ABSTRACT Ablation procedures have become one of the most efficient treatments for termination of ... more ABSTRACT Ablation procedures have become one of the most efficient treatments for termination of atrial arrhythmias. The aim of the present study is the evaluation of the potential use of noninvasive imaging as a clinical tool for the identification of atrial tachycardia origin prior to an ablation procedure. Simultaneous 67-lead body surface potential recordings and 15 intracardiac electrograms (EGM) were obtained for one patient during sinus rhythm and pacing the left superior pulmonary vein. 3D heart and torso geometries were obtained by using computed axial tomography images. Epicardial activation sequences were computed by solving the inverse problem of the electrocardiology. Reconstructed activation sequences were consistent with recorded EGMs. Measured and estimated activation time differences between right and left atria were 93 ms and 102 ms during sinus rhythm respectively and 49 ms and 71 ms respectively during left atrial pacing.
Burden of atrial fibrillation (AF) can be reduced by ablation of sources of electrical impulses d... more Burden of atrial fibrillation (AF) can be reduced by ablation of sources of electrical impulses driving AF but driver identification is still challenging. This study presents a new methodology based on causality analysis that allows identifying the hierarchically dominant areas driving AF. Identification of dominant propagation patterns was achieved by computing causal relations between intracardiac multi-electrode catheter recordings of four paroxysmal AF patients during sinus rhythm, pacing and AF. In addition, realistic mathematical models of the atria during AF were used to validate the methodology both in the presence and absence of dominant frequency (DF) gradients. During electrical pacing, sources of propagation patterns detected by causality analysis were consistent with the location of the stimulating catheter. During AF, propagation patterns presented temporal variability, but a dominant direction accounted for significantly more propagations than other directions (49 ± 15% vs. 14 ± 13% or less, p < 0.01). Both in patients with a DF gradient and in mathematical models, causal maps allowed the identification of sites responsible for maintenance of AF. Causal maps allowed the identification of atrial dominant sites. In particular, causality analysis resulted in stable dominant cause-effect propagation directions during AF and could serve as a guide for performing ablation procedures in AF patients.
ABSTRACT This study proposes a non-invasive methodology to detect higher atrial frequencies in AF... more ABSTRACT This study proposes a non-invasive methodology to detect higher atrial frequencies in AF patients, which may be related to localized drivers, responsible of AF maintenance. The proposed algorithm extracts a signal from a Body Surface Potential Mapping (BSPM) recording from the linear combination that maximizes a cost function that measures periodicity within a given range. By applying iteratively this algorithm in 1.5Hz-width bands from 5Hz to 20Hz in steps of 0.25Hz, several candidates for AF signals with increasing frequency are obtained. Signals with high spectral concentration, low kurtosis and repeatability in 5 consecutive steps were considered compatible with AF. Among these signals, the one with the highest frequency was selected as candidate for AF driver. This frequency was compared with spectral analysis of surface signals in segments under adenosine effects, i.e. with absence of ventricular activity. The algorithm was applied to 18 BSPM recordings from AF patients. In all cases, the high frequency was consistent with the spectral analysis of the segments with adenosine. High atrial frequency values were 9.61 ± 2.12, spectral concentration was 0.415±0.096 and kurtosis 0.60±0.81. The non-invasive detection of high frequency atrial sources may help to define the most appropriate therapy, e.g. for ablation of atrial regions with high activation rates.
The diagnosis of Brugada syndrome based on the ECG is hampered by the dynamic nature of its ECG m... more The diagnosis of Brugada syndrome based on the ECG is hampered by the dynamic nature of its ECG manifestations. Brugada syndrome patients are only 25% likely to present a type 1 ECG. The objective of this study is to provide an ECG diagnostic criterion for Brugada syndrome patients that can be applied consistently even in the absence of a type 1 ECG. We recorded 67-lead body surface potential maps from 94 Brugada syndrome patients and 82 controls (including right bundle branch block patients and healthy individuals). The spatial propagation direction during the last r' wave and the slope at the end of the QRS complex were measured and compared between patients groups. Receiver-operating characteristic curves were constructed for half of the database to identify optimal cutoff values; sensitivity and specificity for these cutoff values were measured in the other half of the database. A spontaneous type 1 ECG was present in only 30% of BrS patients. An orientation in the sagittal plane<101º during the last r' wave and a descending slope<9.65mV/s enables the diagnosis of the syndrome with a sensitivity of 69% and a specificity of 97% in non-type 1 Brugada syndrome patients. Spatiotemporal characteristics of surface ECG recordings can enable a robust identification of BrS even without the presence of a type 1 ECG. This article is protected by copyright. All rights reserved.
