Comprehensive Echo Assessment of Aortic Stenosis Smonporn Boonyaratavej, MD, MSc King Chulalongkorn Memorial Hospital Bangkok, Thailand
Management of Valvular AS Medical and interventional approaches to the management of patients with valvular AS depend on Accurate diagnosis of the cause and Stage of the disease process
2014 ACC AHA Guidelines Stage A At Risk of AS MPG < 15 mmhg AVA >2 cm 2 Stage B Mild to Moderate AS MPG < 40 mmhg AVA > 1 cm 2 StageC Asymptomatic Severe AS Vmax > 4m/s MPG >40 mmhg LVEF > 50% Vmax > 4 m/s MPG >40 mmhg LVEF < 50% 4 m/s Bicuspid AV AV sclerosis Mild/Moderate Valvular AS High gradient Normal EF Asymptomatic High gradient Low EF Asymptomatic AVR Class III Class IIa/IIb Class I
MPG >40 mmhg AVA <1cm 2 2014 ACC AHA Guidelines Stage D :Symptomatic Severe AS D1 D2 D3 D4 MPG < 40 mmhg AVA <1 cm 2 LVEF <50% MPG < 40 mmhg AVA <1 cm 2 LVEF >50% SVI < 35 ml/m 2 MPG < 40 mmhg AVA <1 cm 2 LVEF >50% SVI >35 ml/m 2 4 m/s Paiborot 2012 High gradient Symptomatic Classical Low Flow Low Gradient Paradoxical Low Flow Low Gradient Normal Flow Low Gradient AVR Class I Class IIa Class IIa Class?
Causes of Aortic Stenosis Bicuspid AS Degenerative calcific AS Rheumatic AS
2014 ACC AHA G
Aortic stenosis affects not just the valve, but the entire vascular system, including the left ventricle and systemic vasculature Otto CM, JACC 2006
Parameters for the Assessment of Aortic Stenosis Quantification of Valvular Obstruction Parameter Peak aortic jet velocity (Vpeak) Mean gradient Criteria for Severe Utility and Advantages Limitations >4 m/s Easy to measure Highly flow dependent Low interobserver/ intraobserver variability High specificity >40 mmhg Same as peak aortic jet velocity Over estimates LV energy loss in patients with small aortas May under or overestimate stenosis severity in presence of hypertension Under estimates stenosis severity in low flow states Same as peak aortic jet velocity
Location of the Highest Peak Velocity Aortic Stenosis Location of highest peak velocity Thaden et al. JASE 2015
Parameters for the Assessment of Aortic Stenosis Quantification of Valvular Obstruction Parameter Criteria for Severe Utility and Advantages Limitations Valve effective orifice area EOA = SVLVOT/VTIAo Indexed EOA EOAI = EOA/BSA 1.0 cm2 0.6 cm2/m2 Less flow dependent than gradient or peak velocity Reflects intrinsic severity of valvular obstruction Susceptible to measurements errors Over estimates LV energy loss in patients with small aortas May under or over estimate stenosis severity in presence of hypertension May over estimate stenosis severity in low flow states EOA may over estimate severity in pts with small body size Indexed EOA may overestimate severity in obese patients
Anatomic Orifice Area (AOA) Planimetry TEE, CT, CMR Effective Orifice Area (EOA) Continuity Equation EOA <AOA 1. valve inflow geometry 2. flow rate Tardif. JACC1997 LV workload are related to the EOA of the valve and not to its AOA
Measurement Pitfalls LVOT diameter Parasternal long axis Mid systole Proximal and parallel to plane of stenotic aortic valve From inner edge of septal endocardium to edge of AMVL Limitation Poor image quality Annular calcification Sigmoid septum Underestimation LVOT elliptical Image truncated Overestimation Oblique measure
LVOT Velocity Measurement Apical 5 chamber or ApLAX Small sample volume With PW, start apically & advance > LVOT until welldefined laminar peak velocity curve is obtained (if broadens, back out apically) LVOT Diameter and Velocity signals recorded at the same anatomic site
Stroke volume index (SVI) quartiles and adjusted survival 405 patients 1 Jan 2006 31 Dec 2011 (1) AVA <1.0 cm2 (2) LV EF 50% (3) Mean PG <40 mm Hg (4) absence of prosthetic valves, complex CHD, supraor subvalvular AS, HCM, concomitant moderate or severe native valvular lesions Symptom onset, need for aortic valve intervention (valvuloplasty, transcatheter or surgical aortic valve replacement (AVR)) Eleid MF, et al. Heart 2015;101:23 9
Stroke volume index quartiles and adjusted survival Eleid MF, et al. Heart 2015;101:23 9
Blood Flow and Pressure Across LVOT, Aortic Valve, and Ascending Aorta During Systole Paiborot & Dumesnil. JACC 2012
Bland Altman Plot Mean PG AV by Doppler Echo vs Cardiac Cath ascending aorta <3 cm ascending aorta >3 cm Baumgartner et al JACC 1999;33:1655-61
Many patients with AS can still be managed adequately with the use of simple parameters of disease severity such as peak jet velocity, mean gradient, EOA, valve morphology, and LV ejection fraction (LVEF) Mode of presentation of many patients with calcific AS is more complex than previously believed and thus warrants more comprehensive evaluations, which can include the following:
Parameters for the Assessment of Aortic Stenosis Quantification of Valvular Obstruction Parameter Criteria for Severe Utility and Advantages Limitations Energy loss index ELI AA = asc AO area 0.5 0.6 cm 2 /m 2 EOA AA AA EOA BSA Less flow dependent than gradient or peak velocity Takes into account pressure recovery and is ± equivalent to EOA measured by catheter Reflects true LV energy loss caused by stenosis Should be measured in pts with small aortas Susceptible to measurements errors May under- or overestimate stenosis severity in presence of HT May over-estimate stenosis severity in low flow states
