AORTIC STENOSIS

Normal Aortic valve Three cusps, crescent shaped3 commissures 3 sinusessupported by fibrous annulus

3.0 to 4.0 cm2

Aortic stenosis- CausesMost common Bicuspid aortic valve with calcificationSenile or Degenerative calcific ASRheumatic ASLess commonCongenitalType 2 HyperlipoproteinemiaOnchronosis

Etiology & Morphology

Bicuspid Aortic valve

Two cusps are seen in systole with only two commissures framing an elliptical systolic orifice(the fish mouth appearance).

Diastolic images may mimic a tricuspid valve when a raphe is present.

Bicuspid Aortic valve Fusion of the right and left coronary cusps (80%)

Fusion of the right and non-coronary cusps(20%) Schaefer BM et al. Am J Cardiol 2007;99:68690 Schaefer BM et al.Heart 2008;94:16341638.

Types of Bicuspid Aortic valve

J Am Coll Cardiol Img. 2013;6(2):150-161.doi:10.1016/j.jcmg.2012.11.007

Bicuspid Aortic valveParasternal long-axis echocardiogram may showSymmetric closure lineSystolic domingDiastolic prolapse of the cuspsIn adults, stenosis typically is due to calcific changes, which often obscures the number of cusps, making determination of bicuspid vs. tricuspid valve difficult

Bicuspid Aortic valve

Unicuspid & Quadricuspid valves

Which of the following is a predictor of outcome (death or need for valve replacement due to symptoms) in patients with severe, asymptomatic aortic stenosis?A. Patient ageB. Diabetes mellitusC. Bicuspid aortic valve morphologyD. The presence of moderate to severe calcificationQuestion

Calcific Aortic Stenosis Nodular calcific masses on aortic side of cuspsNo commissural fusionFree edges of cusps are not involvedstellate-shaped systolic orifice

The degree of valve calcification is a predictor of clinical outcome.

Calcific Aortic StenosisParasternal long axis view showing echogenic and immobile aortic valveParasternal short-axis view showing calcified aortic valve leaflets. Immobility of the cusps results in only a slit like aortic valve orifice in systole

Aortic sclerosisThickened calcified cusps with preserved mobility

Typically associated with peak doppler velocity of less than 2.5 m/sec

Rheumatic aortic stenosisCharacterized by

Commissural fusionTriangular systolic orificeThickening & calcification

Accompanied by rheumatic mitral valve changes.

Subvalvular aortic stenosisThin discrete membrane consisting of endocardial fold and fibrous tissueA fibromuscular ridge Diffuse tunnel-like narrowing of the LVOTAccessory or anomalous mitral valve tissue.

Long axis view in a patent with a subaortic membrane (arrow).

Supravalvular Aortic stenosisType I - Thick, fibrous ring above the aortic valve with less mobility and has the easily identifiable 'hourglass' appearance of the aorta. Type II - Thin, discrete fibrous membranelocated above the aortic valve Type III- Diffuse narrowing

Stages of Valvular AS

Stages of Valvular AS

Should Aortic Valve Area Be Indexed?Indexing valve area is important in children, adolescents, and small adultsBSA < 1.5 m2BMI < 22 kg/m2height < 135 cmIn obese patients, valve area does not increase with excess body weight, and indexing for BSA is not recommended

Valve anatomy, etiologyExclude other LVOTOStenosis severity jet velocitymean pressure gradientAVA continuity equationLV dimensions/hypertrophy/EF/diastolic fnAorta- aortic diameter/ assess COAAR quantification if more than mild MR- mechanism & severityPulmonary pressure

Approach

2D Echo-Long axis viewDiastoleSystole

2D Echo-Short axis viewDiastoleSystole

Y or inverted Mercedes-Benz sign

Which of these M-mode images is suggestive of valvular aortic stenosis?

