1) A significant proportion of patients with severe aortic stenosis can present with low flow and low gradient despite preserved ejection fraction, representing a more advanced stage of disease. 2) Multiple factors can contribute to this pattern, including increased afterload, concentric left ventricular hypertrophy, and diastolic dysfunction. 3) Identifying these "low-flow, low-gradient" patients is challenging but important, as standard echocardiography criteria may underestimate severity; imaging modalities like cardiac MRI and CT can provide more accurate assessment of left ventricular outflow tract dimensions and function.

1. Unravelling low-flow, low-gradient
aortic stenosis
The Role of Imaging
Prof. Fausto J. Pinto, FESC, FACC
Head, Cardiology Dpt/University Hospital Sta Maria-HPV
University of Lisbon, Portugal

2. • No conflict of interest to declare regarding
this talk.

3. Philippe Pibarot , Jean G. Dumesnil
Different Patterns of Severe AS According to Flow, Gradient, and LV Geometry
Journal of the American College of Cardiology, Volume 60, Issue 19, 2012, 1845 - 1853

4. Hachita et al. Circulation 2007
512 pts with Severe AS
AVA≤ 0,6 cm2/m2, EF >50%
331 pts
Systolic Vol > 35 ml/m2
181 pts
Systolic Vol ≤ 35 ml/m2
Follow-up 25±19 months

5. Hachita et al. Circulation 2007

6. Geometry and LV Function
Hachita et al, 2007

7. Survival
Hachita et al. Circulation 2007

8. Predictors of Survival
Hachita et al. Circulation 2007

9. Pts with severe AS and low flow Pts com Severe AS, low flow and
normal EF
Ann Throrac Surg 2009

10. These studies suggest…
• A significant proportion of pts with reduced
AVA may have low flow and low gradient
despite preserved EF.
• A pattern of increased afterload, concentric
LVH and impaired survival suggests a more
advanced stage of AS.
• This situation may be under diagnosed and
not be timely treated with surgery.

11. Questions
• What is the mechanism underlying low flow/low
gradient in pts with severe AS and preserved
EF?
• Can we identify those pts using the currently
available techniques and criteria?
– Inconsistencies of echocg for the current criteria?
– Different severity criteria?
• What is the prognosis and treatment?

12. Criteria for AS Severity
Guidelines valvular heart disease. ESC, EACTS, 2012

13. Carabello et al, NEJM 2002

14. Minners J et al. EHJ, 2008
Retrospective study; 2427 pts with preserved EF and AVA ≤ 2 cm2
ØMean gradient 40 mmHg – 0,75 cm2 and peak velocity 4 m/s – 0,8 cm2

15. AVA < 0,8 cm2

16. 333 pts, FE≥ 30% and AVA< 2cm2 – hemodynamics + echo
ØInconsistency of AVA and mean gradient
ØPartially explained by low flow (systolic volume ≤35ml/m2)
Minners J et al. Heart 2010

17. ØThe underestimation of LVOT is one of the factors
that may lead to a false diagnosis of low flow
Estimated area 381 mm2 Estimated area 581 mm2
Inadequate measurement of LVOT/ellipsoid configuration (eco 3D, CT, MRI)
Utsunomiya et al. Int J Cardiol 2011

18. - Handgrip and fenilefrine
- Presence of HTN  pseudodiagnosis of low flow impair the AoV
resistance and AVA, regardless of aortic compliance; in addition the gradient
has an inconsistent variability
Litle SH et al. Heart 2007

19. If we exclude the
inconsistencies how to
explain?

20. 1. Increased vascular afterload
• Increase of the vascular afterload (age,
atherosclerosis) and valvular
– Symptoms in pts with moderate AS
– Increased valvulo-arterial impedance and
impaired vascular compliance associated
with LV dysfunction in AS in the older pts
(Briand etl, JACC 2005)
– Increased in pts with severe AS and low
flow (Hachita et al 2009)

21. 2. Diastolic Dysfunction
• Geometry:
– Small size LV (<50 mm, < 60 ml/m2),
– Hypertrophy
• Diastolic Compromise
• Incremental effect if associated to
increased systemic afterload + valvular
Dumesnil et al. Eur Heart J 2010

22. 3. FEJ preservada ≠ Função
preservada
FEJ=55% SL global=-15%

23. AS / low flow and 2D strain
120 pts with severe AS, EF > 50%, with normal vs low flow
Pts with low flow had impaired longitudinal strain = LV Dysfunction
Mielot. EHJ 2009

24. u Prospective multicentric study
u 340 consecutives pts, severe AS
(AVA<0,6 cm2/m2) and EF> 50%

26. uThe low flow/low gradient group (9%),
differed significantly from the other
groups:
uLess HTN but more diabetes
uIncreased afterload (>valvulo-arterial
impedance )
uImpaired basal LV longitudinal strain
uImpaired radial strain

28. Pibarot P, Dusmenil et al. Circulation 2013
Early Diagnosis is critical

29. How to Assess - I
• 1. Exclude pitfals
– LVOT measurement,
– Assess EF by two different
– Use CMR and CT (LVOT; LV function)
• 2. Assess the indices of myocardial deformation
• 3. Confirm low flow low output;
• 4. Assess biomarkers
Dumesnil et al. EHJ 2010

30. How to Assess - II
• 4.Additional indices
of AS severity
– Energy loss index;
Ao<30mm
– Increased resistance
– AoV Calcification +++
• 5. Conditioning
Factors:
– > valvulo-vascular
impedance
– < aortic compliance
– Small and hypertrophic LV
– Females

31. Conclusions
• Severe AS with low flow and preserved
EF may represent up to 25% of the AS
Population
• Medical treatment is associated with an
increased event rate and mortality but
surgery can improve the diagnosis
• Its identification and diagnosis are crucial
• Imaging plays a central role in the correct
diagnosis and patient management