|Year : 2017 | Volume
| Issue : 2 | Page : 83-86
Coronary fractional flow reserve: Clinical importance
Department of Cardiology, CARE Hospitals, Nagpur, Maharashtra, India
|Date of Web Publication||15-Sep-2017|
CARE Hospitals, Nagpur, Maharashtra
Source of Support: None, Conflict of Interest: None
Coronary angiography has an important role in invasive imaging of the coronary arteries. However, it has got limitations in the determination of physiologic significance of individual artery lesions. Coronary pressure derived FFR can be used to rapidly assess the hemodynamic significance of individual coronary artery lesions and can be easily performed in catheterization laboratory. FFR has been shown to effectively help coronary revascularization procedures with improved patient outcomes. FFR is a very important tool for determination of functional significance of coronary stenosis. It combines physiological and anatomical information which can be immediately followed by percutaneous coronary intervention (PCI) if required. The technique for FFR measurement is easy, safe and can be rapidly performed in the catheterization laboratory. PCI can be made more effective by proper and systemic use of FFR in dubious situations. The current clinical evidence for FFR is very encouraging for cardiologist to use this tool in the catheterization laboratory as and when required.
Keywords: Fractional flow reserve, percutaneous coronary interventions, Vipul Seta
|How to cite this article:|
Seta V. Coronary fractional flow reserve: Clinical importance. J Mahatma Gandhi Inst Med Sci 2017;22:83-6
| Introduction|| |
Coronary angiography still has an important role in invasive imaging of the coronary arteries. However, coronary angiography has got limitations in the determination of physiologic significance of coronary stenosis., The most important factor related to outcome is the presence and extent of inducible ischemia., If the coronary stenosis is functionally significant, it should be revascularized if possible.,, On the other hand, if it has no functional significance, medical treatment is indicated., Intracoronary fractional flow reserve (FFR) has proven to be a reliable method for the measurement of physiological significance of coronary stenosis. An FFR value of ≤0.80 indicates coronary stenosis causing ischemia with more than 90% accuracy.,, The information provided by FFR is more specific with better spatial resolution as compared to myocardial perfusion studies, because analysis of every artery or segment is done separately and masking of one over other area is avoided.,
| Definition|| |
FFR is the ratio of maximum blood flow in a stenotic artery to maximum blood flow if the same artery is normal, assuming that these measurements are obtained when the microvascular resistance is minimal and constant.,,,, It can be easily measured by a pressure wire and a guiding catheter. FFR equals Pd/Pa, where Pd is the pressure in the coronary artery distal to stenosis and Pa is the aortic pressure, both measured at maximum coronary hyperemia. FFR is linearly related to the maximum blood flow with a normal value of 1.0. It is irrespective of patient, artery, blood pressure, and so on. It is independent of changes in systemic blood pressure, heart rate, and myocardial contractility, and it is highly reproducible.,,,
| Fractional Flow Reserve – Practical Aspects|| |
Usually, a 6F guiding catheter is used. However, FFR can also be safely measured through a conventional 4F diagnostic catheter.,
Presently, two United States Food and Drug Administration- approved pressure wire systems are available: Pressure Analyzer and Wave Map. Both are 0.014 inch in diameter. The sensor is located 30 mm from the tip.
It is absolutely necessary to achieve maximal vasodilatation of two vascular compartments of coronary circulation for measurement of FFR. These are epicardial vessels and microvascular arteries. A desirable stimulant should have a rapid onset and short duration of action, should be cost-effective, should not have significant side effects, and should achieve a stable steady state. Intracoronary adenosine creates hyperemia for few seconds and can be used in patients with single-vessel disease. Intravenous adenosine is the gold standard for creating hyperemia. However, it is contraindicated in case of severe asthma.,,,
Heparin adjusted to weight is used for anticoagulation to achieve an activated coagulation time of 250 s or it can be used as per the body weight.
| Fractional Flow Reserve – Clinical Relevance|| |
Intermediate coronary lesion
The ability of coronary angiography to evaluate the hemodynamic significance of intermediate lesion is limited. It has been shown that in such cases FFR is more accurate than other modalities. It is strongly recommended to use FFR measurements as a guide to take decision about revascularization in intermediate lesions.
