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Hemodynamics of aortic stenosis Dr Sajeer K T Department of Cardiology, Govt. Medical College, Kozhikode.

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Presentation on theme: "Hemodynamics of aortic stenosis Dr Sajeer K T Department of Cardiology, Govt. Medical College, Kozhikode."— Presentation transcript:

1 Hemodynamics of aortic stenosis Dr Sajeer K T Department of Cardiology, Govt. Medical College, Kozhikode

2 Aortic stenosis Etiology based on - level of obstruction to LVOT - Supravalvular - Valvular - Congenital AS - BAV ± calcification - Rheumatic - Senile degenerative - Subvalvular

3 Pressure gradient across the AV ⇈ es exponentially with ⇊ ing AVA # Severe AS: - small changes in AVA can lead to large changes in hemodynamics

4 Framework for how mechanical stress (σ) is transduced into pressure versus volume overload hypertrophy. (Grossman W, Jones D, McLaurin LP: Wall stress and patterns of hypertrophy in the human left ventricle. J Clin Invest 1975; 53:332-341)

5 Compensatory Mechanisms Chronic pressure overload ➨ concentric LV hypertrophy increased wall thickness normal chamber size ⇈ ed myocardial cell mass and ⇈ ed interstitial fibrosis - diastolic dysfunction Women ➨ normal LV function small, thick walled LV concentric LVH diastolic dysfunction Men ➨ eccentric LV hypertrophy excessive systolic wall stress systolic dysfunction & chamber dilation

6  Mild AS - intracardiac pressures & CO - normal  As the valve becomes more stenotic - unable to increase CO during exercise  Progressive narrowing of the valve - decreased SV and CO even at rest  Moderate to severe AS - patients may develop elevated filling pressures to compensate for the increase in LV EDP  Minority of patients LV systolic failure - further elevation in intracardiac pressures

7 Pulse wave

8 Valvular AS # Slow systolic rise # prominent anacortic notch # late peak HOCM # rapid upstroke # absence of anacortic notch # early systolic dip # second peak in late systole

9 Supra valvular AS - pulse disparity (Coanda effect) - systolic pressure in the right arm > left arm. - relate to the tendency of a jet stream to adhere to a vessel wall selective streaming of blood into the innominate artery Streaming of the jet toward the innominate, RCCA, and right SCA

10 Aortic Stenosis- severity MildModerate Severe Jet velocity (m/sec)<3.03.0-4.0 >4.0 Mean gradient (mm Hg) <2525-40 >40 Valve area (cm 2 ) >1.51.0-1.5 <1.0 Valve area index (cm 2 /m 2 ) <0.6

11 Clinical Spectrum of Severe AS

12 # PLV1 exceeds PLV2 # VC – (2) - maximum velocity - site of minimal pressure # pressure recovery (3) # pressure P1 < P2 Factors involved in generation and interpretation of a pressure gradient

13 Pressure recovery - a source of error in the assessment of AS severity  Severity of AS 1. pressure gradient across the valve or 2. effective orifice area (EOA) of the valve - preferable - less flow dependent  EOA measurement : 1. Doppler echocardiography (continuity equation) 2. Left heart catheterization ( Gorlin formula)  Discrepancies between Doppler and catheter measurements of EOA

14 Pressure recovery phenomenon

15 Valvulo-arterial impedance SAP : systolic arterial pressure ▲ P mean : mean systolic transaortic gradient SVI : stroke volume index. Values of Z va > 4.5 mm Hg. ml -1.m -2 ➲ severe AS “ cost in mmHg for each ml of blood indexed for BSA pumped by LV” Z va = LV systolic pressure / SVI

16  Doppler : maximal pressure drop from the maximal velocity recorded at valve (EOA) level  Catheterization : measures the net gradient between the left ventricle and the ascending aorta  due to pressure recovery phenomenon: : net gradient recorded at catheterization is less than the maximum pressure gradient measured by Doppler (Ao < 3 cm) : EOA by catheterization with Gorlin formula is higher than measured by Doppler  Doppler method : actual area occupied by flow at the valvular level  EOA by Gorlin formula: is a coefficient of the energy lost due to the stenosis