Ablation of high dominant frequency (DF) sources in patients with atrial fibrillation (AF) is an ... more Ablation of high dominant frequency (DF) sources in patients with atrial fibrillation (AF) is an effective treatment option for paroxysmal AF. The aim of this study was to evaluate the accuracy of noninvasive estimation of DF and electrical patterns determination by solving the inverse problem of the electrocardiography. Four representative AF patients with left-to-right and right-to-left atrial DF patterns were included in the study. For each patient, intracardiac electrograms from both atria were recorded simultaneously together with 67-lead body surface recordings. In addition to clinical recordings, realistic mathematical models of atria and torso anatomy with different DF patterns of AF were used. For both mathematical models and clinical recordings, inverse-computed electrograms were compared to intracardiac electrograms in terms of voltage, phase and frequency spectrum relative errors. Comparison between intracardiac and inverse computed electrograms for AF patients showed 8.8 ± 4.4% errors for DF, 32 ± 4% for voltage and 65 ± 4% for phase determination. These results were corroborated by mathematical simulations showing that the inverse problem solution was able to reconstruct the frequency spectrum and the DF maps with relative errors of 5.5 ± 4.1%, whereas the reconstruction of the electrograms or the instantaneous phase presented larger relative errors (i.e. 38 ±15% and 48 ± 14 % respectively, p<0.01). Noninvasive reconstruction of atrial frequency maps can be achieved by solving the inverse problem of electrocardiography with a higher accuracy than temporal distribution patterns. This article is protected by copyright. All rights reserved.
Rotor-guided ablation has opened new perspectives into the therapy of atrial fibrillation (AF). A... more Rotor-guided ablation has opened new perspectives into the therapy of atrial fibrillation (AF). Analysis of the spatio-temporal cardiac excitation patterns in the frequency and phase domains has demonstrated the importance of rotors in research models of AF, however, the dynamics and role of rotors in human AF are still controversial. In this review, the current knowledge gained through research models and patient data that support the notion that rotors are key players in AF maintenance is summarized. We report and discuss discrepancies regarding rotor prevalence and stability in various studies, which can be attributed in part to methodological differences among mapping systems. Future research for validation and improvement of current clinical electrophysiology mapping technologies will be crucial for developing mechanistic-based selection and application of the best therapeutic strategy for individual AF patient, being it, pharmaceutical, ablative, or other approach.
2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2015
Ablation of electrical drivers during atrial fibrillation (AF) has been proved as an effective th... more Ablation of electrical drivers during atrial fibrillation (AF) has been proved as an effective therapy to prevent recurrence of fibrillatory episodes. This study presents a new methodology based on causality analysis that is able to identify the hierarchical dominance of atrial areas driving AF. Realistic mathematical models of the atrial electrical activity during AF were used to assess the validity of our method. Identification of the dominant atrial propagation patterns was achieved by computing causal relations between multiple electrogram signals. The causal relationships between atrial areas during the fibrillatory processes were summarized into a recurrence map, highlighting the hierarchy and dominant areas. Recurrence maps computed from causality analysis allowed the identification of sites responsible for maintenance of the arrhythmia. These maps were able to locate the position of the atrial driver in fibrillatory processes with a single rotor, with 2 rotors or with several drivers. Additionally, the correspondence between the nodal values of the recurrence map and the distance to the rotor core has been established. Causal analysis consistently estimated propagation patterns and location of atrial drivers during AF. This methodology could guide ablation procedures in AF patients.
Atrial arrhythmias are the most common cardiac pathologies and the variety of mechanisms of onset... more Atrial arrhythmias are the most common cardiac pathologies and the variety of mechanisms of onset and progression are not well understood.
Atrial flutter (AFL) is a supraventricular arrhythmia maintained by a macroreentrant circuit. The... more Atrial flutter (AFL) is a supraventricular arrhythmia maintained by a macroreentrant circuit. The circuit responsible of AFL maintenance is difficult to be determined in cases of atypical circuits. In this work, we made use of wavefront propagation maps (WPMs) obtained from 64-lead body surface potential mapping (BSPM) recordings in order to characterize the rotation circuit non- invasively. BSPM recordings were obtained for 8 patients with AFL (5 typical, 3 atypical). AFL waves with a length equal to the dominant atrial cycle length (DACL) were isolated from TQ segments free from ventricular activity. WPMs were constructed for all patients summarizing the electrical activity during AFL and the direction of rotation was determined. In all typical AFL patients directions were consistent with either clockwise or counterclockwise rotations while in atypical AFL patients different directions were found. WPMs appear as a promising tool for the non-invasive determination of the circuit maintaining AFL in each patient non-invasively and thus may help in planning ablation procedures.
