Chronologic evolution and prognostic implications of impaired coronary flow after chronic total occlusion angioplasty

Background: Although vessels have the potential to recover following successful recanalization of chronic total occlusion (CTO), evidence is limited about the clinical significance of slow flow (SF) phenomenon after recanalization. The aim of this study was to evaluate the determinants, development and prognostic impact of SF after percutaneous coronary intervention (PCI) for CTO. Methods: This was a retrospective cohort study, 500 patients were consecutively enrolled undergoing CTO PCI and consecutive follow-up angiography in Zhongshan Hospital, Fudan University, between 2015 and 2020. Coronary flow was assessed by corrected Thrombolysis in Myocardial Infarction (TIMI) frame count (CTFC). The association between SF and outcomes of CTO PCI was evaluated by analyzing the clinical, angiographic, and procedural characteristics. Results: SF was observed in 29 (5.8%) patients immediately after CTO PCI. Prior myocardial infraction, right coronary artery (RCA) revascularization and lack of bilateral collaterals were independent predictors of SF. SF was associated with increased risks of periprocedural myocardial infarction (PMI) [adjusted odds ratio (adOR): 4.12; 95% confidence interval (CI): 1.68–10.07; P=0.002] and target lesion restenosis (adOR: 2.50; 95% CI: 1.10–5.72; P=0.030). In patients with baseline left ventricular ejection fraction (LVEF) ≤60%, systolic improvement was compromised in the SF group (LVEF: 55.4%±9.6% in follow up vs. 52.1%±9.4% before CTO PCI, P=0.147) compared with that of the normal group (LVEF: 55.7%±9.3% vs. 51.6%±8.5%, P<0.001). Conclusions: SF has a significant influence on the prognosis of patients undergoing CTO PCI. Achieving normal coronary flow is essential in CTO revascularization.