scholarly journals Competitive Drivers of Atrial Fibrillation: The Interplay Between Focal Drivers and Multiwavelet Reentry

2021 ◽  
Vol 12 ◽  
Author(s):  
Richard T. Carrick ◽  
Bryce E. Benson ◽  
Oliver R. J. Bates ◽  
Peter S. Spector
Keyword(s):  
Atrial Fibrillation ◽  
Propagation Model ◽  
Surrounding Tissue ◽  
External Boundary ◽  
Tissue Properties ◽  
Excitable Gap ◽  
The Impact ◽  
The Relationship ◽  
Human Atrial Fibrillation

BackgroundThere is debate whether human atrial fibrillation is driven by focal drivers or multiwavelet reentry. We propose that the changing activation sequences surrounding a focal driver can at times self-sustain in the absence of that driver. Further, the relationship between focal drivers and surrounding chaotic activation is bidirectional; focal drivers can generate chaotic activation, which may affect the dynamics of focal drivers.Methods and ResultsIn a propagation model, we generated tissues that support structural micro-reentry and moving functional reentrant circuits. We qualitatively assessed (1) the tissue’s ability to support self-sustaining fibrillation after elimination of the focal driver, (2) the impact that structural-reentrant substrate has on the duration of fibrillation, the impact that micro-reentrant (3) frequency, (4) excitable gap, and (5) exposure to surrounding fibrillation have on micro-reentry in the setting of chaotic activation, and finally the likelihood fibrillation will end in structural reentry based on (6) the distance between and (7) the relative lengths of an ablated tissue’s inner and outer boundaries. We found (1) focal drivers produced chaotic activation when waves encountered heterogeneous refractoriness; chaotic activation could then repeatedly initiate and terminate micro-reentry. Perpetuation of fibrillation following elimination of micro-reentry was predicted by tissue properties. (2) Duration of fibrillation was increased by the presence of a structural micro-reentrant substrate only when surrounding tissue had a low propensity to support self-sustaining chaotic activation. Likelihood of micro-reentry around the structural reentrant substrate increased as (3) the frequency of structural reentry increased relative to the frequency of fibrillation in the surrounding tissue, (4) the excitable gap of micro-reentry increased, and (5) the exposure of the structural circuit to the surrounding tissue decreased. Likelihood of organized tachycardia following termination of fibrillation increased with (6) decreasing distance and (7) disparity of size between focal obstacle and external boundary.ConclusionFocal drivers such as structural micro-reentry and the chaotic activation they produce are continuously interacting with one another. In order to accurately describe cardiac tissue’s propensity to support fibrillation, the relative characteristics of both stationary and moving drivers must be taken into account.

scholarly journals Increased left atrial pressure in non-heart failure patients with subclinical hypothyroidism and atrial fibrillation

2016 ◽  
Vol 5 (3) ◽  
pp. 101-106 ◽  
Author(s):  
Akinori Sairaku ◽  
Yukiko Nakano ◽  
Yuko Uchimura ◽  
Takehito Tokuyama ◽  
Hiroshi Kawazoe ◽  
...  
Keyword(s):  
Heart Failure ◽  
Atrial Fibrillation ◽  
Subclinical Hypothyroidism ◽  
Left Atrial ◽  
Structural Heart Disease ◽  
Thyroid Stimulating Hormone ◽  
The Mean ◽  
V Wave ◽  
The Impact ◽  
The Relationship

Background The impact of subclinical hypothyroidism on the cardiovascular risk is still debated. We aimed to measure the relationship between subclinical hypothyroidism and the left atrial (LA) pressure. Methods The LA pressures and thyroid function were measured in consecutive patients undergoing atrial fibrillation (AF) ablation, who did not have any known heart failure, structural heart disease, or overt thyroid disease. Results Subclinical hypothyroidism (4.5≤ thyroid-stimulating hormone <19.9 mIU/L) was present in 61 (13.0%) of the 471 patients included. More subclinical hypothyroidism patients than euthyroid patients (55.7% vs 40.2%; P=0.04).’euthyroid patients had persistent or long-standing persistent AF (55.7% vs 40.2%; P = 0.04). The mean LA pressure (10.9 ± 4.7 vs 9.1 ± 4.3 mmHg; P = 0.002) and LA V-wave pressure (17.4 ± 6.5 vs 14.3 ± 5.9 mmHg; P < 0.001) were, respectively, higher in the patients with subclinical hypothyroidism than in the euthyroid patients. After an adjustment for potential confounders, the LA pressures remained significantly higher in the subclinical hypothyroidism patients. A multiple logistic regression model showed that subclinical hypothyroidism was independently associated with a mean LA pressure of >18 mmHg (odds ratio 3.94, 95% CI 1.28 11.2; P = 0.02). Conclusions Subclinical hypothyroidism may increase the LA pressure in AF patients.

