Abstract: Objective To investigate the relationship between plaque characteristics of intravascular ultrasound virtual histology (IVUS-VH) and serum adipocytokine C1q/tumor necrosis factor associated protein 9 (CTRP9), serum amyloid A (SAA) and homocysteine (Hcy) in patients with coronary heart disease (CHD). 
Methods A total of 120 patients with CHD treated in our hospital were selected, including 65 patients with acute coronary syndrome (ACS group) and 55 patients with stable angina pectoris (SAP group). Another 50 volunteers were selected as control group, the levels of serum CTRP9, SAA and Hcy in ACS and SAP group were detected, and IVUS-VH was performed in the meantime in both ACS group and SAP group. 
Results The serum CTRP9 in the ACS group was (3.02±0.45)×10-2mg/L, which was significantly lower than that in the SAP group, with statistical significance (P＜0.05), while the levels of SAA and Hcy were (4.45±1.01) mg/L and (24.42±3.36) μmol/L, which were significantly higher than those in the SAP group (P＜0.05). The serum levels of CTRP9, SAA and Hcy in the control group were significantly lower than those in the ACS group and the SAP group (P＜0.05). The IVUS-VH parameter necrotic tissue area and the incidence of thin cap of fibroatheroma (TCFA) in the ACS group were (32.20±7.78)% and 49.23%, respectively, which were significantly higher than those in the SAP group, with statistical significance (P＜0.05). The tissue area was (44.65±11.02)%, which was significantly lower than that of the SAP group (P＜0.05). Necrotic tissue area was negatively correlated with CTRP9 (P＜0.05), but positively correlated with SAA and Hcy (P＜0.05); fibrous tissue area was negatively correlated with SAA (P＜0.05). The serum CTRP9 of TCFA patients was (2.89±0.58)×10-2mg/L, which was significantly lower than that of the non-TCFA group (P＜0.05), while the levels of SAA and Hcy were (4.89±1.12) mg/L and (26.62±3.12) μmol/L, respectively significantly higher than those in the non-TCFA group (P＜0.05).The areas under ROC curve of CTRP9, SAA and Hcy in predicting TCFA were 0.712, 0.815 and 0.844, respectively (P＜0.05). 
Conclusion There are significant differences in serum CTRP9, SAA and Hcy between ACS patients and SAP patients, which are correlated with IVUS-VH parameters, and worthy of further study.

Key words: coronary disease, serum amyloid A protein, homocysteine