17 Energy loss coefficient (ELCo)  adjusts the Doppler EOA for the size of the aorta (A A ) ELCo = (EOA×A A ) / (A A -EOA)  excellent agreement between catheter EOA and ELCo by Doppler  pressure recovery is a clinically relevant in patients with - moderate to severe AS (Doppler EOA between 0.8 - 1.2 cm 2 ) - small aortas (diameter at the sinotubular junction < 30 mm) A A : CSA of the aorta measured at 1 cm downstream of the STJ

18 Cut-off value for severe AS using the energy loss index < 0.55 cm 2 / m 2 Energy loss index Energy loss index (ELI) = [EOA x A A / A A - EOA] BSA 1.Less flow dependent than gradient or peak velocity 2.Takes into account pressure recovery 3.Equivalent to EOA measured by catheter 4.Reflects true LV energy loss caused by stenosis 5.Measured in patients with small aortas

19 Low-Flow, Low-Gradient Aortic Stenosis With Normal and Depressed LVEF # Decreased EF (<40%) - Low Flow –Low Gradient AS # Normal EF ( ≥ 50%) - Paradoxical Low Flow –Low Gradient AS ⇊ in gradient ➨ ⇊ in trans-valvular flow.

20 Low-flow, Low-Gradient severe AS with decreased LVEF # valve area <1 cm 2 # mean aortic valve gradient < 40 mm Hg # ejection fraction <40% # pseudo aortic stenosis ➨ medications that increase cardiac output will usually increase the calculated AVA # Intravenous dobutamine - 5 μg/kg/min ➔➔ 20 μg/kg/min

21 # true severe aortic stenosis (1) a mean aortic valve gradient greater than 30 mm Hg (2) an aortic valve area ≤ 1.2 cm 2 Effects of dobutamine infusion in patients with and without valvular AS # Pseudo severe As Peak stress - MG < 30 mm Hg - EOA >1.0-1.2 cm2 - ab. in EOA> 0.3 cm2

22 Contractile reserve or flow reserve # Definition: Increase in stroke volume of ≥ 20% above baseline # Post AVR : lower peri-operative mortality (5% v/s 32%) ( n=136) # Post AVR: mean improvement in In LVEF Improvement in NYHA class : similar in CR 20%

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25 Paradoxical Low flow –low Gradient Severe AS: - indexed AVA < 0.6 cm 2 /m 2 - Gradient < 40 mmHg - EF > 50% - Stroke volume index (SVi) : < 35 mL/m 2 Paradoxical Low flow –low Gradient Severe AS:

26  Increased global LV hemodynamic load - ⇈ed Z va  Smaller and relatively thicker LV  ⇊ed LV mid-wall radius shortening (pronounced intrinsic myocardial dysfunction)  lower LVEF Paradoxical Low Flow –Low Gradient AS Features : Poor prognosis if treated medically rather than treated surgically

27 Physiopathology : paradoxical LF- AS despite preserved EF Pronounced concentric LV remodelling and smaller LV cavity size ≈ restrictive physiology # Decrease in SV is due to deficient ventricular filling # smaller LV cavity size # deficient ventricular emptying # Intrinsic myocardial dysfunction causing EF lower than expected (50-60%) # Prevalence increases with - older age - female gender - concomitant systemic HTN

28 Impact of AVR on Survival in Patients With Paradoxical LF-LG AS Tarantini G, Covolo E, Razzolini R, et al. Valve replacement for severe aortic stenosis with low transvalvular gradient and left ventricular ejection fraction exceeding 0.50. The Annals of Thoracic Surgery, Volume 91(6), 1808–1815, 2011

29  Cardinal indications: - left ventricular failure, angina pectoris, or syncope. Role of cardiac catheterization AS  What information can be obtained in AS ? - estimation of gradient - estimation of valve area - level of stenosis - valve resistance  Discrepancy between echo findings and patient symptoms

30 Methods of measuring a transvalvular gradient in AS 1.LV via transseptal, AO catheter retrograde above AO valve 2.LV retrograde with pressure wire, AO catheter retrograde above AO valve 3. LV retrograde with pigtail, AO catheter retrograde above AO valve 4. LV and AO retrograde with dual lumen pigtail 5. LV retrograde with pigtail, AO pressure from side arm of long sheath 6. LV retrograde with pigtail, AO pressure from side is of femoral sheath 7. LV retrograde with pigtail and ‘‘pullback’’ pressure from LV to AO

