The integration of electroanatomic maps with highly resolved computed tomography cardiac images p... more The integration of electroanatomic maps with highly resolved computed tomography cardiac images plays an important role in the successful planning of the ablation procedure of arrhythmias. In this paper, we present and validate a fully-automated strategy for the registration and fusion of sparse, atrial endocardial electroanatomic maps (CARTO maps) with detailed left atrial (LA) anatomical reconstructions segmented from a pre-procedural MDCT scan. Registration is accomplished by a parameterized geometric transformation of the CARTO points and by a stochastic search of the best parameter set which minimizes the misalignment between transformed CARTO points and the LA surface. The subsequent fusion of electrophysiological information on the registered CT atrium is obtained through radial basis function interpolation. The algorithm is validated by simulation and by real data from 14 patients referred to CT imaging prior to the ablation procedure. Results are presented, which show the validity of the algorithmic scheme as well as the accuracy and reproducibility of the integration process. The obtained results encourage the application of the integration method in post-intervention ablation assessment and basic AF research and suggest the development for real-time applications in catheter guiding during ablation intervention.
The aim of this study was to investigate the anatomic distribution of critical sources in patient... more The aim of this study was to investigate the anatomic distribution of critical sources in patients with atrial fibrillation (AF) by fusion of biatrial computed tomography (CT) images with cycle length (CL) and wave similarity (WS) maps. B A C K G R O U N D Experimental and clinical studies show that atrial fibrillation (AF) may originate from rapid and repetitive (RR) sources of activation. Localization of RR sources may be crucial for an effective ablation treatment. Atrial electrograms showing rapid and repetitive activations can be identified by combining WS and CL analysis. M E T H O D S Patients with persistent AF underwent biatrial electroanatomic mapping and preprocedural CT cardiac imaging. WS and CL maps were constructed in 17 patients by calculating the degree of repetitiveness of activation waveforms (similarity index [S]) and the cycle length at each atrial site. WS/CL maps were then integrated with biatrial 3-dimensional CT reconstructions by a stochastic approach.
Biophysically detailed and anatomically realistic atrial models are emerging as a valuable tool i... more Biophysically detailed and anatomically realistic atrial models are emerging as a valuable tool in the study of atrial arrhythmias, nevertheless clinical use of these models would be favored by a reduction of computational times. This paper introduces a novel adaptive mesh algorithm, based on multiresolution representation (MR), for the efficient integration of cardiac ordinary differential equation (ODE)-partial differential equation (PDE) systems on unstructured triangle meshes. The algorithm applies a dynamically adapted node-centered finite volume method (FVM) scheme for integration of diffusion. The method accuracy and efficiency were evaluated by simulating propagation scenarios of increasing complexity levels (pacing, stable spirals, atrial fibrillation) on tomography-derived three-dimensional monolayer atrial models, based on a monodomain reaction-diffusion formulation coupled with the Courtemanche atrial ionic model. All simulated propagation patterns were accurately reproduced with substantially reduced computational times (10%-30% of the full-resolution simulation time). The proposed algorithm, combining the MR computational efficiency with the geometrical flexibility of unstructured meshes, may favor the development of patient-specific multiscale models of atrial arrhythmias and their application in the clinical setting.
Journal of cardiovascular medicine (Hagerstown, Md.), Jan 21, 2015
Heterozygous p.(Ser64Arg) mutation in the natriuretic peptide precursor A gene has been associate... more Heterozygous p.(Ser64Arg) mutation in the natriuretic peptide precursor A gene has been associated with atrial fibrillation in the presence of common single nucleotide polymorphisms (rs10033464 and rs2200733; 4q25) that would act as modifiers. We screened natriuretic peptide precursor A gene in 583 individuals and identified three unrelated carriers of the p.(Ser64Arg) mutation (0.5%). Only one of the three mutation carriers had episodes of atrial fibrillation. Cascade screening of the three families identified seven additional mutation carriers, none showing atrial fibrillation. The patients with atrial fibrillation also carried the rs2200733, which was however found in four additional nonatrial fibrillation family members and carriers of the p.(Ser64Arg). The prevalence of atrial fibrillation in p.(Ser64Arg) carriers was 10% and in those combining the mutation with the risk single nucleotide polymorphisms was 20%. In the unique mutated patient with atrial fibrillation, the arrhyth...
