Association of Lymphocyte-to-Monocyte Ratio, Mean Diameter of Coronary Arteries, Uric Acid with Coronary Slow Flow in Isolated Coronary Artery Ectasia

Background The pathophysiology of isolated coronary artery ectasia (CAE) with coronary slow ow (CSF) phenomenon is still unclear. The purpose of this study was to investigate the risk factors for isolated CAE complicated with CSF. Methods A total of 126 patients with isolated CAE were selected retrospectively. The patients were grouped into the no CSF(NCSF) group (n=55) and CSF group (n=71) according to the thrombolysis in myocardial infarction (TIMI) frame count (TFC). Data on demographics, laboratory measurements, left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter (LVEDd), TFC and diameters of three coronary arteries were collected.


Background
Isolated coronary artery ectasia (CAE) refers to the local diameter of a coronary artery being dilated more than 1.5 times the adjacent normal vessels and having no obvious obstruction [1][2][3][4] , with a morbidity of less than 0.32% [5] . Coronary slow ow (CSF) phenomenon is coronary angiography that has no obvious stenosis but slow forward ow perfusion [6,7] . The incidence of CSFP in coronary angiography is less than 1% [7] . However, it can cause serious cardiac events, such as angina pectoris, myocardial infarction, malignant arrhythmia and even sudden death [8] .
There is no consensus on the physiologic mechanism of the above two diseases. Although the change of vascular diameter will affect the velocity of ow, not all patients with CAE have CSF. Since the morbidity of these two diseases is low, large sample studies are lacking. Some small sample studies have suggested the lymphocyte-to-monocyte ratio (LMR), neutrophil-to-lymphocyte ratio (NLR), albumin (ALB) level, high-sensitivity C-reactive protein (hs-CRP) level and uric acid (URIC) level were risk factors for CSF or CAE [1,2,4,7,9−12] . Therefore, the aim of this study was to investigate the risk factors for CSF in patients with isolated CAE.

Subjects
From January 2010 to December 2019, 541 patients who underwent coronary angiography in our hospital and were diagnosed as having isolated CAE were selected. Inclusion criteria were as follows: the diameter of the local coronary artery was more than 1.5 times larger than that of the adjacent normal segment with the degree of stenosis < 20% and cardiac ultrasound showed that the heart structure and left ventricular ejection function (LVEF) were normal. Exclusion criteria were acute coronary syndrome, coronary spasm, coronary artery bypass graft, valve disease, congenital heart disease, Kawasaki disease, left ventricular or ventricular septal hypertrophy, immunological disease, malignant tumor, severe cerebrovascular disease, severe hepatic or renal insu ciency (creatinine > 132 µmol/L, AST or ALT > 2 times upper level of normal), hematological system disease or hemoglobin < 90 g/L, received steroid hormone treatment or acute in ammatory disease within 1 month. A total of 126 patients with isolated CAE were included and grouped into the CSF group (n = 71) and the no CSF(NCSF) group (n = 55).

Angiography data and frame counting
The coronary ow velocity was measured by using the thrombolysis in myocardial infarction (TIMI) frame count (TFC) according to Gibson [13] . The frame was collected at 30 frames/s, counting the number of frames from the start to the distal coronary artery. The rst frame is the contrast agent completely lling the coronary artery, and the forward motion of the contrast agent can be observed. The nal frame is the contrast agent reaching a certain landmark of the coronary artery. The sign of the left anterior descending (LAD) artery was the "whale tail" or "hay fork " at the distal bifurcation. The landmark of the left circum ex (LCX) artery was the distal bifurcation of the obtuse marginal branch, and the rst branch of the posterolateral artery was used for the right coronary artery (RCA). Because the LAD artery is longer, the TFC for this artery should be divided by 1.7 to get a corrected TFC (cTFC). Any vessel with a cTFC ≥ 27 frames is de ned as CSFP. The average number of TFC (Mean TFC) is obtained by summing the TFC of 3 arteries then dividing by 3.
Written informed consent was obtained from each patient included in the study, The study protocol conforms to the ethical guidelines of the 1975 Declaration of Helsinki and the study protocol has been priorly approved by the Institution's ethics committee on research on humans.

Statistical analysis
All analyses were performed using the Statistical Package for the Social Sciences version 22.0 (IBM Corp., Armonk, New York, USA) and MEDCALC (Software bvba 19, Ostend, Belgium) software programs. Continuous variables were presented as the means ± standard deviations (normal distribution) and medias (interval changes) (non-normal distribution). Categorical variables were presented as percentages. Comparisons of categorical variables between the two groups were performed using the Chi-squared (χ2) test. The Kolmogorov-Smirnov test was performed to assess if the variables were normally distributed. Student's t-test or Mann-Whitney U test was used to compare the continuous variables between the two groups according to whether they were normally distributed or not. Spearman's rho correlation analysis was performed to describe the degree of correlation between the parameters related with the mean TFC. To identify the independent predictors of CSF, univariate and multivariate logistic regression analyses (backward LR method) were performed. The variables with a P < 0.1 in the unit analysis were incorporated into the multivariate logistic regression analysis. Receiver operating characteristic (ROC) curve analysis was performed to determine additional assets of parameters found to be independent predictors of CSF. The optimal cutoff value was calculated from the point of maximum sensitivity and speci city (Youden's index). To compare the predictive performance of parameters found to be independent predictors for CSF development, the DeLong et al. test was also used. The results were evaluated within a 95% con dence interval (CI) and at a signi cance level of P < 0.05.

