The importance of the microvasculature in determining clinical outcomes has been highlighted in patients with coronary artery disease (CAD). For patients with stable CAD, despite the success of percutaneous coronary intervention (PCI) in relieving a stenosis in the epicardial coronary artery, microvascular dysfunction may preclude sufficient coronary flow and myocardial perfusion, possibly leading to worse clinical outcome. With the technical development of computational fluid dynamics, angiographic derivation of index of Index of Microcirculatory Resistance (IMR) without pressure wire, hyperemic agents, or theromdilution method is available as a potential alternative for pressure wire-derived IMR. In this regard, the current study will evaluate diagnostic implication of angiography-derived IMR and its prognostic implication after PCI in patients with stable CAD.

The importance of the microvasculature in determining clinical outcomes has been highlighted in patients with coronary artery disease (CAD). For patients with stable CAD, despite the success of percutaneous coronary intervention (PCI) in relieving a stenosis in the epicardial coronary artery, microvascular dysfunction may preclude sufficient coronary flow and myocardial perfusion, possibly leading to worse clinical outcome. With the technical development of computational fluid dynamics, angiographic derivation of IMR without pressure wire, hyperemic agents, or theromdilution method is available as a potential alternative for pressure wire-derived IMR. In this regard, the current study will evaluate diagnostic implication of angiography-derived IMR and its prognostic implication after PCI in patients with stable CAD.

This study cohorts consist with 3 separate cohort: first, internal diagnostic accuracy cohort, which will evaluate correlation between angiography-derived IMR and hyperemic microvascular resistance calculated using Cadmium-Zinc-Telluride Single-Photon Emission Computed Tomography (CZT-SPECT)-derived myocardial blood flow and invasively measured pressure data. For this, 53 consecutive patients with available CZT-SPECT within 3 months of measuring FFR in the left anterior descending coronary artery will be evaluated. Second: external diagnostic cohort, in which diagnostic accuracy of angiography-derived IMR will be assessed in patients with ischemia and no obstructive coronary artery disease (INOCA) and normal controls, whose results were previously published (J Nucl Cardiol. 2020 Sep 30. doi: 10.1007/s12350-020-02252-8.) Among this cohort, 45 patients with no obstructive CAD and normal CZT-SPECT perfusion imaging will be regarded as normal controls, in 35 INOCA patients, vessels with normal corresponding perfusion territory will be regarded as internal control. Third, prognosis cohort, in which 138 consecutive CAD patients received PCI with available angiograms and who were suitable for angiographic fractional flow reserve and IMR measurement will be analyzed. Primary clinical outcome will be cardiac death or congestive heart failure at 2 years from index procedure. Secondary outcome will be any myocardial infarction, ischemia-driven revascularization, definite or probable stent thrombosis, congestive heart failure admission and angina pectoris admission at 2 years from index procedure.

Inclusion Criteria:

• CAD patients with available CZT-SPECT within 3 months of measuring FFR in the left anterior descending coronary artery (Cohort 1)
• INOCA patients and normal controls confirmed by CZT-SPECT and angiography (Cohort 2)
• Stable CAD patients received PCI (Cohort 3)
• analyzable angiograms at the index procedure

Exclusion Criteria:

• Previous coronary artery bypass grafting
• Chronic total occlusion patients
• limited image quality of coronary angiography
• Insufficient angiographic project for TIMI frame count
• Severe tortuosity of target vessel
• No optimal projection for reconstruction

Diagnostic Accuracy Cohort, 53 stable CAD patients who underwent CZT-SPECT MBF and invasive pressure measurements in LAD within 7 days.

Diagnostic Accuracy Cohort, 35 INOCA patients confirmed by CZT-SPECT and coronary angiography and 45 normal controls Prognosis Cohort 138 stable patients received PCI with available angiograms and who were suitable for angiographic FFR and IMR measurement and have 28 months follow-up data.