Microembolism Versus Hemodynamic Impairment in Rosary-Like Deep Watershed Infarcts
A Combined Positron Emission Tomography and Transcranial Doppler Study
Background and Purpose—Deep watershed infarcts are frequent in high-grade carotid disease and are thought to result from hemodynamic impairment, particularly when adopting a rosary-like pattern. However, a role for microembolism has also been suggested, though never directly tested. Here, we studied the relationships among microembolic signals (MES) on transcranial Doppler, rosary-like deep watershed infarcts on brain imaging, and cerebral hemodynamic compromise on positron emission tomography (PET), all in severe symptomatic carotid disease. We hypothesized that rosary-like infarcts would be significantly associated with worse hemodynamic status, independent of the presence of MES.
Methods—Sixteen patients with ≥70% carotid disease ipsilateral to recent transient ischemic attack/minor stroke underwent magnetic resonance imaging including diffusion-weighted imaging, 15O-PET, and transcranial Doppler. Mean transit time, a specific marker for hemodynamic impairment, was obtained in the symptomatic and unaffected hemispheres.
Results—Eleven of 16 patients had rosary-like infarcts (Rosary+) and 8 patients had MES. Mean transit time was significantly higher (P=0.008) in Rosary+ patients than in healthy controls (n=10), and prevalence of MES was not different between Rosary+ and Rosary− patients. Contrary to our hypothesis, however, the presence of MES within the Rosary+ subset was associated (P=0.03) with a better hemodynamic status than in their absence, with a significant (P=0.02) negative correlation between mean transit time and rate of MES/h.
Conclusions—Contrary to mainstream understanding, rosary-like infarcts were not independent of presence and rate of MES, suggesting that microembolism plays a role in their pathogenesis, probably in association with hemodynamic impairment. Pending confirmation in a larger sample, these findings have management implications for patients with carotid disease and rosary-like infarcts.
- Received February 2, 2011.
- Accepted May 19, 2011.
- © 2011 American Heart Association, Inc.