Time-Dependent Changes in the Coronary Circulation Triggered by CTO Revascularization: Insights From Intracoronary Physiology.

Background: Physiological changes in the coronary circulation associated with percutaneous coronary intervention (PCI) for chronic total occlusions (CTOs) remain largely unknown. This systematic review and meta-analysis aimed to investigate physiological changes in the CTO and donor vessel before and immediately after PCI, as well as at follow-up.

Methods: A comprehensive search of PubMed/MEDLINE and Embase identified relevant studies. The primary end point was the mean difference (MD) between fractional flow reserve myocardium (FFR) of the primary donor vessel before and after CTO revascularization. Secondary outcomes included the difference in FFR, FFR collateral (FFR), FFR coronary (FFR), absolute coronary blood flow, coronary flow velocity reserve, and microvascular resistance before and after CTO revascularization and/or at the follow-up.

Results: A total of 17 studies were included. The myocardial blood flow in the donor vessel increased after CTO revascularization (FFR: MD, 0.04; 95% CI, 0.02-0.06; < .01), as well as in the CTO vessel (MD, 0.45; 95% CI, 0.27-0.64; < .01). At follow-up, CTO PCI was associated with a significant shift in collateral (FFR: MD, -0.16; 95% CI, -0.18 to -0.15; < .01) and epicardial blood supply (FFR: MD, 0.09; 95% CI, -0.01 to 0.20; = .06). Time-dependent changes in the microcirculatory domain of the CTO vessel were observed in terms of improved arteriolar dynamicity and decreased microvascular resistance.

Conclusion: Available evidence suggests that CTO revascularization leads to an immediate and long-term improvement in blood supply to downstream myocardium, mediated in part by a favorable time-dependent shift in epicardial vessel, collateral, and microcirculatory function.