The quantification of the degree of organization of the electrical activity during atrial fibrill... more The quantification of the degree of organization of the electrical activity during atrial fibrillation and the spatial localization of organization levels in a highly-resolved anatomical context may support the investigation of the electrophysiological mechanisms underlying the arrhythmia and the refinement of therapeutic approaches. A multi-technique methodology for the integration of organization maps with CT anatomical images is presented, which takes advantage of innovative signal and image processing techniques, recently developed by our group. Specifically, organization maps were constructed by quantifying the degree of morphological similarity of endocardial activation waves acquired by an electroanatomic mapping system. Accurate 3D-CT reconstructions of the atrial anatomy were obtained by a semiautomatic segmentation process based on marker controlled watershed segmentation. Sparse-point wave-similarity maps were fused on CT atrial reconstructions by a fully-automated regist...
... In fact several observations, both in animal and human studies (Lammers et al., 1991; Waxman ... more ... In fact several observations, both in animal and human studies (Lammers et al., 1991; Waxman et al., 1991, 1992; Vulliemin et al ... of mathematical models have sensitively evolved, leading to the modern biophysical models of cardiac tissue (Luo and Rudy, 1994; Courtemanche ...
Heterozygous p.(Ser64Arg) mutation in the natriuretic peptide precursor A gene has been associate... more Heterozygous p.(Ser64Arg) mutation in the natriuretic peptide precursor A gene has been associated with atrial fibrillation in the presence of common single nucleotide polymorphisms (rs10033464 and rs2200733; 4q25) that would act as modifiers. We screened natriuretic peptide precursor A gene in 583 individuals and identified three unrelated carriers of the p.(Ser64Arg) mutation (0.5%). Only one of the three mutation carriers had episodes of atrial fibrillation. Cascade screening of the three families identified seven additional mutation carriers, none showing atrial fibrillation. The patients with atrial fibrillation also carried the rs2200733, which was however found in four additional nonatrial fibrillation family members and carriers of the p.(Ser64Arg). The prevalence of atrial fibrillation in p.(Ser64Arg) carriers was 10% and in those combining the mutation with the risk single nucleotide polymorphisms was 20%. In the unique mutated patient with atrial fibrillation, the arrhythmias was refractory to both pharmacological and ablation treatment, during 16 years of follow-up; his electrophysiological phenotype was characterized by short atrial cycle lengths with a median value of 131 ms that suggests shortening of atrial action potential. The prevalence of p.(Ser64Arg) mutation is low in the general population as is the prevalence of atrial fibrillation in mutation carriers (1/10). Atrial fibrillation in the affected mutated patient was lone at onset and progressively evolved with peculiar electrophysiological patterns.
American journal of physiology. Heart and circulatory physiology, Jan 24, 2015
The causal relationship between atrial and ventricular activities during human atrial fibrillatio... more The causal relationship between atrial and ventricular activities during human atrial fibrillation (AF) is poorly understood. This study analyzed the effects of an increase in atrial rate on the link between atrial and ventricular activities during AF. Atrial and ventricular time series were determined in fourteen patients during the spontaneous acceleration of the atrial rhythm at AF onset. The dynamical relationship between atrial and ventricular activities was quantified in terms of atrioventricular (AV) coupling by AV synchrogram analysis. The technique identified n:m coupling patterns (n atrial beats in m ventricular cycles), quantifying their percentage (pc), maximal length (lmax) and conduction ratio (CR=m/n). Simulations with a difference-equations AV model were performed to correlate the observed dynamics to specific atrial/nodal properties. The atrial rate increase significantly affected AV coupling and ventricular response during AF. The shortening of atrial intervals fro...