ABSTRACT Ablation procedures have become one of the most efficient treatments for termination of ... more ABSTRACT Ablation procedures have become one of the most efficient treatments for termination of atrial arrhythmias. The aim of the present study is the evaluation of the potential use of noninvasive imaging as a clinical tool for the identification of atrial tachycardia origin prior to an ablation procedure. Simultaneous 67-lead body surface potential recordings and 15 intracardiac electrograms (EGM) were obtained for one patient during sinus rhythm and pacing the left superior pulmonary vein. 3D heart and torso geometries were obtained by using computed axial tomography images. Epicardial activation sequences were computed by solving the inverse problem of the electrocardiology. Reconstructed activation sequences were consistent with recorded EGMs. Measured and estimated activation time differences between right and left atria were 93 ms and 102 ms during sinus rhythm respectively and 49 ms and 71 ms respectively during left atrial pacing.
Burden of atrial fibrillation (AF) can be reduced by ablation of sources of electrical impulses d... more Burden of atrial fibrillation (AF) can be reduced by ablation of sources of electrical impulses driving AF but driver identification is still challenging. This study presents a new methodology based on causality analysis that allows identifying the hierarchically dominant areas driving AF. Identification of dominant propagation patterns was achieved by computing causal relations between intracardiac multi-electrode catheter recordings of four paroxysmal AF patients during sinus rhythm, pacing and AF. In addition, realistic mathematical models of the atria during AF were used to validate the methodology both in the presence and absence of dominant frequency (DF) gradients. During electrical pacing, sources of propagation patterns detected by causality analysis were consistent with the location of the stimulating catheter. During AF, propagation patterns presented temporal variability, but a dominant direction accounted for significantly more propagations than other directions (49 ± 15% vs. 14 ± 13% or less, p < 0.01). Both in patients with a DF gradient and in mathematical models, causal maps allowed the identification of sites responsible for maintenance of AF. Causal maps allowed the identification of atrial dominant sites. In particular, causality analysis resulted in stable dominant cause-effect propagation directions during AF and could serve as a guide for performing ablation procedures in AF patients.
ABSTRACT This study proposes a non-invasive methodology to detect higher atrial frequencies in AF... more ABSTRACT This study proposes a non-invasive methodology to detect higher atrial frequencies in AF patients, which may be related to localized drivers, responsible of AF maintenance. The proposed algorithm extracts a signal from a Body Surface Potential Mapping (BSPM) recording from the linear combination that maximizes a cost function that measures periodicity within a given range. By applying iteratively this algorithm in 1.5Hz-width bands from 5Hz to 20Hz in steps of 0.25Hz, several candidates for AF signals with increasing frequency are obtained. Signals with high spectral concentration, low kurtosis and repeatability in 5 consecutive steps were considered compatible with AF. Among these signals, the one with the highest frequency was selected as candidate for AF driver. This frequency was compared with spectral analysis of surface signals in segments under adenosine effects, i.e. with absence of ventricular activity. The algorithm was applied to 18 BSPM recordings from AF patients. In all cases, the high frequency was consistent with the spectral analysis of the segments with adenosine. High atrial frequency values were 9.61 ± 2.12, spectral concentration was 0.415±0.096 and kurtosis 0.60±0.81. The non-invasive detection of high frequency atrial sources may help to define the most appropriate therapy, e.g. for ablation of atrial regions with high activation rates.
The diagnosis of Brugada syndrome based on the ECG is hampered by the dynamic nature of its ECG m... more The diagnosis of Brugada syndrome based on the ECG is hampered by the dynamic nature of its ECG manifestations. Brugada syndrome patients are only 25% likely to present a type 1 ECG. The objective of this study is to provide an ECG diagnostic criterion for Brugada syndrome patients that can be applied consistently even in the absence of a type 1 ECG. We recorded 67-lead body surface potential maps from 94 Brugada syndrome patients and 82 controls (including right bundle branch block patients and healthy individuals). The spatial propagation direction during the last r' wave and the slope at the end of the QRS complex were measured and compared between patients groups. Receiver-operating characteristic curves were constructed for half of the database to identify optimal cutoff values; sensitivity and specificity for these cutoff values were measured in the other half of the database. A spontaneous type 1 ECG was present in only 30% of BrS patients. An orientation in the sagittal plane<101º during the last r' wave and a descending slope<9.65mV/s enables the diagnosis of the syndrome with a sensitivity of 69% and a specificity of 97% in non-type 1 Brugada syndrome patients. Spatiotemporal characteristics of surface ECG recordings can enable a robust identification of BrS even without the presence of a type 1 ECG. This article is protected by copyright. All rights reserved.
