Carotid Revascularized Endarterectomy vs. Stenting Trial
The Carotid Revascularized Endarterectomy vs. Stenting Trial study (CREST) will compare carotid endarterectomy, a common operation to remove plaque causing narrowing in the carotid arteries that supply blood flow to the brain, to a study procedure called carotid artery stenting, where a small spring-like metal device is placed in the area of narrowing to open the vessel lumen. Patients who agree to participate in the CREST study will receive either carotid endarterectomy or carotid artery stenting to treat the area of narrowing in their carotid arteries.
Researchers anticipate this trial will consist of 17,000 ultrasound exams, including certification, pre-procedure and follow-up exams. Results from these exams will provide vital information of the durability of endarterectomy vs. carotid stenting.
Clinical Trials
Neo-Vascular Inflation Trial
We are testing a theory to identify the “vulnerable plaque.” We believe that such plaques contain large neovascular volumes consisting of arterioles, capillaries, venules and shunts supplied by the vasa vasorum. We believe that the normal pressure in the vasa vasorum supplying those intraplaque neovessels is below systolic pressure but the relationship to diastolic pressure is unknown. Because the Bernoulli pressure depression modulates the intraluminal pressure compressing the stenotic plaque during the high velocities of systole, the pressure difference between the intraplaque neovessels and the lumen may favor plaque expansion during systole or during diastole. According to our hypothesis, plaque expansion would be favored during systolic velocities above 400 cm/sec when the Bernoulli pressure depression exceeds 64 mmHg.
We have modified a conventional clinical duplex Doppler ultrasound system to perform both tissue strain imaging of the atherosclerotic plaque and vector Doppler velocimetry. With this instrument we can measure the intrastenotic velocity without Doppler angle correction and measure the plaque strain waveform with ECG timing registration. We are searching for strain plaque thickness waveforms that are not coherent with diametric artery waveforms, and specifically that show plaque thickening during high velocity systolic velocity peaks. We do not know at what pressures the unusual waveforms will occur, so we also want to recruit patients with lower grades of stenosis. We hope to use the strain data from those patients to deduce the pressure in the vasa vasorum.
This study is funded by NIH/NIBIB (National Institute of Biomedical Imaging and BioEngineering). There would be no charge for this study as it is fully funded by the NIH.
We are seeking people with moderate and high grade carotid and femoral artery stenoses.
There are no medical exclusions from the study except those that apply for any noninvasive vascular testing.
Velocity Variability
Ultrasonic Doppler examination with spectral waveform has been used for the classification and surveillance of carotid artery stenosis for more than 25 years. Progression/regression between examinations can be identified with confidence if the velocity measurements change by more than two standard deviations of the repeat measurement difference. Peak systolic velocity and end diastolic velocity measurements were repeated in 50 carotid examinations to measure the measurement variation. Results indicate that differences between sonographers are greater than the differences between ultrasound scan heads or Doppler ultrasound frequencies.
Stent Visualization Study
Ultrasound images of carotid arteries provide anatomic information about the arterial wall, atherosclerotic plaques and implants. To treat carotid stenosis, both endarterectomy and stents are used. The purpose of this study is to analyze 2-dimensional ultrasound B-mode images of the common carotid artery and internal carotid artery to determine whether stents can be reliably visualized and whether the ends can be reliably located. Focal zones, depth of the vessel walls and lumen characteristics are factors which affect the ability to visualize a stent or not. Stents have a characteristic uniform “dot” pattern along the superficial and deep walls of the artery. A similar pattern for uniform sutures can often be seen along the superficial wall in endarterectomy cases. The study will measure the inter-observer variability in stent visualization.