Limitations Single dimension Asymmetrical AV involvement Calcification / thickness LV systolic function CO status

M Mode- Aortic Stenosis

Doppler assessment of ASThe primary haemodynamic parameters recommended

Peak transvalvular velocity

Mean transvalvular gradient

Valve area by continuity equation.(EAE/ASE Recommendations for Clinical Practice 2008)

Peak Transvalvular velocityContinuous-wave Doppler ultrasoundMultiple acoustic windows Apical and suprasternal or right parasternal most frequently yield the highest velocityrarely subcostal or supraclavicular windows may be requiredThree or more beats are averaged in sinus rhythm, with irregular rhythms at least 5 consecutive beats

The Effect of Angle

Doppler Equation- Rearranged

F0: Transmitted frequency of ultrasoundV: velocity of blood.C: Speedq: intercept angle between the interrogation beam and the target

AS jet velocity is defined as the highest velocity signal obtained from any window after a careful examinationAny deviation from a parallel intercept angle results in velocity underestimationThe degree of underestimation is 5% or less if the intercept angle is within 15 of parallel.Angle correction should not be used because it is likely to introduce more error given the unpredictable jet direction.Peak Transvalvular velocity

Which of these continuous-wave spectral Doppler tracings is most suggestive of aortic stenosis?

The shape of the CW Doppler velocity curve is helpful in distinguishing the level and severity of obstruction. With severe obstruction, maximum velocity occurs later in systole and the curve is more rounded in shapeWith mild obstruction, the peak is in early systole with a triangular shape of the velocity curve

Peak Transvalvular velocity

The shape of the CWD velocity curve also can be helpful in determining whether the obstruction is fixed or dynamicDynamic sub aortic obstruction shows a characteristic late-peaking velocity curve, often with a concave upward curve in early systole

Peak Transvalvular velocity

Mean Transvalvular GradientThe difference in pressure between the left ventricle and aorta in systoleGradients are calculated from velocity informationThe relationship between peak and mean gradient depends on the shape of the velocity curve.

Bernoulli equations P max =4 (v max- v2proximal) The maximum gradient is calculated from maximum velocityP max =4v maxThe mean gradient is calculated by averaging the instantaneous gradients over the ejection periodMean Transvalvular Gradient

The simplified Bernoulli equation assumes that the proximal velocity can be ignoredWhen the proximal velocity is over 1.5 m/s or the aortic velocity is ,3.0 m/s, the proximal velocity should be included in the Bernoulli equation P max =4 (v max- v2proximal)ExampleV2 = AS velocity = 4 m/sV1 = LVOT velocity = 2 m/s4 (V22 V12) = 48 mmHg4 V22 = 64 mmHg (overestimation by 33%)Mean transvalvular gradient

Comparing pressure gradients calculated fromdoppler velocities to pressures measured at cardiac catheterization.

Not simultaneousNon-physiologic

Comparing pressure gradients calculated fromdoppler velocities to pressures measured at cardiac catheterization. Currie PJ et al. Circulation 1985;71:1162-1169

Aortic valve area (Continuity equation)

A. Severely decreased LV stroke volumeB. Severe aortic regurgitationC. Severe mitral regurgitationD. Severe dynamic LVOT obstruction (SAM)E. Severe pulmonary hypertensionFor which of the following situations, with AS, is it invalid to use continuity between the LVOT and the aortic valve to calculate aortic valve area?Question

Calculation of continuity-equation valve area requires three measurements AS jet velocity by CWD LVOT diameter for calculation of a circular CSA LVOT velocity recorded with pulsed Doppler.Aortic Valve Area (Continuity Equation)

QuestionA. LVEF = 25%B. Patient also has severe MRC. Sample volume too close to AV for LVOT TVI measurementD. LV diastolic diameter 45 mmE. LVOT diameter measurement too smallFor a patient with aortic stenosis you obtain MG = 30 mmHg and AVA = 0.6 cm2 Which of the following would not explain this discrepancy?

LVOT diameter and velocity should be measured at the same distance from the aortic valve.When the PW sample volume is optimally positioned, the recording shows a smooth velocity curve with a well-defined peak.

