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Echocardiogram May predict Heart Disease & Visceral Fat in HIV: Epicardial fat suggests subclinical atherosclerosis in HIV patients
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2007-06-20
"....increased epicardial fat reflects the increased visceral adiposity and therefore correlates with carotid IMT in patients with HIV...The echocardiographic assessment of epicardial fat may also have the potential to be a simple and reliable marker of atherosclerosis and increased cardiovascular risk, as previously suggested.13, 14, 15, 16, 17, 18 and 19 Because echocardiography is likely to be routinely performed in high-risk cardiac patients, as well as in HIV-infected patients, this objective measure may be readily available at no extra cost...."
NEW YORK (Reuters Health) - Epicardial adipose tissue, an index of cardiac adiposity, appears to be significantly related to subclinical atherosclerosis in HIV-infected patients who are on highly active antiretroviral therapy (HAART), according to researchers in Canada and Italy.
"Scientific and clinical interest in epicardial adipose tissue, the visceral fat located around the heart, is new but rapidly emerging," lead investigator Dr. Gianluca Iacobellis told Reuters Health. He pointed out that "epicardial fat is clinically related to coronary artery disease, atherosclerosis and major anthropometric and metabolic predictors of increased cardiovascular risk."
Dr. Iacobellis of McMaster University, Hamilton and colleagues used echocardiography in 103 HIV-infected patients receiving HAART to evaluate if echocardiographically determined subepicardial adipose tissue was related to carotid intima-media thickness, an indicator of subclinical atherosclerosis.
As a result of HAART, HIV-infected patients frequently develop lipid abnormalities, including the accumulation of abdominal adiposity, features of the metabolic syndrome, and other factors that increase cardiovascular risk.
The correlation was "excellent" and this approach was more predictive than other anthropometric and clinical correlates of atherosclerosis, the researchers report in the May 15th issue of the American Journal of Cardiology.
"Echocardiographic epicardial fat measurement has the potential to be a reliable and easy diagnostic marker of visceral adiposity and cardio-metabolic risk and an effective therapeutic target for treatments modulating the adipose tissue." Dr. Iacobellis concluded.
Am J Cardiol 2007;99:1470-1472.
"Relation of Subepicardial Adipose Tissue to Carotid Intima-Media Thickness in Patients With Human Immunodeficiency Virus"
Gianluca Iacobellis MD, PhDa, Adriano M. Pellicelli MDc, Arya M. Sharma MDa, Benvenuto Grisorio MDd, Giorgio Barbarini MDe and Giuseppe Barbaro MDb
aCardiovascular Obesity Research and Management at the Michael G. deGroote School of Medicine, McMaster University, Hamilton, Ontario, Canada
bCardiology Unit, Department of Medical Pathophysiology, University "La Sapienza", Rome, Italy
cDepartment of Internal Medicine, S. Camillo Hospital, Rome, Italy
dInfectious Diseases Unit, General Hospital, Foggia, Italy
eDepartment of Infectious and Parasitic Diseases, Policlinico S. Matteo, Pavia, Italy.
Patients infected with human immunodeficiency virus (HIV) are at increased risk for subclinical atherosclerosis. Whether increased cardiac adiposity may be related to HIV subclinical atherosclerosis is still unexplored. The objective of this study was to evaluate whether echocardiographically determined subepicardial adipose tissue, an index of cardiac adiposity, is related to carotid intima-media thickness (IMT), an index of subclinical atherosclerosis, in HIV-infected patients receiving highly active antiretroviral therapy. Echocardiographic epicardial fat thickness and ultrasonographic IMT were measured in 103 consecutive HIV-infected Caucasian subjects receiving highly active antiretroviral therapy. Echocardiographic subepicardial adipose tissue showed an excellent correlation with IMT (r = 0.92, p <0.01). Multiple regression analysis showed that IMT was best predicted by epicardial fat thickness (r2 = 0.81, p <0.01). In conclusion, this study suggests, for the first time, that epicardial adipose tissue, an index of cardiac adiposity, may be significantly related to subclinical atherosclerosis in HIV-infected patients.
The objective of this study was to evaluate whether echocardiographic epicardial adipose tissue, an index of cardiac adiposity,1 and 2 is related to carotid intima-media thickness (IMT), an index of subclinical atherosclerosis, in patients infected with human immunodeficiency virus (HIV) who are receiving highly active antiretroviral therapy (HAART).
Methods and Results
Men and women aged 18 to 70 years with documented HIV-1 infection were recruited over a 1-year period. We selected 103 consecutive HIV-infected Caucasian outpatients with HAART-associated metabolic syndrome. Metabolic syndrome was identified by the presence of ≥3 risk factors according to the guidelines of the National Cholesterol Education Program Adult Treatment Panel III.3 Exclusion criteria were the presence of opportunistic infectious disease and/or malignancies, renal and/or liver diseases, and cigarette smoking. The study was conducted in accordance with the guidelines proposed in the Declaration of Helsinki and was approved by the local ethics committee. All patients gave their informed consent.
