Association of Calcium Index and Myocardial Blood Flow in Non-Obstructive Atherosclerotic Lesion of the Coronary Arteries

Background. Over the past few years, scientific data have demonstrated that patients with non-obstructive coronary artery disease can have high risk for adverse cardiovascular events (ACE) despite the absence of severe coronary obstruction. From this point of view, some patients require special monitoring and treatment; we have to find new methods for stratification of the risk of ACE. Aims — to study the association of coronary artery calcification (CCA) with indicators of myocardial blood flow (MBF) and myocardial flow reserve (MFR) in patients with non-obstructive coronary artery disease (CAD). Methods. The study included patients (n = 52) with non-obstructive CAD (< 50%), identified by CCTA. All patients received dynamic myocardial SPECT according to the two-day “rest-stress” protocol with the radiopharmaceutical agent 99mTc-methoxy-isobutyl-isotnitrile and the pharmacological stress-test (adenosine triphosphate 160 mcg/kg/min) to determine quantitative indicators of MBF and MFR. Depending on the calcium index (CI), three groups of patients were formed: 1 — without CCA (CI = 0 Agatston units), 19 patients; 2 — Mild CCA (CI = 1–100 Agatston units), 21 patients; 3 — Moderate CCA (CI = 101–400 Agatston units), 12 patients. Results. The study included 52 patients (age 55.0 ± 9.8 years, 36 men). The groups differed statistically significantly (p < 0.05) in terms of quantitative scintigraphic parameters: stress-MBF, MFR and ΔMBF. When analyzing the groups in pairs, it was found that stress-MBF and ΔMBF were significantly lower in the group with moderate CCA compared to the group without CCA, and MFR was lower in the group with moderate CCA compared to the groups without CCA and with mild CCA. Correlation analysis revealed significant relationships between CI and scintigraphic parameters: stress-MBF (ρ = –0.46; p = 0.003), MFR (ρ = –0.48; p = 0.001), ΔMBF (ρ = –0.48; p = 0.0008), SSS (ρ = 0.34; p = 0.02) and SDS (ρ = 0.28; p = 0.046). Conclusions. Even with non-obstructive CAD, identified by CCTA, there is a decrease in MBF and MFR inversely proportional to the level of CI, which can be considered as an early marker of impaired vasodilation reserve of the vascular wall, which develops in atherosclerosis of the coronary artery.