Background & purpose: 
Intraplaque hemorrhage (IPH) is an important feature of plaque vulnerability. Patients with a history of transient ischemic attack (TIA) or acute ischemic stroke (AIS) are treated with platelet aggregation inhibitors to prevent secondary cardiovascular events. Although antiplatelet medication is effective in reduction of clot formation, it also has adverse effects. This longitudinal study is the first to investigates the effect of antiplatelet agents on the prevalence of IPH in patients with a recent symptomatic stenosis of the internal carotid artery.

Methods: 
63 patients with recent TIA or AIS and an ipsilateral 30-69%  carotid artery stenosis underwent carotid MRI plaque imaging at baseline and after two years of follow-up. Presence of IPH was assessed for both the ipsi- and contra-lateral carotid artery. Medication use before and after the index event and after at 2-years follow-up was collected. A uni- and multivariate binary logistic regression model was used to investigate the association between newly developed IPH and previous use of antiplatelet agents. 

Results: 
A significant higher prevalence of any IPH was found two years after the index event (43% vs. 56%; p = 0.008) compared to the IPH rate at baseline. Patients who were on antiplatelet agents since the index event (n=44) showed a significantly higher prevalence of IPH (39.% vs. 52%, p=0.031) at 2-years follow-up. On the contrary, patients already using on antiplatelet agents before the index event (n=19) did not show an increase of IPH (52.6% vs. 63.2%, p = 0.50) at follow-up. 

Conclusions: 
Patients with recent TIA or stroke, and a ipsilateral 30-69% carotid stenosis, who started antiplatelet therapy after the index event, show a significant increase in IPH two years after inclusion, while no significant changes in IPH status were found in the patients that already use antiplatelet therapy before the index event. Antiplatelet agents started immediately after an event in patients with carotid stenosis may increase the incidence of IPH in the carotid atherosclerotic plaque.

05 - START OF ANTIPLATELET THERAPY INCREASES THE PREVALENCE OF INTRAPLAQUE HEMORRHAGE IN PATIENTS WITH ADVANCED CAROTID ARTERY LESIONS: A LONGITUDINAL MR IMAGING STUDY