A pitfall of fractional flow reserve associated with the presence of collateral circulation

An 82-year-old man had a severe stenosis in the proximal left anterior descending artery (LAD) and an intermediate stenosis in the distal right coronary artery (RCA). The territory of mid to distal LAD was perfused via an angiographically well-developed collateral circulation from the distal RCA. Fractional flow reserve (FFR) in the distal RCA was 0.84. After successful coronary intervention for the proximal LAD, repeat FFR in the distal RCA was 0.96. In this case, the severity of the stenosis in the donor artery was overestimated by using FFR due to the presence of well-developed collateral circulation.