Dataset Information

Dynamic approximate entropy electroanatomic maps detect rotors in a simulated atrial fibrillation model.

ABSTRACT: There is evidence that rotors could be drivers that maintain atrial fibrillation. Complex fractionated atrial electrograms have been located in rotor tip areas. However, the concept of electrogram fractionation, defined using time intervals, is still controversial as a tool for locating target sites for ablation. We hypothesize that the fractionation phenomenon is better described using non-linear dynamic measures, such as approximate entropy, and that this tool could be used for locating the rotor tip. The aim of this work has been to determine the relationship between approximate entropy and fractionated electrograms, and to develop a new tool for rotor mapping based on fractionation levels. Two episodes of chronic atrial fibrillation were simulated in a 3D human atrial model, in which rotors were observed. Dynamic approximate entropy maps were calculated using unipolar electrogram signals generated over the whole surface of the 3D atrial model. In addition, we optimized the approximate entropy calculation using two real multi-center databases of fractionated electrogram signals, labeled in 4 levels of fractionation. We found that the values of approximate entropy and the levels of fractionation are positively correlated. This allows the dynamic approximate entropy maps to localize the tips from stable and meandering rotors. Furthermore, we assessed the optimized approximate entropy using bipolar electrograms generated over a vicinity enclosing a rotor, achieving rotor detection. Our results suggest that high approximate entropy values are able to detect a high level of fractionation and to locate rotor tips in simulated atrial fibrillation episodes. We suggest that dynamic approximate entropy maps could become a tool for atrial fibrillation rotor mapping.

SUBMITTER: Ugarte JP

PROVIDER: S-EPMC4260907 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Dynamic approximate entropy electroanatomic maps detect rotors in a simulated atrial fibrillation model.

Ugarte Juan P JP Orozco-Duque Andrés A Tobón Catalina C Kremen Vaclav V Novak Daniel D Saiz Javier J Oesterlein Tobias T Schmitt Clauss C Luik Armin A Bustamante John J

PloS one 20141209 12

There is evidence that rotors could be drivers that maintain atrial fibrillation. Complex fractionated atrial electrograms have been located in rotor tip areas. However, the concept of electrogram fractionation, defined using time intervals, is still controversial as a tool for locating target sites for ablation. We hypothesize that the fractionation phenomenon is better described using non-linear dynamic measures, such as approximate entropy, and that this tool could be used for locating the ro ...[more]

PMID: 25489858

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Project description:To develop electrocardiogram (ECG) tools to quantify the number of sources for atrial fibrillation (AF), i.e. spatially stable rotors and focal impulses, and whether they lie in right or left atrium. Intracardiac mapping has recently shown that paroxysmal and persistent AF is sustained by rotors or focal sources that are stable in location and thus targets for limited ablation [focal impulse and rotor modulation (FIRM)] to eliminate AF. Importantly, the numbers and locations of concurrent sources determine both the complexity of AF and the approach for ablation.In 36 AF patients (n = 29 persistent, 63 ± 9 years) in the CONventional ablation with or without Focal Impulse and Rotor Modulation (CONFIRM) trial, we developed phase lock (PL) to quantify spatial repeatability of ECG 'F-waves' between leads over time. Phase lock spectrally quantifies the angle ? between F-wave voltages in planes formed by ECG leads I, aVF, and V1 at successive points in time. We compared PL with ECG spectral dominant frequency (DF) and organizational index (OI) to characterize stable rotors and focal sources validated by intracardiac FIRM mapping. Focal impulse and rotor modulation ablation alone at ?3 sources acutely terminated and rendered AF non-inducible or substantially slowed AF in 31 of 36 patients. Receiver operating characteristics of PL for this endpoint had area under the curve (AUC) = 0.72, and the optimum cut-point (PL = 0.09) had 74% sensitivity, 92% positive predictive value (PPV). Receiver operating characteristics areas for OI and DF were 0.50 and 0.58, respectively. Left (n = 28) or right (n = 3) atrial sources were localized by PL with AUC = 0.85, sensitivity 100%, PPV 30%, and negative predictive value 100%. Spectral DF provided AUC = 0.79. Notably, PL did not comigrate with diagnosis of paroxysmal or persistent AF (P = NS), unlike ECG DF.The novel metric of ECG PL identifies patients with fewer (?3) or greater numbers of stable rotors/focal sources for AF, validated by intracardiac FIRM mapping, and localized them to right or left atria. These data open the possibility of using 12-lead ECG analyses to classify AF mechanistically and plan procedures for right- or left-sided FIRM ablation.

