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Aortic Stenosis

Aortic Stenosis. Randall Harada. Echo conference: 12 Sep 2007. Etiology. Age < 70. Age ≥ 70. Echo conference: 12 Sep 2007. Pathophysiology. Congential AS: turbulent flow → fibrosis, calcification Rheumatic AS: vascularization of leaflets → retraction, stiffening, adhesions, fusion

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Aortic Stenosis

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  1. Aortic Stenosis Randall Harada Echo conference: 12 Sep 2007

  2. Etiology Age < 70 Age ≥ 70 Echo conference: 12 Sep 2007

  3. Pathophysiology • Congential AS: turbulent flow → fibrosis, calcification • Rheumatic AS: vascularization of leaflets → retraction, stiffening, adhesions, fusion • Calcific / degenerative AS: • Similarities to atherosclerosis: lipid accumulation, inflammatory cell infiltration, calcification • Clinical factors mirror CAD risk factors (Dissimilarities: little SM cell proliferation, lack of neovascularization, and more prominent micro-calcification) Echo conference: 12 Sep 2007 Otto CM. Circulation 90; 1994

  4. Pathophysiology Stepwise multiple logistic regression Stewart BF, JACC 29(3) 1997 Echo conference: 12 Sep 2007

  5. Pathophysiology Aortic stenosis Increased afterload Atrial contraction LVH Increased preload Preserved wall stress Normal systolic function Echo conference: 12 Sep 2007

  6. Pathophysiology Aortic stenosis Increased afterload LVH LVH inadequate (afterload mismatch) ↑ O2 demand ↓ coronary perfusion pressure Compression of intramyocardial arteries ↓ CBF per unit of mass Reduced myocardial contractility Myocardial ischemia Echo conference: 12 Sep 2007

  7. Natural history • Long latent period: • Mortality is low during the latent period; similar to age-matched • Progression to symptomatic or severe aortic stenosis has marked individual variability • Average rate of progression 0.10 – 0.12 cm2 per year Horstkotte D, Eur Heart J 9(suppE) 1988 Echo conference: 12 Sep 2007

  8. Natural history • Severe stenosis with symptoms: Ross J, Circ 36(supp IV) 1968 Echo conference: 12 Sep 2007

  9. Clinical care of AS • Assessment of symptoms; patient education • Careful exercise testing for asymptomatic patients with unclear medical histories: • Serum BNP – non-specific marker • Echocardiography: eval AS severity, LV function ACC/AHA, Circ 114, 2006 Echo conference: 12 Sep 2007

  10. Medical therapy • Antibiotic prophylaxis no longer recommended • No medical therapies proven to prevent or delay AS • In severe AS, atrial fibrillation is often poorly tolerated Echo conference: 12 Sep 2007

  11. Medical therapy Rajamannan NM, Circ 110, 2004 Echo conference: 12 Sep 2007

  12. SALTIRE trial (atorvastatin 80 vs placebo) Cowell SJ, NEJM 352, 2005 Echo conference: 12 Sep 2007

  13. RAAVE study • 121 patients • Not randomized • Active arm: patients who need statin due to hyperlipidemia • Mean LDL 160 mg/dL → at end of study: 93 mg/dL • Higher prevalence of HTN and diabetes • Control arm: patients who do not meet guidelines for a statin • Mean LDL 119 mg/dL → at end of study: 118 mg/dL Moura LM, JACC 49, 2007 Echo conference: 12 Sep 2007

  14. RAAVE study Moura LM, JACC 49, 2007 Echo conference: 12 Sep 2007

  15. Ongoing Statin RCTs • Stop Aortic Stenosis (STOP-AS) - U.S. • Simvastatin and Ezetimibe in Aortic Stenosis (SEAS) - Europe • Aortic Stenosis Progression Observation Measuring Effects of Rosuvastatin (???) - Canada ASTRONOMER Echo conference: 12 Sep 2007

  16. Evaluation of AS severity • Maximum aortic velocity • Mean transvalvular gradient • Aortic valve area by continuity equation Echo conference: 12 Sep 2007

  17. Evaluation of AS severity ↔ max instantaneous gradient • Maximum aortic velocity ← 4.2 m/s ← 71 mmHg Echo conference: 12 Sep 2007 http://www.grc.nasa.gov/WWW/K-12/airplane/bern.html

  18. Evaluation of AS severity ↔ max instantaneous gradient • Maximum aortic velocity • Modified Bernoulli equation: ∆P = 4 [(V2)2 – (V1)2] • Simplified equation (assuming V2 >>>V1) : ∆P = 4 V2 Echo conference: 12 Sep 2007

  19. Evaluation of AS severity • Maximum aortic velocity • Most reproducible • Strongest predictor of clinical outcomes • Mild: 2.6 – 3.0 m/s • Moderate: 3 – 4 m/s • Severe: >4 m/s Echo conference: 12 Sep 2007

  20. Evaluation of AS severity • Maximum aortic velocity • Mean transvalvular gradient • Aortic valve area by continuity equation Echo conference: 12 Sep 2007

  21. Evaluation of AS severity • Mean transvalvular gradient Echo conference: 12 Sep 2007

  22. Evaluation of AS severity • Mean transvalvular gradient • Mild: < 25 mm Hg • Moderate: 25 – 40 mm Hg • Severe: > 40 mm Hg Echo conference: 12 Sep 2007

  23. Evaluation of AS severity • Maximum aortic velocity • Mean transvalvular gradient • Aortic valve area by continuity equation Echo conference: 12 Sep 2007

  24. Evaluation of AS severity • Aortic valve area by continuity equation • Volume flow proximal to valve = volume flow thru orifice • CSALVOT x VTILVOT = AVA x VTIAV • CSALVOT x VLVOT = AVA x VAV • AVA = (CSALVOT x VLVOT) / VAV • Velocity ratio = VLVOT / VAV Echo conference: 12 Sep 2007

