Importance of guiding catheter disengagement during measurement of fractional flow reserve in patients with an isolated proximal left anterior descending artery stenosis.

OBJECTIVE: To determine the impact of ostial guiding catheter disengagement during measurement of fractional flow reserve (FFR) in patients with an isolated proximal left anterior descending artery (LAD) stenosis. METHODS: Measurements of FFR were performed in 21 patients with an isolated intermediate lesion of the proximal LAD. Proximal aortic pressure (Pa), distal post stenotic pressure (Pd), and Pd/Pa were recorded at baseline, after at least 90 sec of intravenous (IV) adenosine infusion with the guiding catheter still engaged in the coronary ostium (Pa1 , Pd1 , FFReng ), and after at least 30 sec of guiding catheter disengagement back to the aorta (Pa2 , Pd2 , FFRdis ). RESULTS: The average value of Pd/Pa at baseline was 0.92 ± 0.04. After 110 ± 8 sec of IV adenosine infusion, FFReng was 0.81 ± 0.07, which decreased to 0.77 ± 0.08 (FFRdis ) after 38 ± 6 sec of guiding catheter disengagement. The mean ΔFFR (FFReng - FFRdis ) was 0.05 ± 0.04. As compared to baseline values, the mean change in FFR values was significantly increased after disengagement of the guiding catheter (Pd/Pabaseline - FFRdis vs. Pd/Pabaseline - FFReng , 0.15 ± 0.05 vs. 0.10 ± 0.04, P < 0.0001). Before guiding catheter disengagement, eight patients (38%) had an FFR value ≤ 0.8. Following disengagement of the guiding catheter, the new FFR values decreased below 0.8 in six additional patients (28%), with subsequent change in treatment strategy. CONCLUSIONS: During FFR assessment of isolated intermediate proximal LAD lesions, guiding catheter disengagement is associated with a decrease in mean FFR values. In patients with FFR values lying close to the treatment threshold, this can have an impact on treatment strategy.