Left main coronary artery disease
Left main coronary artery (LMCA) disease has got critical prognostic importance, and it determines the type of treatment. There are significant variations in the assessment of LMCA lesions by different observers. FFR can identify LMCA disease responsible for ischemia. It has been proved that FFR-guided therapy for equivocal LMCA disease is safe and has got favorable clinical outcomes.,,,, The influence of left anterior descending (LAD) and left circumflex (LCx) on FFR of LMCA depends on the severity and location of distal stenosis. Basically, it depends on the amount of myocardium affected by distal stenosis.
They are defined as two separate lesions in the same coronary artery separated by angiographically normal segment and each with more than 50% stenosis., Each lesion will influence the hyperemic blood flow and FFR across other. A pullback maneuver with maximum hyperemia is the best way to define the exact location and physiological importance of such lesions and guide intervention accordingly.
Percutaneous coronary interventions (PCIs) are more challenging for bifurcation lesions than regular lesions. The principle of FFR-guided PCI applies very much for bifurcation lesions.,
Multivessel coronary artery disease
It is very important to determine which particular lesion is physiologically significant and causing reversible ischemia in patients with multivessel coronary artery disease. In such patients, it was demonstrated that one or two physiologically significant lesions identified by FFR yielded a favorable outcome as surgery.
Diffuse and long lesions
FFR is useful in quantifying the severity of coronary artery stenosis in diffusely affected vessels. This can be done by withdrawing the pressure wire from distal to proximal vessel very slowly during maximum hyperemia. The pressure curve represents the pressure gradient over the entire length of vessel and helps to demonstrate the exact location and severity of lesion.
The decrease of viable myocardium and impairment of coronary resistance vessel do not affect the calculation of FFR, and it is still a reliable indicator. The FFR assessment criteria are valid in detecting reversible ischemia after at least 6 days after myocardial infarction (MI).
FFR assessment criteria are also valid in patients with unstable angina. The strategy based on FFR is superior to the approach based on stress perfusion scintigraphy.
Coronary artery bypass graft surgery
The assessment of stenosis severity in such patients is not different from that in native vessels. At present, there are no data available for use of FFR in graft stenosis.
| Special Features|| |
- FFR has a theoretical normal value of 1 for every patient, artery, and myocardium 
- FFR has a well-defined cutoff value. There is a very narrow gray zone between 0.75 and 0.80. Stenoses with FFR <0.75 are almost able to induce myocardial ischemia. Stenoses with FFR >0.80 are almost never associated with exercise-induced ischemia
- FFR is not affected by systemic hemodynamics ,
- FFR always takes into account the blood flow through collaterals.,
| Limitations|| |
Fractional flow reserve at gray zone
Stenoses with FFR between 0.75 and 0.80 have shown conflicting outcome data., It is rational for cardiologists to make decisions based on clinical judgment and other imaging modalities with all available information to deliver safe and suitable care for patients whose FFR is into the gray zone. FFR should never be used as a gatekeeper.
Acute myocardial infarction
During the acute phase of MI, maximum hyperemia cannot be achieved., In addition, thrombus embolization, stunning of myocardium, and microvascular dysfunction may make achieving complete microvascular vasodilation difficult. During the acute phase of MI, FFR measurement cannot reflect the actual value. FFR can be applied as in routine practice usually after 6 days of acute MI.
Usually, myocardial bridge is clinically silent. Sometimes, it may present as angina, MI, arrhythmias, and even sudden cardiac death.,, The flow pattern in bridge segment is entirely different from that in atherosclerotic lesions., There is the possibility that FFR may be abnormal in patients with myocardial bridge. FFR may not be as reliable as in fixed stenosis.
| Conclusion|| |
FFR is very valuable for the determination of functional and physiological significance of coronary stenosis. It combines both anatomical and physiological information. It can be immediately followed by PCI if required. FFR can be performed rapidly, safely, and easily. By proper use of FFR, PCI can be more effective in intermediate lesions and multivessel disease. The current clinical evidence should encourage cardiologists to use FFR routinely in practice.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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