FFR(fractional flow reserve)

fractional flow reserve

1. FFR DIPAK PATADE

2. Challenges in daily practice • Patients with recent myocardial infarction , questions pertain to lesions not responsible for symptoms or infarct—so called “ non culprit ” lesions . • Subsequent cardiovascular events appear equally likely in no culprit lesions following MI . • Patients with stable angina, questions surround the choice between medical therapy and revascularization .Difficulty is identifying specific lesions that are functionally significant or that will likely lead to adverse events. • Frequent occurrence of multivessel disease poses additional challenges. • Noninvasive tests may lack sensitivity and specificity to detect multivessel disease and treatment decisions can be complex .

3. Coronary blood flow ~5% of the total CO increase up to 5 times with exercise, hypoxia, local metabolite release (nitric oxide), and microcirculatory vasodilators microcirculatory resistance is the only resistance to myocardial flow epicardial vessels are just conductance vessels that offer no resistance systolic compression of the microcirculation- left coronary blood flows mainly during diastole (>80% occurs in diastole). Tachycardia- increasing O2 demands + reduces myocardial O2 supply by reducing diastolic time

4. Coronary blood flow tachycardia - increases the relative systolic contribution to coronary flow. RV - thin, its microcirculation is not as affected by systole ;~50% of the mid right coronary-to-RV flow occurs in systole autoregulation, that is, microcirculatory vasodilation, maintains coronary perfusion at a constant level over a wide range of coronary pressure. Reduced perfusion pressure distal to a stenosis is compensated by autoregulatory dilation of resistance vessels. Autoregulation allows myocardial flow past the stenosis to remain normal at rest despite a reduction in pressure; however, flow cannot increase enough with exercise or with maximal vasodilation

5. Determined not only by variations in pressure arising proximally (as in the aorta and other systemic arteries) but also concurrent variations arising distally in the microcirculation inaccurate to assess the severity of a coronary stenosis by measuring the decrease in mean or peak pressure across a stenosis under basal conditions distal coronary pressure is not simply a residuum of the pressure transmitted from the aortic end but is also due to a pressure component arising from active compression and decompression of the coronary microcirculation

6. Pressure flow dynamics at stenotic segment

7. FFR Technique used in coronary catheterization to measure pressure differences across a coronary artery stenosis (narrowing, usually due to atherosclerosis) to determine the likelihood that the stenosis impedes myocardial ischemia. FFR=Pd/Pa

8. Fractional flow reserve • FFR is used to assess the physiologic consequences of obstruction with a goal of predicting benefit from revascularization or which lesions should be treated . • Derived from the ratio of the mean distal coronary artery pressure (Pd) to the mean aortic pressure (Pa) during the period of maximum hyperemia . • Fractional flow reserve is not affected by changes in the hemodynamic conditions or microcirculation. • ‘‘normal’’ ratio is expected to be 1. • Values less than 0.75 to 0.80 are considered functionally ischemic, while those 0.94 to 1.0 normal.

9. What Fractional Flow Reserve Value defines Ischemia ? FFR value <0.75 was associated with reversible ischemia on noninvasive stress testing (exercise stress test, nuclear scan, and dobutamine stress echocardiogram) with 88% sensitivity, 100% specificity, 100% positive predictive value, 88% negative predictive value, and 93% accuracy.

10. What Fractional Flow Reserve Value defines Ischemia ? DEFER study and other studies have used an FFR value of <0.75 as the cutoff for ischemia. FFR value >0.80 has been shown to exclude an ischemia producing lesions, with predictive value of >95%. 3 landmark trials have validated FFR cut off values- DEFER FAME FAME II

11. Coronary stenosis can be arbitrarily classified into 3 groups on the basis of FFR values: a. non–ischemic stenosis with FFR >0.80 b. ischemia-producing stenosis with FFR <0.75. c. gray zone with FFR values between 0.75 and 0.80 .