A Hewlett-Packard Sonos 500 (Hewlett-Packard Corporation, Palo Alto, California) with a 2.5-MHz transducer was used for M-B-mode transthoracic echocardiography. Epicardial fat was identified as the space or layer anterior to the right ventricle with decreased echoreflectivity compared with the myocardium and pericardium. Increased echoreflectivity, as previously found in subjects with massive epicardial fat deposits (>15 mm),4, 5 and 6 was not observed in this study. Epicardial fat thickness was measured in end-diastole on the free wall of the right ventricle from the parasternal long- and short-axis views, as previously described.4 The maximum values at any site were measured, and the average value was considered. Imaging constraints were used to ensure that the epicardial fat thickness was not measured obliquely. Parasternal long- and short-axis views allow the most accurate measurement of epicardial adipose tissue on the right ventricle, with optimal cursor beam orientation in each view. The intraclass coefficient of variation was 2%. Epicardial fat on the right ventricle is recognized as the largest absolute epicardial fat layer thickness. However, echocardiographic subepicardial fat thickness is a linear measurement and therefore may not reflect the total epicardial fat volume.
B-mode ultrasonographic imaging of the common carotid artery was performed using high-resolution real-time ultrasonography with a 7.5-MHz transducer (Hewlett-Packard Corporation) for the measurement of IMT. IMT was measured in the anterior wall of the vessel as the distance from the trailing edge of the adventitia to the leading edge of the intima-media; in the posterior wall of the vessel, it was measured as the distance from the leading edge of the intima-media to the trailing edge of the adventitia. The average of 16 measurements was taken as the mean IMT. IMT images were read by 2 echocardiographic readers who were blinded to patients' data. The coefficient of variation was 2%.
Data are expressed as mean ± SD. Linear and multiple regression analyses were performed to identify correlates of carotid IMT. Two-tailed p values <0.05 were considered to indicate statistical significance. Analysis was performed using Stata version 5.0 (StataCorp LP, College Station, Texas).
The clinical characteristics of the HIV-infected patients are listed in Table 1. Epicardial fat and IMT were not different between genders or between patients taking statins and those taking omega-3 fatty acids. Linear regression analysis showed that epicardial fat thickness was significantly correlated with IMT (r = 0.92, p <0.01) (Figure 1), diastolic blood pressure (r = 0.81, p <0.01), waist circumference (r = 0.80, p <0.01), body mass index (r = 0.72, p <0.01), and fasting insulin (r = 0.50, p <0.05).
In a multiple regression model including carotid IMT as the dependent variable and epicardial fat, body mass index, waist circumference, and blood pressure as independent variables, IMT was best predicted by epicardial fat thickness (r2 = 0.81, p <0.01).
Discussion
In this study, epicardial fat thickness showed an excellent correlation with carotid IMT and predicted it better than other anthropometric and clinical correlates of atherosclerosis. Higher epicardial fat thickness is linearly related to higher left ventricular mass, as previously shown,5 and to carotid IMT thickness. If the former association can be explained by the proximity of the epicardial fat pad to the myocardium and by paracrine interactions, the latter could suggest different mechanisms.
Increased visceral fat, as observed in HIV-infected patients receiving HAART, is associated with higher cardiometabolic risk and accelerated atherosclerosis.7 Although the mechanisms underlying its development are still unclear, it has been suggested that HAART may interfere with adipocyte differentiation and production of adipokines.8 and 9 However, the presence of increased visceral fat in HIV-infected patients is associated with advanced atherosclerotic changes and also subclinical atherosclerosis, independently of HAART.10, 11 and 12 Hence, increased epicardial fat reflects the increased visceral adiposity and therefore correlates with carotid IMT in patients with HIV.
Our findings are consistent with evidence for a potential relation between epicardial fat, an index of cardiac and visceral adiposity, and cardiovascular diseases.13, 14, 15, 16, 17, 18 and 19 However, recent observations have not found a correlation between epicardial fat and coronary heart disease,20 although values of subepicardial fat significantly less than those measured in previous reports4, 5, 6, 13 and 14 could explain the different results.
The echocardiographic assessment of epicardial fat may also have the potential to be a simple and reliable marker of atherosclerosis and increased cardiovascular risk, as previously suggested.13, 14, 15, 16, 17, 18 and 19 Because echocardiography is likely to be routinely performed in high-risk cardiac patients, as well as in HIV-infected patients, this objective measure may be readily available at no extra cost.
References
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2 G. Iacobellis, C.M. Pond and A.M. Sharma, Different "weight" of cardiac and general adiposity in predicting left ventricle morphology, Obesity 14 (2006), pp. 1679-1684.
3 National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III), Third report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) final report, Circulation 106 (2002), pp. 3143-3421.
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19 J. Kremen, M. Dolinkova and J. Krajickova, Increased subcutaneous and epicardial adipose tissue production of proinflammatory cytokines in cardiac surgery patients: possible role in postoperative insulin resistance, J Clin Endocrinol Metab 91 (2006), pp. 4620-4627. View Record in Scopus | Cited By in Scopus
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