Absence of coronary artery disease in high-risk sickle cell anemia patients: a new illustration supporting the protective effect of Bilirubin against atherosclerosis?

Abstract

Abstract Background Sickle cell anemia (SCA) is associated with both cardiac and systemic vascular disorders, which are the leading cause of morbi-mortality. Although these patients cumulate multiple cardiovascular (CV) risk factors, along with chronic inflammation and endothelial activation, some pre-clinical studies underlined a paradoxical protection against atherosclerosis. Purpose The aim of this study was to evaluate the prevalence of coronary artery disease in a high-risk SCA population. Methods From January 2019 to December 2023, consecutive adult patients with SCA were prospectively included in the DREPACOEUR registry to specifically analyze cardiac structure and function. They all had a comprehensive CV evaluation at steady-state in day-hospital including clinical exam, cardiac imaging, rhythm monitoring along with biology analysis. Only patients that underwent coronary imaging (CT coronary angiogram) were included in this study. Results Ninety patients were included. Mean age was 44±12, 50% were male with a high prevalence of systemic hypertension (57%), obstructive sleep apnea (21%) and 10% smokers. Only one patient had history of diabetes while no dyslipidemia (or lipid lowering therapy) was reported. Heart function was mainly preserved with a mean left ventricular ejection fraction (LVEF) of 58±5%. Expectedly, patients showed low hemoglobin level 8,7±1.4g/dL with high hemolysis markers. Glomerular filtration rate was 109 [62; 122] mL/min/m² with 21% having chronic kidney disease. Plasmatic LDLc level was low (0.7±0.3g/L, with 20% <0.5g/l) while triglycerides (TG) were highly variable (1.1±0.7mg/dL). Strikingly, no patient showed signs of significant coronary artery disease, with 87% presenting a calcium score of 0, 77% had a CAD-RADS of 0 while no patient was higher than 2. Correlation and linear regression analysis were performed to find independent parameters associated with LDLc and TG. Total bilirubin was the only variable that correlated with both LDLc and TG (R= -0.37, p<0.001 and R= -0.33, p=0.001 respectively). Conclusion Despite systemic vasculopathy and chronic inflammation, ageing SCA patients showed no significant coronary artery disease. These data are in line with pre-clinical studies suggesting a lipid-lowering role of bilirubin and its protective effect against atherosclerosis.