Purpose HIV-associated morbidity and mortality have decreased following the introduction of highly active antiretroviral therapy. Previous studies have shown that HIV-infected patients are at increased risk for atherosclerosis, independent of other risk factors. Measurement of carotid artery intima media thickness (IMT) is a noninvasive method of assessing atherosclerosis that predicts myocardial infarction and stroke even after adjustment for traditional risk factors. Wherease some studies of HIV patients have shown increased carotid IMT measurements, others have not. We hypothesized that the disparity between these studies may result from different methods used to measure carotid IMT, namely, either including or excluding the bifurcation region.
Methods Carotid IMT data were available from 230 HIV-infected individuals. Measurements were taken on both right and left sides at a total of 12 sites per subject. These included the near and far walls of the common carotid artery (CCA), the bifurcation (BIF), and the internal carotid artery (ICA). A carotid plaque was defined as IMT ≥ 1.5 mm.
Results The mean IMT of all sites (0.97 mm ± 0.40) was significantly higher than the mean taken from only the CCA (0.74 mm ± 0.30; p < .001) or only the ICA (0.92 mm ± 0.53; p = .009) and lower than the mean at the BIF only (1.3 mm ± 0.62; p < .001). Among peak IMT values for each patient, 80% were located in the BIF region, 16% in the ICA, and only 4% in the CCA. Furthermore, 340 plaques were discovered on baseline imaging; more than half (64%) of these plaques were located in the BIF region, 32% were located in the ICA, and only 5% in the CCA.
Conclusion These data suggest that the different results from recent carotid IMT studies in HIV patients may result from important differences in IMT measurement protocols, some of which exclude the most common sites for plaque formation. A standard procedure should be established to be able to compare the results from different centers. As the majority of disease in our HIV patients was found at the BIF region, we recommend a measurement protocol that includes this specific region.
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