1. Low flow aortic stenosis can be caused by either low or normal ejection fraction and is an important entity that is often underdiagnosed. 2. Evaluation of low flow AS involves calculating aortic valve area using continuity equation in addition to gradients, as well as tests like dobutamine stress echocardiogram, CT calcium scoring, and novel markers of left ventricular function. 3. Treatment depends on symptom status and severity of stenosis, with aortic valve replacement generally recommended for symptomatic patients or asymptomatic patients with low ejection fraction, even in the presence of low flow and gradients.

2. LOW FLOW AS
DR. DEEP CHANDH RAJA S

3. • Aortic stenosis is the 3 rd most common CV
disease after HTN and CAD (in western world)
• Prevalence is 2-7% over the age of 65 years
• Evaluation of aortic stenosis is the most
challenging of all valvular heart diseases
Stewart BF, Siscovick D, Lind BK, et al. Clinical factors associated with calcific aortic
valve disease. Cardiovascular Health Study. J Am Coll Cardiol 1997; 29:630–634.

4. 2 MAJOR GUIDELINES
• ACC 2006
• ESC 2012
A FEW IMPORTANT NEW CONCLUSIONS IN ESC
2012 BASED ON EVOLVING NEW CONCEPTS
AFTER 2007 (MISSING IN ACC 2006)

5. ACC/AHA GUIDELINES PUBLISHED IN JACC, 2006

6. GRADIENT = FLOW DEPENDENT VARIABLE
Gradient calculation-
Small reduction in flow can cause great reductions in
gradient

7. AVA calculation is a standard and must be
incorporated into a comprehensive evaluation of
AS severity
AVA=FLOW INDEPENDENT
VARIABLE

9. MISMATCH BETWEEN GRADIENTS
AND VALVE AREA

10. 1. INDEXING TO BSA
2. INACCURACY IN CALCULATION OF LVOT DIAMETER
3. WHO SAID AVA < 1.0 CORRESPONDS TO GRADIENTS > 40 ???
4. LOW FLOW STATE (DEFINED SVi <35 ml/mt2
)

11. • INDEXING TO BSA
Eg: AVA of 0.9 cm2, BSA=1.3, iAVA= 0.7 cm²/m²
AVA of 1.2 cm2, BSA=2.1, iAVA= 0.57 cm²/m²

12. •INACCURACY IN CALCULATION OF LVOT DIAMETER
CSA= .785 X LVOT D 2
Eg: D=2.8, CSA= 6.15
D=2.2, CSA= 3.75

13. • WHO SAID AVA < 1.0 CORRESPONDS TO GRADIENTS > 40 ???
Carabello demonstrated in 2427 patients, that
“a mean gradient of 26 mmHg actually yields to an AVA of 1.0 cm², whereas a
mean gradient >40 is corresponding with a AVA of 0.8 cm2”
INCONSISTENCIES IN GUIDELINES- “FOR NOW, WE NEED TO ACCEPT AVA <1.0, AS
THE REFERENCE CUT OFF TO DEFINE SEVERE AS”

14. • INDEXING TO BSA
• INACCURACY IN CALCULATION OF LVOT DIAMETER
• WHO SAID AVA < 1.0 CORRESPONDS TO GRADIENTS > 40 ???
• LOW FLOW STATE (DEFINED AS SVi<35 ml/mt2
)

15. • H/O
72 yr old Man
HTN,
Dyslipidemia,
CAD
• C/O
DOE & AOE
CLASS II
• AV
GRADIENTS=43/28
• LVEF= 32 %
• iAVA= 0.5 cm2
Case Scenario

16. • H/O
72 yr old Man
HTN,
Dyslipidemia,
CAD
• C/O
DOE & AOE
CLASS II
• AV
GRADIENTS=43/28
• LVEF= 52 %
• iAVA= 0.5 cm2
Case Scenario

17. Causes of low flow state
• Till 2007 low flow due to
LOW EF
• NOW low flow can also be secondary to
Preserved EF
“new entity” Paradoxical Low flow AS

