Coronary Physiology and FFR. David H. Sibley MD FACC, FSCAI, FACP

Transcription

1 Coronary Physiology and FFR David H. Sibley MD FACC, FSCAI, FACP

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7 Braunwald s Heart Disease, 7 th Edition Control of Coronary Blood Flow

8 1. CFR = max flow/basal flow and decreases with increasing stenosis (R1) severity. 2. CFR may also be reduced with abnormal microvasculature

9 The limitation: Because there are 2 components, CFR cannot distinguish between an epicardial stenosis and an impaired microcirculation.

10 Aortic Pressure, PA Coronary wire pressure, Pd Aortic Pressure, PA Coronary wire pressure, Pd

11 The rationale for using coronary physiology is the inability of the angiogram to accurately depict lesion characteristics limiting flow. 75% Dia 20% Dia

12 Aortic, Pa FFR= Pd/Pa = 65/90 = 0.72 Resting pressures Coronary, Pd Adenosine Hyperemic pressures

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14 Myocardial flow (Qs) across stenosis/myocardial flow (Qn) without stenosis = FFR P a P d 1. First Principle: Aortic pressure, Pa, is the same along the length of the normal vessel. 2. Resistance=P/Q 3. Flow, Q=P/R 4. Qs/Qn = (Pd/Rs) (Pa/Rn) 5. If Rs = Rn, then Qs/Qn = Pd/Pa, hence 6. FFR= Pd/Pa, at max hyperemia NHJ Pijls et al. Circulation 1993

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32 Reasons of False Negative FFR Physiologic explanations Small perfusion territory, MI, abundant collaterals, severe microvascular disease (rarely affecting FFR) Technical explanations Insufficient hyperemia Guiding catheter (deep engagement, small ostium,sideholes) Electrical drift Actual false negative FFR Acute phase of ST elevation myocardial infarction Severe left ventricular hypertrophy Exercise-induced spasm From Koolen JJ and Pijls NHJ, Coronary Pressure Never Lies CCI;72:248;2008

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37 Introduction to the ifr Modality instant wave Free Ratio ifr is a registered trademark of Volcano Corporation. instant wave Free Ratio is a trademark of Volcano Corporation.

38 Using Pressure to Get Flow Coronary pressure is simple to measure Flow velocity is more challenging Fundamental Equation for relating Pressure and Flow: P = Q x R Pressure = Flow x Resistance or P Q x R When Resistance is Constant, changes in Pressure are proportional to changes in Flow Change in Pressure = Change in Flow x Constant Resistance Derived from Poiseuille s Law for Fluid Dynamics

39 Resistance is Constant in the Wave Free Period ECG Davies J. PRIMARY Results of ADVISE. TCT Lecture conducted from San Francisco, CA.

40 Resistance is Constant in the Wave Free Period ECG Davies J. PRIMARY Results of ADVISE. TCT Lecture conducted from San Francisco, CA.

41 Pressure (mm Hg) instant wave Free Ratio Introduction of the ifr Modality Definition: Instantaneous pressure ratio, across a stenosis during the wave free period, when resistance is naturally constant and minimized in the cardiac cycle 120 Wave free period Pa 70 Pd Time (ms) Escaned J. ADVISE II: A Prospective, Registry Evaluation of ifr vs. FFR. TCT Lecture conducted from San Francisco, CA.

42 The Meaning of Instantaneous Instantaneous Pd/Pa varies during the cardiac cycle The measurement is stable at any instantaneous point during the ifr window Davies J., A More Functional Future: Moving Physiology from Justifying to Deciding Treatment. TCT Lecture conducted from San Francisco, CA.

43 The ifr Modality Cut Point An ifr cut point of 0.89 matches an FFR cut point of FFR and ifr have a different scale Celsius & Fahrenheit both measure temperature, but have a different scale ifr TREAT DEFER FFR TREAT DEFER 1. An ifr cut point of 0.89 matches best with an FFR ischemic cut point of 0.80 with a specificity of 87.8% and sensitivity of 73.0%. (ifr Operator s Manual )

44 The ifr Modality Cut Point ifr value with best classification for FFR Study ifr Cut Point ADVISE Registry (n=339) 0.89 Seoul Registry (n=238) 0.90 RESOLVE (n=1593) 0.90 ADVISE in Practice (n=392) 0.90 ADVISE II (n=689) An ifr cut point of 0.89 matches best with an FFR ischemic cut point of 0.80 with a specificity of 87.8% and sensitivity of 73.0%. (ifr Operator s Manual )

45 Three Benefits to the ifr Window 11. Noise from compression and suction waves is minimized 2. Resistance is constant so P is proportional to Q (flow) 3. 3 Velocity is higher so better power to discriminate Sen S, et al. Development and validation of a new adenosine independent index of stenosis severity from coronary wave intensity analysis: results of the ADVISE (ADenosine Vasodilator Independent Stenosis Evaluation) study. J Am Coll Cardiol Apr 10;59(15):

46 Higher Velocity = Better Classification Increasing Flow Velocity exaggerates the pressure drop across a stenosis Pd/Pa FFR Bigger pressure drop allows for better classification of stenosis severity Adapted from Gould, K. Pressure flow characteristics of coronary stenoses in unsedated dogs at rest and during coronary vasodilation Circulation research 1978;43:

47 ifr Window Maximizes Flow Velocity ifr Flow is ~30% higher which amplifies the signal vs. Pd/Pa alone 1 ifr Window Wave free flow FFR ~30% increase in mean flow velocity* Pd/Pa ifr Coronary Flow during one full cardiac cycle 2 1. Sen et al. Instantaneous Wave Free Ratio and FFR Are Equivalent (Results from CLARIFY). JACC Vol. 61, No. 13, April 2, 2013: Adapted from Gould, K. Pressure flow characteristics of coronary stenoses in unsedated dogs at rest and during coronary vasodilation Circulation research 1978;43:

