Guide PCI with coronary physiology, the clinically validated choice

FFR and iFR can be obtained during routine coronary angiography by using a pressure wire to calculate the ratio between coronary pressure distal to a stenosis and the proximal aortic pressure. When resistance is constant, this ratio represents the potential decrease in coronary flow distal to the coronary stenosis.

The FFR modality uses hyperemic agents to achieve a state of constant resistance.

Pressure = flow x resistance

Fundamental equation for relating pressure flow derived from Poiseuille's Law for fluid dynamics

The iFR modality measures pressure during the wave-free period of the cardiac cycle when resistance is naturally constant.

Unlike FFR, iFR does not require administration of vasodilators because hyperemia is not necessary when measuring pressure during the wave-free period of the cardiac cycle.

iFR is a Class 1A recommendation and is proven to reduce procedure time, patient discomfort and cost compared to FFR [6,7].

The iFR modality provides a hyperemia-free measurement in as few as five heartbeats.

Both DEFINE FLAIR and iFR Swedeheart were designed with the dichotomous cut-point of iFR in the iFR arm[3,4]. With comparable MACE rates to FFR, these results mean the 0.89 cut-point for iFR is proven and backed by more than 4500 patients of outcome data.

An FFR lower than .80 is generally considered to be associated with myocardial ischemia.