12 Aortic valve disease

Question 1

Which AV cusps are visualised in which views?

Answer 1

In the PLAX view and the A5C view, the RCC and NCC are visualised.

In the PSAX view, the RCC, LCC and NCC are visualised.

Question 2

What are the causes of AS?

Answer 2

Degenerative, BAV, RHD, IE and sub-valvular or supra-valvular obstruction.

In degeneration, lipid infiltration and inflammation cause fibrosis, thickening and calcification of the AV, starting at the base and spreading to the tips.

In patients with a BAV, AV degeneration occurs at a younger age.

In rheumatic AS, bacterial infection causes inflammation. This causes fibrosis and scarring, and, therefore, thickening, calcification and commissural fusion, of the AV. This restricts AV mobility.

In IE, the bacterial infection causes vegetations on the AV which damage the cusps.

Sub-valvular and Supra-valvular AS
Sub-valvular AS is due to a fixed obstruction in the LVOT (fibromuscular structure) or a mobile obstruction (HOCM). Supra-valvular AS is due to a fixed obstruction in the ascending aorta due to a narrowing or membrane.

Question 3

What are the types of BAV?

Answer 3

Type 0 (no raphe), type 1 (1 raphe) and type 3 (3 raphes).

Question 4

What are the TTE characteristics of AS?

Answer 4

Thickened and calcified AV cusps, restricted AV mobility, decreased AVA, increased AV Vmax, increased AV PG and/or MS.

In degenerative AS, there is calcification at the base of the cusps.

In BAV, there is an asymmetric closure line.

In rheumatic AS, there is commisural fusion.

In IE, there are vegetations.

In sub-valvular and supra-valvular AS, the AV is normal but the LVOT is obstructed.

Question 5

What are the symptoms and signs of AS.

Answer 5

Angina, dizziness and/or syncope on exertion and/or dyspnoea.

A slow rising pulse, low systolic blood pressure and narrow pulse pressure, sustained apex beat (due to LVH), soft aortic component to S2 (A2), ejection click, ejection systolic murmur and/or signs of HF (severe AS).

Question 6

What are the BSE values for AS assessment?

Answer 6

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Question 7

How are the maximum pressure gradient and mean pressure gradient calculated?

Answer 7

The maximum PG is estimated using the AV Vmax +/- the LVOT Vmax.

If the LVOT Vmax is <1m/s, the simplified Bernoulli equation is used, and, if the LVOT Vmax is >1cm/s, the full Bernoulli equation is used.
∆Pmax = 4 x V2
∆P max = 4 x (V2/2 – V2/1)

The mean PG is estimated using the maximum PG.
∆P mean = (∆P max )/1.45 + 2mmHg

Question 8

How is the AVA calculated?

Answer 8

Continuity equation

CSA LVOT = 0.785 x (LVOT diameter)2
EOA AV = (CSA LVOT x VTI LVOT) / (VTI AV)

Planimetry

Question 9

How is the velocity ratio calculated?

Answer 9

VR = (Vmax LVOT) / (Vmax AV)

Question 10

What are the effects of AS on chamber size and chamber function?

Answer 10

LV concentric hypertrophy, LV diastolic dysfunction, LV dilatation (chronically), LV systolic dysfunction (chronically), LA dilatation, decreased LA strain, pulmonary hypertension and pulmonary congestion, RV hypertrophy, dilatation and dysfunction (chronically).

AS causes LV pressure overload which causes LV concentric hypertrophy (increased LV wall thickness but normal LV mass). In the early stages, LV concentric hypertrophy maintains CO, but, in the late stages, it increases LV stiffness which impairs LV relaxation which causes LV diastolic dysfunction. This increases LV filling pressures which causes LA dilatation, decreasing LA strain and increasing the risk of AF. This causes pulmonary hypertension and the symptoms of pulmonary congestion. Chronically, this also causes RV hypertrophy, dilatation and dysfunction, causing right sided HF and TR. Chronically, LV pressure overload causes LV dilatation which causes LV systolic dysfunction. LV concentric hypertrophy also increases myocardial oxygen demand which causes ischemia which impairs LV function.

Question 11

What is low flow low gradient AS and what are the two types of low flow low gradient AS?

Answer 11

LF LG AS is characterised by a decreased AVA (<1cm2 and/or <0.6cm2/m2) but decreased maximum transaortic velocities (<4m/s) and mean transaortic PGs (<40mmHg) and decreased SVI (<35ml/m2).

Classical LF LG AS is characterised by a decreased LVEF (<50%). In classical LF LG AS, the decreased LV systolic function decreases SV which decreases CO.