31 Simultaneous LV and central Aortic pressures in severe AS Ideal method

32 METHODEASE OF USEDISADVANTAGE PULLBACK+++++LEAST ACCURATE FEMORAL SHEATH+++++PRESSURE AMPLIFICATION ILIAC ARTERY STENOSIS DOUBLE ARTERIAL PUNCTURE +++EXTRA VASCULAR ACCESS RISK PIG TAIL- DOUBLE LUMEN +++DAMPING TRANSEPTAL++RISK

33 Artifacts can result when a multiple-side-hole pigtail catheter is incompletely advanced into the LV chamber

34 Simultaneous measurement of aortic and FA pressure demonstrating peripheral amplification Peripheral amplification # increase in peak systolic pressure and pulse pressure in peripheral arteries as compared to the central aorta

35 A.The tracings demonstrating the significant time delay for the pressure waveform to reach the RFA. B. Realignment using tracing paper.

36  Peak aortic pressure and LV pressures are temporarily separated  Gradient described as # Peak-peak # Peak instantaneous # Mean gradient  Peak-peak gradient: - absolute difference between peak Ao systolic pressure and peak LVSP  Peak instantaneous gradient: - max. gradient between Ao and LV at single point in time  Mean Gradient : - area b/n LV & Ao hemodynamic tracing - best quantify severity of AS

37 peak-to-peak gradient measured by catheterization is lower than the peak instantaneous gradient measured by echo  Doppler data # Peak instantaneous gradient over time  Cath data # Peak to peak data  calculated mean pressure Gradients are comparable

38 Carabello Sign  rise in arterial blood pressure during left heart catheter pullback in patients with severe aortic stenosis  Mechanism : related to partial obstruction of an already narrowed aortic orifice by the retrograde catheter & relief of this obstruction when the catheter is withdrawn AVA<0.6cm 2

39 Supra Valvular AS Valvular AS Sub valvular AS Aorta pull back tracing- level of stenosis

40 1.Torricelli's law: flow across a round orifice F = AV C C F = flow rate A = orifice area V = velocity of flow C C = coefficient of orifice contraction Calculation of stenotic valve area  GORLIN FORMULA: 2. relates pressure gradient and velocity of flow - Torricelli's law V = velocity of flow C v = coefficient of velocity - correcting for energy loss as pressure energy is converted to kinetic or velocity energy h = pressure gradient in cm H 2 O g = gravitational constant (980 cm/sec 2 ) for converting cm H 2 O to units of pressure A = F VC C A = F VC C

41 C = empirical constant accounting for C V and C C h = mm Hg (rather than cm H 2 O)  GORLIN FORMULA: C - empirical constant ( 0.85 for mitral valve, 1.0 for Aortic valve)

42 Flow (F) = is the total cardiac output expressed in terms of the seconds per minute during which there is actually forward flow across the valve. F= CO (ml or cm 3 /min) SEP (sec/min) x HR cm 3 x min Min x Sec cm 3 /sec

43 Hakki formula Heart rate x SEP or DFP x constant ≈1

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45 Mean GD Automated computerized analysis

46 Hypertension + aortic stenosis  Concomitant hypertension mask the signs of AS severity  Evaluation of AS severity - performed when BP control is optimal  Progression of valvulo-arterial disease - pseudo-normalization of BP due to a reduction in SV  LV : faces a double pressure overload - develop symptoms at an earlier age

47 Conclusion # diagnosis of severe AS should be based on results for AVA and indexed AVA rather than on gradients # Paradoxical low flow-low gradient AS : better prognosis if treated surgically than medically # Newer parameters for severity of AS - Energy loss index - Valvulo-arterial impedance # Pressure recovery : Catheterization v/s Doppler gradient

48 References 1.Braunwald's Heart Disease: A Textbook Of Cardiovascular Medicine 9 th Edition 2.Grossman's Cardiac Catheterization, Angiography, & Intervention, 7th Edition 3.Otto And Bonow : Valvular Heart Diseases 4.Kern- Hemodynamics 5.George A. Stouffer Cardiovascular Hemodynamics For The Clinician 6.Yang-hemodynamics 7.Morton G Kern-cardiac Catherization 8.Kanu-chaterjee-text Book Of Cardiovascular Medicine 9.Hemodynamic Rounds –Kern 10.Regosta- Hemodynamics 11.Uptodate – aortic stenosis Journals 1.Jaac 2.Circulation 3.Can J Cardiol 4.Europian Heart Journal 5.Bmj Heart 6.Chest Journal