scholarly journals THE ROLE OF INFLAMMATION AND COAGULATION CASCADE IN THE PATHOGENESIS OF ATRIAL FIBRILLATION

ASJ. ◽  
2020 ◽  
Vol 3 (41) ◽  
pp. 8-10
Author(s):  
L. Hazarapetyan ◽  
S. Grigoryan ◽  
A. Sarksyan
Keyword(s):  
Atrial Fibrillation ◽  
Coagulation Cascade ◽  
Control Group ◽  
Atrial Remodeling ◽  
Inflammation Markers ◽  
Reactive Protein ◽  
Gender And Age ◽  
The Impact ◽  
The Relationship

Introduction: Atrial fibrillation (AF) is associated with prothrombotic or hypercoagulable states, various inflammation markers such as interleukin-6 (IL-6) and hsC-reactive protein (hsCRP) have also been associated with AF. The aim of this study is to investigate the relationship between inflammation markers and the prothrombotic state in the setting of AF and the impact on outcome in patients with AF. Methods: We observed 141 patients with non-valvular AF. As a control group patients similar in gender and age without AF were examined. Clinical, instrumental and laboratory tests were performed on the observed patients. The markers of the coagulation cascade (TF and F) and of inflammatory markers (hsCRP and IL-6) were studied additionally by ELISA on the analyzer "Stat Fax 303 Plus". Studies were conducted using SPSS 13.0 and EXCEL-2013. Results: The obtained results showed that compared to the control group, AF patients had significantly higher levels of IL-6 (p = 0.043), hsCRP (p = 0.002), TF (p = 0.026), and F (p = 0.025). Moreover, levels of hsCRP were higher among AF patients at "high" risk of stroke by CHA2DS2-VASc Score (p = 0.003). Besides, the levels of hsCRP and IL-6 were markedly elevated in patients with dilated left atrium (p = 0.001), poorly functioning left atrial appendage (p = 0.023) and longer duration of AF (p = 0.002). Conclusion: We have demonstrated that the increased plasma levels of IL-6 and hsCRP are related to indices of the coagulation cascade and contribute to structural atrial remodeling in patients with AF.

P2843Impact of bipolar vector orientation and inter-electrode spacing on electrograms during human atrial fibrillation

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
D Linz ◽  
S Saha ◽  
R Kutieleh ◽  
K Kadhim ◽  
D Lau ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Shannon Entropy ◽  
Low Voltage ◽  
Dominant Frequency ◽  
Electrode Spacing ◽  
Peak Voltage ◽  
Vector Orientation ◽  
The Impact ◽  
Mapping Catheter ◽  
Human Atrial Fibrillation