19. Prevalence of low flow state
– LOW EF
5- 10 % of all patients of AVA < 1.0
– PRESERVED EF
10-25 % of all patients of AVA < 1.0
IMPLICATION-
“IF WE DON’T CALCULATE AVA, WE WILL MISS 15-35 %
OF CASES OF CRITICAL AS, MORE IMPORTANTLY WE
WILL DEPRIVE THESE PATIENTS OF THE POTENTIAL
BENEFIT OF AVR ON THEIR SYMPTOMS/SURVIVAL”
Pibarot P, Dumesnil J. Low-Flow, Low-Gradient Aortic Stenosis With Normal and
Depressed Left Ventricular Ejection Fraction. J Am Coll Cardiol 2012;60:1845–53

20. LOW FLOW STATE
• LOW EF
• PRESERVED EF

21. • PATHOPHYSIOLOGY
• DIAGNOSIS
• TREATMENT OPTIONS
• PROGNOSIS

22. LOW FLOW, LOW EF, SEVERE AS

23. Case Scenario
• H/O
72 yr old Man
HTN,
Dyslipidemia,
CAD
• C/O
DOE & AOE
CLASS II
• AV GRADIENTS=44/26
• iAVA= 0.5 cm2
• LVEF= 30 %
LOW FLOW, LOW GRADIENT, SEVERE AS WITH LOW EF

24. Prevalence of low flow state
LOW EF
5- 10 % of all patients of AVA < 1.0
PRESERVED EF
10-25 % of all patients of AVA < 1.0
Pibarot P, Dumesnil J. Low-Flow, Low-Gradient Aortic Stenosis With Normal and
Depressed Left Ventricular Ejection Fraction. J Am Coll Cardiol 2012;60:1845–53

25. PATHOPHYSIOLOGY
• LOW FLOW secondary to LOW EF
• LOW EF is due to myocardial
dysfunction
“whether this myocardial dysfunction is
-secondary to AS
-secondary to other causes, or
-primary myocardial disease, needs to be
evaluated”

26. MYOCARDIAL DYSFUNCTION SECONDARY
TO CAUSES OTHER THAN AS
-DILATED CARDIOMYOPATHIES (1O
MYOCARDIAL
DYFUNCTION)
-ISCHEMIC HEART DISEASE
-HTN HEART DISEASE (AFTER LOAD MISMATCH)
In all these patients, AVA was misjudged as <1.0
due to incomplete opening of AV due to low EF and
 labelled as “PSEUDO SEVERE AS”

27. MYOCARDIAL DYSFUNCTION
SECONDARY TO AS
• “ True severe AS”
• Removal of the only afterload-AS can lead to
dramatic improvements in patients’
symtoms/survival compared to medical
therapy alone

28. DIAGNOSIS

29. DIAGNOSIS
• FIRST SUSPICION GRADIENT-AVA MISMATCH
during routine echo
• GRADIENT < 40 mmhg, AVA <1.0, EF <40 %
• Dobutamine stress echo (exercise stress echo)
Class IIA recommendation

30. Dobutamine stress echo
• Low dose protocol upto 20 µg/kg/mt
• We look for three things:
-Flow reserve
-Change in EOA
-Change in Gradient

31. 30-40%
20-30%

32. Projected EOA
TOPAS (True or Pseudo Severe AS) STUDY

33. CT AV CALCIUM SCORING
Cueff et al. suggested that a score >1,650 Agatston units
provides good accuracy (93 % sensitive, 75 % specific) to
distinguish true severe from pseudosevere AS

34. Treatment Decisions

35. • SYMPTOM STATUS
• VALVULAR SEVERITY
“ANY SYMPTOMATIC SEVERE AS, IRRESPECTIVE
OF EF AND FLOW RESERVE, HAS TO BE
INTERVENED (class I)”
WITHOUT AVR, 1 YR. MORTALITY IS 30-50% (Turina et al EhJ 1987)

36. Severe ‘Asymptomatic’ AS WITH LOW EF
• WITH NORMAL EF-management is challenging, an abnormal response to
exercise stress testing and elevated BNP may identify a higher-risk group
that might benefit from closer followup and earlier surgery
Recommendation:
AVR for patients who have no symptoms and
whose left ventricular ejection fraction is less
than 50% (class I indication, level of evidence C)

