Instantaneous Wave-Free Ratio versus Fractional Flow Reserve guided intervention (iFR-SWEDEHEART): Rationale and design of a multicenter, prospective, registry-based randomized clinical trial.
Instantaneous wave-free ratio (iFR) is a new hemodynamic resting index for assessment of coronary artery stenosis severity. iFR uses high frequency sampling to calculate a gradient across a coronary lesion during a period of diastole. The index has been tested against fractional flow reserve (FFR) and found to have an overall classification agreement of 80% to 85%. Whether the level of disagreemen