Abstract Background In patients with atrial fibrillation (AF), local atrial bipolar electrograms (EGM) are clinically used to determine peak-to-peak voltage (Vpp), dominant frequency (DF) and Shannon Entropy (ShEn) for electroanatomical substrate characterization and substrate-based ablation. The effect of bipolar vector orientation and inter-electrode spacing on these EGM-derived measures during AF is unclear. Methods To quantify the impact of bipolar vector orientation and inter-electrode spacing, bipolar EGM (10,496 and 20,968 atrial sites, respectively) were reconstructed from unipolar EGM recorded with an array of 18 electrodes in 14 patients with persistent AF. We compared Vpp, DF and ShEn between any two adjacent bipolar vectors with a difference of 45 degree. Vpp, DF and ShEn values were ranked into different classes from highest to lowest value. To quantify the effect of inter-electrode spacing, bipolar EGM were constructed from electrodes spaced 4mm, 8mm, and 12mm apart, respectively. Results First, bipolar vector orientation significantly impacts Vpp (maximal difference: 1.341±2.169 mV vs. 0.595±0.652 mV; p<0.01) and the percentage of atrial low voltage areas (Vpp<0.05mV) (maximal difference: 62.31% vs. 32.54%). Bipolar vector orientation also influences DF (maximal difference: 8.547±2.971 Hz vs. 6.360±1.077 Hz; p<0.01) and ShEn (maximal difference: 4.898±0.488 vs. 4.120±0.650; p<0.01) measurements. Second, inter-electrode spacing affects Vppincreasing from 0.854±1.299 mV to 1.013±1.302 mV for 4mm, and 12mm, respectively (p<0.01). The percentage of atrial low voltage areas differed between 53.77% and 42.03% for 4mm and 12mm, respectively. Furthermore, inter-electrode spacing alters DF (maximal difference: 7.316±2.239 Hz vs. 7.234±2.124 Hz; p<0.01) and ShEn (maximal difference: 4.364±0.714 vs. 4.514±0.624; p<0.01) measurements. Conclusions Bipolar vector orientation and inter-electrode spacing both significantly affect bipolar EGM-derived measures that may result in significant uncertainty around the electroanatomical substrate characterization in AF patients, which should be considered in the development of future mapping catheter tools and algorithms.

scholarly journals Blood Pressure and Risk of Atrial Fibrillation: A Mendelian Randomization Study

2020 ◽  
Author(s):  
Matthew Craig Hyman ◽  
Michael Craig Levin ◽  
Dipender Gill ◽  
Venexia Walker ◽  
Marios K Georgakis ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Blood Pressure ◽  
Calcium Channel ◽  
Mendelian Randomization ◽  
European Ancestry ◽  
Summary Statistics ◽  
Uk Biobank ◽  
International Consortium ◽  
The Impact ◽  
The Relationship

Abstract Importance: Observational studies have shown an association between hypertension and atrial fibrillation (AF). Aggressive blood pressure management in patients with known AF reduces overall arrhythmia burden, but it remains unclear whether hypertension is causative for AF. Objective: The primary objective of this study was to investigate the relationship between blood pressure and risk of AF using genetic proxies for blood pressure within a Mendelian randomization (MR) framework. We secondarily explored the relationship between genetically proxied use of anti-hypertensive drugs and risk of AF. Design: Two-sample MR was performed using an inverse-variance weighted meta-analysis with weighted median MR and Egger intercept tests performed as sensitivity analyses. Genetic proxies for the anti-hypertensive drug classes were used to investigate the impact of these therapies on the risk of AF. Setting: International Consortium of Blood Pressure, UK Biobank and Atrial Fibrillation Genetics Consortium. Participants: Summary statistics for systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse pressure (PP) were obtained from the International Consortium of Blood Pressure and the UK Biobank discovery analysis (>750,000 individuals of European ancestry). Summary statistics for AF were obtained from the 2018 Atrial Fibrillation Genetics Consortium multi-ethnic GWAS (>65,000 AF cases and >522,000 referents). Exposure: Genetically predicted SBP, DBP and PP as quantified by risk scores. Main Outcome: Odds ratio for AF per 10 mmHg increase in genetically proxied blood pressure. Results: Ten mmHg increases in genetically proxied SBP, DBP or PP were associated with increased odds of AF (SBP: OR 1.17, 95% CI 1.11-1.22, p=1x10-11; DBP: OR 1.25, 95% CI 1.16-1.35, p=3x10-8; PP: OR 1.1, 95% CI 1.0-1.2, p=0.05). Ten mmHg decreases in SBP estimated by genetic proxies of anti-hypertensive medications showed calcium channel blockers (OR 0.66, 95% CI 0.57-0.76, p=8x10-9) and beta-blockers (OR 0.61, 95% CI 0.46-0.81, p=6x10-4) decreased the risk of AF. Conclusions and Relevance: Blood pressure-increasing genetic variants were associated with increased risk of AF, consistent with a causal relationship between blood pressure and AF. These data support the concept that blood pressure reduction through pharmacologic intervention, and specifically calcium channel blockade or beta blockade could reduce the risk of AF.

scholarly journals Impact of malnutrition on the relationship between obesity and mortality in patients with atrial fibrillation

