5012 Theory 2: Post midterm

Describe anatomy of aortic valve (4 components)

• Annulus: provides structural support to cusps

• Cusps: 3 half-moon (semilunar) in shape; right, left, non-coronary

• Commissures: where the cusps come together

• Interleaflet triangles: extensions of the ventricular outflow tract

Describe anatomy of aortic root/ Sinuses of Valsalva, includes 4 components

• section between the LVOT and Asc. Ao

  • specifically the inferior attachment of the aortic cusps to the ST junction

• Includes:

  • aortic cusps

  • Sinuses of Valsalva

  • Comissures

  • Interleaflet triangles

Differentiate aortic valve stenosis from sclerosis

• Aortic Stenosis: reduced (restricted) opening of the aortic valve in systole via calcium build up over time

  • valve appears brighter than normal, does not open well, has velocity over 2.5 m/s

• Aortic Sclerosis: thickening of the valve leaflets with no restriction of blood flow

  • valve appears brighter than normal, still opens well, has velocity less than 2.5 m/s

Describe pathology causes of aortic stenosis (3) and how common

1) Congenital: roughly 30-40% of cases

2) Acquired: Calcific: > 50% of cases

3) Acquired: Rheumatic: <10% of cases

What are some specific details of congenital AS?

• bicuspid aortic valve is most common causes of AS in <50 yros, not all bicuspids will be stenotic

• unicuspid (discovered at birth) or quadricuspid aortic valve

• subvalvular or supravalvular stenosis is most rare

What are some specific details of calcific AS?

• acquired, most common cause of AS in elderly

• calcium deposits build up on the valve over time preventing normal opening in systole

  • “chunks” of brightness (calcium) seen, uneven brightness

• commissural fusion common absent

• MAC and CAD commonly associated

What are some specific details of rheumatic AS?

• complication of strep throat → occurs years after acute rheumatic fever

  • often co-exist with mitral stenosis

• scar tissue forms on the valve, which narrows opening

  • scar tissue creates rough surface where calcium deposits can collect

• chronic inflammation → thickening & calcification/ stiffness

• commissural fusion → triangular systolic orifice

• slightly brighter than normal, uniformly thickened leaflets

What are the 2 types of congenital bicuspid aortic valves

• Without a raphe

  • rare

  • cusps usually equal in size

• With a raphe (seam/union)

  • common

  • most common location of raphe is between the RCC and LCC

  • cusps unequal in size

What part of cardiac cycle do you assess aortic valves?

Systole

What are the consequences of congenital bicuspid AoV? (4)

1) Aortic root dilation: higher risk for aortic aneurysm or dissections

2) Coarctation of aorta: narrowing in desc. ao

3) Supravalvular aortic stenosis

4) Ventricular septal defects

Describe congenital subvalvular stenosis

• fibrous membrane or muscular ring in LVOT → obstruction in the outflow

• Leads to: narrow LVOT → septal hypertrophy = thicker IVS → dynamic obstruction → mitral valve may get “sucked up”

  • dynamic because degree of stenosis varies depending on loading conditions

What is dynamic obstruction?

• degree of stenosis varies depending on loading conditions, or variable blockage of blood flow instead of fixed narrowing

  • severity changes based on: cardiac cycle, HR, volume, movement of leaflets

Describe congenital supravalvular stenosis

• uncommon

• dysplasia of the aortic wall (hour glass type)

• membrane with central orifice

• hypoplasia of ascending aorta

Describe hemodynamic consequences of aortic stenosis (2)

• Concentric LVH

  • narrowed AoV → increased pressure load → LV wall thickens to compensate (concentric LVH) → LV stiff + lower compliance

    • lead to diastolic dysfunction → LV does not relax well → poor filling

    • increased LAP → back into lungs → increase pulmonary pressures → SOB

  • Usually, normal EF, but will drop in severe cases

• Ischemia

  • increased muscle mass due to LVH → increase oxygen demand

  • compressed coronary vessels due to LVH → decrease oxygen supply

  • angina: decrease oxygen → decrease LV contractility → systolic dysfunction

Big picture of the hemodynamics summary:

• Pressure overload → LVH (thick)

• Stiff ventricle → diastolic dysfunction → pulmonary congestion

• Oxygen mismatch → ischemia (starved)→ possible systolic failure in late stages (weak, low EF)

List signs and symptoms of aortic stenosis (4)

• Systolic Ejection Murmur (SEM)

  • can be diastolic, systolic, or both

  • most common, based on symptoms, timings of the murmurs

• Angina- patient may have coexistent CAD

  • may be worsen by LVH

  • increased myocardial oxygen demand of LVH

  • decreased coronary artery perfusion pressure/perfusion time

• Syncope (fainting)/ presyncope (feeling light-headed)

