Aortic Stenosis Flashcards
What is the most common cause of Aortic Stenosis?
Calcific Degeneration.
Calcific Degeneration is characterised by progressive fibrosis and calcification of the aortic valve and is similar to what process?
Atherosclerosis.
The early stage of Aortic Stenosis is termed what?
Aortic sclerosis.
What is another common cause of Aortic Stenosis (other than Calcific Degeneration)?
Bicuspid AOV.
Patients who require surgery for stenosis of a bicuspid AOV do so on average how much earlier than those with calcific degeneration of a tricuspid AOV valve?
5 Years.
Identification of the number of AOV leaflets should occur in systole or diastole?
In Systole.
Why should identification of the number of AOV leaflets occur in systole?
Because the leaflets of bicuspid valves are unequal in size, and raphe in larger leaflets can, when closed, give the appearance of a tricuspid valve.
True of False; Bicuspid AOVs are often familial.
True.
Bicuspid AOVs are commonly associated with what?
Coarctations of the Ao and dilated aortic roots.
Bicuspid AOVs are found in what percentage of coarctation cases?
70-80%.
Bicuspid AOVs are also associated with what (but rarely)?
Bicuspid pulmonary valves.
Bicuspid AOVs show what kind of closure line?
An eccentric closure line.
True or False; Rheumatic AS is more common than rheumatic MS.
False.
How is rheumatic AS identifiable?
Commissural fusion (appearing functionally bicuspid) with a doming leaflet appearance.
True of false; in sub- and supravalvular AS, the valve itself is unaffected and the obstruction lies below or above the valve.
True.
Subvalvular AS can result from a fixed obstruction in the LVOT, usually due to what?
A fibromuscular ridge or membrane.
Other than a fixed obstruction in the LVOT, subvalvular AS can also result from what other type of obstruction (as seen in HOCM)?
A dynamic obstruction.
A dynamic obstruction (as seen in HOCM), causes obstruction in what part of systole or diastole?
Mid-late systole.
In supravalvular aortic stenosis, which is uncommon, there is fixed obstruction where?
In the Asc Ao.
In supravalvular aortic stenosis, what causes the fixed obstruction in the Asc Ao?
A diffuse narrowing or discrete membrane.
What can aid in the differentiation of true valvular stenosis from fixed supra- or subvalvular obstruction?
PW Doppler.
What are the most common symptoms of AS?
Angina, exertional dizziness and syncope, and breathlessness.
A sign of AS is a slow-rising or collapsing pulse?
Slow-rising.
A sign of AS is a low systolic BP and a narrow pulse pressure or a low diastolic BP and a wide pulse pressure?
A low systolic blood pressure and a narrow pulse pressure.
A sustained apex beat is a sign of AS, this is a result of what?
LVH.
In terms of the second heart sound, what is considered a sign of AS?
A soft aortic component to second heart sound (A2).
True of False; ejection click and an ejection systolic murmur are signs of AS.
True.
Typically a bicuspid AOV shows an eccentric closure line, can they still show a central closure line?
Yes.
How does CW Doppler differ between severe and mild AS?
In severe AS, the trace is rounded in shape with a peak velocity occurring in mid-systole. In mild AS, the trace has a more triangular shape with an early systolic peak.
With regards to the LV, what are common echo findings in long-term AS?
LVH, LV dilatation and impaired LV function.
How is △P calculated using the Bernoulli equation; long form and simplified?
Simplified; △P= 4 X V*2
Long Form; △P=4 X (V22 - V12)
When must the full Bernoulli equation be used?
When the peak velocity in the LVOT >1m/s.
Patients with Marfan’s syndrome should be considered for root repair/replacement when?
When the Ao root diameter is ≥4.5cm.
Marfan’s syndrome is what type of disorder?
A connective tissue disorder.
In the Bernoulli equation, what do V1 and V2 represent?
V2 = peak distal velocity (AOV) and V1 = peak proximal velocity (LVOT).
The transaortic gradients measured by cardiac catheterisation are what type of gradients?
peak-to-peak.
The transaortic gradients measured by echo are what type of gradients?
