International Stroke Conference
Richa Sharma, MD, MPH
This was a very interesting presentation about a stroke etiology that we need to study further, namely symptomatic carotid plaque not resulting in severe stenosis. Currently, there is no compelling evidence for intervention more than medical management. However, the presenter, Vijay Sharma, argued that there are certain characteristics that make a plaque at risk for embolizing even if it does not meet NASCET criteria for severe stenosis. The researchers embarked on identifying imaging characteristics that are associated with a higher risk of embolization of these plaques. They utilized FDG-PET/CT and high-resolution, fat-suppressed MRI as modalities to help different plaque risk. A prospective study included patients with carotid plaque resulting in 50 to 70% stenosis, which was ipsilateral to a recent infarct which occurred within 30 days. These patients underwent FDG-PET to identify any regions of inflammation in the plaque since this may be an initiating event for plaque rupture. They also underwent MRI with high-resolution of the carotid, which yielded a ratio of the T1 hyperintensity of the plaque to the intensity of the ipsilateral sternocleidomastoid. The MRI presumably detects the lipid-rich necrotic core of the plaque and intraplaque hematoma. The endpoint of the study was whether the patients developed a recurrent stroke within a 90-day follow-up period. Interestingly, 11% of these patients suffered from a recurrent ischemic stroke (N=11), and these patients on average had higher T1 carotid-sternocleidomastoid ratios (p<0.0001) and higher SUV values by PET in the carotid plaque (p<0.0001). In multivariable modeling, a higher T1 carotid-sternocleidomastoid ratio and higher SUV values independently predicted recurrent ischemic stroke.
These results are indicating that there is a subset of carotid plaque that results in < 70% stenosis but can still be symptomatic due to intrinsic features of the plaque itself. These plaques can potentially be identified by high resolution MRI and PET scan. These data lend support for potential intervention for secondary stroke prevention after the carotid was recently symptomatic based on a radiographic profile of the plaque. However, it is unclear what type of intervention would be beneficial, such as aggressive medical management, carotid stenting, or carotid endarterectomy.
This study hypothesizes that the mechanism of stroke from severe carotid stenosis is via regional hypoperfusion; however, there are several studies that have shown that there are micro-emboli associated with the plaques, which result in severe stenosis independent of blood velocities.[1, 2] With regards to risk stratification, in some centers, performing a PET/CT and high-resolution MRI may be feasible. However, in the majority of healthcare institutions, these machines may not be available, and even if they were, their output may be difficult to interpret by radiologists who are not specifically trained.
This exciting research generates a hypothesis that there are potentially patients with symptomatic carotid plaques resulting in less than severe stenosis who may benefit from treatment more aggressive than watchful waiting, which is currently the standard of care. Thus, there is a role for a randomized clinical trial aimed at assessing patients after acute stroke putatively due to an ipsilateral symptomatic carotid artery with less than 70% stenosis as the most likely etiology. Since there is currently equipoise, these patients may be selected if they have high-risk plaque determined by radiographic modalities such as high-resolution MRI and PET/CT and randomized to aspirin, dual antiplatelet therapy, stenting, or carotid endarterectomy.
- Ali Zandieh, Ava Liberman, Caitlin Loomis, Jonathan Raser-Schramm, Christina Wilson, Jose Torres, Koto Ishida, Swaroop Pawar, Nichole Gallatti, Melissa Yates, Rebecca Davis and Brett Cucchiara. Frequency of Microemboli in Symptomatic Carotid Stenosis Compared to Carotid Occlusion. Neurology, April 5, 2016 (86).
- T. Zuromskis, R. Wetterholm, J. Lindqvist, S. Svedlund, C. Sixt, D. Jatuzis, D. Obelieniene, K. Caidahl, R. Volkmann. Prevalence of Micro-Emboli in Symptomatic High Grade Carotid Artery Disease: A Transcranial Doppler Study. European Journal of Vascular and Endovascular Surgery, May 2008, Volume 35 (5): 534-540.