1) Low flow, low gradient severe aortic stenosis can occur with both low and preserved ejection fraction. Dobutamine stress echocardiography is important to differentiate true from pseudo-severe stenosis. 2) For low ejection fraction, aortic valve replacement is recommended irrespective of symptoms or flow reserve. 3) For preserved ejection fraction, alternatives to ejection fraction like valvulo-arterial impedance and global longitudinal strain can help identify intrinsic myocardial dysfunction and predict outcomes. Aortic valve replacement may be better than medical management in these patients.

1. LOW FLOW LOW GRADIENT
SEVERE AORTIC STENOSIS
» DR.ANUJ MEHTA(DNB- CTU)
» GKNM Hospital,Coimbatore
1

2. LOW FLOW, LOW GRADIENT, SEVERE AS
LOW EF
5- 10 % of all patients of AVA < 1.0
PRESERVED EF
10-25 % of all patients of AVA < 1.0
2

3. PATHOPHYSIOLOGY
• LOW FLOW secondary to LOW EF
-myocardial dysfunction
-secondary to AS
-secondary to other causes, or
-primary myocardial disease, needs to be evaluated. 3

4. MYOCARDIAL DYSFUNCTION SECONDARY
TO CAUSES OTHER THAN AS
-DILATED CARDIOMYOPATHIES (1O MYOCARDIAL
DYFUNCTION)
-ISCHAEMIC HEART DISEASE
-HTN HEART DISEASE (AFTER LOAD MISMATCH)
4
AVA can be misjudged as <1.0 due to incomplete
opening of AV due to low EF and labelled as
“PSEUDO SEVERE AS”

5. MYOCARDIAL DYSFUNCTION
SECONDARY TO AS
• “ True severe AS”
• Removal of the only afterload-AS can lead to
dramatic improvements in patients’
symptoms/survival compared to medical therapy
alone
5

6. DIAGNOSIS
• FIRST SUSPICION — GRADIENT-AVA
MISMATCH during routine echo
• GRADIENT < 40 mm Hg, AVA <1.0 , EF <40
%
• Dobutamine stress echo (exercise stress echo)
6

7. Dobutamine stress Echo
• Provides information regarding:
-Flow reserve
-Change in EOA
-Change in Gradient
7

8. Dobutamine stress Echo
• Low dose - 2.5 to 5 mcg/kg/min. and incremental dose
every 3-5 minutes .
• Max. dose-10-20 mcg/kg/min
• To stop —> positive result obtained
—>H.R. increase >10-20 bpm over baseline or
exceeds 100 bpm.
8

9. 9
30-40%
20-30%

10. CT AV CALCIUM SCORING
• Score >1,650 Agatston units provides good accuracy (93 %
sensitive, 75 % specific) to distinguish true severe from
pseudo-severe AS
10

11. Treatment Decision
• SYMPTOM STATUS
• VALVULAR SEVERITY
“ANY SYMPTOMATIC SEVERE AS, IRRESPECTIVE
OF EF AND FLOW RESERVE, HAS TO BE
INTERVENED (class I)”
11

12. 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
12
Recommendation:
AVR (class I indication, level of evidence C)

13. • PERIOP RISK- FLOW RESERVE (+)=5-8%,
• FLOW RESERVE (-)=30%*
13

14. Role of TAVI
• 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, TAVI associated with a higher incidence of perivalvular
regurgitation, stroke, vascular complications which may eventually
have a negative impact on outcomes
• PARTNER A & B .
14

15. 15
• Normal flow reserve:
Medical followup every 6 months vs AVR (ESC class IIa)–based on the clinician’s
judgement
• Low flow reserve:
1.IHD-Medical management ± revascularisation
2.HTN- to be treated
3.Optimal heart failure management strategy
4.AVR (class IIb)

16. • 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%)
16
Group I= Flow reserve +
Group II= Flow reserve -
Patients benefit more with AVR than medical management in both groups.
PROGNOSIS

17. LOW FLOW NORMAL EF SEVERE AS
“PARADOXICAL”
17
LOW EF
5- 10 % of all patients of AVA < 1.0
PRESERVED EF
10-25 % of all patients of AVA < 1.0
-Mean gradient < 40 mmHg,
-AVA < 1.0 cm2,
-Flow <35 ml/mt2,
-EF≥40 %

18. PATHOPHYSIOLOGY OF LOW FLOW NORMAL EF
SEVERE AS
• Myocardial fibrosis
• Restrictive physiology
• Small LV cavity
• Resembles heart failure with preserved EF (Diastolic Heart
failure)
• Impaired LV function yet normal EF
(around 50-60%)
18

19. DIAGNOSIS
19

20. “Normal LVEF Does Not Mean Normal Myocardial Function”
• LVEF is a late and insensitive marker for study of LV
function.

21. 21
ALTERNATIVES TO ‘EF’
>5.5
>0.42
< 12 mm
< 10%
>1650 AU
>550 pg/ml
• Valvulo-Arterial Impedance (Zva)
• MPI (Tei Index)
• Mitral annular displacement (By TDI)
• Global LV Strain
• CT AV Calcium Scoring
• BNP levels

22. Valvulo-Arterial impedance (Zva)
• Quantifies the total afterload, that helps in prognostication
• Values > 3.5 Zva (mmHg·mL-1·m2) call for reduction in
load- (both valvular and vascular)
22

23. TREATMENT DECISIONS
23

24. • 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
24
The Annals of Thoracic Surgery,
LOW FLOW, NORMAL EF, SEVERE AS

25. LOW FLOW, NORMAL EF, SEVERE AS
• Worse than severe AS with high gradient group
lower overall 3-year survival
• Two-fold increase in mortality for AVR in the low-
gradient AS compared to the high gradient group
25
PROGNOSIS

26. SUMMARY
26

27. • ACCURATE AVA CALCULATION BY CONTINUITY
EQUATION MUST BE A STANDARD IN EVALUATION OF
A.S BY ECHO
• MISS 30 % CASES OF SEVERE AS
• LOW FLOW AS COULD BE DUE TO BOTH NORMAL AND
REDUCED EF
• INSTITUTION PROTOCOLS TO BE DESIGNED
27

28. • Low Flow due to low EF
• DSE to differentiate True from Pseudo Severe
AS
• EOA & CT AV Ca Score
• AVR irrespective of EF and Flow reserve
28

29. • Low Flow due to intrinsic myocardial
dysfunction
• Better picked up by novel methods of LV
function like Tei index, Strain apart from Zva,
BNP levels
• AVR better than medical management
29

30. 30
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)

31. 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”
31

32. GREY AREAS
• AS WITH AR
• AS WITH MITRAL VALVE DISEASE
• RHEUMATIC AS
“Inadequate, less reliable literature”
32