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Valvular Stenosis

Valvular Stenosis

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Valvular Stenosis

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  1. Valvular Stenosis Susan A. Raaymakers, MPAS, PA-C, RDCS (AE)(PE) Radiologic and Imaging Sciences - Echocardiography Grand Valley State University, Grand Rapids, Michigan

  2. Basic PrinciplesApproach to Evaluation Valvular Stenosis Complete echocardiographic evaluation • Diagnostic imaging of the valve to define the etiology of stenosis • Quantification of stenosis severity • Evaluation of coexisting valvular lesions • Assessment of left ventricular systolic function • Response to chronic pressure overload of other upstream cardiac chambers, and the pulmonary vascular bed • Echocardiographic information integration with pertinent clinical data

  3. Fluid Dynamics of Valvular StenosisHigh Velocity Jet • Characterized by formation of a laminar, high velocity jet in the narrowed orifice • Flow profile in cross section of origin is flat (blunt) – • Remains blunt as the jet reaches the narrowest cross-sectional area in the vena contracta • Physiologic cross-sectional area < anatomic cross-sectional area

  4. Fluid Dynamics of Valvular StenosisHigh Velocity Jet • Length of high velocity jet is dependent on: • Orifice geometry • Examples: • Very short jet across a deformed, irregular calcified aortic valve • Longer jet along smoother tapering symmetric rheumatic mitral valve

  5. Rheumatic Heart Disease • Heart valves are damaged by a disease process that begins with a sore throat from streptococcal infection.  • Untreated, the streptococcal infection can develop into acute rheumatic fever. • Rheumatic fever is an inflammatory disease that can affect many connective tissues of the body, especially those of the heart, joints, brain or skin. • Who is at risk of rheumatic heart disease? • Anyone can get acute rheumatic fever, but it usually occurs in children five to fifteen  years old. The resulting rheumatic heart disease can last for life. • What are the symptoms of rheumatic heart disease? • The symptoms vary greatly from person to person. Often the damage to heart valves is not immediately noticeable. • A damaged heart valve either does not completely close or does not completely open.

  6. Rheumatic Heart Disease • Mitral stenosis • Progressive fibrosis • Thickening and calcification of valve • Enlargement of LA • Formation of mural thrombi • Funnel shaped “fish-mouthed” mitral valve • MS and MR • AS and AI

  7. Non-dynamic images

  8. Fluid Dynamics of Valvular StenosisRelationship between Pressure Gradient and Velocity • Simply stated: Simplified Bernoulli equation 4V2

  9. Fluid Dynamics of Valvular StenosisDistal Flow Disturbance • Distal to stenotic jet • Flowstream becomes disorganized w/multiple blood flow velocities and directions • Distance that flow disturbance propagates downstream is related to stenosis severity • Aortic proximal flow patterns • Proximal to a stenotic valve • Flow is smooth and laminar (organized) with normal flow velocity • “Flat” flow profile

  10. Fluid Dynamics of Valvular StenosisDistal Flow Disturbance • Mitral valve proximal velocities • Left atrial to left ventricular pressure gradient drives flow passively from the left atrium abruptly across the stenotic orifice • Proximal flow acceleration is prominent over a large region of the left atrium • 3D velocity profile is curved: flow velocities are • Faster adjacent to and in the center of a line continuous with the jet direction through the narrowed orifice • Slower at increasing radial distances from the valve orifice • Hemi-elliptical in comparison to a stenotic semilunar valve

  11. Fluid Dynamics of Valvular StenosisDistal Flow Disturbance • Take home message • Stroke volume • Calculated proximal to a stenotic valve • Based on knowledge of cross-sectional area of flow and spatial mean flow velocity over a period of flow

  12. Aortic Stenosis

  13. Classified as Three Types • Valvular • Subaortic • Supra-valvular

  14. Diagnostic Imaging of the Aortic Valve Aortic stenosis most often due to: • Calcific aortic stenosis • Congenital valve disease (most often bicuspid. In rare instances or unicuspid or quadracuspid) • Rheumatic valve disease

