Carotid Magnetic Resonance Imaging Depicted Intraplaque Hemorrhage and a High-Risk Cardiovascular and Cerebrovascular Phenotype

Intraplaque hemorrhage is an independent marker of cardiovascular outcomes including stroke and myocardial infarction. Magnetic resonance imaging allows for the direct visualization of intraplaque hemorrhage in the vessel wall of the carotid arteries. This thesis reports data from an institutional magnetic resonance depicted intraplaque hemorrhage experience and clinical trials. The work herein addresses areas particularly sparse on the relationship of intraplaque hemorrhage with cardiovascular risk factors and its potential role in stroke, specifically reporting on i) age-specific sex differences in low-grade stenosis, ii) the role in ipsilateral embolic stroke of undetermined source, and iii) the relationship with a high-risk cardiovascular phenotype. The results in this thesis support our hypotheses that i) males have greater age-specific odds of magnetic resonance imaging depicted carotid intraplaque hemorrhage compared to females, and that with increasing age, the odds of carotid intraplaque hemorrhage in females becomes closer to that of males, ii) patients with embolic stroke of undetermined source have carotid intraplaque hemorrhage ipsilateral to the affected brain, and iii) patients with carotid intraplaque hemorrhage are of a high-cardiovascular risk. The culmination of projects supports the notion that intraplaque hemorrhage is related to a high-risk cardiovascular phenotype and a need for the quantification of intraplaque hemorrhage is realized to further understand the significance of volume of intraplaque hemorrhage, longitudinal changes in intraplaque hemorrhage over time, and relationship of intraplaque hemorrhage with clinical outcomes. The final project in this thesis therefore reports the development of a quantitative imaging analysis protocol, as well as its reliability and agreement with an established standard. The protocol is intended for use on carotid trial imaging data presently being acquired as part of the Canadian Atherosclerosis Imaging Network Project 1.Ph.D