Blood Flow Patterns in the Proximal Human Coronary Arteries: Relationship to Atherosclerotic Plaque Occurrence

Atherosclerotic plaques in human coronary arteries are focal manifestations of systemic disease, and biomechanical factors have been hypothesized to contribute to plaque genesis and localization. We developed a computational fluid dynamics (CFD) model of the ascending aorta and proximal sections of the right and left coronary arteries of a normal human subject using computed tomography (CT) and magnetic resonance imaging (MRI) and determined the pulsatile flow field. Results demonstrate that flow patterns in the ascending aorta contribute to a pro-atherosclerotic flow environment, specifically through localization of low and oscillatory wall shear stress in the neighborhood of coronary orifices. Furthermore, these patterns differ in their spatial distribution between right and left coronary arteries. Entrance effects of aortic flow diminish within two vessel diameters. We examined relationships between spatial distributions of wall shear stress and reports of plaque occurrence in the literature. Results indicate low wall shear stress is co-located with increased incidence of lesions, and higher wall shear stresses are associated with lesion-resistant areas. This investigation does not consider plaque progression or advanced lesions, inasmuch as the CFD model was developed from a normal individual and the clinical data used for comparisons were obtained from autopsy specimens of subjects who died from non-cardiovascular causes. The data reported are consistent with the hypothesis that low wall shear stress is associated with the localization of atherosclerotic lesions, and the results demonstrate the importance of aortic flow on flow patterns in the proximal segments of the coronary arteries

Intra-MRI extraction of diagnostic electrocardiograms using carotidal magnetohydrodynamic voltages

The electrocardiogram (ECG) is commonly utilized for patient monitoring during magnetic resonance imaging (MRI) despite known magnetohydrodynamic voltage (VMHD) overlays, which often eclipse the true sinus rhythm and render the signal to be non-diagnostic. This can complicate MRI gating and at-risk patient monitoring, causing alternative low-fidelity signals to become preferred. We aimed to develop a method of isolating the true sinus rhythm from VMHD in order to enable the use of high-fidelity ECGs during MRI procedures. Twelve-lead ECGs were acquired in two healthy volunteers (n = 2) in a 3T MRI scanner, while a secondary single lead monitor was positioned across the left common carotid artery to directly record VMHD while cancelling out the true sinus rhythm. Carotid MHD was used to adaptively train a least mean squares filter to update a 12-lead ECG VMHD template and produce: (1) clean 12-lead ECGs and (2) an accurate stroke volume (SV) estimate. The adaptive filtering method was shown to reduce VMHD in 12-lead ECGs. This was demonstrated by an average cross-correlation of 0.81 across all ECG leads calculated between filtered ECG taken inside the MRI scanner and the ECG taken outside the MRI scanner. Residual noise formed <5% of the R-wave amplitude. Additionally, the method required only a short training phase. A method to extract real sinus rhythm beats from intra-MRI 12-lead ECGs was presented and shown to provide accurate dynamic measurements of induced VMHD using flow in the carotid artery as a source of dynamic feedback

A method to determine regional mechanical left ventricular dyssynchrony based on high temporal resolution short axis SSFP cine images

Left ventricular (LV) mechanical dyssynchrony has been proposed as a parameter to select patients for cardiac resynchronization therapy (CRT) [Bax et al JACC 2005].Several recent studies have shown that placing the LV pacing lead in the most delayed regions yields a better response to CRT [Ansalone et al JACC 2002]. However, most imaging-based methods assess global LV dyssynchrony providing a single value for the entire LV. Regional maps of LV dyssynchrony are required for planning LV lead placement. The objective of this study was to develop a method to create a map of regional left ventricular mechanical dyssynchrony based on short-axis SSFP cine images

Characterization of the size and location of dyssynchronous regions in patients undergoing CRT

The amount and location of left ventricular (LV) mechanical dyssynchrony affects an individual’s ability to respond positively to cardiac resynchronization therapy (CRT) [Bax et al JACC 2005]. By using high temporal resolution short-axis cines, it is possible to derive radial motion curves throughout the LV. These radial motion curves can be used to create maps showing dyssynchronous regions in patients enrolled for CRT. The objective of this study was to characterize the size and location of areas of mechanical dyssynchrony in patients scheduled for CRT by comparing their radial wall motion curves to radial motion curves from normal subjects

Two Stories of Distrust in America

This report presents the findings of multiple largescale national surveys of Americans about the state of trust in America. It finds significant evidence for deep and widespread levels of distrust across society. Among national institutions—government, media, and business— More in Common tested in December 2020, none earned the trust of a majority of Americans. Levels of interpersonal trust were similarly concerning, with a majority of Americans saying you "can't be too careful in dealing with other people" and one in three Americans saying there is no community outside of friends and family where they feel a strong sense of belonging.These topline findings paint a stark picture. If we probe deeper, however, we discern important distinctions in the probable drivers of distrust. Understanding these nuances does not make the overall picture brighter, but it can illuminate potential solutions and pathways to renew trust. Two distinctive "stories" of distrust are evident in the data—an ideological 'us versus them' distrust and a 'social distrust' that tracks interactions and feelings of belonging, dignity, and equality. These two stories are not fully comprehensive of the myriad drivers of distrust in America, but they capture distinctive ways distrust relates to ideology and experience. It is a challenging moment to generate broader consensus that building trust should be a national priority. This report focuses on how drivers of distrust vary among Americans as these distinctions may provide new opportunities for such efforts