There is increasing recognition that structural factors ' referred to as the 'atrial substrate' such as left atrial (LA) size, LA and LA appendage (LAA) blood flow and stasis, and LA strain, are involved in the development of AF and also related to occurrence of ischemic stroke, subclinical cerebral infarction (SCI), and vascular cognitive impairment, even in the absence of AF. Key observations including the apparent inability of AF rhythm control strategies to lower stroke risk, and lack of a strong temporal association between paroxysmal AF and stroke in patients using prolonged rhythm monitoring, have heightened the search for additional factors that could account for AF development and progression, as well as for stroke, subclinical cerebral infarction, and dementia, beyond the rhythm disturbance itself. In this study, we will build on a cohort of well-characterized older adults who have participated for years in the Multi-Ethnic Study of Atherosclerosis (MESA). We will perform advanced 4D flow cardiac magnetic resonance imaging (MRI) to further characterize the atrial substrate, consistent with the theme of this AHA Center. We will include novel structural and functional MRI measures including atrial 4D blood flow as predictors of AF and also predictors of clinically defined ischemic stroke and SCI detected by brain MRI, even in the absence of documented AF. Aim 1: Determine associations between measures defined by cardiac MRI (LA volume, 4D flow including LA and LAA stasis, and LAA flow velocity) with diagnosed AF in a substudy of participants in the MESA study. We will assess the independent association of the MRI measures with AF, in addition to other clinical factors that are known to be associated with occurrence of AF (e.g., age, obesity, blood pressure). Aim 2: Determine associations between measures defined by cardiac MRI (as above) and SCI on brain MRI, in the presence or absence of AF in a substudy of the MESA cohort. Our hypothesis is that specific MRI measures, in particular LA and LAA stasis, will be associated with prevalence of SCI, even in the absence of prior history of clinical stroke or AF. We also hypothesize that prevalence of SCI will be significantly higher in participants with AF compared to those without AF. Secondary Aim: Evaluate the relationship between measures defined by cardiac MRI (as above) and cognitive impairment in presence or absence of AF and whether SCI (or other brain lesions on MRI) mediate this relationship.
|Program type||Strategically Focused Research Network|
|Effective start/end date||07/01/2018 → 06/30/2022|