Coronary flow indices after percutaneous coronary intervention in relation to major adverse cardiovascular events at long-term follow-up in chronic coronary syndrome

Abstract Introduction Impaired coronary microvascular function, as assessed with index of microcirculatory resistance (IMR), after elective percutaneous coronary intervention (PCI) is associated with periprocedural myocardial infarctions (MI) in patients with chronic coronary syndrome (CCS). Other measures of coronary microvascular function, including coronary resting flow indices could be associated with long-term outcome. Purpose To investigate the association of thermodilution-derived post PCI coronary flow indices in the LAD, with major adverse cardiovascular events (MACE) at long-term follow-up in CCS patients. Methods We analyzed 79 patients with CCS, included in two prospective studies conducted at two hospitals, undergoing PCI of the LAD. Post PCI coronary flow in the LAD was assessed with thermodilution technique. Mean transit time (Tmn), aortic pressure (Pa) and distal LAD pressure (Pd) were registered at rest and hyperemia. IMR was calculated as Pahyper × Tmnhyper × (1.35 × Pdhyper/Pahyper − 0.32), hyperemic flow velocity (HFV) as the inverse of Tmnhyper, baseline resistance index (BRI) as Pdrest × Tmnrest, resting flow velocity (RFV) as the inverse of Tmnrest, coronary flow reserve (CFR) as Tmnrest/Tmnhyper, fractional flow reserve as Pdhyper/Pahyper and microvascular resistance reserve (MRR) as (CFR/FFR) × (Parest/ Pahyper). Associations of indices in relation to patient- and procedural characteristics were analyzed with linear regression. Skewed variables were log-transformed. Survival analyses of coronary flow indices in relation to MACE (composite of death, MI and heart failure hospitalization) were performed with Cox-regression and Kaplan Meier survival curves. Death and cardiovascular events were assessed through the tax registry, medical records and phone calls. Results Mean age was 65 years, 71 patients were men, and 12 (15%) patients had a previous myocardial infarction. Medium follow-up was 5.4 years. Median IMR after PCI was 15 (interquartile range IQR 9.7-23) and associated with the total implanted stent length in the LAD (p=0.027), female gender (p=0.046) and absence of diabetes (p=0.048). Median RFV was 1.34 (IQR 0.86-1.77) and not associated with patient characteristics or procedural variables. Median MRR was 4.4 (IQR 2.8-6.6), associated with creatinine clearance (p=0.026), male gender (p=0.011) and inversely with age (p=0.020). Post PCI RFV and BRI were associated with MACE before and after adjustments in Cox regression whereas IMR, HFV, CFR and MRR were not (Table 1). Post PCI RFV stratified by a cut-off of 1.79 and MRR stratified by a cutoff of 3.0 were associated with MACE (Figure 1). Conclusion Post PCI thermodilution-derived coronary resting flow indices in the LAD were associated with MACE in CCS-patients at long-term follow-up, whereas coronary hyperemic flow indices were not. Reduced post PCI non-endothelial dependent vasodilatory capacity was associated with MACE in the same population.