Serial fractional flow reserve, coronary flow reserve and index of microcirculatory resistance after percutaneous coronary intervention in patients treated for stable angina pectoris assessed with PET.

Background: Cardiac 15 O-water PET is a noninvasive method to evaluate epicardial and microvascular dysfunction and further quantitate absolute myocardial blood flow (MBF).

Aim: The aim of this study was to assess the impact of revascularization on MBF and myocardial flow reserve (MFR) assessed with 15 O-water PET and invasive flow and pressure measurements.

Methods: In 21 patients with single-vessel disease referred for percutaneous coronary intervention (PCI), serial PET perfusion imaging and fractional flow reserve (FFR), coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) were performed during PCI and after 3 months.

Results: In the affected myocardium, stress MBF and MFR increased significantly from before revascularization to 3 months after revascularization: stress MBF 2.4 ± 0.8 vs. 3.2 ± 0.8; P  < 0.001 and MFR 2.5 ± 0.8 vs. 3.4 ± 1.1; P  = 0.004. FFR and CFR increased significantly from baseline to after revascularization and remained stable from after revascularization to 3-month follow-up: FFR 0.64 ± 0.20 vs. 0.91 ± 0.06 vs. 0.91 ± 0.07; P  < 0.001; CFR 2.4 ± 1.2 vs. 3.6 ± 1.9 vs. 3.6 ± 1.9; P  < 0.001, whereas IMR did not change significantly: 30.3 ± 22.9 vs. 30.1 ± 25.3 vs. 31.9 ± 25.2; P  = ns. After revascularization, an increase in stress MBF was associated with an increase in FFR ( r  = 0.732; P  < 0.001) and an increase in MFR ( r  = 0.499; P  = 0.021). IMR measured before PCI was inversely associated with improvement in stress MBF, ( r  = -0.616; P  = 0.004).

Conclusion: Recovery of myocardial perfusion after PCI was associated with an increase in FFR 3 months after revascularization. Microcirculatory dysfunction was associated with less improvement in myocardial perfusion.