Coronary chronic total occlusions and collateral circulation: physiological impact of percutaneous coronary intervention

Introduction: Coronary chronic total occlusion (CTO) is common and is present in a quarter of all patients with obstructive coronary artery disease. Coronary physiology guided-percutaneous coronary intervention (PCI) with fractional flow reserve (FFR) and instantaneous-wave-free ratio (iFR) improve outcomes. However, in the presence of a CTO, donor vessel FFR is influenced by the collateralisation to the CTO territory making the decision-making process for complete revascularisation challenging. Furthermore, the physiological impact of CTO PCI and the influence of collateral regression upon donor vessel and CTO vessel resting indices (Distal coronary pressure/Aortic pressure (Pd/Pa) and iFR) and FFR are unknown making the indication and / or timing of donor vessel revascularisation and CTO vessel optimisation challenging. Methodology:(i) In patients with CTO of the right coronary artery (RCA); resting Pd/Pa, iFR and FFR were measured in donor vessels pre-CTO PCI, immediately post and at four months follow-up. (ii) In patients with CTO of the RCA; resting Pd/Pa, iFR and FFR were measured in the RCA CTO vessel pre-CTO PCI, immediately post and at 4 months follow-up. Results:(i) Successful recanalisation of a RCA CTO resulted in a modest yet significant increase in the predominant donor vessel coronary pressure-derived indices immediately post CTO PCI in the case of iFR and at four months follow-up for resting Pd/Pa, iFR and FFR compared to baseline, accompanied by a concomitant reduction in collateral function. (ii) Successful recanalisation of a RCA CTO resulted in a significant increase in Pd/Pa, iFR and FFR immediately and at four months follow-up compared to pre-PCI. However, only FFR increased significantly at four months follow-up compared to immediately post-PCI. Conclusions: These results have implications for physiological coronary lesion assessment in the presence of a CTO, the timing of the assessment and subsequent revascularisation in this setting. iFR and FFR may be used to document improvement in the CTO vessel coronary haemodynamics post-CTO PCI and guide the decision-making process for stent optimisation following CTO PCI.