BERLIN – The risk of cardiovascular events in patients with systemic lupus erythematosus is sevenfold higher than the risk predicted by the Framingham equation, a study shows.
The role of risk factors varies widely, with the presence of high triglyceride levels upping the risk nearly fourfold while use of cyclophosphamide, which may be a proxy for disease severity, raises the risk almost 17-fold, Dr. Sarah Skeoch, a clinical research fellow at the Arthritis Research UK Epidemiology Unit at the University of Manchester, England, said at the annual European Congress of Rheumatology.
The research also showed that triglyceride level was the only independent traditional risk factor, with a 3.6-fold increased risk association. Damage related to lupus, according to the Systemic Lupus International Collaborating Clinics (SLICC) damage index, increased risk 10-fold. Cyclophosphamide therapy was associated with a 16.7-fold increase in risk.
Although the patients have more of the classical risk factors, this does not seem to account for all the increased risk. Disease characteristics such as chronic inflammation or treatments may contribute, she suggested.
"We wanted to look at the association between risk and disease, for example, how active their lupus is, damage accrued over time, whether they have renal disease, and also whether their treatments are associated with CV events like heart disease and stroke," Dr. Skeoch added.
The study looked at these factors in 200 patients who were diagnosed between 2000 and 2003.
At baseline, 12 patients of the eventual 124 who were followed up had experienced a prior CV event. Also at baseline, the SLE disease activity index (SLEDAI) score was 1, indicating low disease activity, and the SLICC damage index was low.
All patients included in the study were over 18 years of age, female, and white. Their lupus was stable with therapy for at least 2 months prior to inclusion in the study. "They were a relatively well population of patients," said Dr. Skeoch.
Blood tests and clinical assessments were carried out to determine levels of traditional risk factors, lupus disease activity, and lupus-related damage, as well as measurements related to disease therapies.
After a 5-year interval, patients were invited back for assessments and the incidence of CV events, including coronary events, cerebral events, and peripheral vascular disease over the elapsed time period, was recorded.
Next, a comparison was made between the predicted CV risk at baseline according to the Framingham equation and the observed results in 112 patients with no prior CV disease.
CV Risk Higher Than Expected
Upon follow-up, patients were, on average, 56 years old and had had disease for approximately 16 years. Out of the 124 patients followed up over approximately 5 years, 12 (9.7%) had a CV event. Coronary events accounted for seven of these, cerebrovascular events were recorded in five patients, and peripheral vascular disease occurred in one patient. "One patient had both a coronary event and a cerebral event within the follow up," Dr. Skeoch said.
In those who had no prior CV event at baseline, predicted risk of a CV event according to the Framingham equation suggested that 1% of patients should have an event in the next 5 years. "In fact, we found 7% had an event – so seven times higher than predicted. This excess risk is most likely attributed to uncaptured traditional risk factors or alternatively, the disease itself, which is more likely," she commented.
The investigators looked at independent risk factors for a CV event regardless of which other risk factors a patient had and found that triglyceride levels were the only traditional risk factor, with an odds ratio (OR) of 3.61 (95% confidence interval, 1.23-10.56). Triglyceride levels often were not the primary target of lipid-lowering therapy, which was usually aimed at reducing total cholesterol or cholesterol ratio, she noted.
Other multivariable analyses of baseline characteristics associated with CV events suggested that the risk was elevated by two factors: the SLICC damage score (OR, 9.62; CI, 1.46-63.5) and cyclophosphamide therapy (OR, 16.7; CI, 1.46-123). "Factors associated with the patients’ lupus disease included having had a venous thromboembolism, damage related to SLE in the past, cyclophosphamide exposure, and a higher steroid dose at baseline which predisposed the patient to having an event," Dr. Skeoch said.
Marker for Disease Severity
"This is the first time cyclophosphamide [therapy] has been marked as an example of an independent predictor of CV risk. We don’t think it is the cyclophosphamide itself because it has been used in a number of diseases and there’s no known evidence to suggest it causes heart disease, but we think it is a measure of people with severe disease. Also, patients exposed to cyclophosphamide tend to have had more steroids," she explained.