2.1 Study population
Patients were enrolled in the the Third Xiangya Hospital, Central South University between January 2019 and December 2020.This was a retrospective, single-center observational study. 155 consecutive coronary artery disease (CAD) patients accepted PCI were enrolled.The inclusion criteria were:(1)Patients who underwent PCI. (2)Patients who were evaluated using IVUS.The exclusion criteria were: (1)Chronic kidney disease (CKD), which was defined as an estimated glomerular filtration rate(eGFR) of < 30mL/min/1.73 m 2;(2)Adequate IVUS images were not obtained;(3)In-stent restenosis (ISR) , stent thrombosis or the same culprit vessel was treated, previously. Patients were divided into 2 groups: low Lp(a) group, <150mg/L; high Lp(a) group, ≥ 150mg/L8. Finally, 139 lesions in 123 patients were included in (Fig.1).
This study was approved by the medical ethic committee of our institute, and written informed consent was obtained from each patient.
2.2 Measurement of Lp(a) levels
At baseline,blood samples were obtained by certified technicians from each participant in the early morning after overnight fasting. Lp(a) level was measured inserum by Biochemical Diagnostics Laboratory (third Xiangya Hospital,Changsha,China) using a latex-enhanced turbidimetric immunoassay (Hitachi 7600, Tokyo, Japan), with a total imprecision <5%.
After injection of 100 U/kg of unfractionated heparin, PCI was performed with a 6Fr or 7Fr guide catheter. Balloon dilation and the stenting procedure were performed at the operator’s discretion.The image acquisition was performed with IVUS system(Volcano corporation, Rancho Cordova, USA) and the 20 MHz IVUS catheter was advanced>5 mm beyond the lesion, and an imaging was performed to a point>5 mm proximal to the lesion.
IVUS images of the culprit lesion were obtained before PCI. All IVUS images were analyzed by analysts who were blinded to patient and procedural information.
2.4 Data analysis
2.4.1 Angiographic image acquisition and analysis
Quantitative coronary angiography (QCA) analysis was performed Pre- and post-PCI using an off-line quantitative coronary angiographic system(Medis Medical Imaging Systems,Leiden, Netherlands).Using the guiding catheter for magnification calibration, the reference diameter, minimal lumen diameter, and lesion length, and the percent diameter stenosis were measured.
2.4.2 IVUS image analysis
After intracoronary administration of 0.1–0.2mg nitroglycerin, IVUS imaging of the target lesion segment was performed before PCI. Segments were selected for analysis by using proximal and distal side branches as reference points.Conventional IVUS measurements included the cross-sectional area (CSA) of the external elastic membrane (EEM), lumen, and plaque plus media (EEM CSA minus lumen CSA) at each segment.The plaque burden was calculated as the plaque plus media CSA divided by the lesion EEM CSA multiplied by 100.The qualitative IVUS variables included calcifcation was defined as brighter echoes than adventitia with acoustic shadowing.Attenuated plaque(AP)was defined as hypoechoic plaque with deep ultrasonic attenuation despite the absence of bright calcification9.The maximum angle of the calcifcation was measured(Fig.2A).Thin calcifcation was defined as smooth surface with a reverberation pattern, and irregular surface without reverberation was the thick calcifications6(Fig.2 B,C).
2.5 Statistical analysis
Quantitative data are presented as mean±standard deviation (SD) or median[interquartile range (IQR)] and compared with (Student's t-test). Categorical variables were expressed as frequencies and compared with chi-square or Fisher exact test.Unconditional logistic regression was performed for estimates of odds ratios (ORs) and 95% confidence intervals (CIs). Logistic regression analysis was perfprmed to compare the odds ratios (ORs) of the calcified plaque (maximum calcified angle ≥180°) and the feature of calcified plaque（maximum calcified angle ≥180°＋thick calcification）between 2 groups (low Lp(a) group<150mg/L and high Lp(a) group, ≥150mg/L).For all analyses, P<0.05 was considered statistically significant.All statistical analyses were conducted using SPSS (version 19; IBM-SPSS, Chicago, IL).