37. • EURO SCORE, STS SCORE
• PERIOP RISK- FLOW RESERVE (+)=5-8%,FLOW RESERVE (-)=30%*

38. Role of TAVI
• Operative risk for open heart surgery is generally very
high in absence of flow reserve
• TAVI - valuable alternative in these patients
• Recent studies reported a greater and more rapid
improvement of LVEF in patients treated by TAVR than
those treated by surgical AVR *
• RATIONALE related to a lesser incidence of patient–
prosthesis mismatch.
• In contrast, TAVR associated with a higher incidence of
paravalvular regurgitation, stroke, vascular
complications which may eventually have a negative
impact on outcomes
• PARTNER A & B and STACCATO TRIALS
*
Clavel et al. Circulation 2010;122:1928 –36

39. • Normal flow reserve:
Medical followup every 6 months vs AVR (ESC class IIa)–based on the clinician’s
judgement
• Low flow reserve:
1.IHD-OMT ± revascularisation
2.HTN- to be treated
3.Optimal heart failure management strategy
4.AVR (ESC class IIb)

40. Concerns after AVR
• Patient-Prosthesis MISMATCH
• LOW EF patients are known to be more
vulnerable than patients with normal LVEF to
the excess in LV load
• Can cause acute decompensation of LV or
inadequate improvement of LV functions after
AVR
• Paravalvular leak, Stroke in TAVI (Kodali et al.NEJM 2012)

41. PROGNOSIS

42. Prognosis
• Concomitant CAD (46-79 %)
• LOW EF SEVERE AS compared to Normal EF severe AS
have higher periop mortality rates (6-33%), depending
on presence of myocardial contractile reserve (5-8%)
or not (22-33%)
• BUT, irrespective of degree of myocardial dysfunction
or contractile reserve, the patients benefit more from
AVR than medical treatment only
“Severe LV dysfunction IS NOT A CI FOR AVR, albeit the
high risk of surgery in these patients”

43. Group I= Flow reserve +
Group II= Flow reserve -

44. Predictors of late mortality
• Preop. Contractile reserve
• EuroSCORE, STS score,
• Atrial fibrillation,
• Multivessel CAD,
• Low pre-operative gradient,
• High plasma levels of BNP, and
• Patient–prosthesis mismatch

45. • Low Flow due to low EF
• DSE to differentiate True from
Pseudo Severe AS
• EOA (proj) & CT AV Ca Score
• AVR irrespective of EF and
Flow reserve

47. LOW FLOW NORMAL EF SEVERE AS
“PARADOXICAL”

48. Case Scenario
• H/O
72 yr old Man
Dyslipidemia,
CAD
• C/O
DOE & AOE
CLASS II
• AV
GRADIENTS=53/32
• LVEF= 62 %
• iAVA= 0.5 cm2
• Gr 2 DD
e/e’=12
LOW FLOW, LOW GRADIENT, SEVERE AS WITH NORMAL

49. Prevalence of low flow state
LOW EF
5- 10 % of all patients of AVA < 1.0
PRESERVED EF
10-25 % of all patients of AVA < 1.0
Hachicha Z, Dumesnil JG, Bogaty P, Pibarot P. Paradoxical low flow, low gradient
severe aortic stenosis despite preserved ejection fraction is associated with higher
afterload and reduced survival. Circulation 2007;115:2856–64

50. New Entity
• First reported in 2007 by Hacicha et al. in 512
pts. (CIRCULATION)
• ECHO PROFILE:
-Mean gradient < 40 mmhg,
-AVA < 1.0 cm2
,
-Flow <35 ml/mt2
,
-EF≥40 %

51. PATHOPHYSIOLOGY AND
CHARACTERISTICS OF LOW FLOW
NORMAL EF SEVERE AS

52. • Myocardial fibrosis
• Restrictive physiology
• Small LV cavity
• Resembles heart failure
with preserved EF
(Diastolic Heart failure)
• Pseudo-normalization of
blood pressure
• Impaired LV function yet
normal EF
(around 50-60%)

53. DIAGNOSIS

54. “Normal LVEF Does Not Mean
Normal Myocardial Function”
• LVEF is a late and insensitive marker for study of
LV functions
• Not too far that LVEF will be replaced by other
better markers of LV function

55. ALTERNATIVES TO ‘EF’
• Valvulo-Arterial Impedance (Zva)
• MPI (Tei Index)
• Mitral annular displacement (By TDI)
• Global LV Strain
• CT AV Calcium Scoring
• BNP levels
>5.5
>0.42
< 12 mm
< 10%
>1650 AU
>550 pg/ml

