Natural History of Carotid Plaque as Determined by 3D Ultrasound

Overview

This proposed follow-up study aims to recruit participants from the original BioImage cohort for a one-time follow-up examination. The repeat ultrasound scan of the carotid arteries will provide information on the natural history of carotid atherosclerosis and factors that contribute to plaque progression. Renewal of the HIPAA authorization will also be sought for 5 years to continue to monitor claims and other information for major cardiovascular events, other outcomes and healthcare utilization.

The design and objectives of the BioImage study (NCT00738725) have been published in detail. In brief, the BioImage study is investigating whether imaging of target arteries for subclinical atherosclerosis and measurement of ABI and circulating biomarkers add to the predictive value of traditional risk factor scoring systems, namely, the Framingham Risk Score. Enrollment in the BioImage study (January 2008 to June 2009) resulted in inclusion of 7,687 asymptomatic Americans ages 55 to 80 years from the Humana Health System resident in Chicago, Illinois, or Fort Lauderdale, Florida. Of these, 6,104 entered the imaging arm of the study. Analysis of the BioImage study cross- sectional baseline findings has yielded important novel findings related to presence and severity of subclinical atherosclerosis and the role of markers of subclinical disease to identify those at elevated risk for near-term atherothrombotic events. One of the striking novel findings in the BioImage study was the prevalence of subclinical atherosclerotic disease in the carotid arteries as determined by a novel 3D ultrasound method. 3D carotid imaging was used to identify lesions located in the cervical part of the common carotid arteries (CCA) and internal carotid artery. 3D carotid imaging was initially performed using a high- resolution, linear array 2-dimensional transducer and scanning the artery in cross-section, slowly moving the transducer manually in the cranial direction from the proximal CCA into the distal internal carotid artery (i.e., from the clavicle to jawbone). The resulting 10-s digital video clip of this "manual 3D" cross-sectional sweep was examined in the core ultrasound laboratory for the presence and quantification of plaque. In the second phase of the study an electromechanical transducer was used to accomplish a similar sweep, replacing the manual sweep with a controlled movement of the transducer. This ultrasound technique identified carotid plaques in 78% of cases. Carotid plaque burden was found to correlate stronger with CACS (chi-square 450, p \< 0.0001) than did cIMT (chi-square 24, p \< 0.0001)15. Analyses have indicated that subclinical atherosclerosis as determined by 3D ultrasound is an important risk factor with marked incremental value over conventional risk-factor based scores such as the Framingham Risk Score.