Instantaneous.
Are instantaneous of peak-to-peak gradients greater?
Instantaneous.
Are transaortic gradients measured by cardiac catheterisation or echo greater?
Echo.
How can △Pmean be estimated from △Pmax?
△Pmean = (△Pmax/1.45) + 2mmHg
△Pmean also approximates what?
2.4V*2
Conditions that increase what can lead to an overestimation of transaortic pressure gradients?
Stroke volume.
What conditions can increase stroke volume?
Aortic regurgitation and pregnancy.
Transaortic pressure gradients are underestimated in the presence of what?
LV impairment and mitral stenosis.
When and where should LVOT diameters be measured?
Zoom mode, mid-systole, 0.5-1cm from annulus (where PW Doppler would be measured). Minimum 3 beats (5 if AF). Measure inner edge to inner edge.
How is EOA(AV) calculated?
EOA(AV) = CSA(LVOT) X VTI(LVOT) / VTI(AV)
Some versions of the continuity equation use what, instead of using VTIs, to calculate EOA?
Peak velocities in the LVOT/AOV
Does Doppler or planimetry provide the best assessment of valve area?
Doppler.
Why does Doppler provide the best assessment of valve area?
Because planimetry is difficult to reproduce accurately.
AR can overestimate pressure gradients/velocities. Is AVA calculated by continuity still accurate in the presence of AR?
Yes.
Why is AVA calculated by continuity still accurate in the presence of AR?
Because SV(LVOT) is still equal to SV(AOV).
What else can be used to calculate stroke volume, that may be more accurate than stroke volume derived from measurements of the LVOT diameter and PW Doppler.
3D LV volumes.
What criteria are used to assess AS severity?
AV(Vmax), mean PG, AVA and DSI.
What AV(Vmax) figures suggest mild, moderate and severe AS?
Mild; <2.9m/s, Moderate; 3.0-3.9m/s, Severe >4m/s.
What mean PG figures suggest mild, moderate and severe AS?
Mild; <25mmHg, Moderate; 25-40mmHg, Severe >40mmHg.
What AVA figures suggest mild, moderate and severe AS?
Mild; 1.5-2.0cm2, Moderate; 1.0-1.4cm2, Severe <1cm*2.
What DSI figures suggest mild, moderate and severe AS?
Mild; >0.5, Moderate; 0.25-0.5, Severe ≤0.25.
True or false; pressure gradients/velocities are affected by flow rate.
True.
In true severe AS (with normal LV Function), what could be the cause of reduced velocities/gradients?
Low flow secondary to a small LV cavity and/or increased arterial afterload (hypertension).
How can flow be assessed?
By using stroke volume index (SVi).
A stroke volume index of less than what indicates low flow?
<35ml/m*2.
SVi permits the calculation of what?
Valvular-arterial impedance (Zva).
Valvular-arterial impedance (Zva) is a measure of what?
The global LV haemodyanmic load (the double afterload on LV from the stenosed AOV and from the vascular system).
How is Zva calculated?
Zva = (PGmean + systolic BP)/SVi
A Zva of what indicates increased impedance to flow?
> 5.5mmHg/ml/m2
In non-severe AS, when can AVA <1cm*2?
Because of a small body habitus or as a result of reduced valve opening (because of poor cardiac output).
AVA should be indexed. An AVAi of what indicates severe AS?
<0.6cm2/m2.
In true severe AS (with impaired function), what could be the cause of reduced velocities/gradients?
Simply as a consequence of poor cardiac output.
What can be helpful in distinguishing true severe AS from functional severe AS?
A dobutamine stress echo.
How can a dobutamine stress echo be helpful in distinguishing true severe AS from functional severe AS>
It augments/increases cardiac output.
Sometimes pressure gradients and velocities can indicate severe AS but the AVA does not. When can this occur?
- If patients have a high flow state and 2. In individuals with a large body habitus.
When can high flow states (across the AOV) be seen?
With co-existent AR, or with clinical conditions associated with a high cardiac output such as, anaemia, thyrotoxicosis and arteriovenous fistula or haemodialysis.