Aortic Valve Area (Continuity Equation)

QuestionThe largest source of error in calculation of aortic valve area by the continuity equation is:A. Peak velocity across the aortic valveB. LVOT diameterC. Peak velocity across the LVOTD. Timevelocity integral of aortic valve CW spectral Doppler displayE. Timevelocity integral of LVOT PW spectral Doppler display

LVOT Diameter

Well validated - clinical & experimental studies. Zoghbi WA et al. Circulation 1986;73:452-9. Oh JK et al. J Am Coll Cardiol 1988;11:1227-34.

Measures the effective valve area, the weight of the evidence now supports the concept that effective, not anatomic, orifice area is the primary predictor of clinical outcome. Baumgartner et al. J Am Society Echo 2009; 22,1, 1-23.Aortic valve area (Continuity equation)

Limitations Of Continuity-equation Valve AreaIntra- and interobserver variability AS jet and LVOT velocity 3 to4%. LVOT diameter 5% to 8%.When sub aortic flow velocities are abnormal SV calculation at this site are not accurateSample volume placement near to septum or anterior mitral leaflet

Observed changes in valve area with changes in flow rate AS and normal LV function, the effects of flow rate are minimalThis effect may be significant in presence concurrent LV dysfunction.Limitations Of Continuity-equation Valve Area

Serial measurementsDuring follow-up any significant changes in results should be checked in detail:Make sure that aortic jet velocity is recorded from the same window with the same quality (always report the window where highest velocities can be recorded). when AVA changes, look for changes in the different components incorporated in the equation. LVOT size rarely changes over time in adults.

Another approach to reducing error related to LVOT diameter measurements is removing CSA from the simplified continuity equation.This dimensionless velocity ratio expresses the size of the valvular effective area as a proportion of the CSA of the LVOT. Velocity ratio= VLVOT/VAVIn the absence of valve stenosis, the velocity ratio approaches 1, with smaller numbers indicating more severe stenosis.Velocity ratio

Aortic valve area -PlanimetryPlanimetry may be an acceptable alternative when Doppler estimation of flow velocities is unreliablePlanimetry may be inaccurate when valve calcification causes shadows or reverberations limiting identification of the orifice

Marie Arsenault, et al. J. Am. Coll. Cardiol. 1998;32;1931-1937

Aortic valve area - Planimetry

3D Planimetry

Modified continuity equation (CE)3D echo assessment of SV

3D is more accurate than Doppler CE and than 2D volumetric methods to calculate AVA Limitations: arrhythmias, significant mitral regurgitation

Maximal aortic cusp separation (MACS) Vertical distance between right CC and non CC during systole M Mode- Aortic StenosisAortic valve areaMACS MeasurementPredictive valueNormal AVA >2Cm2Normal MACS >15mm100%AVA>1.0> 12mm96%AVA< 0.75 < 8mm97%Gray area8-12 mm..

DeMaria A N et al. Circulation.Suppl II. 58:232,1978

Experimental descriptors of stenosis severity(Level 3 EAE/ASE Recommendations -not recommended for routine clinical use)

Valve resistanceRelatively flow-independent measure of stenosis severity Depends on the ratio of mean pressure gradient and mean flow rateResistance = (Pmean /Qmean) 1333There is a close relationship between aortic valve resistance and valve areaThe advantage over continuity equation not established

Left ventricular stroke work lossLeft ventricle expends work during systole to keep the aortic valve open and to eject blood into the aortaSWL(%) = (100Pmean)/ Pmean+SBPA cutoff value more than 25% effectively discriminated between patients experiencing a good and poor outcome. Kristian Wachtell. Euro Heart J.Suppl. (2008) 10 ( E), E16E22

Energy loss index Damien Garcia.et al. Circulation. 2000;101:765-771.Fluid energy loss across stenotic aortic valves is influenced by factors other than the valve effective orifice area .An experimental model was designed to measure EOA and energy loss in 2 fixed stenoses and 7 bioprosthetic valves for different flow rates and 2 different aortic sizes (25 and 38 mm). EOA and energy loss is influenced by both flow rate and AA and that the energy loss is systematically higher (152%) in the large aorta. Damien Garcia.et al. Circulation. 2000;101:765-771.

