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Fractional flow reserve

An index of physiological significance of coronary stenosis: defined as the ratio of maximal blood flowis a stenotic artery to a normal maximal flow.

Fractional flow reserve performed during invasive coronary angiography provides lesion specific data on ischemia which when used to direct revascularization procedures, leads to improved clinical outcomes.

It is an invasive measurement using coronary angiography to assess the potential of a coronary stenosis to induce myocardial ischemia.

Fractional flow reserve is the ratio of the mean coronary artery pressure distal to an obstructive coronary lesion relative to the mean aortic pressure during maximum coronary blood flow and represents a physiologic measure of coronary stenosis.

Measured during coronary angiography by calculating the ratio of distal coronary pressure measured with a coronary pressure guidewire to aortic pressure measured simultaneously with a catheter.

It is readily calculated in the heart catheterization laboratory by measuring the pressure gradient across stenosis during reactive hyperemia.

A pressure wire based index used during coronary angiography assessing potential of coronary stenosis to induce myocardial ischemia.

In a normal coronary artery is 1.0.

A value of 0.8 or less identifies ischemic associated coronary artery stenosis and has an accuracy of more than 90% (Pijls).

Fractional flow reserve is a pressure derived measure of maximal myocardial  blood flow beyond stenosis divided by theoretical normal maximal flow in the absence of stenosis, such as fractional flow reserve in a vessel with no obstruction is 1.0.

Fractional flow reserve is a reproducible, lesion specific measure of stenosis severity that correlates with determined ischemia by non-invasive testing.

Fractional flow reserve is measured by advancing a pressure sensor beyond the stenosis  in question and measuring vasodilating in the resistance vessels by administering a potent vasodilator usually adenosine.

Revascularization procedures of lesions below .80 results in better outcomes than does medical therapy.

PCI is not recommended for nonischemic functional flow reserve lesions of greater than 0.80 because it is not been demonstrated to be beneficial and may even be harmful.

Fractional flow reserve values of 0.75 or less reliably correlate with objective ischemia, whereas values of more than 0.8 rarely do, regardless of the angiographic appearance of the coronary artery.

The benefit of PCI as initial treatment patients with stable coronary artery disease is controversial as the result depends on the extent and degree of myocardial ischemia.

Fractional flow reserve value of 0.8 or less, as measured with coronary pressure wire during catheterization, indicates potential of a stenosis to induce myocardial ischemia.

In the study of 1220 patients with stable coronary artery disease FFR (fractional flow reserve)-guided PCI as compared with medical therapy alone, improves the outcome (De Bruyne B et al ).

Provides information similar to myocardial perfusion but is more specific analyzing separately segments or coronary arteries and prevents the masking of ischemic areas.

FFR is measured at a steady state and can be followed with a vasodilator such as adenosine, that causes hyperemic flow that results in an invasive pharmacological stress test.

Deferring the placement of stents in lesions assessed by FFR results in an annual rate of death or myocardial infarction of 1% in patients with single coronary artery disease, which is a lower percentage than associated with routing stenting.

In patients with stable coronary artery disease and functionally significant stenosis a fractional flow reserve guided PCI plus the best available medical therapy, as compared with the best medical therapy alone, decreased the need for urgent revascularization. (FAME 2 trial investigators).

In the above study, patients without ischemia, the outcome appeared to be favorable with the best available medical therapy alone.

The benefit of PCI as initial treatment patients with stable coronary artery disease is controversial as the result depends on the extent and degree of myocardial ischemia.

Fractional flow reserve value of 0.8 or less, as measured with coronary pressure wire during catheterization, indicates potential of a stenosis to induce myocardial ischemia.

In the study of 1220 patients with stable coronary artery disease FFR (fractional flow reserve)-guided PCI as compared with medical therapy alone, improves the outcome (De Bruyne B et al ).

In a retrospective study of 9106 patients with PCI as compared with no PCI was significantly associated with a lower rate of major adverse cardiac events at  five years among patients with ischemic FFR measurements (31.5% versus 39.1%) and a higher rate of major adverse cardiac events at five years among patients with nonischemic FFR measurements at 33.3% versus 24.4% (Sud M).
 
In patients with chronic coronary syndrome or acute coronary syndrome with out ST- segment elevation, the use of fractional flow reserve measurement during percutaneous coronary intervention to assess the functional severity of coronary lesions, results in a lower risk of major cardiovascular events than myocardial revascularization guided by angiography.
Among patients with ST-segment elevation myocardial infarction (STEMI) and multivessel disease, complete revascularization of non-culprit lesions guided by FFR or  angiography results in lower frequency repeat revascularization than revascularization of only the culprit lesion.
However,  in patients   with STEMI undergoing complete revascularization, FFR guided strategy did not have a significantly benefit over angiographic guided strategy with respect to risk of death, myocardial infarction, urgent revascularization at one year.
In patients with three vessel coronary artery disease, FFR guided PCI was not inferior to CABG with respect to the incidence of a composite of death, myocardial infarction, stroke or repeat revascularization at one year (FAME 3 investigators).

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