Calculation of what can help identify patients with high flow states?
Stroke volume.
What is Thyrotoxicosis?
The clinical manifestation of excess thyroid hormone.
Asymptomatic patients with an AV Vmax >4m/s should be re-assessed how often?
Every six months.
Asymptomatic patients with an AV Vmax >4m/s should be considered for surgery if AV Vmax increases by how much per year?
> 0.3m/s.
For those with lesser degrees of AS, how often should they be re-assessed?
Yearly.
What can of drug therapy may potentially slow the progression of AS?
Station Therapy.
What is the definitive treatment for AS?
Surgical replacement of the valve.
Biological prosthetic valves are generally preferred for who?
Older patients, or for those who wish to avoid the use of long term anticoagulation.
Mechanical prosthetic valves are generally preferred for who?
Younger patients.
Surgery is indicated for severe symptomatic AS, when should asymptomatic patients be considered for surgery?
If they have LV dysfunction, or a fall in BP/complex ventricular arrhythmias on exercise.
Replacement of moderate or severely stenosed AOVs is usually advisable if patients who are what?
Due to undergo heart surgery for another reason.
What can be used as a bridge to replacement in unstable patients, or for patients who need urgent non-cardiac surgery?
Balloon valvuloplasty.
What is a relatively new technique for AVR patients who are at high risk or excluded from conventional valve surgery?
TAVI.
True or False; when measuring the Ao annulus, you should measure from cusp hinge points, ignoring all calcification.
True.
Why is planimetry of AVA not recommended as a routine measure?
Because the “effective” rather than “anatomic” orifice is the primary indicator of outcome.
When is planimetry of AVA accepted?
When Doppler estimation is unreliable (e.g in the presence of coexisting LVOT obstruction).
The blind probe can be used to “hunt for maximum AV velocity” in which views?
Right parasternal, apical, suprasternal and subcostal.
What are the three causes of AS?
Rheumatic, calcific degenerative and congenital/bicuspid.
What is known to affect operative risk and prognosis?
RV size and function/pulmonary artery pressure.
Discrepancies in AOV parameters may occur in what percentage of cases?
Up to 25%.
The DSI is a useful measure as it removes the potential inaccuracies of LVOT measurements. However, what does it ignore?
Inaccuracies due to abnormal LVOT anatomy (e.g in isolated basal hypertrophy).
Degenerative aortic stenosis (AS) may be associated with a reduction in systemic arterial compliance due to what?
Rigid arterial vessels.
A reduction in systemic arterial compliance due to rigid arterial vessels (seen in degenerative AS) is clinically manifested as what?
Systolic HTN.
The additional afterload due to HTN can result in an underestimation or overestimation of AS severity?
Underestimation.
If AVA suggests severe AS, but AV max and mean PG do not (in the presence of impaired LV function), what are the differential diagnosis?
Truly severe AS or moderate/less severe AS with poor valve opening due to poor cardiac output.
When a low-dose dobutamine stress test is used to determine the severity of AS; AS is considered severe when what?
AVA remains <1.0cm*2 and/or mean PG increases >40mmHg.
When a low-dose dobutamine stress test is used to determine the severity of AS; AS is considered pseudosevere (moderate or less) when what?
AVA increases >1.0cm*2 and/or mean PG remains <40mmHG.
With regards to dobutamine stress testing, when are you unable to comment on the severity of AS?
If there is no contractile reserve (change in SV) and no change in AVA and mean PG.
If AVA suggests severe AS, but AV max and mean PG do not (in the presence of normal LV function), what are the differential diagnosis?
Low-flow severe AS or moderate/less severe AS for that individual (such as one with a smaller body habitus).
In over-weight patients, indexing AVA may overestimate or underestimate AS severity?
Overestimate.
When should low flow severe AS be considered (with normal LVEF)?
If SVi <35 and/or Zva >5.5.
If AVA does not suggest severe AS, but AV max and mean PG do, what are the differential diagnosis?
Either, 1. The AVA is correct and there is moderate/or less severe AS with high flow states OR 2. Truly severe AS in a patient with a larger body habitus.