56. Valvulo-Arterial impedance (Zva)
• A measurement of “afterload”
• Just quantifies the total load, that helps in
prognostication
• Values > 3.5 Zva(mmHg·mL-1
·m2
) call for
reduction in load- (both valvular and vascular)
• Does not differentiate between the type of
load –valvular vs vascular
• Does not differentiate moderate vs severe AS
(SBP + Mean AV Gradient) / i SV

57. TREATMENT DECISIONS

58. • 2012 ESC guidelines class IIa
indication for AVR
• “This subgroup of patients
seems to be at a more
advanced stage and has a
poorer prognosis if treated
medically rather than
surgically”
• It remains to be determined if
TAVI could not be a better
alternative in these patients
Tarantini G, Covolo E, Razzolini R, et al.
The Annals of Thoracic Surgery, Volume 91(6)
LOW FLOW, NORMAL EF, SEVERE AS

59. PROGNOSIS

60. LOW FLOW, N.EF, SEVERE AS
• Worse than moderate AS (albeit contradictory reports)
• Worse than severe AS with high gradient group
lower overall 3-year survival
(76% versus 86%; P<0.006 in 512 patients By Hacicha et al.)
• Two-fold increase in mortality and an almost
50% lower referral rate for AVR in the low-
gradient AS compared to the high gradient
group (Barasch et al)

61. FUTURE TERMINOLOGY
• SEVERE AS WITHOUT MYOCARDIAL DYSFUNCTION
• SEVERE AS WITH MYOCARDIAL DYSFUNCTION
-SEVERE AV STENOSIS BASED ON AVA
-IRRESPECTIVE OF FLOW, GRADIENTS, EF

62. SUMMARY

63. • ACCURATE AVA CALCULATION BY CONTINUITY
EQUATION MUST BE A STANDARD IN
EVALUATION OF A.S BY ECHO
• ELSE WE ARE GOING TO MISS 30 % CASES OF
SEVERE AS
• LOW FLOW AS COULD BE DUE TO BOTH NORMAL
AND REDUCED EF
• INSTITUTION PROTOCOLS TO BE DESIGNED FOR
EVALUATION AND TREATMENT OF LOW FLOW
STATES

64. • Low Flow due to low EF
• DSE to differentiate True from
Pseudo Severe AS
• EOA (proj) & CT AV Ca Score
• AVR irrespective of EF and
Flow reserve

65. • Low Flow due to intrinsic
myocardial dysfunction
• Better picked up by novel methods
of LV function like MAD, Tei index,
Strain apart from Zva, BNP levels
• AVR better than medical
management

66. SEVERE AS (indexed AVA < 0.6 cm2
)
ASYMPTOMATIC NORMAL EF NORMAL FLOW EXERCISE TESTING(IIa) &
FOLLOW UP
ASYMPTOMATIC LOW EF LOW FLOW AVR (I)
SYMPTOMATIC NORMAL EF NORMAL FLOW AVR (I)
SYMPTOMATIC LOW EF
(EVEN IF FLOW RESERVE IS LOW)
LOW FLOW AVR (I)
SYMPTOMATIC NORMAL EF LOW FLOW AVR (IIa)
PSEUDO-SEVERE AS (AVA <1.0 cm2
in ECHO, AVA >1.2 cm2
in DSE)
SYMPTOMATIC LOW EF NORMAL FLOW RESERVE AVR (IIa)
SYMPTOMATIC LOW EF LOW FLOW RESERVE AVR (IIb)
MODERATE AS (AVA 1-1.5 cm2
)
ASYMPTOMATIC NORMAL EF FOLLOW UP
SYMPTOMATIC NORMAL EF FOLLOW UP, AVR (IIb)

67. Simplified Statement
“Irrespective of AV Gradients and LVEF,
symptomatic patients with iAVA < 0.6 cm2
,
and CT AV calcium score > 1650 AU, should
be referred for AVR”

68. GREY AREAS
• AS WITH AR
• AS WITH MITRAL VALVE DISEASE
• RHEUMATIC AS
“Inadequate, less reliable literature”

69. “TAVI may eventually prove to be an attractive
alternative to surgical AVR in both types of LF-LG
severe AS, but this remains to be confirmed by
future randomized studies”