Paradoxical LF LG AS is characterised by a normal LVEF (>50%). In paradoxical LF LG AS, other factors, including decreased LV size, LV hypertrophy or LV diastolic dysfunction decrease the SV which decreases the CO.

Question 12

What are the non-standard views used to assess AS?

Answer 12

The right parasternal view, the subcostal short axis view and the suprasternal view.

Question 13

What is the effect of flow on velocity?

Answer 13

Transvalvular flow rate is affected by HR, SV and CO. The transvalvular velocity is directly proportional to the flow rate (SV) and inversely proportional to the area. Therefore, in AS, the area is decreased so the velocity increases to maintain the SV and CO.

In high flow states (e.g. exercise, pregnancy and AR), the velocity increases so the pressure gradients and AS severity are overestimated.

In low flow states (e.g. HFrEF), the velocity decreases so the pressure gradients and AS severity are underestimated.

Question 14

What are the causes of discordant parameters in AS?

Answer 14

In patients with normal systolic function with non-severe AS (EOA <1cm², Vmax <4m/s, peak PG <40mmHg) there may be a low flow state due to a small LV size or hypertension.

In patients with normal systolic function with non-severe AS (EOA >1cm², Vmax >4m/s, peak PG >40mmHg) there may be a high flow state due to coexistent AR or a high CO.

In patients with normal systolic function with true severe AS (false high EOA >1cm², Vmax >4m/s, peak PG >40mmHg) the patient may be big with a high BMI. An EOA indexed of <0.6cm² indicates true severe AS.

In patients with normal systolic function with non-severe AS (false low EOA >1cm², Vmax >4m/s, peak PG >40mmHg) the patient may be small with a low BMI. An EOA indexed of <0.6cm² indicates true severe AS.

In patients with impaired systolic function with true severe AS (EOA <1cm²) the decreased velocities and gradients are due to a low CO.

In patients with systolic dysfunction with non-severe (functional) AS (measured EOA <1cm² but true EOA >1cm²) the EOA is underestimated due a low CO.

Question 15

How is SVI and Zva used to differentiate true severe AS and pseudo severe AS?

Answer 15

In patients with a low SV (low output state) or hypertension (increased arterial impedance), AS severity is underestimated. Therefore, SVI and Zva are used to differentiate true AS from pseudo AS.

A LV SVI < 35ml/m² indicates a low flow state.

Zva = (Pmean + SBP) / SVI. A Zva of > 5.5mmHg/ml/m² indicates an increased impedance.

Question 16

What are the differences between TTE derived and catheterisation derived pressure gradients?

Answer 16

TTE derived gradients, based on AV Vmax and LVOT Vmax, are greater than catheterisation derived gradients, based on maximum AV pressure and maximum LV pressure, because instantaneous gradients are greater than peak to peak gradients.

Catheterisation derived gradients are more accurate than TTE derived gradients, but are not routinely used, because catheterisation measures the gradients and TTE estimates the gradients based on the velocities, but catheterisation is invasive.

Question 17

How is AS monitored and managed?

Answer 17

Perform a TTE every 6 months for severe AS. Perform a TTE every year for mild to moderate AS.

Valvuloplasty is indicated for unstable patients. TAVI is indicated for older patients. Surgical AV replacement is indicated for severe AS.

Surgery is indicated for severe symptomatic AS, asymptomatic AS with LV dysfunction or symptoms during ETT, moderate AS but undergoing other cardiac surgery or if the if the Vmax increases by >0.3m/s per year.

Question 18

What are the BSE values for AS assessment?

Answer 18

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Question 19

What are the causes of AS?

Answer 19

BAV, RHD, IE and aortic root disease.

In patients with a BAV, AV degeneration occurs at a younger age.

In rheumatic AR, bacterial infection causes inflammation. This causes fibrosis and scarring, and, therefore, thickening, calcification and commissural fusion, of the AV. This impairs AV coaptation.

In IE, the bacterial infection causes vegetations on the AV which damage the leaflets.

In aortic root disease, aortic root dilatation causes aortic annular dilatation. This impairs AV cusp coaptation and causes central AR.

Question 20

What are the TTE characteristics of AR?

Answer 20

Thickened AV cusps, impaired AV coaptation, diastolic regurgitant flow.

In BAV, there is an asymmetric closure line.

In rheumatic AS, there is commisural fusion.

In IE, there are vegetations (echogenic), aortic root abscesses (echolucent) and/or cusp perforation or cusp flail.

In aortic root disease, there is aortic root dilatation.

Question 21

What are the symptoms and signs of AR?

Answer 21

HF symptoms and symptoms of the underlying cause.

