The effect of atherogenic index on collateral development in patients with coronary chronic total occlusion

Introduction and Objective: Chronic total occlusion (CTO) in coronary arteries is defined as the total blockage of the vascular lumen for at least 3 months. Coronary collateral circulation (CCC) may be defined as a natural feature of the heart consisting of vascular structures that develop between different segments of the same coronary artery or between separate coronary arteries as a chronic adaptive response to allow blood supply to the ischemic myocardium in order to maintain perfusion and viability of the myocardial tissue at the distal portion of a lesion in the presence of total occlusion or critical stenosis disrupting normal blood flow. While a series of cardiovascular risk factors have been shown to play negative roles in the development of coronary collateral circulation, the reasons of differences noted in formation of an adequate collateral network across patients remain unclear. The present study aims to demonstrate the correlation between CCC and atherogenic plasma index (AİP), one of the factors associated with the formation of collateral vessels. Materials and Method: Data were retrospectively screened through a series of coronary angiography procedures performed at Dicle University Faculty of Medicine Heart Hospital, Cardiology Clinic during 03/2014-11/2018. Hospital records of patients with chronic total occlusion (100% stenosis) in at least one coronary artery were evaluated. Triglycerides, HDL level, triglyceride/HDL ratio and atherogenic plasma index before coronary angiography were assessed for the 451 patients who met the study criteria. Collateral circulation was evaluated according to the Rentrop collateral classification. Those with Rentrop grade 0 and 1 were stratified as 'weak collateral' while grade 2 and 3 were stratified as 'good collateral' circulation. Routine blood tests, clinical risk factors and coronary collateral circulation classification of the patients were documented together with their atherogenic plasma indexes. Results: The analysis on demographics and clinical characteristics of patients by collateral classification revealed higher mean rates of diabetes mellitus (p<0.001) and smoking history (p<0.001) with statistical significance in the weak collateral group, and rates of hypertension (p=0.123) and family history (p=0.059) were also higher, although without statistical significance. The analysis of angiography findings showed an overall higher CTO rate in RCA in the comparison of all three coronary arteries. As a response to the CTO lesions in RCA, a higher rate of good collateral formation was observed, although not statistically significant (p=0.133). For the CTO lesions in LAD (p=0.397) and Cx (p=0.724), weak collateral formation appeared to have a higher rate, although not meeting statistical significance. Comparison of the two groups in terms of laboratory and echocardiography findings showed that fasting glucose level (158.5±75.60 vs 132.3±55.23, p<0.001), triglycerides (186.7±86,75 vs 143.9±69.16, p<0.001), total cholesterol level (183.9±47.95 vs 173.4±46.63, p=0.019), triglyceride/HDL ratio (5.04±3.13 vs 3.56±2.12, p<0.001) and AİP (0.63±0.25 vs 0.48±0.25, p<0.001) were higher with statistical significance in the weak collateral group. The correlation analysis between collateral formation and AİP revealed a weak yet statistically significant negative correlation (rs= -0.299, p<0.001). The multivariate logistic regression analysis performed to explore the association between AİP and development of collateral vessels demonstrated statistical significance as a standalone factor (OR: 0.083, 95% CI: 0.035-0.196, p=0.000). Accordingly, low AİP was found to be a standalone predictor of good collateral artery formation. The ROC analysis revealed an association between weak collateral formation and atherogenic plasma index with 64.7% sensitivity and 66.2% specificity using a cut-off value of 0.58 for AİP. Conclusion: When determining subjects at risk of cardiovascular disease, especially those with family history of coronary heart disease, atherogenic plasma index should be carefully considered since it offers a simple, non-invasive, cost-effective method providing rapid results as well as substantial predictive value. The present study has demonstrated that a high atherogenic plasma index is a standalone factor associated with weak collateral formation. Therefore, close monitoring of parameters that constitute the atherogenic plasma index and attempts to lower this index may help reducing development of cardiovascular disease. It is also important in terms of decreasing the unfavorable effects on collateral formation in cardiovascular patients. Keywords: Collateral formation, chronic total occlusion, atherogenic plasma index, triglyceride/HDL ratio