Ablation of high dominant frequency (DF) sources in patients with atrial fibrillation (AF) is an ... more Ablation of high dominant frequency (DF) sources in patients with atrial fibrillation (AF) is an effective treatment option for paroxysmal AF. The aim of this study was to evaluate the accuracy of noninvasive estimation of DF and electrical patterns determination by solving the inverse problem of the electrocardiography. Four representative AF patients with left-to-right and right-to-left atrial DF patterns were included in the study. For each patient, intracardiac electrograms from both atria were recorded simultaneously together with 67-lead body surface recordings. In addition to clinical recordings, realistic mathematical models of atria and torso anatomy with different DF patterns of AF were used. For both mathematical models and clinical recordings, inverse-computed electrograms were compared to intracardiac electrograms in terms of voltage, phase and frequency spectrum relative errors. Comparison between intracardiac and inverse computed electrograms for AF patients showed 8.8 ± 4.4% errors for DF, 32 ± 4% for voltage and 65 ± 4% for phase determination. These results were corroborated by mathematical simulations showing that the inverse problem solution was able to reconstruct the frequency spectrum and the DF maps with relative errors of 5.5 ± 4.1%, whereas the reconstruction of the electrograms or the instantaneous phase presented larger relative errors (i.e. 38 ±15% and 48 ± 14 % respectively, p<0.01). Noninvasive reconstruction of atrial frequency maps can be achieved by solving the inverse problem of electrocardiography with a higher accuracy than temporal distribution patterns. This article is protected by copyright. All rights reserved.
Rotor-guided ablation has opened new perspectives into the therapy of atrial fibrillation (AF). A... more Rotor-guided ablation has opened new perspectives into the therapy of atrial fibrillation (AF). Analysis of the spatio-temporal cardiac excitation patterns in the frequency and phase domains has demonstrated the importance of rotors in research models of AF, however, the dynamics and role of rotors in human AF are still controversial. In this review, the current knowledge gained through research models and patient data that support the notion that rotors are key players in AF maintenance is summarized. We report and discuss discrepancies regarding rotor prevalence and stability in various studies, which can be attributed in part to methodological differences among mapping systems. Future research for validation and improvement of current clinical electrophysiology mapping technologies will be crucial for developing mechanistic-based selection and application of the best therapeutic strategy for individual AF patient, being it, pharmaceutical, ablative, or other approach.
2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2015
Ablation of electrical drivers during atrial fibrillation (AF) has been proved as an effective th... more Ablation of electrical drivers during atrial fibrillation (AF) has been proved as an effective therapy to prevent recurrence of fibrillatory episodes. This study presents a new methodology based on causality analysis that is able to identify the hierarchical dominance of atrial areas driving AF. Realistic mathematical models of the atrial electrical activity during AF were used to assess the validity of our method. Identification of the dominant atrial propagation patterns was achieved by computing causal relations between multiple electrogram signals. The causal relationships between atrial areas during the fibrillatory processes were summarized into a recurrence map, highlighting the hierarchy and dominant areas. Recurrence maps computed from causality analysis allowed the identification of sites responsible for maintenance of the arrhythmia. These maps were able to locate the position of the atrial driver in fibrillatory processes with a single rotor, with 2 rotors or with several drivers. Additionally, the correspondence between the nodal values of the recurrence map and the distance to the rotor core has been established. Causal analysis consistently estimated propagation patterns and location of atrial drivers during AF. This methodology could guide ablation procedures in AF patients.
Atrial arrhythmias are the most common cardiac pathologies and the variety of mechanisms of onset... more Atrial arrhythmias are the most common cardiac pathologies and the variety of mechanisms of onset and progression are not well understood.
Atrial flutter (AFL) is a supraventricular arrhythmia maintained by a macroreentrant circuit. The... more Atrial flutter (AFL) is a supraventricular arrhythmia maintained by a macroreentrant circuit. The circuit responsible of AFL maintenance is difficult to be determined in cases of atypical circuits. In this work, we made use of wavefront propagation maps (WPMs) obtained from 64-lead body surface potential mapping (BSPM) recordings in order to characterize the rotation circuit non- invasively. BSPM recordings were obtained for 8 patients with AFL (5 typical, 3 atypical). AFL waves with a length equal to the dominant atrial cycle length (DACL) were isolated from TQ segments free from ventricular activity. WPMs were constructed for all patients summarizing the electrical activity during AFL and the direction of rotation was determined. In all typical AFL patients directions were consistent with either clockwise or counterclockwise rotations while in atypical AFL patients different directions were found. WPMs appear as a promising tool for the non-invasive determination of the circuit maintaining AFL in each patient non-invasively and thus may help in planning ablation procedures.
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Papers by Maria Guillem