Objective: Conventional risk factors for coronary artery disease fail to explain the increased frequency or cardiovascular morbidity in systemic lupus erythematosus (SLE) patients. This study was conducted to determine the possible influence of autoimmune and inflammatory phenomena markers on coronary artery calcifications and myocardial perfusion abnormalities in SLE patients.
Materials and methods: Multi-detector computed tomography (MDCT)-based coronary calcium scoring and single photon emission computerized tomography (SPECT) studies (Tc-99m sestamibi) were performed in 60 SLE patients in stable clinical condition, without a prior history of coronary artery disease. Laboratory evaluation included serum C-reactive protein (CRP), complement C3c and C4 components and antiphospholipid antibodies (aPL). The latter included anticardiolipin (aCL) and anti-β2-glycoprotein I (aβ2GPI) antibodies, of both IgG and IgM classes, and lupus anticoagulant (LA) in plasma.
Results: SPECT revealed persistent perfusion defects in 22 (36.7%) patients and exercise-induced defects in eight (13.3%), while MDCT revealed coronary calcifications in 15 (25%). Calcium scores ranged from 1 to 843.2 (mean 113.5 ± 259.7). No association was found between conventional coronary artery disease risk factors (obesity, hypertension, tobacco use, hyperlipidaemia, diabetes) nor CRP, C3c or C4 levels and coronary calcifications or myocardial perfusion defects. On the contrary, in patients with these pathologies, augmented autoimmunization was found, reflected by increased aCL IgG and antiβ2GPI IgG levels. In patients with aCL IgG >20 RU/ml or antiβ2GPI IgG >3 RU/ml, the relative risk of coronary calcification formation was 4.1 compared to patients with normal values. Accordingly, in LA-positive patients the relative risk of coronary calcification formation was 4.4 compared to LA-negative patients.
Conclusions: Conventional risk factors for coronary artery disease as well as markers of an ongoing inflammation did not show any association with perfusion defects and/or coronary artery calcifications in SLE patients. On the contrary, calcified atherosclerotic plaques and myocardial perfusion defects were observed mainly in patients with elevated levels of anticardiolipin and aβ2GPI antibodies of the IgG class. It might be speculated that coronary artery calcifications and perfusion defects are a result of antiphospholipid antibodies-induced coronary artery microthrombosis.