Results
Comparison of the demographic and clinical characters is shown in Table 1. The proportion of males(84.5% vs 61.8%, p = 0.004) and smoking history(63.4% vs 43.6%, p = 0.021) in the CSF group was signi cantly higher than that in the NCSF group, and there was no signi cant difference in age, BMI, hypertension, type 2 diabetes mellitus, and medications between the two groups.  In the Spearman correlation analyses (Table 3)

Discussion
The main discoveries of this study can be summarized as follows: 1) the in ammatory indicators were higher in the CSF group than in the NCSF group; 2) LMR, mean diameter of coronary arteries and URIC level were independent predictors in predicting CSF phenomenon in patients with isolated CAE; and 3) the predictive power of LMR was not inferior to that of the combination.
As is known, monocytes and lymphocytes are vital immune cells. They also play an important role in the atherosclerosis process [3,9,10,15−20] . In response to the stimulation of in ammatory cytokines, monocytes are recruited into the intima and subintima by the assistance of adhesion molecules during the initial stage [7,17] . After migration, monocytes differentiate into macrophages, devouring oxidized LDL-C and releasing a large number of in ammatory factors, such as interleukin(IL)-1, IL-6, tumor necrosis factor (TNF)-α, and macrophage colony stimulating factor, which attract more monocytes [20] . Lymphocytes can enhance the immune response by regulating catecholamine and cortisol levels in the anti-in ammatory milieu. However, as catecholamine and cortisol levels increase, lymphocyte numbers will gradually decline. The hypothesis of this phenomenon includes decreased lymphocyte proliferation, lymphocyte apoptosis and differentiation of lymphocytes in the redistribution of lymphoid organs [16,17,20] .
Because the LMR combines two kinds of immune cells, it has long been used as an indicator of the cancer patient condition and treatment [21][22][23] . In recent years, studies have found that the LMR is related to stable angina [16,17] , acute coronary syndrome (ACS) [24] and CSF [7] , and it even can be used as an independent predictor of major adverse cardiac events (MACE) [18,20,24] . Yildirim et al [15] . found that the expression of active markers on monocyte-derived dendritic cells in patients with CAE was signi cantly higher compared to that in patients with CAD. Yayla [7] investigated the LMR in CSF and the normal coronary group found that a low LMR was independently associated with CSF. Kalyoncuoglu et al [9] . found that a higher monocyte-to-HDL-C ratio (MHR) and lower LMR values were independent predictors of slow ow/no re ow in patients with non-ST-elevated myocardial infarction (NSTEMI). In our study, the LMR was signi cantly lower in the CSF group and was found to be an independent risk factor for CSF development in isolated CAE.
URIC can impair nitric oxide generation in endothelial cells through multiple pathways, leading to endothelial dysfunction [4,12,25,26] . Studies have shown that it can also induce vascular smooth muscle cell (VSMC) proliferation and differentiation by activating mitogen-activated protein kinases [27] . VSMCs migrated from the middle layer to the subintima and participated in the formation and development of atherosclerotic plaques. Our study suggested that URIC was an independent predictor of CSF in isolated CAE, speculating that the progress of atherosclerosis was accelerated in this group. Both the LMR and URIC level played an exclusive role in the early formation of atherosclerotic plaques and the growth of the lipid core, suggesting that early rapid atherosclerotic formation and development in a population with CAE might be an important factor for CSF.
The deep impression of CAE in angiography is local or diffuse vascular expansion. It is viewed in the cross-section of a coronary artery as circular, according to the ow equation Q = πr 2^v , where Q is tra c, r is radius, and v is ow velocity. It is known that when the tra c is constant, ow velocity is inversely proportional with the square of the radius. This was consistent with our study, showing that the Mean D in the CSF group was larger than that in the NCSF group.
Other studies also found that some in ammation indicators relate to CAE or CSF, such as the NLR and albumin level. Yilmaz [11] suggested the NLR was signi cantly higher in patients with CAE, CSF and CAD compared to those in the normal group and was an independent predictor of these diseases. ALB is also a kind of negative acute phase protein [1,28] . Cetin [1] found that the ALB level was signi cantly lower in the CSF group than in the normal group and was an independent predictor of CSF. This study also found that both the NLR and albumin level were signi cantly different in both groups. However, the predictive power of the NLR and albumin level in CSF didn't reach statistical signi cance. A possible reason might be the different control groups in these studies. The control group in our study was patients with isolated CAE who had a certain level of in ammation, resulting in the prediction ability of in ammation indicators not reaching statistical signi cance.
The combination of the LMR, URIC and Mean D generated a new combination predictor. Comparison of the areas under the 4 ROC curves suggested the predictive power of the combination was superior to URIC and Mean D (P < 0.001), but there was no statistically signi cant difference with the LMR.

Limitation
There are some limitations in this study. The rst limitation relates to its retrospective design. Some risk factors, such as the matrix metalloproteinase family, tissue inhibitors of metalloproteinases [29,30] and adropin [3] , which have a signi cant role in CAE development, couldn't be collected. Second, multivariable logistic regression analyses were performed to identify independent predictors of CSF in CAE; however, it was impossible to control for unknown confounders. In addition, this study has reviewed the cases in the center over a 10-year period, and due to the low morbidity of both diseases, the sample size was still not large enough to re ect more latent risk factors.

Conclusion
Patients with CAE combined with CSF have a more signi cant development of atherosclerosis and serious in ammatory reactions. The LMR, URIC level and Mean D were independent predictors of CSF in CAE, and the predictive power of the LMR was not inferior to the combination. Authors' contributions: ZXY and SBQ contributed to drafting and revising the manuscript. JSY contributed to the clinical data collection and coronary angiography operation. JGC contributed to analysis and interpretation of data. All the authors critically revised the manuscript and gave nal approval and agreed to be accountable for all aspects of the work, ensuring both its integrity and accuracy.