  15. Diagnostic Imaging of the Aortic ValveCalcific Aortic Stenosis • Most common etiology of aortic stenosis • Degenerative age related calcification • Occurs slowly over many years • Initially presents as “sclerosis” area of increased echogenicity typically at base of valve leaflets sans significant obstruction to left ventricular outflow

  16. Aortic StenosisCalcific/Degenerative • Mean age 60 – 70 • Clinically significant obstruction occurs typically from age 70-85 years old • Most common cause of aortic stenosis 10-007 Feigenbaum

  17. Pathologic specimen of a severely stenotic trileaflet aortic valve, which demonstrates gross nodular athero-calcific changes on the aortic side ofthe leaflets.

  18. Aortic StenosisCalcific/Degenerative • Systolic leaflet excursion of less than 15 mm by 2D or M-mode • Severe obstruction is reliably excluded Again 10-007 Feigenbaum

  19. Aortic StenosisCalcific/Degenerative • Planimetry of aortic valve is possible in some patients • Interpretation with caution due to complex 3D anatomy of the orifice in calcific degenerative stenosis • Ensure image plane is aligned at narrowest orifice of the valve • 2D represents anatomic valve area – Doppler data reflects functional valve area

  20. Planimetry 10-006b Feigenbaum

  21. Aortic Stenosis - Bicuspid Valve • Severe calcification: difficult to differentiate between bicuspid and tricuspid aortic valve

  22. Aortic Stenosis - Bicuspid Valve • Average age of onset of calcific stenosis symptom is younger: usually 45 to 65 years old

  23. Aortic Stenosis - Bicuspid Valve • Can be identified best in parasternal short-axis view • Football shaped opening • Long-axis: “dome-like” appearance • Typically leaflets are unequal in size • If anterior-posterior opening: anterior leaflet is larger • If lateromedial opening: rightward leaflet is larger

  24. Aortic Stenosis - Bicuspid Valve • Often have raphae (seam-like line or ridge) in the larger leaflet: closed valve appears trileaflet • Identify as trileaflet only in systole 18-34a & b Feigenbaum

  25. Aortic Stenosis – Unicuspid Valve

  26. Aortic Stenosis - Rheumatic • Rheumatic valvular disease preferentially involves mitral valve • Rheumatic aortic stenosis occurs concurrently with rheumatic mitral valve disease • Results in commissural fusion of the aortic leaflets similar to rheumatic mitral disease • Appears similar to calcific aortic stenosis (if mitral involved suspect aortic stenosis due to rheumatic disease)

  27. Summary

  28. Aortic Stenosis - Congenital • Usually diagnosed at childhood • May not become symptomatic until young adulthood • May be resultant from re-stenosis after surgical valvotomy

  29. Aortic StenosisDifferential Diagnosis Left ventricular outflow tract obstruction • Fixed valvular obstruction • Subaortic membrane or a muscular subaortic stenosis • Dynamic subaortic obstruction • Hypertrophic cardiomyopathy • Supravalvular stenosis

  30. Aortic StenosisDifferential Diagnosis

  31. Aortic StenosisDifferential Diagnosis Fixed valvular obstruction • Subaortic membrane • Suspect when valve anatomy is not clearly stenotic even though Doppler velocity and color flow indicates stenosis • TTE vs TEE 10-027 Feigenbaum

  32. Subaortic Membrane – Fixed Subvalvular Stenosis 18-30 Feigenbaum

  33. Dynamic Subvalvular Stenosis 19-29a Feigenbaum

  34. Supravalvular stenosis in a 30 year old with familial hypercholesterolemia Non-dynamic

  35. Aortic StenosisQuantitation of Stenosis Severity • Measurement of maximum aortic jet velocity • Calculation of mean and maximum gradient • Determination of continuity equation valve area • Ratio of outflow tract to aortic jet velocity