  25. Evaluation of AS severity • Aortic valve area by continuity equation • Severity by AHA criteria: • Mild: > 1.5 cm2 • Moderate: 1.0 – 1.5 cm2 • Severe: < 1.0 cm2 • Severity by BIDMC criteria: • Mild: > 1.2 cm2 • Moderate: 0.8 – 1.2 cm2 • Severe: < 0.8 cm2 • Dimensionless ratio < 0.25 corresponds to severe AS Echo conference: 12 Sep 2007

  26. Evaluation of AS severity • Aortic valve area by continuity equation • Assumes: • Geometry of the LVOT is round • Acquired imaging plane (PLAX) is parallel to the LVOT • 3D-echo may improve measurements Echo conference: 12 Sep 2007 Doddamani S. Echocardiography 24;2007

  27. Evaluation of AS severity • 55 consecutive patients w/ nl AV • Estimations of LVOT area: • 2D-echo PLAX: (π r2) • 3D-echo idealized PLAX: (π r2) • 3D-echo planimetry in the “transverse plane” • 3D-echo “ellipse”: (π x LVOTlong x LVOTshort) Echo conference: 12 Sep 2007 Doddamani S. Echocardiography 24;2007

  28. Evaluation of AS severity • Eccentricity index = 1 – (LVOTshort / LVOTlong) median ←Round Oblate → Echo conference: 12 Sep 2007 Doddamani S. Echocardiography 24;2007

  29. Evaluation of AS severity • Comparison of LVOT area estimations Echo conference: 12 Sep 2007 Doddamani S. Echocardiography 24;2007

  30. Evaluation of AS severity • Comparison of LVOT area estimations Echo conference: 12 Sep 2007 Doddamani S. Echocardiography 24;2007

  31. Timing of valve replacement Echo conference: 12 Sep 2007 Otto CM, JACC 47, 2006

  32. Timing of valve replacement Echo conference: 12 Sep 2007 Otto CM, JACC 47, 2006

  33. Asymptomatic patients • Risk of sudden death with AS < 1% • What is the risk of surgery? Echo conference: 12 Sep 2007

  34. In-hospital, post-op mortality Echo conference: 12 Sep 2007 Ambler G, Circ 112, 2005

  35. In-hospital, post-op mortality Echo conference: 12 Sep 2007 Ambler G, Circ 112, 2005

  36. Exceptions to the asymptomatic rule Undergoing other cardiac sx Echo conference: 12 Sep 2007 Otto CM, JACC 47, 2006

  37. Problematic situations • Hypertension • May mask the severity of AS • For a given AVA, transaortic ∆P (velocity) decreases when systemic arterial compliance decreases. Echo conference: 12 Sep 2007 Otto CM, JACC 47, 2006

  38. Problematic situations • LV dysfunction • Primary cardiomyopathy vs. secondary due to true AS • Low stroke volume may reduce leaflet motion in a non-stenotic valve • Dobutamine stress echo to differentiate • Flexible leaflets: increase in EF, leaflet excursion, and AVA • Severe AS: increase in EF, no change in AVA • “Lack of contractile reserve”: no increase in EF Echo conference: 12 Sep 2007

  39. Congenital AS • Subvalvar • Supravalvar • Valvar Echo conference: 12 Sep 2007

  40. Subvalvar / Subaortic stenosis • Dynamic stenosis: • HOCM • Fixed stenosis: • Thin membrane • Thick fibromuscular ridge Echo conference: 12 Sep 2007

  41. Subvalvar / Subaortic stenosis Echo conference: 12 Sep 2007

  42. Subvalvar / Subaortic stenosis Echo conference: 12 Sep 2007

  43. Subaortic stenosis • Pathophysiology • Underlying abnormality of LVOT structure • Turbulent flow → progressive LVOT fibrosis → AV leaflet thickening → AR 55% • Infectious endocarditis 12% • Timing of surgery • Children: gradient ≥ 30 mm Hg • Adults: gradient ≥ 50 mm Hg • AR • Recurrence rate: 15 - 27% reoperation Echo conference: 12 Sep 2007

  44. Supravalvar stenosis • Hourglass deformity (discrete constriction) 60-75% • Diffuse narrowing of variable length in ascending aorta 25-40% Echo conference: 12 Sep 2007

  45. Supravalvar stenosis • Etiologies • Homozygous familial hypercholesterolemia • Familial autosomal dominant form – mutation of elastin gene • Sporadic mutation form • As a feature of Williams syndrome • Gene deletions (including elastin) • Short stature, facial abnormalities, visuospatial cognition defects, renovascular HTN, mental retardation • Endocarditis prophylaxis • Indications for surgery uncertain Echo conference: 12 Sep 2007

  46. Valvar AS • Unicuspid or unicommissural valve • Bicuspid or bicommissural valve • Aortic annular hypoplasia Echo conference: 12 Sep 2007

  47. Bicuspid AV • Prevalence estimate: 0.5-2% • 3:1 male:female • Peak age of symptom onset: 40 – 60 years-old • Familial • Present in ~9% 1st degree relatives Echo conference: 12 Sep 2007 Huntington K, JACC 30, 1997

  48. Bicuspid AV Echo conference: 12 Sep 2007

  49. Bicuspid AV Echo conference: 12 Sep 2007

  50. Bicuspid AV • Aortic abnormalities • Coarctation: 6% • Dilatation of aortic root and/or ascending aorta: ~50% • Predictor of ascending aorta aneurysm or dissection • Presence is independent of the functional state of the AV • Defects in aortic media Echo conference: 12 Sep 2007

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