12. Applications for Fractional Flow Reserve in Coronary Artery Disease Single-Vessel Disease- • DEFER study has shown that patients with single vessel stenosis and FFR >0.75 who did not undergo PCI had excellent outcomes. • The risk of cardiac death or myocardial infarction (MI) related to the stenosis was <1% per year and was not reduced with PCI. • patients with single-vessel stenosis and FFR <0.75 are 5× more likely to experience cardiac death or MI within 5 years, despite undergoing revascularization. • medical treatment of patients with proximal left anterior descending stenosis and FFR >0.80had excellent 5-year outcomes

13. patients with small coronary arteries (diameter <2.8 mm), FFR can safely determine stenosis that necessitate revascularization . • In the Physiologic and Anatomical Evaluation Prior to and After Stent Implantation in Small Coronary Vessels (PHANTOM) trial, 60 patients with small coronary arteries underwent FFR. group with FFR <0.75 underwent revascularization. • At 1 year, there was no occurrence of MI or death in either group. • patients with FFR <0.75, 24% underwent a repeat PCI, but only 2.6% of patients with FFR >0.75 underwent revascularization.

14. Left Main Stenosis • Nonischemic FFR values (>0.80) in left main lesions are associated with excellent long-term outcomes. • accurate LM FFR reflects flow through both the LAD and the CFX. • myocardial bed for the LM is the summed territories of both the LAD and the CFX. • LM bed can be even larger if the RCA is occluded and there is collateral supply from the left coronary system. • isolated LM narrowing with no LAD, CFX, or RCA stenosis reflects the physiologic significance of just the LM narrowing. • LM narrowing plus LAD stenosis could produce a higher LM FFR because the LM bed is reduced in size. • LM FFR alone cannot be accurately measured just as when there are serial lesions.

15. Tandem Lesions- • Tandem lesions are defined as 2 separate lesions with >50%stenosis each in the same coronary artery, separated by an angiographically normal segment. • If the FFR is<0.75 PCI for the stenosis that showed marked narrowing first and then repeating the FFR measurement. • If the FFR remains<0.75,the other stenosis was revascularized as well , In contrast, if the FFR value of the first lesion increased after PCI to >0.75, then these second lesion was treated only medically.

16. diffuse coronary disease If FFR < 0.80 but pressure pullback reveals a gradual decline in pressure without focal drop-This may be seen in patients with mild or moderate diffuse disease and small coronary arteries. 8% of arteries with mild diffuse coronary atherosclerosis without a focal stenosis have a graded continuous fall in pressure along the arterial length with FFR <0.75, explaining myocardial ischemia and angina without angiographically obstructive disease.

17. FFR and a bypass graft myocardial territory receiving a bypass graft is supplied by 2 vessels graft native vessel if not totally occluded During hyperemia, the drop in pressure distal to a graft stenosis reflects the drop in flow across the supplied myocardium an angiographically severe stenosis across the graft may not lead to a significant flow reduction, depending on the adequacy of native vessel flow. FFR reflects a net FFR from all sources of flow to that region.

18. Ostial disease Ostial disease with too deeply engaged GC- pressure at its tip does not correspond to the aortic pressure but to the pressure distal to the lesion. guiding pressure (false Pa) and the sensor pressure (Pd) correlate closely and the FFR is falsely increased. guiding catheter is outside the ostium but the wire is just distal to the ostium-pressure distal to the stenosis is equalized to the aortic pressure FFR may be overestimated and the lesion underestimated disengage the guiding catheter and the sensor part of the wire during equalization. guide may then be temporarily engaged while wiring the artery but must be disengaged when FFR measurements are obtained.

19. MI and FFR Maximal hyperemia is lower FFR may be overestimated (lesion underestimated). not be used to assess the culprit lesion of MI that occurred within the last 5 days.

20. Old infarcted myocardium When part of the territory supplied by a coronary artery is infarcted, this territory receives reduced myocardial flow , maximal achievable flow across this myocardial territory is reduced. FFR dependent - amount of viable myocardium and the severity of microcirculatory impairment. FFR <0.75 correlates not only with the size large increase in transstenotic pressure gradient or flow with adenosine -sign of the presence of viable myocardium with healthy microcirculation absence of a vasodilatory response -sign of non-viability ( ie , "FFR" number remains unchanged before and after adenosine infusion

21. Persistent low FFR after PCI incomplete stent expansion stent malapposition geographical miss plaque protrusion edge dissection plaque shift at the stent edge pullback manoeuvre :continuous gradual reduction in FFR = diffuse CAD. diffuse CAD -impaired post-stent FFR, despite an angiographically optimal PCI

22. FFR Limitation & Disadvantage FFR assess of lesion severity. FFR invasive test and allows real-time estimation of the effects of a narrowed vessel. No plaque morphology information. physical exercise or some intravenous medication is to increase the workload and oxygen demand of the heart muscle, and ischemia is detected using ECG changes or Nuclear imaging.