Carotid Revascularization and Medical Management for Asymptomatic Carotid Stenosis Trial - Hemodynamics
We aim to determine whether cognitive impairment attributable to cerebral hemodynamic impairment in patients with high-grade asymptomatic carotid artery stenosis is reversible with restoration of flow. To accomplish this aim CREST-H will add on to the NINDS-sponsored CREST-2 trial (parallel, outcome-blinded Phase 3 clinical trials for patients with asymptomatic high-grade carotid artery stenosis which will compare carotid endarterectomy plus intensive medical management (IMM) versus IMM alone (n=1,240), and carotid artery stenting plus IMM versus IMM alone (n=1,240) to prevent stroke and death). CREST-H addresses the intriguing question of whether cognitive impairment can be reversed when it arises from abnormal cerebral hemodynamic perfusion in a hemodynamically impaired subset of the CREST-2 -randomized patients. We will enroll 500 patients from CREST-2, all of whom receive cognitive assessments at baseline and yearly thereafter. We anticipate identifying 100 patients with hemodynamic impairment as measured by an inter-hemispheral MRI perfusion "time to peak" (TTP) delay on the side of stenosis. Among those who are found to be hemodynamically impaired and have baseline cognitive impairment, the cognitive batteries at baseline and at 1 year will determine if those with flow failure who are randomized to a revascularization arm in CREST-2 will have better cognitive outcomes than those in the medical-only arm compared with this treatment difference for those who have no flow failure. We hypothesize that hemodynamically significant "asymptomatic" carotid disease may represent one of the few examples of treatable causes of cognitive impairment. If cognitive decline can be reversed in these patients, then we will have established a new indication for carotid revascularization independent of the risk of recurrent stroke.
CREST-H will use existing CREST-2 cognitive assessment infrastructure -- the Survey Research Unit at University of Alabama Birmingham. Added to the current CREST-2 battery is the Oral Trail Making A & B as an additional measure of executive function, which will be administered to every CREST-2 patient, regardless of their participation in CREST-H. Cognitive assessments in CREST-H must take place prior to revascularization or within two weeks after assignment to medical therapy alone. Testing in CREST-2 is repeated at 44 days, and every year thereafter up to 4 years. At each test interval, a composite (mean) Z-score is derived from published normative samples for each test outcome. The CREST-H primary outcome will be at 1 year in which the change in the composite Z-score from baseline will be calculated. Covariates will include age, education and depression. The test battery will be administered the same way for all CREST-2 and CREST-H enrolled patients. The cognitive domains being assessed in CREST-2/H are entirely consistent with those encompassed within the NINDS Common Data Elements (CDE).
Multimodal MRI, including routine parenchymal sequences and PWI utilizing dynamic susceptibility contrast technique, will be acquired at each participating CREST H site. Imaging will take place within 14 days after CREST-H enrollment and prior to any CREST 2 intervention for those randomized to CEA or CAS.
Standardized contrast agent injection protocol, appropriate preparation, and IV setup is used to ensure good scan quality. An antecubital vein IV catheter of 18-20 gauge is required. A test injection will be performed with approximately 10 ml of normal saline solution.
MRI image acquisition DWI/ADC (b=0, 1000 s/mm2 applied in each of three principal gradient directions), FLAIR, high-resolution T1, and GRE sequences will be acquired on 1.5-3.0 T scanners equipped with echo-planar imaging capability, using standard clinical protocols at participating CREST-H sites Total scanning time will be approximately 40 minutes. PWI acquisition protocol will be standardized across all CREST-H sites, using sequential T2*-weighted (gradient echo) EPI time sequence scanning. A modified 2-phase contrast injection scheme will be used to perform CEMRA and DSC perfusion imaging, without need for additional contrast.
Perfusion imaging analysis.
PWI source images will be sent to the core laboratory at UCLA and processed with the OleaSphere software platform, using deconvolution of tissue and arterial signals in an expedited manner, yielding standardized data regardless of the acquisition system at each site. Hemodynamic impairment is defined as TTP >2 sec in the middle cerebral artery and anterior cerebral artery territories of the ipsilateral hemisphere to the carotid lesion compared with the same territory in the opposite hemisphere. Longitudinal analyses will investigate the change in the TTP >2 sec lesion at 1 year comparing the revascularization versus the medical only arm. Continuous values for this volumetric change will be used to calculate the correlation between degree of cognitive change and degree of perfusion change. The continuous Tmax variable, as well as standard perfusion parameters of CBV, CBF Tmax, and MTT will be analyzed on the serial imaging studies in each case. Co-registered, voxel-based changes in serial perfusion values will also be explored with multiparametric (e.g. CBV, CBF, Tmax, MTT) values.
