Measuring the volume of fat around the heart can help predict which HIV-positive patients have an increased risk of cardiovascular disease, an Italian study published in the online edition of AIDS suggests.
Investigators used CT scans to monitor volume of epicardial adipose tissue in over 800 HIV-positive patients with experience of antiretroviral therapy. Their results showed an association between epicardial adipose tissue and coronary artery calcium - a marker of hardening of the arteries, a well-established risk factor for cardiovascular disease.
“EAT [epicardial adipose tissue] shows promise as a marker of cardiovascular risk in HIV patients,” comment the investigators, “the clear advantage of measuring EAT is that in the same CT imaging session, one can obtain information on CAC [coronary artery calcium].”
It is now well established that HIV-positive patients have an increased risk of cardiovascular disease, and monitoring for such diseases is an important part of HIV care.
Investigators therefore wished to assess the association between epicardial adipose tissue and coronary artery calcium, a marker for atherosclerosis, or hardening of the arteries.
Analyses were also conducted to see if epicardial adipose tissue was associated with HIV infection, antiretroviral therapy, and the presence of lipodystrophy – body fat changes caused by some older anti-HIV drugs.
Their cross-sectional study included 876 adult patients who had at least 18 months experience of antiretroviral therapy. CT scans were used to assess volume of epicardial adipose tissue, coronary artery calcium, and lipodystrophy. Blood tests were also carried out to assess CD4 cell count, viral load and lipid levels.
A coronary artery calcium score of 100 and above has been shown to be highly predictive of hardening of the arteries. Lipodystrophy was divided into three types: fat loss; fat accumulation; or a mixture of the two.
Most (67%) of the patients were men, and their mean age was 47 years. They had been living with diagnosed HIV-infection for a mean of 15 years.
Mean epicardial adipose tissue volume was 78.58 cm3. The median coronary artery calcium score was 0, the mean 40, and 9% of patients had a score of 100 or above. Metabolic syndrome was diagnosed in 16% of individuals.
Volume of epicardial adipose tissue was significantly larger in patients with metabolic syndrome than without (87 vs. 70 cm3, p < 0.001).
Lipodystrophy was diagnosed in 61% of patients. Fat loss was detected in 29% of patients; fat gain in 8%; and a mixture of loss and gain in 25% of individuals. Epicardial adipose tissue volume was significantly greater in patients with a combination of fat loss and fat gain than in individuals with no lipodystrophy (83.4 cm3 vs. 64.6 cm3).
Analysis showed that a number of traditional and HIV-related factors were associated with volume of epicardial adipose tissue.
These included age (p = 0.03), male sex (p = 0.035), total cholesterol (p = 0.011), waist circumference (p = 0.037), volume of visceral adipose tissue – a marker for lipodystrophy (p < 0.01), current CD4 cell count (p = 0.019), and duration of therapy with an NRTI (p = 0.046).
Further analysis showed that there was a significant relationship between increased epicardial adipose tissue volume and a higher coronary artery calcium score above 100 (p = 0.011). Other factors included male sex (p = 0.001), older age (p < 0.001), and diabetes (p = 0.005).
“This cross sectional study showed a clear association between EAT volume, some HIV-specific factors such as current CD4 cell count, and both central fat accumulation and mixed lipodystrophy phenotypes,” comment the investigators.
“We were also able to demonstrate an association between EAT and CAC greater than 100, a marker of subclinical atherosclerosis and increased cardiovascular risk.”
They call for further studies “to investigate the contribution of immune-reconstitution to the development of systemic inflammation, EAT, and atherosclerosis.”
Guaraldi G et al. Epicardial adipose tissue is an independent marker of cardiovascular risk in HIV-infected patients. AIDS 25, online edition: doi: 10.1097/QAD.0b013e3283474b9f, 2011 (click here for the free abstract).