Progress in biophysics and molecular biology, 2014
The identification of suitable markers for critical patterns during atrial fibrillation (AF) may ... more The identification of suitable markers for critical patterns during atrial fibrillation (AF) may be crucial to guide an effective ablation treatment. Single parameter maps, based on dominant frequency and complex fractionated electrograms, have been proposed as a tool for electrogram-guided ablation, however the specificity of these markers is debated. Experimental studies suggest that AF critical patterns may be identified on the basis of specific rate and organization features, where rapid organized and rapid fragmented activities characterize respectively localized sources and critical substrates. In this paper we introduce the logical operator map, a novel mapping tool for a point-by-point identification and localization of AF critical sites. Based on advanced signal and image processing techniques, the approach combines in a single map electrogram-derived rate and organization features with tomographic anatomical detail. The construction of the anatomically-detailed logical ope...
2010 Annual International Conference of the IEEE Engineering in Medicine and Biology, 2010
Although atrial fibrillation (AF) is a common complication of cardiac surgery, its pathophysiolog... more Although atrial fibrillation (AF) is a common complication of cardiac surgery, its pathophysiology remains unclear. The study of post-operative AF demands for the recording of cardiac electrical activity in correspondence of AF onset and progression. Long-term recordings in post-surgery patients could provide this information, but, to date, have been limited to surface signals, which precludes a characterization of the arrhythmic
2014 8th Conference of the European Study Group on Cardiovascular Oscillations (ESGCO), 2014
ABSTRACT The mechanisms underlying the onset of postoperative atrial fibrillation (POAF) are stil... more ABSTRACT The mechanisms underlying the onset of postoperative atrial fibrillation (POAF) are still poorly understood. Enhanced atrial automaticity and alterations in autonomic tone following surgery have been suggested as critical predisposing factors. This paper proposes an unified framework for the combined analysis of ectopic activity and autonomic function preceding POAF. Atrial intervals series were automatically extracted from long-term atrial signal recordings in postoperative patients, and processed with an adaptive filter to separate normal from abnormal beats. Normal intervals were addressed to classical frequency-domain heart rate variability analysis, while ectopic beats were further processed to characterize their occurrence, coupling interval distribution and type. Preliminary application of the analysis showed concurrent changes in autonomic function and ectopic activity in the three hours preceding POAF onset. These results suggest the potential of the combined analysis to disclose interaction patterns between autonomic tone and automaticity leading to the onset of post-operative arrhythmias.
Atrial fibrillation (AF), a cardiac arrhythmia classically described as completely desynchronized... more Atrial fibrillation (AF), a cardiac arrhythmia classically described as completely desynchronized, is now known to show a certain amount of synchronized electrical activity. In the present work a new method for quantifying the level of synchronization of the electrical activity recorded in pairs of atrial sites during atrial fibrillation is presented. A synchronization index (Sy) was defined by quantifying the degree of complexity of the distribution of the time delays between sites by Shannon entropy estimation. The capability of Sy to discriminate different AF types in patients was assessed on a database of 60 pairs of endocardial recordings from a multipolar basket catheter. The analysis showed a progressive and significant decrease of Sy with increasing AF complexity classes as defined by Wells (AF type I Sy = 0.73 ± 0.07, type II Sy = 0.56 ± 0.07, type III Sy = 0.36 ± 0.04, p < 0.001). The extension of Sy calculation to the whole right atrium showed the existence of spatial heterogeneities in the synchronization level. Moreover, experiments simulated by a computer model of atrial arrhythmias showed that propagation patterns with different complexity could be the basis of different synchronization levels found in patients. In conclusion the quantification of synchronization by Shannon entropy estimation of time delay dispersion may facilitate the identification of different propagation patterns associated with AF, thus enhancing our understanding of AF mechanisms and helping in its treatment.
We validated a prototype cuff-free device for noninvasive estimation of blood pressure (BP). The ... more We validated a prototype cuff-free device for noninvasive estimation of blood pressure (BP). The system assumed a linear relation between BP values and the inverse of arterial blood pulse transit time, measured as time interval between the R wave on the electrocardiograph and the onset of the peripheral pulse wave on a finger plethysmogram. Thirty-three healthy subjects were analyzed at rest and during increasing stress exercise. To estimate subject-specific linear model parameters, the system was calibrated ad personam with reference to BP measures obtained by a cuff sphygmomanometer. High correlation values (R(2) = 0.89 and 0.78 for systolic and diastolic BP, respectively) and differences consistent with clinical requirements (mean discrepancy of -0.058 and -0.25 mm Hg; 95% confidence interval of -13.0 to +12.9 mm Hg and -11.3 to +10.8 mm Hg, for systolic and diastolic BP, respectively) were observed between device and reference measurements. Calibration parameter stability and accuracy level were confirmed in a midterm evaluation, 30 days after calibration. These findings suggest the suitability of the device for noninvasive BP monitoring and its potentiality for clinical applications. Improvements can be achieved by further investigation of the calibration procedure and sensor placement.
