12 Aortic valve disease Flashcards
Which AV cusps are visualised in which views?
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.
What are the causes of AS?
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.
What are the types of BAV?
Type 0 (no raphe), type 1 (1 raphe) and type 2 (2 raphes).
What are the TTE characteristics of AS?
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.
What are the symptoms and signs of AS?
Angina, dizziness, 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).
What are the BSE values for AS assessment?
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How are the maximum pressure gradient and mean pressure gradient calculated?
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
How is the AVA calculated?
Continuity equation
CSA LVOT = 0.785 x (LVOT diameter)2
EOA AV = (CSA LVOT x VTI LVOT) / (VTI AV)
Planimetry
How is the velocity ratio calculated?
VR = (Vmax LVOT) / (Vmax AV)
What are the effects of AS on chamber size and chamber function?
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.
What is low flow low gradient AS and what are the two types of low flow low gradient AS?
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.
What are the non-standard views used to assess AS?
The right parasternal view, the subcostal short axis view and the suprasternal view.
What is the effect of flow on velocity?
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.
What are the causes of discordant parameters in AS?
In patients with discordant parameters (AVA <1cm2, Vmax >4m/s, PG >40mmHg), AVA indexed (<0.6cm/m2), VR (<0.25), Vmax (increase of 0.3m/s/year), GLS (>-14%) may be helpful. Use AVA indexed in patients with a BSA of <1.7m2. Zva is not used.
In patients with normal systolic function with severe AS (EOA <1cm², Vmax <4m/s, peak PG <40mmHg) there may be a low flow state (SVI <35ml/m2) 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. This is high gradient has high valve area AS and may be due to measurement errors.
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 (LVEF <40%) with true severe AS (EOA <1cm²) the decreased velocities and gradients are due to a low CO.
In patients with systolic dysfunction (LVEF <40%) with non-severe (functional) AS (measured EOA <1cm² but true EOA >1cm²) the EOA is underestimated due to a low CO.
How is SVI and Zva used to differentiate true severe AS and pseudo severe AS?
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.