Collapsing pulse, low diastolic blood pressure and wide pulse pressure, displaced apex beat (due to LV dilatation), early diastolic murmur and/or HF signs (severe AR).

Question 22

How does AR cause MS?

Answer 22

The AR jet hits the anterior MV leaflet and forces it back during diastole. This causes diastolic MV leaflet fluttering and doming. This causes premature MV closure which causes functional MS. This causes an Austin Flint murmur (diastolic murmur in severe AR).

Question 23

What are the BSE values for AR assessment?

Answer 23

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Question 24

What are the qualitative methods used to assess AR?

Answer 24

AR size (AR jet size to LV size), AR origin, and AR direction (central or eccentric).

Abnormal aortic cusps, LV size, AR jet width, colour flow convergence, AR jet density with CWD and descending aorta diastolic flow reversal.

Question 25

What are the quantitative methods used to assess AR?

Answer 25

Regurgitant volume, regurgitant fraction, regurgitant orifice area, vena contracta, jet width to LVOT diameter, AR CSA to LVOT CSA and descending aorta diastolic flow velocity.

Question 26

What are the effects of AR on chamber size and function?

Answer 26

LV dilatation and increase LVEDV, LV diastolic dysfunction, LV eccentric hypertrophy and increased LVEDP, LV systolic dysfunction, LA dilatation and pulmonary hypertension and pulmonary congestion.

Acute AR increases LVEDV and LVEDP but the LV is normal in size. The volume overload and pressure overload cause LV dysfunction and the increased wall stress decreases CO.

Chronic AR causes LV volume overload which causes LV dilatation. At the start, LV dilatation maintains the CO. The increased LVEDV increases the LVEDP. This decreases LV compliance and causes LV diastolic dysfunction and HFpEF. The LV volume overload causes eccentric LV hypertrophy (increase in LV mass but normal wall thickness). The LV volume overload decreases myocardial contractility which causes LV systolic dysfunction and HFrEF. Chronic AR and LV volume overload increase LA volume and LA pressure. This causes LA dilatation. This causes pulmonary hypertension and pulmonary congestion which causes RV dilatation, hypertrophy and dysfunction.

Question 27

What are the associated TTE characteristics of AR?

Answer 27

Coexistent AS or other valve disease, LV dilatation, LV diastolic dysfunction, aortic root dilatation and the presence of aortic coarctation (BAV).

Question 28

How are regurgitant volume, regurgitant fraction and regurgitant area calculated for AR?

Answer 28

CSA = 0.785 x (diameter)2

SV = CSA x VTI

RV = SV LVOT - SV MV

RF = RV / (SV MV) x 100

ROA = RV / VTI AR

Question 29

How are jet width to LVOT diameter and AR CSA to LVOT CSA calculated for AR?

Answer 29

In PLAX, use colour M-mode, measure the AR jet width during diastole and LVOT diameter during systole and calculate the ratio (AR width /LVOT diameter).

Calculate the AR and LVOT CSA and calculate the ratio. CSA = 0.785 x (diameter)2.

Question 30

How is descending aorta diastolic flow reversal assessed?

Answer 30

In suprasternal, use PWD, assess diastolic flow reversal qualitatively and quantitatively.

In AR, the incompetent AV causes the blood to flow from the aorta to the LV during diastole due pressure gradient reversal. This is transmitted downstream causing retrograde blood flow in the descending aorta.

Question 31

How is AR monitored and managed?

Answer 31

Perform a TTE every 6-12 months for severe AR with normal LV function. Perform a TTE every 2 years for mild to moderate AR.

Surgery is indicated for severe asymptomatic AR with LV dysfunction (EF <50%), LV dilatation (LVEDD >7cm or LVESD >5cm) or other cardiac surgery (e.g. CABG).

Surgery is indicated for severe asymptomatic AR with aortic root disease with an aortic root measuring >4.5cm in Marfan syndrome, >5cm in BAV, and >5.5cm in other patients.

Surgery involves AV repair or replacement with or without aortic root grafting.

Question 32

How is dobuatmine stress echo used to differentiate true severe AS and pseudo severe AS in patients with low grade low flow AS?

Answer 32

In patients with true AS, the AVA will be constant (<1.2cm2) but the mean PG will increase (>30mmHg) with stress. However, in patients with functional AS, the AVA will increase more relatively and the mean PG will increase less relatively with stress.

Question 33

How is dobuatmine stress echo used to assess LV contractile reserve in patients with low grade low flow AS?

Answer 33

A LV contractile reserve are indicated by an increase in the SV by ≥20% with dobutamine stress. If there is no LV contractile reserve (increase in SV of <20%), it is true AS, and, if there is LV contractile reserve there is functional (pseudo) AS.