2021 ◽  
Vol 42 (Supplement_1) ◽  
Author(s):  
M Cespon Fernandez ◽  
E Abu-Assi ◽  
A Lizancos Castro ◽  
J.A Parada Barcia ◽  
C Barreiro Pardal ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Nutritional Status ◽  
Large Population ◽  
Normal Weight ◽  
Overweight And Obesity ◽  
Nutrition Status ◽  
Severe Malnutrition ◽  
Systemic Embolism ◽  
The Impact ◽  
The Relationship

Abstract Introduction A protective effect of obesity has been previously reported in patients with atrial fibrillation (AF) – the so-called `obesity paradox”. Nutritional status could behave as a confounding factor, but there are no studies that analyze the interaction of malnutrition in the relationship between obesity and mortality in AF patients. Aim The objective of this study was to determine the impact of nutritional status on the relationship between body mass index (BMI) and mortality in AF patients. Methods A retrospective, multicenter, population-based cohort study of patients with diagnosis of AF from January 1, 2014 to December 31, 2017, in Vigo, Spain, was conducted. We created three separate groups according to BMI (normal-weight, overweight, and obesity) and three separate cohorts based on nutritional status according to CONUT score (good nutrition, mild malnutrition, and moderate-severe malnutrition). The primary outcome was all-cause mortality. Secondary outcomes included embolic events (systemic embolism and stroke) and major bleeding. A combined endpoint of mortality, embolic and haemorrhagic events was assessed (clinical net outcome). Results A total of 14,849 AF patients aged ≥75 years (75.6±10.3 years, 50.9% women) were followed-up during 44.4±1.8 years. Overweight and obesity was observed in 42.6% and 46.0%, respectively, whereas malnutrition was observed in 34.3%. Malnutrition rates were lower as BMI increased: from 48.1% in patients with underweight, to 36.8%, 35.1% and 33.0% in patients with normal weight, overweight, and obesity, respectively (p-value &lt;0.001 for the trend). BMI was inversely associated with mortality (HR 0.96, 95% CI 0.95–0.97; p&lt;0.001) in the univariate analysis; however, this association was lost when adjusted analysis by nutritional status was performed (HR 0.99, 95% CI 0.99–1.00; p=0.285). Thus, neither overweight nor obesity were predictors of mortality nor net outcome when we adjusted by nutritional status: after stratifying for presence of malnutrition, survival of patients with a BMI&gt;25 kg/m2 was similar to that of patients with BMI ≤25 kg/m2. Regarding to nutritional status, both mild and moderate-severe malnutrition were associated with higher rates of mortality, stroke/systemic embolism and bleeding in all BMI groups (normal-weight, overweight and obesity). In this real-world observational study, we have assessed the interaction of nutritional status in the association between BMI and prognosis of AF patients. We concluded that 1) Malnutrition is common in AF patients, even among patients with overweight and obesity; 2) Malnutrition is a strong predictor of mortality in patients with AF; and 3) BMI was not associated with worse prognosis after adjusting for nutritional status. Conclusion The analysis of a large population of AF patients showed that the association between improved mortality and obesity/overweight is confounded by malnutrition status. FUNDunding Acknowledgement Type of funding sources: None. Impact of nutrition status and weight Clinical outcomes in different groups

Wavelength and vulnerability to atrial fibrillation: Insights from a computer model of human atria

EP Europace ◽  
2005 ◽  
Vol 7 (s2) ◽  
pp. S83-S92 ◽  
Author(s):  
Vincent Jacquemet ◽  
Nathalie Virag ◽  
Lukas Kappenberger
Keyword(s):  
Atrial Fibrillation ◽  
Computer Model ◽  
A Priori ◽  
Temporal Organization ◽  
A Priori Information ◽  
Clinical Methods ◽  
Spatio Temporal ◽  
Priori Information ◽  
The Impact ◽  
The Relationship

