Influence of chronic inflammation and autoimmunity on coronary calcifications and myocardial perfusion defects in systemic lupus erythematosus patients

The study was performed in 60 consecutive patients treated for systemic SLE in the Department of Internal Medicine, Jagiellonian University Medical College, Krakow, Poland. All patients fulfilled at least four American College of Rheumatology classification criteria for SLE [10, 11]. Before the study, informed consent was obtained from each patient. The study protocol conforms to the ethical guidelines of the 1975 Declaration of Helsinki. The study was approved by the Ethical Committee of the Jagiellonian University in Krakow.

Inclusion criteria comprised stable clinical conditions of SLE (no need for immunosuppressive therapy intensification, i.e. current immunosuppressive drug dose increase or introduction of an additional immunosuppressive drug within the last 3 months). Exclusion criteria were as follows: prior history of coronary artery disease, known cancer, clinical symptoms of heart failure (NYHA III or IV class), renal failure (creatinine clearance <30 ml/min) and/or respiratory failure.

In the group of 60 patients examined, 54 (90%) were females andsix(10%) males, aged 20–73 years (mean age 51.8 years). The duration of the disease at the time of examination was between 2 and 32 years (mean 15.5 years). Three patients had been previously diagnosed with antiphospholipid syndrome (APS) based on the revised APS classification criteria [8]. One of the three suffered from an objectively confirmed pulmonary embolism. There were two tobacco smokers; none of the patients was obese. The history revealed arterial hypertension in three subjects; there were no diabetic patients. ECG recordings at rest were normal in all the patients. The results of peripheral blood count, serum sodium, potassium, glucose, creatinine and urinalysis were all normal. The distribution of the patients according to their SLEDAI score [12] is shown in Table 1. The main complaints at inclusion were arthralgias and, among laboratory findings, low complement levels and increased ANA titers (see below). The immunosuppressive treatment included methylprednisolone in 32 (53.3%) subjects (≤4 mg for clinical stability maintenance), prednisone in two (3.3%), chloroquine derivate in five (8.3%), azathioprine in four (6.7%), cyclophosphamide in three (5%), and methotrexate in two (3.3%). The remaining patients had not used any immunosuppressive drugs in the last 12 months of observation. Other treatment included angiotensin-converting enzyme inhibitors in four (6.7%) subjects, beta-blockers in three (5%) and calcium channel blockers in two (3.3%). APS patients were treated with anticoagulant (warfarin, two patients) or antiplatelet therapy (aspirin, one patient).

The presence and types of autoantibodies identified in the patients examined as well as the concentrations of CRP and complement C3c and C4 components are shown in Table 2.

In all the patients SPECT studies (ECAM Gamma Camera, Siemens, Germany) were performed at rest and during exercise in a 2-day protocol. On the first day, at near maximal stress, a 25–40 mCi dose of Tc-99m sestamibi was injected (the actual dose was modified taking into account the patient’s weight) and the exercise was continued forone additional minute after the injection. Tc-99m sestamibi SPECT imaging was begun 15–30 min later. On the second day, rest examinations were performed. SPECT was performed using a circular 180° acquisition for 60 projections at 20 s per projection. Myocardial perfusion was assessed in 17 left ventricle myocardial segments. The number of segments with persistent or exercise-induced perfusion defects were assessed visually by analysts blinded to any other information.

Coronary calcium scoring was performed using a multidetector CT imager (Somatom Definition, Siemens, Germany). The images were ECG-triggered with 3-mm-thick sections obtained covering the whole heart. Coronary artery calcifications were defined as lesions with attenuation greater than 130 HU in more than four adjacent pixels. In order to quantify coronary calcium, 3D Leonardo application (Siemens, Germany) was used. The number of atherosclerotic plaques in particular coronary arteries and their volume were assessed. The Agatson calcium score was calculated [13].

Standard laboratory tests were performed. Additionally, the levels of CRP (high-sensitivity) and complement system C3c and C4 factors were assessed by nephelometry (Siemens, Germany).

Serum levels of anticardiolipin (aCL) and anti-β2-glycoprotein I (aβ2GPI) antibodies (of both IgG and IgM classes) were measured using a home-made ELISA with Sapporo standard for antiβ2GPI antibody measurements (HCAL for IgG, EY2C9 for IgM) [9]. The values exceeding the 99th percentile of a healthy population sample were considered positive.

Lupus anticoagulant (LA) determination was performed in accordance with the three-step procedure recommended by the International Society on Thrombosis and Haemostasis [14].

Statistical analysis was performed using Statistica Six Sigma software. All numerical data were expressed as mean values ± standard deviations or as proportions. Continuous variables were compared using the t test. The chi-square test was used to examine differences in proportions. The level for statistical significance was predetermined at p < 0.05. To adjust for the confounding effect of age on SPECT and MDCT results, an ANOVA model was used with age as a covariate.