Browsing by Subject "atrial fibrillation"

Now showing 1 - 4 of 4
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    Arrhythmia Management: Control of Alternans & VIEgram for analysis and visualization of electrograms to aid Atrial Fibrillation Treatment
    (2020-07) Thakare, Sanket Yograj
    Arrhythmia management - prediction, prevention and control of arrhythmias, is difficult mainly due to its spatiotemporal complexity and the poor understanding of mechanisms causing them. Therapies for managing arrhythmias can be focused at two macroscopic levels, namely cellular level and tissue/organ level. At cellular level, arrhythmias can be prevented by reviving the abnormal electrophysiological function of myocytes and thus preventing it from getting evolved into dangerous reentrant arrhythmias at the tissue level. For example, ventricular arrhythmias can be prevented by employing a pacing protocol to control cardiac alternans at cellular level. Whereas at tissue/organ level, the arrhythmia which is already present can be controlled. For example, the catheter ablation procedure, a procedure where tissue causing abnormal electrical activity is ablated, is used to treat AF on an organ level to return the heart back to its normal sinus rhythm. Also, at an organ level we can deal with the pre-existing factors contributing to arrhythmogenesis. Furthermore, a visualization of all the manifestations of arrhythmias on an organ level (3D models of a patient's heart) will not only help in understanding the complex spatiotemporal mechanisms behind them but will also facilitate the development of new techniques to treat them.
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    Atrial Fibrillation In Older Adults: Relation To Proteomics, Risk Prediction, And Urban/Rural Disparities In Treatment And Outcomes
    (2020-07) Norby, Faye
    Atrial fibrillation (AF), a cardiac arrhythmia, is a major public health problem. AF is largely a disease of advancing age and contributes to other cardiovascular complications. Identification of novel protein biomarkers could advance understanding of AF mechanisms and may improve the prediction of incident AF. Additionally, it is unknown if disparities exist in AF treatment and outcomes in rural versus urban areas of the US. For manuscripts 1 and 2, we used data from the Atherosclerosis Risk in Communities (ARIC) study, a cohort of older-aged adults in the US. For manuscripts 3 and 4, we used a sample of Medicare beneficiaries enrolled from 2011-2016 with residential zip code categorized into 4 rural/urban areas. In the first manuscript, we examined the association of plasma proteins and identified 40 novel protein biomarkers associated with incident AF. These biomarkers provide insight into mechanistic pathways of AF development. In the second manuscript, we derived and validated a series of 5-year incident AF prediction models that are better targeted and calibrated to older populations. Incorporating biomarkers, including proteomics data, into the models improved AF risk prediction. In the third and fourth manuscripts, we examined the initiation of anticoagulation use and compared the risks of subsequent stroke, heart failure, myocardial infarction, and mortality in newly-diagnosed AF patients in rural versus urban areas. Patients in rural areas were more likely to initiate anticoagulant treatment; however, they were less likely to initiate a newer class of anticoagulants compared to those in urban areas. Those in rural areas had modestly higher risk of cardiovascular outcomes and mortality compared to those in urban areas. Proteomics aids in understanding AF mechanisms and improves risk prediction. Future research should validate our prediction models, develop meaningful ways to incorporate protein biomarkers in clinical practice, and focus on improving AF treatment in rural areas.
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    Refining Prediction Of Atrial Fibrillation-Related Stroke Using The P2-Cha2Ds2-Vasc Score
    (2018-02) Maheshwari, Ankit
    Introduction: In people with atrial fibrillation (AF), periods of sinus rhythm present an opportunity to detect pro-thrombotic atrial remodeling through measurement of P-wave indices (PWIs)—prolonged P-wave duration, abnormal P-wave axis, advanced inter-atrial block, and abnormal P-wave terminal force in lead V1. We hypothesized that addition of PWIs to the CHA2DS2-VASc score would improve its ability to predict AF-related ischemic stroke. Methods: We included 2229 Atherosclerosis Risk in Communities (ARIC) study and 700 Multi-Ethnic Study of Atherosclerosis (MESA) participants with incident AF and without anticoagulant use within 1 year of AF diagnosis. PWIs were obtained from study visit ECGs before development of AF. AF was ascertained using study visit ECGs and hospital records. Ischemic stroke cases were based on physician adjudication of hospital records. We used Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (95% CIs) of PWIs for ischemic stroke. Improvement in 1-year stroke prediction was assessed by C-statistic, categorical net reclassification improvement (NRI), and relative integrated discrimination improvement (IDI). Results: Abnormal P-wave axis was the only PWI associated with increased ischemic stroke risk (HR, 1.84; 95% CI, 1.33-2.55) independent of CHA2DS2-VASc variables and that resulted in meaningful improvement in stroke prediction. The beta estimate was approximately twice that of the CHA2DS2-VASc variables, thus abnormal P-wave axis was assigned 2 points to create the P2-CHA2DS2-VASc score. This improved the C-statistic (95% CI) from 0.60 (0.51-0.69) to 0.67 (0.60-0.75) in ARIC and 0.68 (0.52-0.84) to 0.75 (0.60-0.91) in MESA (validation cohort). In ARIC and MESA, the categorical NRI (95% CI) were 0.25 (0.13-0.39) and 0.51 (0.18-0.86), respectively, and the relative IDI (95% CI) were 1.19 (0.96-1.44) and 0.82 (0.36-1.39), respectively. Conclusions: Abnormal P-wave axis—an ECG correlate of left atrial abnormality— improves ischemic stroke prediction in AF. Compared with CHA2DS2-VASc, the P2-CHA2DS2-VASc is a better prediction tool for AF-related ischemic stroke.
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    Studies of Ablation Complications During the Treatment of Atrial Fibrillation
    (2015-09) Quallich, Stephen
    The complication rates during transcatheter cardiac ablation procedures remain concerning. The transseptal puncture procedure, the relative navigation of catheters to difficult anatomies, and the application of ablation modalities to ensure transmural lesions are all primary areas where therapeutic complications may arise. In my thesis projects, our work targeted these three areas while also specifically considering a means to reduce such complications. Specifically, iatrogenic atrial septal defect formation was investigated by assessing the biomechanical changes of the atrial septum that may occur during transseptal punctures and the further injury the septum may incur during subsequent catheter manipulations. Furthermore, the contact forces required to perforate the atria were characterized in order to determine the boundary force conditions associated with both catheter navigation and ablation energy application. In addition, the biophysical changes manifested during and following the application of ablation modalities, as well as, the parameters that facilitate the development of explosive steam pops were investigated. Finally, the cryothermal tolerances of cardiac tissues were identified to aid in reducing collateral injury and to optimize dose delivery. The insights gained from these translational studies will help define various parameters and boundary conditions that should improve both the safeties and efficacies of clinical cardiac ablation procedures. In addition to characterizing these factors, the direct visualization of such complications provides invaluable insights to engineers as well as clinicians.