function. Summary of grading of diastolic function, based on the echo Doppler mitral inflow pattern and the medial mitral annular tissue Doppler e’

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  FIGURE 12. Transthoracic echocardiography (5-CH view) imaging of dynamic left ventricular outflow tract obstruction. Panel a shows the continuous wave (CW) Doppler pattern of a dynamic left ventricular outflow tract (LVOT) obstruction due to dobutamine stimulation. Note the typical dagger shape morphology due to the late systolic peak flow. This CW flow pattern differs from the aortic stenosis CW signal. Panel B shows a systolic frame during low-dose dobutamine stress echo at a dose of 20 mg kg-1 min-1. The thickened proximal interventricular septum causes flow acceleration and turbulence in the LVOT