Project description:Maintenance of paroxysmal atrial fibrillation (AF) by fast rotors in the left atrium (LA) or at the pulmonary veins (PVs) is not fully understood. To gain insight into this dynamic and complex process, we studied the role of the heterogeneous distribution of transmembrane currents in the PVs and LA junction (PV-LAJ) in the localization of rotors in the PVs. We also investigated whether simple pacing protocols could be used to predict rotor drift in the PV-LAJ. Experimentally observed heterogeneities in IK1, IKs, IKr, Ito, and ICaL in the PV-LAJ were incorporated into two- and pseudo three-dimensional models of Courtemanche-Ramirez-Nattel-Kneller human atrial kinetics to simulate various conditions and investigate rotor drifting mechanisms. Spatial gradients in the currents resulted in shorter action potential duration, minimum diastolic potential that was less negative, and slower upstroke and conduction velocity for rotors in the PV region than in the LA. Rotors under such conditions drifted toward the PV and stabilized at the shortest action potential duration and less-excitable region, consistent with drift direction under intercellular coupling heterogeneities and regardless of the geometrical constraint in the PVs. Simulations with various IK1 gradient conditions and current-voltage relationships substantiated its major role in the rotor drift. In our 1:1 pacing protocol, we found that among various action potential properties, only the minimum diastolic potential gradient was a rate-independent predictor of rotor drift direction. Consistent with experimental and clinical AF studies, simulations in an electrophysiologically heterogeneous model of the PV-LAJ showed rotor attraction toward the PV. Our simulations suggest that IK1 heterogeneity is dominant compared to other currents in determining the drift direction through its impact on the excitability gradient. These results provide a believed novel framework for understanding the complex dynamics of rotors in AF.

Project description:Experimental and clinical data demonstrate that atrial fibrillation (AF) maintenance in animals and groups of patients depends on localized reentrant sources localized primarily to the pulmonary veins (PVs) and the left atrium(LA) posterior wall in paroxysmal AF but elsewhere, including the right atrium (RA), in persistent AF. Moreover, AF can be eliminated by directly ablating AF-driving sources or "rotors," that exhibit high-frequency, periodic activity. The RADAR-AF randomized trial demonstrated that an ablation procedure based on a more target-specific strategy aimed at eliminating high frequency sites responsible for AF maintenance is as efficacious as and safer than empirically isolating all the PVs. In contrast to the standard ECG, global atrial noninvasive frequency analysis allows non-invasive identification of high-frequency sources before the arrival at the electrophysiology laboratory for ablation. Body surface potential map (BSPM) replicates the endocardial distribution of DFs with localization of the highest DF (HDF) and can identify small areas containing the high-frequency sources. Overall, BSPM had a sensitivity of 75% and specificity of 100% for capturing intracardiac EGMs as having LARA DF gradient. However, raw BSPM data analysis of AF patterns of activity showed incomplete and instable reentrant patterns of activation. Thus, we developed an analysis approach whereby a narrow band-pass filtering allowed selecting the electrical activity projected on the torso at the HDF, which stabilized the projection of rotors that potentially drive AF on the surface. Consequently, driving reentrant patterns ("rotors") with spatiotemporal stability during >70% of the AF time could be observed noninvasibly after HDF-filtering. Moreover, computer simulations found that the combination of BSPM phase mapping with DF analysis enabled the discrimination of true rotational patterns even during the most complex AF. Altogether, these studies show that the combination of DF analysis with phase maps of HDF-filtered surface ECG recordings allows noninvasive localization of atrial reentries during AF and further a physiologically-based rationale for personalized diagnosis and treatment of patients with AF.

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Dynamic approximate entropy electroanatomic maps detect rotors in a simulated atrial fibrillation model.

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Dynamic approximate entropy electroanatomic maps detect rotors in a simulated atrial fibrillation model.

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