Investigating a Novel Activation-Repolarisation Time Metric to Predict Localised Vulnerability to Reentry Using Computational Modelling.

Exit sites associated with scar-related reentrant arrhythmias represent important targets for catheter ablation therapy. However, their accurate location in a safe and robust manner remains a significant clinical challenge. We recently proposed a novel quantitative metric (termed the Reentry Vulnerability Index, RVI) to determine the difference between activation and repolarisation intervals measured from pairs of spatial locations during premature stimulation to accurately locate the critical site of reentry formation. In the clinic, the method showed potential to identify regions of low RVI corresponding to areas vulnerable to reentry, subsequently identified as ventricular tachycardia (VT) circuit exit sites. Here, we perform an in silico investigation of the RVI metric in order to aid the acquisition and interpretation of RVI maps and optimise its future usage within the clinic. Within idealised 2D sheet models we show that the RVI produces lower values under correspondingly more arrhythmogenic conditions, with even low resolution (8 mm electrode separation) recordings still able to locate vulnerable regions. When applied to models of infarct scars, the surface RVI maps successfully identified exit sites of the reentrant circuit, even in scenarios where the scar was wholly intramural. Within highly complex infarct scar anatomies with multiple reentrant pathways, the identified exit sites were dependent upon the specific pacing location used to compute the endocardial RVI maps. However, simulated ablation of these sites successfully prevented the reentry re-initiation. We conclude that endocardial surface RVI maps are able to successfully locate regions vulnerable to reentry corresponding to critical exit sites during sustained scar-related VT. The method is robust against highly complex and intramural scar anatomies and low resolution clinical data acquisition. Optimal location of all relevant sites requires RVI maps to be computed from multiple pacing locations.

An activation-repolarization time metric to predict localized regions of high susceptibility to reentry.

BACKGROUND: Initiation of reentrant ventricular tachycardia (VT) involves complex interactions between front and tail of the activation wave. Recent experimental work has identified the time interval between S2 repolarization proximal to a line of functional block and S2 activation at the adjacent distal side as a critical determinant of reentry. OBJECTIVES: We hypothesized that (1) an algorithm could be developed to generate a spatial map of this interval ("reentry vulnerability index" [RVI]), (2) this would accurately identify a site of reentry without the need to actually induce the arrhythmia, and (3) it would be possible to generate an RVI map in patients during routine clinical procedures. METHODS: An algorithm was developed that calculated RVI between all pairs of electrodes within a given radius. RESULTS: The algorithm successfully identified the region with increased susceptibility to reentry in an established Langendorff pig heart model and the site of reentry and rotor formation in an optically mapped sheep ventricular preparation and computational simulations. The feasibility of RVI mapping was evaluated during a clinical procedure by coregistering with cardiac anatomy and physiology of a patient undergoing VT ablation. CONCLUSION: We developed an algorithm to calculate a reentry vulnerability index from intervals between local repolarization and activation. The algorithm accurately identified the region of reentry in 2 animal models of functional reentry. The clinical application was demonstrated in a patient with VT and identified the area of reentry without the need of inducing the arrhythmia.

Challenges to recruitment and retention of African Americans in the gene-environment trial of response to dietary interventions (GET READI) for heart health.

In this paper, challenges to recruiting African Americans specifically for a dietary feeding trial are examined, learning experiences gained and suggestions to overcome these challenges in future trials are discussed. A total of 333 individuals were randomized in the trial and 234 (167 sibling pairs and 67 parents/siblings) completed the dietary intervention and required DNA blood sampling for genetic analysis. The trial used multiple strategies for recruitment. Hand distributed letters and flyers through mass distribution at various churches resulted in the largest number (n = 153, 46%) of African Americans in the trial. Word of mouth accounted for the second largest number (n = 120, 36%) and included prior study participants. These two recruitment sources represented 82% (n = 273) of the total number of individuals randomized in GET READI. The remaining 18% (n = 60) consisted of a combination of sources including printed message on check stubs, newspaper articles, radio and TV appearances, screening events and presentations. Though challenging, the recruitment efforts for GET READI produced a significant number of African American participants despite the inability to complete the trial as planned because of low recruitment yields. Nevertheless, the recruitment process produced substantial numbers that successfully completed all study requirements.

The Healthy Connections project: a community-based participatory research project involving women at risk for diabetes and hypertension.

BACKGROUND: The Healthy Connections (HC) project was a community health worker (CHW) intervention that built upon existing social networks to encourage African American and Latina women to obtain screening for type 2 diabetes and hypertension. OBJECTIVES: This community-based participatory research (CBPR) project involved identifying and training CHWs, known as HC Advocates (HCAs). The HCAs provided screening through House Parties and shared health information and practical support with members of their social networks and broader networks of individuals. METHODS: Data collection methods included project documentation, participant observation, group interviews, closed-ended surveys, and written examinations to ensure HCAs had the required knowledge and skills to perform their roles. Data collection and analysis incorporated both qualitative and quantitative methods, and used a formative approach that integrated results from key aspects of the project into ongoing decision-making and project activities. RESULTS: Eight community residents completed training and the required exams to become HCAs. Together, they conducted 124 House Parties, screened 1,428 individuals for high blood pressure and glucose levels, and shared health information with those individuals as well as 218 additional members of HCAs informal social networks. Of those who attended the House Parties, 93% were African American, 4% Latina, 2% non-Hispanics whites, and 1% other racial and ethnic groups. CONCLUSION: The HC project demonstrated the potential for using a CBPR approach to develop, implement, and evaluate a CHW intervention designed to reach African American and Latina women at high risk for hypertension and type 2 diabetes. Participation from relevant communities in the design of the intervention and evaluation, with particular attention to recruitment and retention of representatives from communities who face challenges accessing health care, can help to increase involvement of community residents in screening and educational programs aimed at addressing disparities in type 2 diabetes and hypertension.

Air pollution-associated changes in lung function among asthmatic children in Detroit.

In a longitudinal cohort study of primary-school-age children with asthma in Detroit, Michigan, we examined relationships between lung function and ambient levels of particulate matter < or = 10 microm and < or = 2.5 microm in diameter (PM10 and PM2.5) and ozone at varying lag intervals using generalized estimating equations. Models considered effect modification by maintenance corticosteroid (CS) use and by the presence of an upper respiratory infection (URI) as recorded in a daily diary among 86 children who participated in six 2-week seasonal assessments from winter 2001 through spring 2002. Participants were predominantly African American from families with low income, and > 75% were categorized as having persistent asthma. In both single-pollutant and two-pollutant models, many regressions demonstrated associations between higher exposure to ambient pollutants and poorer lung function (increased diurnal variability and decreased lowest daily values for forced expiratory volume in 1 sec) among children using CSs but not among those not using CSs, and among children reporting URI symptoms but not among those who did not report URIs. Our findings suggest that levels of air pollutants in Detroit, which are above the current National Ambient Air Quality Standards, adversely affect lung function of susceptible asthmatic children.

Community involvement in the conduct of a health education intervention and research project: Community Action Against Asthma.

There is a need for more guidance on how to implement community-based participatory research, particularly on the roles of community members, throughout the process. This article focuses on how a Steering Committee, composed of representatives from community-based organizations, a local health department, an integrated health care system, and academia from the University of Michigan, participated in the design and implementation of a children's asthma study in Detroit, Michigan: Community Action Against Asthma. In addition, this article focuses on the role of community members as data collectors, examining a variety of sophisticated data collection roles. A description and analysis of how community members shaped and participated in the project, the lessons learned, and recommendations for practitioners are also presented.