instantaneous wave-free ratio
Resting pressure-derived index for assessing coronary stenosis functional significance without hyperemic agents.
Full Definition
Instantaneous wave-free ratio (iFR) is a pressure-derived index that assesses the functional significance of coronary stenoses during a specific period of diastole called the wave-free period, when resistance is naturally low and stable. Unlike FFR, iFR is measured at rest without the need for hyperemic agents like adenosine. The wave-free period spans approximately 25% of the cardiac cycle during mid-to-late diastole when pressure and flow are most linear. iFR ≤0.89 indicates hemodynamically significant stenosis requiring revascularization, while values >0.89 suggest functionally non-significant disease.
Usage
Usage note: Abbreviate as 'iFR' in most contexts; full term used in formal definitions or educational material.
In Context
- "The iFR value of 0.87 confirmed functional significance of the intermediate RCA lesion." — Catheterization report
- "iFR-guided revascularization showed non-inferiority to FFR-guided strategy in the DEFINE-FLAIR trial." — Clinical trial summary