[2] The result is an absolute number; an FFR of 0.80 means that a given stenosis causes a 20% drop in blood pressure.
During coronary catheterization, a catheter is inserted into the femoral (groin) or radial arteries (wrist) using a sheath and guidewire.
FFR uses a small sensor on the tip of the wire (commonly a transducer) to measure pressure, temperature and flow to determine the exact severity of the lesion.
Fractional flow reserve can provide a functional evaluation by measuring the pressure decline caused by a vessel narrowing.
For example, FFR takes into account collateral flow, which can render an anatomical blockage functionally unimportant.
There are newly developed technologies that can assess both plaque vulnerability and FFR from CT by measuring the vasodilitative capacity of the arterial wall.
[citation needed] FFR allows real-time estimation of the effects of a narrowed vessel, and allows for simultaneous treatment with balloon dilatation and stenting.
On the other hand, FFR is an invasive procedure for which non-invasive (less drastic) alternatives exist, such as cardiac stress testing.
In this test, physical exercise or intravenous medication (adenosine/dobutamine) is used to increase the workload and oxygen demand of the heart muscle, and ischemia is detected using ECG changes or nuclear imaging.
In the DEFER study, fractional flow reserve was used to determine the need for stenting in patients with intermediate single vessel disease.
After one year, the primary endpoint of death, nonfatal myocardial infarction, and repeat revascularization were lower in the FFR group (13.2% versus 18.3%), largely attributable to fewer stenting procedures and their associated complications.