Impact of right atrial pressure on fractional flow reserve calculation in the presence of a chronic total occlusion

Background : The aim of this study was to assess the impact of right atrial pressure (Pra) on non-CTO vessels FFR measurements in patients with a chronic total occlusion. Methods : Consecutive patients who underwent PCI for a CTO of the right coronary artery (RCA) were included. Prior to RCA recanalization, FFR and FFRmyo were measured in non-CTO vessels. FFR was calculated using the Pd/Pa equation during maximum hyperaemia and also accounting for right atrial pressure (Pd-Pra/Pa-Pra). Non-CTO vessels were characterised as major or minor donors based on angiographic assessment of provided collaterals. Results : FFR and FFRmyo were measured in 68 arteries (34 LAD and 34 Cx) in 34 consecutive patients with successful RCA CTO PCI. Patients' mean age was 62 ± 10 years old and 88% were male. Mean left ventricular ejection fraction was 51% ± 20. During maximum hyperaemia, mean Pra, Pa, and Pd were 4.1 ± 3.8 mm Hg, 82.6 ± 12.2 mm Hg, and 63.8 ± 14.3 mm Hg, respectively. In the major donor vessel, FFRmyo showed a difference of 0.007 to FFR (0.760 ± 0.113 vs. 0.767 ± 0.112, p = 0.004). In the minor donor vessel the difference was 0.004 (0.895 ± 0.067 vs. 0.899 ± 0.065, p < 0.001). There was a strong positive correlation between the FFR and FFRmyo in both the major and minor donor vessel groups (r = 0.993, p < 0.001 and r = 0.996, p < 0.001 respectively). Conclusion: In the presence of a CTO, RA pressure adjustment of FFR in the non-CTO vessels leads to trivial numerical changes, which are statistically significant but clinically negligible.