Virtual fractional flow reserve: computer modelled …BCIS ACI, Young Investigators Award , London...

$: Virtual fractional flow reserve: computer modelled …BCIS ACI, Young Investigators Award , London 2013 Background: Adjunctive physiology • COURAGE • COURAGE sub-study • DEFER$
Virtual fractional flow reserve: computer modelled coronary physiology from angiography

Dr Paul Morris

British Heart Foundation Clinical Research Training Fellow

University of Sheffield and Sheffield Teaching Hospitals

BCIS Advanced Cardiovascular Intervention, Young Investigators Award London Hilton Metropole January 23rd-25th 2013

BCIS Advanced Cardiovascular Intervention, Young Investigators Award London Hilton Metropole January 23rd-25th 2013

NO CONFLICT OF INTEREST TO DECLARE

65% 20% 4%

BCIS ACI, Young Investigators Award , London 2013

Background: Visual angiography ≠ physiology

• Lumenography

• Unreliable detecting ischaemia

• QCA not much better

• More challenging in LMS disease

Tonino et al. Journal of the American College of Cardiology 2010;55:25

Joshua et al. American Journal of Cardiology 2002;90:210–215 Lindstaedt et al. International Journal of Cardiology 2007;120:254–261


Background: Adjunctive physiology • COURAGE

• COURAGE sub-study

• DEFER

• FAME

• FAME II

Boden et al. N Engl J Med. 2007 12;356(15):1503-16. Shaw et al. Circulation. 2008 11;117(10):1283-91. Pijls et al. J Am Coll Cardiol. 2007 29;49(21):2105-11. Tonino et al. N Engl J Med. 2009;360:213-24. De Bruyne et al. N Engl J Med. 2012 Sep 13;367(11):991-1001.


Why is FFR not used in all cases?

• <10% PCIs

• ~0% diagnostic angiograms

• Why?

Ludman PF. BCIS Audit Returns; Adult Interventional Procedures 2010. BCIS, Birmingham 2011.


Hypothesis: • FFR can be predicted from coronary angiography

• Using computational fluid dynamics (CFD) modelling

FFR CFD


VIRTU1 study VIRTUal fractional flow reserve: computer modelled coronary physiology from angiography

• 20 patients • Rotational angiography • FFR measured

• Data exported

• 3D VRML files (Philips) • GIMIAS • ANSYS CFX solver

• vFFR compared with mFFR

VS


VIRTU1 Results

• 20 patients • 1 exclusion (MI) • Mean age 64yrs • 60% male

• 35 lesions

• 10 RCA (5*PCI) • 12 LCA (8*PCI)

• CFD analysis in all cases

• Analysis c12-24 hrs

Morris et al. J Am Coll Cardiol Cardiovasc Interv. In press, 2012.


VIRTU1 Results: Diagnostic accuracy (FFR > or < 0.80)

All cases % 95% CI

Sensitivity 86% 0.48-0.97

Specificity 100% 0.87-1.0

Positive predictive value

100% 0.60-1

Negative predictive value

97% 0.82-0.99

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

FFR


Accuracy = 97%


VIRTU1 Results: Quantitative accuracy (agreeability)

RCA cases LCA cases Total

Bias (mean delta SD)

0.03 (0.08) 0.01 (0.09) 0.02 (0.09)

Accuracy (mean error[SD])

±0.07 (0.08) ±0.06 (0.09) ±0.06 (0.09)



Study limitations: Challenges for the future

• Few cases

• Simple cases

• Speed

• Geometry

• Microvasculature

• Interface


Conclusions

• Feasibility of vFFR from 2D angiogram images

• Without pressure wires or adenosine infusion

• Next phase • distal boundary conditions • acceleration • validate in more complex disease


Dr Julian Gunn Prof Rod Hose

Prof Patricia Lawford

Dr Des Ryan Dr Susan Smith

Dr Allison Morton

Team Sponsors


Questions?