Image de-identification and blinding.
All MR image files will be de-identified under the supervision of an unblinded Investigator (UI) at each institution and uploaded to the CREST-2 Imaging Core site at U Maryland. In order to assure that the PWI scan information from CREST-H does not compromise the integrity of the parent trial, the results of the perfusion scan will be blinded to the investigator team.
Participating sites will utilize the same file transfer protocol (ftp) to transfer images to U Maryland for CREST-H as is already established for CREST-2. The images will be stored in a HIPAA-compliant, firewall protected server within the U Maryland archival system. A CREST-2 dedicated ftp linkage between the VIC at U Maryland and UCLA; and the VIC at U Maryland and Mayo-Rochester will be utilized to make each perfusion image file available for download by UCLA (Liebeskind lab) and each structural image (DWI, FLAIR, GRE) by Mayo-Rochester (Huston lab).
MRI structural analysis.
Structural MRI analysis at Mayo-Rochester will utilize NIH NINDS Common Data Elements developed for the CREST-2 grant. The following definitions apply:
1. silent infarct --- non-confluent hyperintense lesion >1mm on FLAIR sequence on 1-year MRI not present on baseline FLAIR MRI.
2. Cerebral microbleed - hypointense 1-2mm non-confluent lesion on baseline GRE sequence.
3. WMH volume -- White matter hyperintensity volume refers to confluent periventricular high intensity lesions on FLAIR imaging, and will be derived using an automated T2 WMH quantification at the Huston lab.
Data from image analysis (TTP delay, WMHV, silent infarct count, microbleed count) performed at UCLA and Mayo-Rochester will be entered electronically on CREST-H data forms via the CREST-2 SDCC website at UAB, where it will be stored on a separate webpage linked to the rest of the CREST-2 data, including baseline and yearly cognitive assessments. The electronic data entry system (eDES) for CREST-2 is a mature system, successfully reviewed by FDA audit in other studies, providing standard approaches for entry-confirmation-locking of data forms, and supporting range and validity checking for data provided.
Specific Aim 1. To determine whether cognition can be improved by revascularization among a subset of CREST-2 patients with hemodynamic impairment at baseline.
The primary hypothesis is to assess if the magnitude of the treatment differences (revascularization versus medical management alone) differs between those with flow failure compared to those without flow failure using the Z-scored cognitive outcomes (C0, C(1). That is, the primary hypothesis is an interaction hypothesis that will be assessed using linear regression, specifically: (C1 - C0) = β0 + β1T + β2F + β3TF + β4C0 + (other covariates), where C1 is the cognitive z-score at year 1, C0 the cognitive z-score at baseline, T the treatment indicator variable, F the flow failure indicator variable, and βi the regression parameters to be estimated. The parameter of interest for the primary hypothesis is then β3 that would assess if the magnitude of treatment difference in the change in cognitive score between baseline and 1-year is similar for those with versus without flow failure.
Secondary Aims: To determine if the number of silent infarcts and white matter hyperintensity volume at 1 year is different between the revascularization and the medical-only arms.
For the secondary aims we will calculate the number of new silent cerebral infarctions occurring over the first year, and the change in the WMH volume. The approach for analysis of the number of new silent infarcts will depend on the average number and distribution of the number of new infarcts. The analytic approach will be linear regression if the number of new infarcts is large (considered more likely the case), or Poisson Regression if the number is smaller (considered less likely the case). The analysis of the change in WMH will use a linear regression approach.
35 Years to 86 Years
Accepting Healthy Volunteers?
- Enrolled and randomized into CREST-2 (parent study)
- Inclusion criteria for CREST-2
- age 35-86
Exclusion Criteria (in addition to the exclusion criteria for CREST-2):
- unable to undergo MRI (e.g. metal in body, pacemaker)
- known allergy gadolinium contrast dye
- pre-existing diagnosis of dementia
- contralateral ICA stenosis >70% by MRA, CTA or Doppler ultrasound
- history of severe head trauma
- major depression
- education less than 8 years