Residual functional risk after recanalization of chronic total occlusion: association of post-percutaneous coronary intervention Murray law-based quantitative flow ratio

Residual functional impairment after successful chronic total occlusion (CTO) percutaneous coronary intervention (PCI) may increase the risk of adverse events. The Murray law-based quantitative flow ratio (μQFR) is an angiography-derived physiological index for post-PCI assessment, but its association with major adverse cardiovascular events (MACE) in CTO patients remains unclear. This study retrospectively analyzed 120 patients undergoing PCI for CTO. An exploratory cutoff of 0.86 for post-PCI μQFR was identified by selecting the threshold that maximized the log-rank statistic for MACE, and patients were classified into post-PCI μQFR > 0.86 and ≤ 0.86 groups. Cox regression, receiver operating characteristic (ROC) curve analysis, and sensitivity analyses were performed to evaluate the association between post-PCI μQFR and MACE. During a median follow-up of 540 days (interquartile range [IQR], 389.5–540 days), 44 patients (36.7%) developed MACE. The composite endpoint was predominantly driven by repeat revascularization: 42 of the 44 patients with MACE (95.5%) underwent repeat revascularization, whereas no all-cause deaths and only two non-fatal myocardial infarctions occurred. Patients with post-PCI μQFR ≤ 0.86 had a significantly higher incidence of MACE than those with μQFR > 0.86 (71.4% vs. 26.1%, P < 0.001). In multivariable Cox regression analysis, post-PCI μQFR ≤ 0.86 was associated with a 2.47-fold higher risk of MACE than a post-PCI μQFR > 0.86 (hazard ratio [HR] 2.47, 95% confidence interval [CI] 1.29–4.71, P = 0.006). Post-PCI μQFR yielded an AUC of 0.734 (95% CI 0.639–0.828) for MACE. Sensitivity analyses indicated that the results were robust. Post-PCI µQFR ≤ 0.86 was associated with a higher 18-month risk of MACE after CTO PCI, with repeat revascularization accounting for most events. Low post-PCI µQFR may help identify residual angiographic or physiological impairment after technically successful CTO PCI.