Obstructive Lesions

• Any lesion (valvular, muscular or vascular) that impedes forward flow from the heart
• Aortic Stenosis
• Pulmonic Stenosis

• Coarctation of Aorta 

Levels of Obstruction

• Valvar- at the valve
• Subvalvar-before the valve
• Supravalvar-after the valve

Types of AS

Valvar

• Bicuspid
• Unicuspid
• Quadricuspid

Subvalvar

• Muscular
• Discrete, Membranous
• Fibromuscular

Supravalvar

• Tunnel shaped and most associated with William’s Syndrome 

Cardiac Changes and AS

• LV is usually hypertrophic from pressure generated from the blood "pushing" against the pressure of the stenosis
• Presence of LVH suggests long standing significant LVOT obstruction
• Increased afterload on the LV causes LVH
• Hypertrophy depends on the degree of stenosis
• LVH is an important compensatory mechanism for pressure overload
• May indicate intervention
• Formula : M-Mode (short Axis): (IVSd + LVPWd)/LVIDd if >.36 = LVH present

• Symptoms may not be present immediately
• As PDA closes and the pressures on the LV side increase, symptoms become more recognizable
• Systemic circulation becomes more dependent on LV function

• There is an increase Oxygen demand and subendocardial ischemia may occur
• Arrhythmias
• Sudden death: Usually with moderate to severe AS
• More severe, untreated AS can result in LV dysfunction, heart failure and sudden death
• Mild AS: 20 to 40 mmHg
• Moderate AS: 40 to 60 mmHg
• Severe AS: > 60 mmHg
• Intervention is needed to decrease risk of sudden death.
• Hypoplastic annulus is associated with high mortality
• Natural history of valvar AS is progressive
• Calcification of cusps develop slowly in 3rd decade of life in patients with mild stenosis or bicuspid aortic valves (Bi AoV)
• Patients may develop obstruction as an adult even though as a child there was mild or no stenosis present

Valvar AS

• Obstruction at the valve level due to abnormal valve anatomy 
• Accounts for 60 to 75% of LVOT obstructions
• Congenital or acquired. Can be a sporadic finding, genetic, familial, or acquired (rheumatic fever)
• Natural history of AS is progressive with increasing obstruction. Rate of progression is variable
• Less severe AS: variable presentations
• Asymptomatic, syncope 

Etiology of AS

Leaflet thickening (age/calcification)

Speed at which calcification occurs based on:

• Severity of initial obstruction 
• Infection of valve
• Athletic activities
• Gende males more common
• Calcium metabolism (calcification of AoV not seen in pediatric population)
• And/or fusion of leaflets  

Unicusp AV

• Rare
• Associated with very dysplastic valve and severe stenosis
• Common form of critical AS
• Small opening in or near center 

Bicuspid AV

• Most common is L-R fusion of coronary cusps
• Fish-mouth or football shaped (Bi AoV)
• Between left and right cusp: 75% of functional Bi AoV

Quadricusp AV

Even more rare than unicuspid

More associated with AI

May or may not have obstruction

Commissure Fusion

• Abnormal valve can still have the Y shape when valve is closed, but when valve opens it will look abnormal
• partial or complete (various shape)
• Hint: when echoing slow picture down to distinguish anatomy of leaflets 

   

Valvar AS 2D

Evaluation of valve leaflets

• Number
• Mobility
• Doming 
• Thickness

Ao annular ring: measure the size of annular ring at insertion point (obtain in any and all views possible) 

Look for coronary arteries 

Doming of valve

Measure sinus, sinotubular junction and ascending Ao, (Asc. Ao may be dilated)

Evaluate degree of AI

Doppler in views that you are most in line with (apical 5c, subcostal 5c)

Valvar AS and Doppler

Color doppler: can see where the turbulent flow is as well as presence of AI

Doppler derived pressure gradients:

• Peak Velocity 
• Peak pressure gradient
• Mean pressure gradient

Parallel as possible to flow will give most accurate measurement, measure in more than one view

• PW at valve level
• CW to get peak gradient (measure the VTI )

