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 disagreement is clinically relevant is unknown. Clinical outcome data on iFR are scarce. This study is a registry-based randomized clinical trial, which is a novel strategy using health quality registries as on-line platforms for randomization, case record forms, and follow-up.