Parameters for the Assessment of Aortic Stenosis Quantification of Valvular Obstruction Parameter Criteria for Severe Utility and Advantages Limitations Stroke work loss SWL = 100 (ΔPMean/SBP+Δ PMean) >25% Less flow dependent than gradient or peak velocity Takes into account pressure recovery May under estimate stenosis severity and LV energy loss in presence of hypertension
Parameters for the Assessment of Aortic Stenosis Parameter Aortic valve calcification score Criteria for Severe Utility and Advantages Limitations Echo 4/4 Can be estimated by echo and quantitatively measured by multislice CT Echo, semiquantitative assessment CT >1,650 AU Correlates well with stenosis severity and predicts rapid stenosis progression Independent of hemodynamic conditions Useful in low flow states when echo assessment of stenosis hemodynamic severity is inconclusive CT, exposure to radiation
Parameters for the Assessment of Aortic Stenosis Quantification of vascular load Parameter Criteria for Severe Utility and Advantages Limitations Systemic BP >140/90 mm Hg Easy to measure Highly flow dependent SBP/DBP Often pseudonormalized in AS patients Underestimates severity of HT in low flow states 1) Evaluation of AS severity should ideally be performed when BP control is optimal; 2) Serial evaluations should take BP and flow levels into account 3) In case of discrepancies between Doppler echo and cath data, potential differences in BP and transvalvular flow rates during each exam should be considered
Parameters for the Assessment of Aortic Stenosis Quantification of Vascular load Parameter Systemic arterial compliance SAC = SVI/SBP DBP Systemic vascular resistance SVR = 80 MBP/CO Criteria for Severe Utility and Advantages Limitations 0.6 ml mmhg 1 m 2 >2,000 dyne s cm 5 Can be measured by Doppler echocardiography Most frequent cause of increased arterial load in AS pts Can unmask HT in pts with pseudonormalized BP Can be measured by Doppler echocardiography Susceptible to measurements errors Susceptible to measurements errors
Parameters for the Assessment of Aortic Stenosis Quantification of LV Hemodynamic Load Parameter Valvuloarterial impedance (Zva) Zva = (SBP+ΔPMean)/ SVI Criteria for Severe Utility and Advantages Limitations >4.5 mm Hg ml 1 m2 Zva = (SBP+ΔPnet)/SVI Can be measured by Doppler echocardiography eflects global (valvular+arterial) load imposed on LV Potentially superior to predict occurrence of symptoms and events Susceptible to measurements errors Does not permit to discriminate the valvular versus the arterial contribution to the global LV load ΔPnet = Doppler ΔPmean {4v 2 [2(AVA/AoA) (1 AVA/AoA)]}
Blood Flow and Pressure Across LVOT, Aortic Valve, and Ascending Aorta During Systole Paiborot & Dumesnil. JACC 2012
Parameters for the Assessment of Aortic Stenosis Quantification of LV systolic dysfunction Parameter Criteria for Severe Utility and Advantages Limitations LVEF < 50% Widely used and validated with regard to outcome data Susceptible to measurements errors Also influenced by LV geometry Under estimates the degree of myocardial systolic dysfunction in presence of LV concentric remodeling
Parameters for the Assessment of Aortic Stenosis Quantification of LV systolic dysfunction Parameter Global longitudinal strain Criteria for Severe Utility and Advantages Limitations < 15% Less influenced by LV geometry Superior to LVEF to assess intrinsic myocardial function Cutoff values need to be further validated
Parameters for the Assessment of Aortic Stenosis Quantification of LV systolic dysfunction Parameter Myocardial fibrosis Criteria for Severe Utility and Advantages Limitations Can be measured by CMR Predicts poor outcomes after AVR High cost and low availability of CMR
Assessment of Myocardial Fibrosis by CMR and Echocardiography in AS Herrmann et al. J Am Coll Cardiol, 2011
Asymptomatic Severe AS and normal LVEF Truly asymptomatic? : Exercise testing Standard parameters High risk asymptomatic 1) Severe aortic valve calcification 2) Rapid hemodynamic progression of the stenosis at serial echocardiographic examinations and/or 3) Very severe AS
Asymptomatic Severe AS and normal LVEF 1) Energy loss index EOA between 0.8 and 1.0 cm2 and Small aorta diameter (<30 mm) 2) Zva determine the global (valvular plus arterial) LV hemodynamic load 3) Global longitudinal strain confirm that myocardial systolic function is intrinsically normal 4) Plasma BNP assess the global impact of the diseases on the myocardium
Symptomatic Moderate AS with HT If Zva is high, an optimal treatment of hypertension would appear reasonable If Zva is low, associated conditions such as coronary artery disease, cardiomyopathy, pulmonary disease, and so forth, should be considered
Conclusions Degenerative or calcific AS is a complex, multifaceted, and systemic disease not limited to the valve Need for a more comprehensive assessment of AS severity beyond the simple measurement of the standard parameters Stress testing provide important tools to unmask symptoms, lack of valve opening reserve, and/or latent myocardial systolic dysfunction Other imaging modalities such as CT and CMR may also be helpful Comprehensive approach integrating these parameters is essential to appropriately assess patient with aortic stenosis
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