Low adiponectin and high lipoprotein(a) [Lp(a)] levels are associated with endothelial dysfunction, atherosclerosis, and coronary artery disease. Cardiac syndrome X (CSX) is characterized by anginal symptoms, positive stress test, and documentation of normal epicardial coronary arteries with angiography. In this study we aimed to investigate the relationship between CSX and circulating levels of adiponectin and Lp(a).

We enrolled 53 female patients with CSX and 33 patients as the control group. The diagnosis of CSX was made according to presence of angina, findings suggestive of ischemia during stress electrocardiography or myocardial perfusion scintigraphy, and documentation of normal coronary arteries in coronary angiography. The control group consisted of patients with atypical angina and normal stress electrocardiography test results. Both groups were matched in terms of hypertension, diabetes mellitus, and metabolic syndrome.

Adiponectin levels were significantly decreased in patients with CSX (4.57 μg/ml vs. 13.18 μg/ml; p=0.001); however, Lp(a) levels were significantly increased (36.30 mg/dl vs. 7.24 mg/dl; p < 0.001). Low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG) concentrations did not differ between the case group and the control group (p=0.14, p=0.62, p=0.64, respectively). There was no significant difference between groups in terms of age, body mass index, waist circumference hypertension, hyperlipidemia, diabetes mellitus, or metabolic syndrome. In multivariate analysis, Lp(a) and adiponectin were found to be independent predictors of CSX. An Lp(a) level of > 21 mg/dl had 84 % sensitivity and 96 % specificity {area under the curve (AUC)= 0.922, p < 0.0001, 95 % CI [0.842–0.970]} and an adiponectin level of ≤ 5.18 μg/ml also had 58.7 % sensitivity and 82.1 % specificity (AUC=0.726, p=0.0003, 95 % CI [0.609–0.823]) for detecting CSX.

We detected low adiponectin and high Lp(a) levels in patients with CSX and these findings may be related to the microvascular injury in CSX.