49 Thank you

50 1.What is the calculated aortic valve area by Gorlins formula from the following parameters? # CO-4400ml/min, # SEP- 0.5sec, # HR-50 beat/min # Mean aortic gradient =100mmHg a)0.7 cm 2 b)0.2 cm 2 c)0.9cm 2 d)0.4cm 2

51 2. common pitfalls in the estimation of aortic valve area in the catheterization lab all except? a) Peripheral amplification b) Aortoiliac stenosis c) Aortic regurgitation d) Low gradient AS e) Alignment match

52 3. True regarding Carabello’s sign except? a)rise in pulse pressure by > 5 mm Hg when a catheter is removed from the LV b)Phenomenon is seen in aortic valve area < 0.6cm 2 c)Not seen when AVA> 0.7 cm 2 d)Mechanism: additional occlusive effect of the catheter across the valve – decreasing aortic pressure

53 4. True about paradoxical low flow-low gradient AS except? a)LVEF> 50% b)Indexed AVA <0.6cm 2 /m 2 c)Stroke volume index< 35 ml/m 2 d)Mean Gradient < 50 mmHg

54 5. In Dobutamine SE- pseudo severe AS is identified by a) Peak stress Mean gradient <30 mmHg b)Peak stress EOA > 0.6 cm 2 c)absolute increase in EOA > 0.3 cm 2 d) Stroke volume < 35 ml/m 2

55 6. True about Paradoxical LF-LG severe AS except? a)More in females b)Prevalence decreases with age c)Prevalence Increases with concomitant systemic HTN d)AVR (class II a recommendation ) is better than Medical treatment

56 7. True regarding hypertension and aortic stenosis except? a)Hypertension mask AS severity b)Pseudo normalization of blood pressure occurs c)HTN + AS – vary late onset of AS symptoms d)LV faces more global LV hemodynamic load

57 8. True regarding contractile reserve except? a)Increase in stroke volume of ≥ 30% above baseline b)Lower contractile reserve –higher peri-operative mortality after AVR c)mean improvement in In LVEF more in higher contractile reserve patients with severe AS after AVR d)Improvement in NYHA class- similar in high and low contractile reserve groups with severe AS after AVR

58 9. All are features of paradoxical low- flow, low - gradient AS except? a) Increased global LV hemodynamic load - ⇈ ed Z va b) Smaller and relatively thicker LV c) intrinsic myocardial dysfunction d) Survival better after medical management than AVR

59 10. True about Energy loss index (ELI) except? a)Cut-off value for severe AS < 0.55 cm 2 / m 2 b) Less flow dependent than gradient or peak velocity c)Takes into account pressure recovery d)Equivalent to EOA measured by catheter e) Measured in patients with large aorta ( size >35 mm)

60

61 Valve resistance  mean pressure gradient divided by the flow rate ratio.  UNIT = dyne-seconds cm −5  > 300 dyne-seconds cm −5 ➨ severe aortic stenosis

62 Hypertrophic cardiomyopathy  dynamic intraventricular pressure gradient  no systolic pressure gradient at rest  gradient - provoked with : Valsalva maneuver : extra systole : systemic vasodilator (amyl nitrate) : inotropic stimulation

63  dynamic outflow obstruction ➨ characteristic arterial pressure waveform “spike-and-dome configuration HOCM : spike-and- dome configuration of pulse wave  early spike ➨ rapid LV ejection by the hypercontractile myocardium  pressure dip & doming ➨ reflect the dynamic outflow obstruction

64 Valsalva maneuver : produces a marked increase in the gradient : change in the FA pressure waveform to a spike-and- dome configuration. LV and FA pressure tracings in HCM

65 Brokenbrough-Braunwald-Morrow sign  Post PVC potentiation in HOCM  PVC ➨⇈ in intracavitary gradient ➨⇈ed contractility (⇈ed Ca 2 + ) # Post PVC beat is associated with a reduction in aortic systolic pressure and pulse pressure ≈ B-B-M sign


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