Fractional Flow Reserve Assessment of Left Main Stenosis in the Presence of Downstream Coronary Stenoses

Background—Several studies have shown that fractional flow reserve (FFR) measurement can aid in the assessment of left main coronary stenosis. However, the impact of downstream epicardial stenosis on left main FFR assessment with the pressure wire in the nonstenosed downstream vessel remains unknown. Methods and Results—Variable stenoses were created in the left main coronary arteries and downstream epicardial vessels in 6 anaesthetized male sheep using balloon catheters. A total of 220 pairs of FFR assessments of the left main stenosis were obtained, before and after creation of a stenosis in a downstream epicardial vessel, by having a pressure-sensor wire in the other nonstenosed downstream vessel. The apparent left main FFR in the presence of downstream stenosis (FFRapp) was significantly higher compared with the true FFR in the absence of downstream stenosis (FFRtrue; 0.80±0.05 versus 0.76±0.05; estimate of the mean difference, 0.035; P<0.001). The difference between FFRtrue and FFRapp correlated with...