Increased circulating levels of malondialdehyde-modified low-density lipoprotein in patients with coronary microvascular dysfunction

Coronary microvascular dysfunction (CMD) is associated with angina symptoms and adverse clinical outcomes in patients without obstructive coronary artery disease (CAD). Malondialdehyde-modified low-density lipoprotein (MDA-LDL) is reportedly a marker of the initiation and acceleration of epicardial coronary atherosclerosis. However, its impact on CMD remains unclear. We aimed to investigate the relationship between CMD and MDA-LDL levels. This study included 95 patients who did not receive lipid-lowering medications and had no obstructive CAD. Obstructive CAD was defined as >50 % diameter reduction on coronary angiography or fractional flow reserve of ≤0.80. We retrospectively analyzed coronary flow reserve (CFR), index of microcirculatory resistance (IMR), and MDA-LDL levels. CMD was defined as either CFR <2.0 or IMR ≥25. CMD was observed in 29 (31 %) patients. MDA-LDL levels were significantly higher in patients with CMD than in those without CMD (124.8 ± 37.6 vs. 95.3 ± 29.5 U/L; < 0.01). Univariable logistic regression analysis indicated a significant relationship between CMD and MDA-LDL levels (odds ratio (OR): 1.03; < 0.01). In the multivariable model, MDA-LDL levels were significantly associated with CMD (OR: 1.02; < 0.01). Regression analysis showed a significant correlation between MDA-LDL levels and CFR (r = -0.42, < 0.01) and IMR (r = 0.35, < 0.01). In the multiple regression analysis, MDA-LDL levels were independently associated with CFR (β = -0.30, < 0.01) and IMR (β = 0.26, = 0.02). MDA-LDL levels were associated with CMD in patients without obstructive CAD.