48 ifr Amplifies the Signal ifr with 30% higher flow spreads the scale to deliver the most differentiation possible at rest Pd/Pa 18 unit spread ( ) ifr 31 unit spread ( ) With a wider scale, ifr is less susceptible to procedural noise 238 consecutive lesions in real clinical practice were measured with Pd/Pa, FFR and ifr (calculated off-line). 95% of the Pd/Pa data fell within 0.19 points [ ] vs 0.31 points for ifr [ ] and 0.36 points for FFR [ ]. Park JJ.et al., Clinical validation of the resting pressure parameters in the assessment of functionally significant coronary stenosis; results of an independent, blinded comparison with fractional flow reserve. Int J Cardiol Oct 9;168(4):

49 Vasodilators do not improve physiological diagnostic accuracy Data source n p Difference in accuracy % (either match or ROC) Sen et al p=ns Van de Hoef et al p=ns Johnson et al p<0.01 Petraco et al p<0.01 ifr better ifr better De Waard et al p=ns Favors Hyperemia (FFR) BETTER Favors Resting (ifr) BETTER 1. Sen S et al. Development and validation of a new adenosine-independent index of stenosis severity from coronary wave-intensity analysis: results of the ADVISE (ADenosine Vasodilator Independent Stenosis Evaluation) study. J Am Coll Cardiol Apr 10;59(15): J Am Coll Cardiol. 2013;61(13): Van de Hoef T, et al. Basal Stenosis Resistance Index and Instantaneous Wave-Free Ratio Have the Same Diagnostic Performance as Fractional Flow Reserve to Detect Myocardial Ischemia Using Myocardial Perfusion Imaging. Abstract presented at ACC Sen S, et al. Diagnostic classification of the instantaneous wave-free ratio is equivalent to fractional flow reserve and is not improved with adenosine administration. Results of CLARIFY (Classification Accuracy of Pressure-Only Ratios Against Indices Using Flow Study). J Am Coll Cardiol Apr 2;61(13): Petraco R, et al. Hybrid ifr-ffr decision-making strategy: implications for enhancing universal adoption of physiology-guided coronary revascularisation. EuroIntervention Feb 22;8(10): de Waard et al. Hyperemic FFR and Baseline ifr have an equivalent diagnostic accuracy when compared to myocardial blood flow quantified by H 2 O 15 PET Perfusion Imaging. Abstract presented at ACC 2014

50 Simplifying Workflow The ifr modality provides a hyperemia free measurement in as few as five heartbeats

51 The Hybrid ifr /FFR Approach 94.0% match to FFR % of patients may be free from hyperemic agents 2 1. Using the ifr cut points of 0.85 and 0.94 matches best with an FFR ischemic cut point of 0.80 with a specificity of 90.7% and sensitivity of 96.2%. 2. The ADVISE II study illustrated a 5.8%, i.e. (17+23)/690, classification discordance between the ifr Hybrid Approach and FFR. Among 477 lesions that would be assessed without hyperemia by the ifr Hybrid Approach, 40 (17+23) were due to classification discordance. 3. An ifr cut point of 0.89 matches best with an FFR ischemic cut point of 0.80 with a specificity of 87.8% and sensitivity of 73.0%. (ifr Operator s Manual )

52 Hybrid ifr /FFR Approach: ADVISE II 94.0% match to FFR % of patients may be free from hyperemic agents 2 TREAT Perform FFR DEFER 1. Using the ifr cut points of 0.85 and 0.94 matches best with an FFR ischemic cut point of 0.80 with a specificity of 90.7% and sensitivity of 96.2%. (ifr Operator s Manual ) 2. The ADVISE II study illustrated a 5.8%, i.e. (17+23)/690, classification discordance between the ifr Hybrid Approach and FFR. Among 477 lesions that would be assessed without hyperemia by the ifr Hybrid Approach, 40 (17+23) were due to classification discordance.

53 Functional Lesion Assessment of Intermediate stenosis to guide Revascularisation Study Objectives: Determine safety and efficacy of PCIguided ifr vs. FFR Determine if ifr is non-inferior to FFR to guide PCI Primary Endpoints: Major adverse cardiac events (MACE) rate in the ifr and FFR groups at 1 year MACE (combined endpoint of death, nonfatal MI, or unplanned revascularization) Largest Physiology Study to Date n= Sites, 17 countries

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55 The ifr Modality Cost Savings Hyperemic Agent Calculator Institution: St. Mary's Hospital Annual PCI Volume 1,000 Annual FFR Wire Usage 150 FFR Penetration 15% Monthly FFR Wire Usage 12.5 Volcano Market Share 80% Volcano Wires per Month 10 Hyperemic Agent Cost per Case $350 Percentage of FFR Cases not requiring hyperemic agent 1,2 50% Cost Savings per Year $21,000 Year 1 Year 2 Year 3 Hyperemic Agent Savings $21,000 $21,000 $21,000 ifr Upgrade Investment -$25,000 Net Savings -$4,000 $21,000 $21,000 3 Year Return On Investment 152%

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57 ,5,6 Morphologic factors producing Pressure Loss across a stenosis Energy loss due to friction, separation, turbulence. Energy is taken out as heat and pressure loss results. The loss of distal pressure is related to the blood flow rate Pressure and flow move on a curvelinear line P d

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60 Diffused CAD can produce abnormal FFR in the absence of epicardial stenoses DeBruyne et al, Circulation :

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62 Pressure pull back to assess lesion significance FFR(a+b)=Pd/Pa FFRa=Pm/Pa FFRb= Pd/Pm

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