Medical Physics Group

Department of Cardiovascular Science

School of medicine


Backup slides



School of medicine


System acceleration

• Mesh optimisation optimise mesh structure. c50% reduction in execution time

achievable

• Increased computational power ANSYS-CFX operates in parallel and achieves near linear scaling, and we could reduce computational time by an order of magnitude by using a more powerful machine – still at very reasonable cost.

• Optimised GPU processing a further commercialisation option, beyond the scope of the current programme of work, would be to deploy a GPU-enabled CFD solver.

• OD or 1D modelling 0D or 1D approximation model. Should this prove true then there is the exciting potential for near real-time ‘on table’ results.



School of medicine




School of medicine


Potential applications • Ideally

• comprehensive intra-coronary physiological assessment • real-time • user friendly interface

• Or (currently) • initial screening tool • rule in or rule out tool

• Alternatively • two-tier system • quick screening option • detailed analysis



School of medicine


VIRTU1 Results: Example




School of medicine


Problems with FFR (&CFR) • FFR is the current Gold standard

• Makes no estimation of flow

• Unlike HSR CFR

• Assumes constant R2 resistance (independent of R1)

• Reproducibility variable

4 12

100 100

4 4

FFR=0.50 FFR=0.75

50 75



School of medicine


Baseline characteristics

Mean age, years (range) 64 (45-81)

Male 12 (60)

Mean body-mass index 29

Comorbidities

Hypertension 16 (80)

Hyperlipidaemia 19 (95)

Diabetes 1 (5)

Current smoker 4 (20)

Prior myocardial infarction 1 (5)

Stroke 0 (0)

Peripheral vascular disease 0 (0)

Medication

Aspirin 17 (85)

Beta-blocker 15 (75)

Nitrate 3 (15)

Statins 20 (100)

ACE inhibitors 11 (55)

Calcium-channel blockers 6 (30)

Clopidogrel 20 (100)

ARBs 0 (0)



School of medicine


Pat

ien

t

Do

min

ance

Ve

sse

l

%d

iam

ete

r

ste

no

sis

Bif

urc

atio

n

Tort

uo

us

Lon

g

Dif

fuse

SYN

TAX

Ste

nte

d

1 R RCA >70 2 Y

2 R LAD 30-70 5 Y

3 R LAD 30-70 Y 7

4 R RCA 30-70 Y 3

5 R LAD >70 Y 9 Y

6 R RCA 30-70 2

7 R RCA >70 Y Y Y 6 Y

8 R LAD 30-70 7

9 R LAD 30-70 7 Y

10 R RCA >70 Y 3 Y

11 R LAD 30-70 7 Y

12 R RCA 30-70 2

LAD 30-70 Y 5 Y

13 R RCA 30-70 Y 4 Y

14 R RCA 30-70 Y 6

15 R LCx 30-70 3 Y

16 R RCA 30-70 2

LAD 30-70 Y 8

17 R LAD 30-70 Y 10 Y

18 R LAD 30-70 7

19 R RCA >70 Y 3 Y

OM >70 2



School of medicine


HeartFlow Inc (per-patient)

iFR (per lesion)

VIRTU (per-lesion)

sensitivity 73% 85% 86%

specificity 90% 91% 100%

PPV 54% 91% 100%

NPV 60% 85% 97%

accuracy 84% 85% 97%

n 252 157 35

No direct competition

• HeartFlow inc (JAMA 2012;308:1237)

• iFR (JACC 2012;59:1392)



School of medicine


Advantages of vFFR

• single investigation (for anatomy and physiology)

• only geometry required

• widen access to IPA

• reduced heart attacks, deaths, cost

• reduced interventions, investigations

• further cost reductions

• software based

• virtual stenting tool • further reductions in stent numbers?

• measured data tool

• integratable into existing infrastructure



School of medicine


a posteriori correction

• Distal impedance is important

• To account for this we re-worked results using the measured impedance

• Assumption: impedance of the 3D domain is unchanged

• When applied to pre- and post-stent cases average absolute error was reduced from ±0.07 to ±0.05

Virtual fractional flow reserve: computer modelled …BCIS ACI, Young Investigators Award , London...

Documents

Transcript of Virtual fractional flow reserve: computer modelled …BCIS ACI, Young Investigators Award , London...