Entropy Mapping Approach for Functional Reentry Detection in Atrial Fibrillation: An In-Silico Study

Catheter ablation of critical electrical propagation sites is a promising tool for reducing the recurrence of atrial fibrillation (AF). The spatial identification of the arrhythmogenic mechanisms sustaining AF requires the evaluation of electrograms (EGMs) recorded over the atrial surface. This work aims to characterize functional reentries using measures of entropy to track and detect a reentry core. To this end, different AF episodes are simulated using a 2D model of atrial tissue. Modified Courtemanche human action potential and Fenton–Karma models are implemented. Action potential propagation is modeled by a fractional diffusion equation, and virtual unipolar EGM are calculated. Episodes with stable and meandering rotors, figure-of-eight reentry, and disorganized propagation with multiple reentries are generated. Shannon entropy ( S h E n ), approximate entropy ( A p E n ), and sample entropy ( S a m p E n ) are computed from the virtual EGM, and entropy maps are built. Phase singularity maps are implemented as references. The results show that A p E n and S a m p E n maps are able to detect and track the reentry core of rotors and figure-of-eight reentry, while the S h E n results are not satisfactory. Moreover, A p E n and S a m p E n consistently highlight a reentry core by high entropy values for all of the studied cases, while the ability of S h E n to characterize the reentry core depends on the propagation dynamics. Such features make the A p E n and S a m p E n maps attractive tools for the study of AF reentries that persist for a period of time that is similar to the length of the observation window, and reentries could be interpreted as AF-sustaining mechanisms. Further research is needed to determine and fully understand the relation of these entropy measures with fibrillation mechanisms other than reentries.

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In silico study on the effects ofIKurblock kinetics on prolongation of human action potential after atrial fibrillation-induced electrical remodeling

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.01229.2007 ◽

2008 ◽

Vol 294 (2) ◽

pp. H793-H800 ◽

Cited By ~ 18

Author(s):

Kenji Tsujimae ◽

Shingo Murakami ◽

Yoshihisa Kurachi

Keyword(s):

Atrial Fibrillation ◽

Action Potential ◽

Short Pulse ◽

Stimulus Frequency ◽

Human Action ◽

Antiarrhythmic Agents ◽

Dependent Manner ◽

Promising Target ◽

In Silico Study ◽

Kinetics Of

Pharmacological treatment with various antiarrhythmic agents for the termination or prevention of atrial fibrillation (AF) is not yet satisfactory. This is in part because the drugs may not be sufficiently selective for the atrium, and they often cause ventricular arrhythmias. The ultrarapid-delayed rectifying potassium current ( IKur) is found in the atrium but not in the ventricle, and it has been recognized as a potentially promising target for anti-AF drugs that would be without ventricular proarrhythmia. Several new agents that specifically block IKurhave been developed. They block IKurin a voltage- and time-dependent manner. Here we use mathematical models of normal and electrically remodeled human atrial action potentials to examine the effects of the blockade kinetics of IKuron atrial action potential duration (APD). It was found that after AF remodeling, an IKurblocker with fast onset can effectively prolong APD at any stimulus frequency, whereas a blocker with slow onset prolongs APD in a frequency-dependent manner only when the recovery is slow. The results suggest that the voltage and time dependence of IKurblockade should be taken into account in the testing of anti-AF drugs. This modeling study suggests that a simple voltage-clamp protocol with a short pulse of ∼10 ms at 1 Hz may be useful to identify the effective anti-AF drugs among various IKurblockers.

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Abstract 2168: Efficient Detection of Atrial Fibrillation and Congestive Heart Failure in Single-Lead Devices

Circulation ◽

10.1161/circ.118.suppl_18.s_680-b ◽

2008 ◽

Vol 118 (suppl_18) ◽

Author(s):

Randall Moorman ◽

Yuping Xiao ◽

Douglas Lake

Keyword(s):

Heart Failure ◽

Atrial Fibrillation ◽

Congestive Heart Failure ◽

Primary Prevention ◽

Rr Intervals ◽

High Entropy ◽

Efficient Detection ◽

Entropy Measures ◽

Ectopic Beats ◽

Roc Area

Patients receiving primary prevention single lead ICDs are at risk for atrial fibrillation (AF) and congestive heart failure (CHF). No such device reports AF burden, and only a single CHF measure, trans-thoracic impedance, is available. Entropy measures that count the number of matching RR intervals have promise, as AF is random (high entropy) and CHF is often marked by reduced heart rate variability (RR intervals with many matches) and ectopic beats (few matches). We designed entropy-based measures to detect AF (high entropy) and CHF (mixture of RR intervals with many and with few matches). For real-world implementation, we used only 12 RR intervals, and calculated the result every 30 minutes in 24-hour Holter monitor records from the MIT-BIH databases. The Figure shows distinction among AF, NSR and CHF records using HR and S.D. (panel A) or the new entropy-based measures. Panel A shows poor diagnostic performance of conventional measures. In Panel B, the y-axis, COSEn, is the coefficient of sample entropy. The AF records all have higher values, and the ROC area is 1.00. The x-axis is a measure of template match counts. It distinguishes between normals and CHF patients with ROC area 0.92. With only 12 RR intervals every 30 minutes, entropy calculations allow for efficient detection of AF and CHF. We propose that single lead devices can be employed as monitors in the primary prevention population, where risk of AF and CHF is high.

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