Carotid atherosclerosis is a major stroke risk factor and treatment has been predicated on degree of stenosis and ischemia within the ipsilateral territory. Plaque features, such as intraplaque hemorrhage (IPH), may also be important. Plaques with IPH have higher risk of rupture and embolization. IPH can be visualized using high-resolution carotid MRI but clinical characteristics have not been widely studied. In this study, the authors investigated the association between clinical patient characteristics and carotid IPH in setting of recently symptomatic mild to moderate carotid stenosis.
Baseline data from 100 patients were used. These patients were included in the Plaque At RISK (PARISK) study. In this study, inclusion criteria included of ischemic infarct or TIA within 3 months and ipsilateral stenos is of <70%. Risk factors, history, and use of anti-platelet or anti-coagulation were documented and high-resolution MRI of the carotid arteries was performed. IPH on the imaging was defined as a hyperintense signal in the plaque. Two independent observers scored the ipsilateral artery. In total, IPH was present in 45 patients with 31 exclusively on the symptomatic side. There was a higher prevalence of IPH among men and patients with anti-platelet use prior to the index event.
The results in this study suggest that previous use of antiplatelet agents is associated with carotid IPH. This conclusion is troubling as IPH is associated with increased risk of stroke. The counterintuitive conclusion, then, is that antiplatelet agents are associated with increased risk of stroke. However, as the authors point out, the stroke protective effect of antiplatelet agents are relatively small and certainly not full-proof. Patients do have recurrent ischemia following antiplatelet therapy and perhaps IPH can at least be a contributing factor but overall, the clinical significance of IPH remains unclear. This study had relatively low number of patients and there is no follow-up data on patients with IPH to determine if indeed there was a higher stroke recurrence rate in this population (PARISK trial will finish in 2016). Furthermore, antiplatelet use had largest effect on patients with bilateral IPH suggesting such agents cause a systemic effect. Therefore, it is premature to recommend carotid revascularization or antiplatelet discontinuation solely based on the presence of IPH.