  • on exertion

  • caused by decreased cerebral perfusion

• Shortness of breath and fatigue

  • insufficient oxygen supply

Describe treatment options for aortic stenosis

• medical → alleviate symptoms

• surgical/percutaneous → only definitive therapy

  • surgical: bioprosthetic /mechanical valve replacement

  • percutaneous: Trans Aortic Valve Implantation (TAVI)

Role of sonography in aortic stenosis (6)

• determine presence of AS

  • differentiate between sclerosis vs stenosis

• determine etiology

  • congenital or acquired (via age→ calcific or rheumatic)

• assess LV wall thickness

  • wall thickness/LVH and AS= afterload problems

  • can lead to diastolic dysfunction, but patients have normal systolic function

• measure aorta

  • post-stenotic dilation, measure @ ED

  • be wary in biscuspid bc they have higher dilation and aneurysm risk

• estimate severity of aortic stenosis

  • gradients, continuity equation, velocity ratio

• identify associated lesions (regurgitation)

What are the 3 extra steps to assess AS (summary)

• 1) Use PEDOF probe in multiple windows to try to find the highest V through the valve

• 2) Mean Gradient and Peak V via CW trace of highest AoV velocity

• 3) Continuity equation (add on to step 2: PW LVOT trace, LVOT diameter) for machine to calculate AVA

How do we quantify the severity of disease in aortic valve stenosis?

• Mean average gradients: different in pressure between LV and Ao in systole

• Continuity equation: valve area

• Velocity ratio: AS jet

What is the continuity principle? How is it related in normal vs stenotic valve?

• states what flows in, must flow out

• in normal valves: the velocity should be the same before and after the valve

• in stenotic valves: blood will have to speed up to get through the valve due to narrowing

How to assess AS Jet velocity, what are normal values?

• CW Doppler through maximum flow through AoV

• Assess multiple windows, but only use highest velocity

• PEDOF probe: when jet is > 3 m/s

How to assess pressure mean gradient, what are normal values?

• CW Doppler through maximum flow through AoV

• trace around the CW Doppler spectral trace

• machine automatically calculates mean pressure gradient between LV and Asc. Ao

How to assess aortic valve area (AVA), what are normal values?

• utilizes the continuity equation/principle

• stroke volume of blood in LVOT must be the same as the stroke volume of blood in the AoV

• Three measurements needed (any order, will auto calculate after all measurements)

  • AoV VTI: trace area under CW Doppler of AoV

    • through AoV, at max aliasing

  • LVOT VTI: trace area under PW Doppler of LVOT

    • 0.5 cm proximal to AoV

  • CSA of LVOT: 2D of the LVOT diameter

    • zoom, inner-inner, MS, 0.3-1 cm inferior to AV cusp → CSA = πr²

What is VTI and why do we use it?

• What: area under Doppler curve

  • Unit is cm because VTI = velocity/time

• Why: In human body, velocity is not constant at any given time and varies at different parts of the vessel

  • VTI sums up all the individual velocities over time to find a representative overall velocity

Continuity Equation formula for AoV

Can you use continuity equation of AoV when there is LVOT obstruction?

• no, bc equation compares normal flow to stenotic flow

• with LVOT obstruction → velocity is already high in LVOT and the velocity in AoV will still be high since there was no time to slow down

• Have to assess visually or perform a valve planimetry in SAX

What is 2D Planimetry of AVA

• @ PSAX

• trace opening in mid systole

• not routinely performed due to many pitfalls

• could be used to double check the AVA if clearly seen

What is dimensionless velocity ratio (DVI)?

• removes error associated with LVOT diameter by removing CSA from the continuity equation

  • velocity ratio = V_LVOT/ V_AoV

• smaller #s= severe, closer to 1= normal

What is the velocity profile and acceleration time (AT) in severe stenosis?

• Normal valve:

  • short ejection time and acceleration time

  • blood flows easily into the ascending ao, hitting peak V quickly

  • looks like a shark tooth?

