Aortic Stenosis Flashcards
Aortic stenosis - underlying patholophysiology
- Degenerative calcification: 2/2 long-term shear stress -> proliferative and inflammatory changes -> calcifications at base of cusps (7th and 8th decades)
- BAV: early degeneration and calcification due to altered flow patterns (5th and 6th decades)
- Rheumatic AS: commissural fusion
LaPlace’s law
Wall stress inversely proportional to wall thickness
Tension = transmural pressure x radius / 2 x wall thickness
T = PR/2w
LV response to AS
LV experiences increased workload and wall stress
- LVH (LaPlace’s law)
- Diastolic dysfunction (2/2 LVH)
- Myocardial fibrosis –> systolic failure
- Decreased EF
Classic triad of symptoms in AS
Angina, dyspnea, syncope
- Angina: decreased O2 delivery due to LVH and elevated LVEDP, endocardial compression
- Dyspnea: LVH is no longer sufficiently compensatory
- Syncope: arrhythmias, inability to sufficiently augment CO with activity, vasoplegia
How is low flow-low gradient AS defined?
- Low flow state (EF <50%, SVI <35cc/m2)
- AVA <1.0cm2
- MG <40mmHg on TTE
What are the three subcategories of low flow-low gradient AS?
- Classic LF/LG AS
- Pseudo LF/LG AS
- Paradoxical LF/LG AS
How does classic LF/LG AS respond to a dobutamine challenge?
- CO and SVi increases
- mean AV gradient increases to >40mmHg
- AVA remains <1.0cm2
If CO increases >20% with dobutamine, patient has ejection reserve (important for risk w/ surgical AVR)
How does pseudo LF/LG AS respond to a dobutamine challenge?
- CO and SVi increases
- AVA increases to >1.0cm2 (b/c now there is enough flow to open the leaflets more)
Not a candidate for AVR; use medical management
What is paradoxical LF/LG AS?
This is a separate clinical entity characterized by:
- normal LVEF
- decreased SVi
- MG <40
- AVA <1.0cm2
- Seen in elderly patients with LVH, small LV cavity, and diastolic dysfunction
- Diagnosis confirmed by indexed AVA <0.6cm2/m2
How does HTN cause underestimation of degree of stenosis?
Hypertension causes a second pressure load on the LV –> lower forward stroke volume –> lower measured transaortic pressure gradient
(AHA 2020 guideline on valve disease)
When is balloon angioplasty indicated for the AV?
- pediatric patients (to allow growth until ready for surgery)
- bridge to TAVR in refractory pulmHTN/CHF
- for QOL in patients who are not candidates for SAVR/TAVR
Does not improve survival, short-lived improvement in sx
What are the indications for AVR in symptomatic severe AS?
- Dyspnea, CHF, angina, syncope or presyncope
- Classic and paradoxical LF/LG AS
What are the indications for AVR in asymptomatic severe AS?
- Undergoing cardiac surgery for other indications
- Decreased exercise tolerance/drop in BP >10mmHg with exertion
- BNP >3x normal
- Peak velocity increasing by >0.3m/s per year
- Peak velocity >5m/s
What is the indication for AVR in asymptomatic moderate AS?
- Undergoing cardiac surgery for other indications
How does perioperative mortality compare between TAVR and SAVR?
Is actually similar