Abstract Aim To explain the contradictory results related to the concept of critical cardiac wavelength in the initiation and perpetuation of atrial fibrillation (AF). Methods A biophysically based computer model was used to: (1) study the relationship between wavelength and AF perpetuation in the presence of multiple re-entrant wavelets, (2) evaluate the performance of different existing methods for wavelength estimation in the presence of different arrhythmogenic substrates, and (3) document the impact of either heterogeneities in refractoriness or the presence of a mother rotor on wavelength estimation. Results The simulations confirmed that the wavelength must be below a critical value for AF to be sustained, when the perpetuation mechanism relies on multiple re-entrant wavelets. The estimated value of wavelength was not the same for all methods tested and depended in part on the nature of the spatio-temporal organization of the AF dynamics. Conclusion A priori information about the underlying wavelet dynamics is needed for a correct interpretation of the cardiac wavelength as estimated by the current clinical methods.

scholarly journals The impact of diabetes mellitus on restoring and maintaining of sinus rhythm in patients with persistent atrial fibrillation

2002 ◽  
Vol 130 (5-6) ◽  
pp. 189-192 ◽  
Author(s):  
Tatjana Potpara ◽  
Jelena Marinkovic-Eric ◽  
Miodrag Grujic ◽  
Biljana Radojkovic-Cirovic ◽  
Bosiljka Vujisic-Tesic ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Atrial Fibrillation ◽  
Sinus Rhythm ◽  
Persistent Atrial Fibrillation ◽  
Recurrent Atrial Fibrillation ◽  
The Impact ◽  
The Relationship

We concluded that diabetes mellitus independently predicts the presence of recurrent atrial fibrillation but does not influence the possibility of sinus rhythm restoration. The relationship between atrial fibrillation and diabetes mellitus needs further investigation.

Effect of Non-Uniform Tissue Configuration on Conductance Catheter Measurement for Arterial Lumen Sizing

2011 ◽  
Author(s):  
Hyo Won Choi ◽  
Ghassan S. Kassab
Keyword(s):  
Electric Field ◽  
Surrounding Tissue ◽  
Medium Size ◽  
Conductance Catheter ◽  
Cross Sectional ◽  
Tissue Properties ◽  
Arterial Lumen ◽  
Novel Approach ◽  
Parallel Conductance ◽  
The Impact

A novel approach of two bolus injections of saline solutions has been proposed for conductance catheter measurement of cross-sectional area (CSA) and parallel conductance for medium size arteries [1–2]. The parallel conductance or current leakage through surrounding tissue is dependent on how differently the combined configuration of lumen, surrounding tissue, and conductance catheter forms an electric field. Arteries have a variety of surrounding tissue geometries and electrical conductivities depending on their anatomic situations. Specifically, coronary/peripheral arteries are often characterized by their superficial anatomic positions so that surrounding tissue has asymmetric configurations. Such notions highlight the need for addressing the impact of anatomically relevant tissue properties on the performance of conductance catheter measurement. In the present study, we computationally probe how asymmetric surrounding tissue thickness and/or inhomogeneous/anisotropic electric conductivity of tissue can modulate the electric field and hence accuracy of CSA measurement for a medium size artery.

Accent Policy and Accent Modification Enterprises as Potential Indicators of Intercultural Power Relations: A Call for an Updated Research Agenda

2013 ◽  
Vol 3 (1) ◽  
pp. 22-33 ◽  
Author(s):  
Brynne D. Ovalle ◽  
Rahul Chakraborty
Keyword(s):  
International Relations ◽  
Identity Construction ◽  
Social Theory ◽  
Power Relations ◽  
Linguistic Diversity ◽  
Cultural Organization ◽  
Using Data ◽  
The Individual ◽  
The Impact ◽  
The Relationship

This article has two purposes: (a) to examine the relationship between intercultural power relations and the widespread practice of accent discrimination and (b) to underscore the ramifications of accent discrimination both for the individual and for global society as a whole. First, authors review social theory regarding language and group identity construction, and then go on to integrate more current studies linking accent bias to sociocultural variables. Authors discuss three examples of intercultural accent discrimination in order to illustrate how this link manifests itself in the broader context of international relations (i.e., how accent discrimination is generated in situations of unequal power) and, using a review of current research, assess the consequences of accent discrimination for the individual. Finally, the article highlights the impact that linguistic discrimination is having on linguistic diversity globally, partially using data from the United Nations Educational, Scientific and Cultural Organization (UNESCO) and partially by offering a potential context for interpreting the emergence of practices that seek to reduce or modify speaker accents.

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