  36. Aortic StenosisQuantitation of Stenosis Severity • Dependence of pressure gradients on volume flow rate • Coexisting aortic regurgitation = high transaortic pressure gradient • Depressed ejection fraction/coexisting mitral regurgitation = low transaortic pressure • Coexisting conditions common in adults with aortic stenosis

  37. Aortic StenosisQuantitation of Stenosis Severity • Continuity Equation • Stroke volume proximal to valve = transvalvular stroke volume • CSA LVOT X VTI LVOT = CSA Ao X VTI Ao

  38. Aortic StenosisAortic Valve Index Effect of body size into account AVA index = AVA/BSA

  39. Aortic StenosisTechnical Considerations and Pitfalls • Continuity equation valve areas: well validated in comparison with Gorlin formula • Continuous wave Doppler needed d/t high velocities • Use of non-imaging transducer learning curve • Parallel to flow: utilize several windows • Outflow tract diameter: measure in mid-systole (inner edge to leading edge)

  40. Aortic StenosisCoexisting Valvular Disease • Approximately 80% of patients with predominate aortic stenosis have coexisting aortic regurgitation • Regurgitation does not alter continuity calculation valve area calculations

  41. Aortic StenosisResponse of the Left Ventricle to Valvular Aortic Stenosis • Chronic overload • Concentric left ventricular hypertrophy • LV systolic function typically preserved until late in disease course • Dysfunction due to increased afterload and often reversible post repair

  42. Aortic StenosisResponse of the Left Ventricle to Valvular Aortic Stenosis Female vs. male • Female: • More hypertrophy • Smaller ventricles • Preserved systolic function • Male: • Less hypertrophy • More left ventricular dilation • Higher prevalence of systolic dysfunction

  43. Aortic StenosisClinical Applications in Specific Patient Populations Symptomatic Aortic Stenosis Doppler evaluation • Aortic jet maximum velocity: simplest and most quantitative • >4 m/sec considered surgical • May have >4 m/sec and coexisting MR = not surgical • <3 m/sec significant aortic stenosis unlikely; valve replacement unnecessary • Caution: parallel to flow and systolic dysfunction

  44. Aortic StenosisClinical Applications in Specific Patient Populations Asymptomatic Aortic Stenosis: Disease Progression and Prognosis • Reproducibility • Recording variability • Intercept angle, wall filters, signal strength, acoustic window • Measurement variability • Identification of the maximum velocity, outflow tract diameter • Physiologic variability • Interim changes in heart rate, stroke volume, or pressure gradient

  45. Aortic StenosisClinical Applications in Specific Patient Populations Asymptomatic Aortic Stenosis: Disease Progression and Prognosis • Doppler echocardiography • Prognosis depends o presence or absence of clinical symptoms and not on hemodynamics severity • Rate of hemodynamic progression is variable from patient to patient • On average: • Increase of 0.3 m/sec per year • Increase of mean pressure of 7 mmHg per year • Valvular size decrease of 0.1 cm2 per year • Concurrent decrease in volume flow rate may obscure disease progression resulting in no change in jet velocity

  46. Aortic Stenosis 2D Criteria • Systolic “doming” and diastolic prolapse represent congenital features • Usually thickened valve leaflets with restricted motion. Doming during early systole. • Concentric left ventricular hypertrophy with normal LV cavity size. LA size will be increased (late in course of AS)

  47. Aortic StenosisDobutamine Echocardiography • Dobutamine is a drug used to increase stroke volume across the stenotic valve. • Mild to moderate stenosis valve leaflets will open wider with increase in stroke volume. • True severe stenosis • Valve will not open wider • Dobutamine infusion will increase the maximum velocity of both the outflow tract and the jet proportionally. • In milder forms of stenosis, increase in velocity of the left ventricular outflow tract will be much greater than that of the jet (due to the increase in valve area) • Limitation of zero change in velocity results

  48. Aortic StenosisDobutamine Stress Echocardiography 10-022 Feigenbaum

  49. Additional Information •