Non-Stenotic Carotid Plaques and Rate of DWI-positive MRI in Patients with Lower-Risk Transient or Persistent Minor Neurologic Events: DOUBT Sub Study

Abstract

Background & purpose: Non-stenotic (< 50%) carotid plaques are increasingly recognized as a potential mechanism for ischemic stroke. We assessed the prevalence of such plaques in patients with low-risk neurologic events and evidence of DWI (Diffusion Weighted Imaging)-positive ischemia.

Methods: This is a post-hoc exploratory analysis from the DOUBT study, a prospective, observational, multicenter study of patients with low-risk transient or persistent minor focal neurological symptoms. Patients who had baseline CT angiography (CTA) and an MRI within 8 days of their event were included in the study. We aimed to assess the prevalence of non-stenotic carotid disease in patients with versus without DWI-positive events, and in patients with ipsilateral DWI-positive events. A carotid-level analysis with univariable logistic regression analysis was performed to assess whether any of the assessed plaque features were associated with ipsilateral stroke.

Results: Of the 334 patients (mean age 62.7 years, 50.4% females) with available vascular neuroimaging, 153 (45.9%) had non-stenotic carotid plaques (≤50% stenosis), 174 (52.1%) had no stenosis and 7 (2.1%) patients had >50% stenosis. Of those with non-stenotic carotid plaques, 31/153 (20.3%) had evidence of DWI-positive ischemia, approximately half (15/31; 48.4%) of which was in the territory of the carotid plaque. Amongst patients with DWI-positive ischemia, non-stenotic plaques were significantly more common on the side of DWI-positive lesions [31/49 (63.3%) versus 18/49(36.7%)]. Presence of non-stenotic plaque was a risk marker for DWI-positive events (RR 1.4, 95% CI 1.1-1.8, p 0.012). On matched analysis, non-stenotic plaques were more likely on the side of DWI+ ischemia (odds ratio 1.14, 95% CI 0.36-3.70, McNemar's p value 0.80). Plaque features, including hypodensity, irregularity and greater plaque thickness were significantly associated with a higher likelihood of ipsilateral DWI+ ischemia.

Conclusion: In patients with low-risk transient or persistent neurologic events, non-stenotic carotid plaques are more common in patients with DWI-positive ischemia. Plaque features like hypodense and irregular plaque were more common with DWI-positive changes in the territory of the affected carotid.

Keywords: Carotid plaque; Ischemic stroke; Minor stroke; Non-stenotic carotid plaque; Transient ischemic attack.