iFRguided

iFRguided refers to a strategy for guiding coronary revascularization decisions using instantaneous wave-free ratio (iFR) measurements rather than relying solely on angiography or adenosine-induced FFR. iFR is a non-hyperemic index that compares distal coronary pressure to aortic pressure during the wave-free period in diastole, a phase in which microvascular resistance is minimized. Measurements are obtained with a pressure wire, and no pharmacologic hyperemia is required.

In clinical practice, an iFR value typically at or below 0.89 indicates functionally significant stenosis and supports proceeding with percutaneous coronary intervention (PCI); values above this threshold favor medical therapy or further assessment. Some operators may adjust thresholds or use iFR in conjunction with other assessments in equivocal cases.

Evidence from DEFINE-FLAIR and iFR-SWEDEHEART (both reported in 2017) showed that an iFR-guided strategy is non-inferior to an FFR-guided strategy for guiding PCI in terms of major adverse cardiac events at 12 months, with similar safety and efficacy. Advantages of iFR-guided PCI include avoidance of adenosine, improved patient comfort, shorter procedure times, and potential for broader adoption of physiology-guided revascularization.

Limitations include ongoing discussions about optimal thresholds for certain lesion types, the need for operator expertise in pressure-wire techniques, and potential variability in diffuse disease or microvascular dysfunction where iFR may have reduced interpretive clarity. iFR does not provide qualitative information about lesion morphology beyond its pressure ratio.

See also: Fractional flow reserve, Coronary physiology, Percutaneous coronary intervention.