iFR and FFR

The instantaneous wave-free ratio (iFR) and fractional flow reserve (FFR) are diagnostic tools used to assess whether a blockage or narrowing in the blood vessel is limiting blood flow to a significant extent in the coronary arteries. During FFR a medication such as adenosine (or similar medication known as regadenoson) is given intravenously to increase the blood flow through the vessels supplying the heart. During iFR no additional medication is necessary. Both tests measure the pressure beyond and before the narrowing. The ratio of the two measurements is calculated. If this valve is lower than a pre-specified value (i.e. 0.80 for FFR and 0.89 for iFR), then a decision is usually made to treat the narrowing with percutaneous coronary intervention (PCI).  These tests are typically performed in intermediate lesions, where it is unclear if a particular blockage is limiting blood flow or not.