Energy loss coefficient (EOA AA)/(AA - EOA) accurately predicted the energy loss in all situations . It is more closely related to the increase in left ventricular workload than EOA. To account for varying flow rates, the coefficient was indexed for body surface area in a retrospective study of 138 patients with moderate or severe aortic stenosis. The energy loss index measured by Doppler echocardiography was superior to the EOA in predicting the end points An energy loss index #0.52 cm2/m2 was the best predictor of diverse outcomes (positive predictive value of 67%).

Energy loss index Damien Garcia.et al. Circulation. 2000;101:765-771.

Effects of concurrent conditions on assessment of severity

Effect of concurrent conditions

Left ventricular hypertrophySmall ventricular cavity & small LV ejects a small SV so that, even in severe AS the AS velocity and mean gradient may be lower than expected. Continuity-equation valve area is accurate in this situation

Left ventricular systolic dysfunctionLVEF often underestimates myocardial dysfunctionGlobal longitudinal function is more sensitive to identify intrinsic myocardial dysfunction (i.e. GLS < 16%)

Hypertension3545% of patients primarily affect flow and gradients but less AVA measurements Control of blood pressure is recommendedThe echocardiographic report should always include a blood pressure measurement

Effect of concurrent conditions contd

Aortic regurgitation About 80% of adults with AS also have aortic regurgitationHigh transaortic volume flow rate, maximum velocity, and mean gradient will be higher than expected for a given valve areaIn this situation, reporting accurate quantitative data for the severity of both stenosis and regurgitationEffect of concurrent conditions contd

Mitral valve diseaseWith severe MR, transaortic flow rate may be low resulting in a low gradient .Valve area calculations remain accurate in this settingA high-velocity MR jet may be mistaken for the AS jet. Timing of the signal is the most reliable way to distinguishEffect of concurrent conditions contd

High cardiac outputRelatively high gradients in the presence of mild or moderate AS The shape of the CWD spectrum with a very early peak may help to quantify the severity correctlyAscending aortaAortic root dilationCoarctation of aortaEffect of concurrent conditions contd

Exercise EchocardiographyShould not be performed in symptomatic patientsCan be useful in asymptomatic patientsCriteria For Positive Exercise ECG (less accurate in elderly subjects > 70 y)symptom development +++ (recommendation for surgery class IC)abnormal blood pressure response: lack of rise ( 20 mmHg) or fall in blood pressure ++ (recommendation for surgery class IIaC)ST changes or complex ventricular arrhythmias (minor criteria)

Exercise EchocardiographyQuantify exercise-induced changesMean pressure gradientContractile reserve (changes in LV ejection fraction/strain)Pulmonary arterial systolic pressure (PASP)Criteria of poor outcome with exercise echoIncrease in mean aortic gradient > 1820 mmHg (recommendation for surgery class IIbC)Weak change in LV ejection fractionPulmonary hypertension (PASP > 60 mmHg)

Rules for Quantitation of Aortic Stenosis by EchocardiographyCW Doppler from multiple windowsSee the base of the aortic cusps before you measure the LVOT diameterFor the PW exam, go with the blue flowCompare calculated SVI to LV size and EFCheck for concordance between AVA and MG, or explain discordance

Thanks for your patience listening

The conversion of potential energy to kinetic energy across a narrowed valve results in a high velocity and a drop in pressure.

Distal to the orifice, flow decelerates again. Kinetic energy will be reconverted into potential energy with a corresponding increase in pressure, the so-called PRPressure recovery

Pressure recovery is greatest in stenosis with gradual distal widening Aortic stenosis with its abrupt widening from the small orifice to the larger aorta has an unfavorable geometry for pressure recoveryPR= 4v 2EOA/AoA (1-EOA/AoA)

Pressure recovery