• Aortic stenosis

  • longer ejection time and acceleration time

  • more rounded, symmetrical shape

  • hard to push blood into aorta, so everything takes longer

What are some specifications of PEDOF Probe

• Known as: Pulsed Echo Doppler Flow aka pencil probe

• non-imaging CW probe, only shown is Doppler trace

• small footprint allows this probe to easily fit between small rib spaces

• may be used for AS protocol, can be used anywhere but common in the right parasternal window (usually higher velocity)

Quantify severity of disease in the setting of supravalvular AS

• extremely rare

• not stenotic: attempt continuity equation with PW only (using multiple PW gates sampling until high velocity to prove the location)

  • AoV PW in sinuses of valsalva, prior to the supravalvular stenotic area

  • use values for max V, mean gradient, and continuity equation

• then:

  • place CW through stenosis area

  • document mean, max gradient, and max velocity in asc, ao

  • indicate valve itself is normal

• show stenosis in 2D and explain why there is an increase in velocity

Quantify severity of disease in the setting of dynamic subvalvular obstruction

• continuity equation and peak/mean gradients will not work (bc high velocity in LVOT)

  • assess 2D AoV, esp PSAX

  • grade based on 2D images

  • some sits may as for planimetry

• record mean and peak gradients through LVOT

  • use PW if possible, but may be forced to use CW

• clearly indicate on report that high gradients are from the LVOT and not AoV

• assess health on 2D images

Quantify severity of disease in the setting of low output AS

• defined as valve area < 1.0 cm² with an aortic velocity < 4.0 m/s or pressure gradient < 40 mmHg, and a poor EF

  • stenotic AoV, but normalish velocity through valve

• significantly reduced EF → little blood pushed through valve → low velocities and pressure gradients through valve

What is aortic insufficiency (AI) / aortic regurgitation (AR) ?

• inability of the aortic valve leaflets to remain closed during diastole

• results in portion of the left ventricular stroke volume leaking back from the aorta into the left ventricle

• added volume of regurgitant blood produces an increase in left ventricular end-diastolic volume

• aortic regurgitation occurs in diastole and includes both isovolumetric periods

List the common etiologies of AI/AR (4)

• aortic annulus/ aortic root dilation

• cusp abnormalities

• loss of aortic cusp (commissural) support

What is aortic annulus/ aortic root dilations? What are the main causes (5+3 sub)

• aortic root dilatations prevent normal leaflet coaptation → unable to close normally in diastole

• causes include:

  • congenital conditions:

    • bicuspid AoV

    • Marfan synfrom

    • Ehlers-Danlos/ Loeys-Dietz syndromes

  • aortic stenosis (turbulent flow in Asc. ao)

  • atherosclerosis

  • untreated infection

  • trauma → dissections cause leakage

What is Marfan syndrome (congenital, aortic root dilation)? Characteristics (5)?

• most common systemic connective tissue disease (genetic) → leaky connective tissue

• fault connective tissue weakens blood vessels

• characteristics of Marfan syndrome are:

  • tall/scoliosis/hypermobility of joints

  • high palate/poor vision/long limbs

  • mitral valve prolapse (60% of cases)

  • dilatation of Asc Ao/ dissection

  • AR due to dilation of aortic root

What is bicuspid AoV related to congenital, aortic root dilation?

• just more susceptible to dilation and aneurysm

• inherently different→ need to assess well in Asc Ao

Difference between dilation and aneurysm

• Aortic aneurysm:

  • dilatation involving all layers of the aorta 1.5x greater than normal diameter

• Aortic dilatation:

  • diltation involving all layers of the aorta, larger than accepted normal values, but not large enough to be considered an aneurysm

Operation on an aneurysm @ the following levels:

• normal patient: 55 mm

• bicuspid AoV: 50 mm

• Marfan syndrome: 45 mm

• OR if growth of aorta is >0.5 cm per year

What are reasons for cusp abnormalities (4)

• rheumatic fever

• calcific changes

  • calcium can block complete closure of the valve

• infective endocarditis

  • bacteria on valve

• bicuspid/quadricuspid

  • quad more associated with AI than AS

What are reasons for loss of aortic cusp (commissural) support? (3)

• ventricular septal defects (holes/shunts)

• aortic dissection

• trauma

Whats are some causes of acute vs chronic AI?

• causes of acute AI:

  • trauma

  • dissection

  • infective endocarditis

• causes of chronic AI:

  • bicuspid AoV

  • rheumatic AoV

  • calcific AoV

What are some hemodynamic consequences for Acute AI?

if severe enough → medical emergency & immediate valve replacement needed

What are some hemodynamic consequences for Chronic AI- early stages?

• eccentric hypertrophy/ LA dilation also help reduce wall stress (LaPlace’s Law)

• note: LV pressure may remain normal without changing SV too → patient asymptomatic

• EF remain normal

What are some hemodynamic consequences for Chronic AI- long standing?

• as LV dilates more:

  • myofibrils pass their optimal length and contractility decreases → EF decreases and eventually patient goes into systolic heart failure

  • pericardium reaches max size, cannot accommodate excess blood → LV filling pressure increase → diastolic heart failure