 Aortic valve alone cannot be an effective way to assess stenosis since obstruction may not be only at valvular level  

In presence of LV systolic dysfunction, doppler gradients may be low in presence of severe stenosis

Gradient may be low in newborn until LV pressures change completely

Valvar AS Associated Conditions

• Coarctation of Aorta (COA): especially in presence of Bi AoV
• VSD’s
• Sudden death

Valvar AS Treatment

Type of intervention is based on:

• Age
• History of interventions
• Associated anatomical lesions
• Presence of Aortic insufficiency (AI)
• Gradient across valve

Surgical/Interventional Options:

• Catheter based balloon valvuloplasty
• Surgery to re-construct valve
• Valve replacement

Subaortic Stenosis

• Obstruction below the valve
• Associated with hypertrophic obstructive cardiomyopathies
• May occur in isolation or with other defects

Variations of Sub AS

• Discrete Membranous
• Fibromuscular
• Diffuse tunnel-like narrowing
• Asymmetrical Septal Hypertrophy
• Accessory MV tissue

Discrete Membranous Sub AS

• Thin fibrous membrane located beneath aortic valve
• Presence of AI (up to 55%)
• Systolic Fluttering and early partial closure of aortic valve

Fibromuscular Sub AS

• "Collar" of tissue beneath aortic valve

Diffuse Tunnel-like Sub AS

• Hypoplasia of aortic annulus and tunnel-like area under artic valve

Severe Sub AS

• LVH
• Decreased LV function
• Heart failure
• Sudden death (especially during physical exertion)
• Sub AS is progressive in 50% of patients
• Increased re-occurrence rate post surgery
• Risk factor of re-occurrence : if the distance of membrane to AoV < 6mm and peak gradient ≥ 60 mmHg 

Sub AS 2D

• Best view: Apical 5 Chamber
• Similar interrogation as valvar PS
• PW at point of turbulence to show where gradient is coming from then CW to get peak gradient
• Pressure ½ time of AI

Sub As Doppler

• Use Pedoff CW Doppler probe
• Determine peak velocity
• Peak instantaneous pressure gradient
• Mean pressure gradient

Sub AS Intervention

Indication for intervention

• Exercise intolerance
• Severity of obstruction
• AI
• LVH

Intervention

• Surgical resection is treatment of choice for hemodynamically significant sub AS
• Simple resection of membrane

• Konno procedure- Septal Obstruction is resected and a VSD patch is put in  

Supravalvar AS

• Relatively uncommon
• Seen in patients with William’s Syndrome
• Subcostal view: you see abdominal aorta. Normal is pulsatile…with a CoA it won’t hit the baseline. Severe CoA will look like tardus parvus without touching baseline. 

Sup AS Associated Conditions

• PS

• COA

• Abdominal COA

• Seen in patients with William’s Syndrome

Williams Syndrome

• The association of supravalvar AS, elfin facies, mental retardation was described by Williams in 1961
• Also called "cocktail personality"
• May also see peripheral pulmonary stenosis

Types of Sup AS

• Discrete Membranous
• Hourglass
• Hypoplastic
• Iatrogenic

Discrete Membranous Sup AS

• Thin membrane directly above the sinus of Valsalva at the sinotubular junction without narrowing of the external Ao

Hourglass Sup AS

• Small narrowed segment of ascending Ao, both internal and external narrowing. Most common form.

Hypoplastic/Tubular/Diffuse Sup AS

• Uniform and diffuse hypoplasia extending from the sinuses of valsalva to the origin of the innominate artery. 20% of patients with supra AS have hypoplasia of the ascending aorta.

Iatrogenic Sup As

• Supravalvar AS at an anastomosis site after surgery (Ross procedure, arterial switch, conduit).

Sup AS Presentation

• With mild , isolated supra AS patient can be assymptomatic
• Initial finding with supra AS is a hypertrophic LV. The degree of hypertrophy depends on the severity of supra AS
• Chest pain, tachycardia because of coronary ostial stenosis
• Exercise intolerance

Best views

• Parasternal long axis
• High right parasternal long axis of aorta
• Suprasternal notch-long axis