It has been recently suggested that many episodes of atrial fibrillation (AF) may be partially or... more It has been recently suggested that many episodes of atrial fibrillation (AF) may be partially organized at the onset and thus more suitable for antitachycardia pacing therapy. Nevertheless, the time course of organization in the first minutes of AF has not been quantified yet. Twenty episodes of paroxysmal AF were studied. Electrograms were recorded from the right atrium (RA), distal (CSd), and proximal coronary sinus (CSp). The time course of AF cycle length (AFCL) and the regularity of wave morphology (similarity index S) were beat-to-beat measured at each recording site during the first 7 minutes of AF. AFCL and S showed a decreasing trend after the onset of AF. AFCL decreased from 208 +/- 31 to 171 +/- 21 msec (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001), from 206 +/- 40 to 169 +/- 23 msec (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001) and from 190 +/- 42 to 152 +/- 18 msec (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05), respectively, in RA, CSd, and CSp. Similarly, the similarity index decreased in CSd from 0.37 +/- 0.27 to 0.12 +/- 0.09 (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01) and in RA from 0.40 +/- 0.18 to 0.17 +/- 0.16 (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). The 80% of the decrease occurred during the first 3 minutes of the arrhythmia, while after this time both cycle length and similarity index did not change significantly anymore. Conversely, the electrical activity in CSp was highly disorganized (S = 0.05 +/- 0.03) even in the first minute of AF, and no decreasing temporal trend was observed. Higher levels of organization and longer fibrillation intervals exist at the onset of AF. The degree of organization of the electrical activity decays within less than 3 minutes. Since antitachycardia pacing success rate increases with high levels of organization, these results suggest an early delivery of pacing treatment.
The integration of electroanatomic maps with highly resolved computed tomography cardiac images p... more The integration of electroanatomic maps with highly resolved computed tomography cardiac images plays an important role in the successful planning of the ablation procedure of arrhythmias. In this paper, we present and validate a fully-automated strategy for the registration and fusion of sparse, atrial endocardial electroanatomic maps (CARTO maps) with detailed left atrial (LA) anatomical reconstructions segmented from a pre-procedural MDCT scan. Registration is accomplished by a parameterized geometric transformation of the CARTO points and by a stochastic search of the best parameter set which minimizes the misalignment between transformed CARTO points and the LA surface. The subsequent fusion of electrophysiological information on the registered CT atrium is obtained through radial basis function interpolation. The algorithm is validated by simulation and by real data from 14 patients referred to CT imaging prior to the ablation procedure. Results are presented, which show the validity of the algorithmic scheme as well as the accuracy and reproducibility of the integration process. The obtained results encourage the application of the integration method in post-intervention ablation assessment and basic AF research and suggest the development for real-time applications in catheter guiding during ablation intervention.
The aim of this study was to investigate the anatomic distribution of critical sources in patient... more The aim of this study was to investigate the anatomic distribution of critical sources in patients with atrial fibrillation (AF) by fusion of biatrial computed tomography (CT) images with cycle length (CL) and wave similarity (WS) maps. B A C K G R O U N D Experimental and clinical studies show that atrial fibrillation (AF) may originate from rapid and repetitive (RR) sources of activation. Localization of RR sources may be crucial for an effective ablation treatment. Atrial electrograms showing rapid and repetitive activations can be identified by combining WS and CL analysis. M E T H O D S Patients with persistent AF underwent biatrial electroanatomic mapping and preprocedural CT cardiac imaging. WS and CL maps were constructed in 17 patients by calculating the degree of repetitiveness of activation waveforms (similarity index [S]) and the cycle length at each atrial site. WS/CL maps were then integrated with biatrial 3-dimensional CT reconstructions by a stochastic approach.
Biophysically detailed and anatomically realistic atrial models are emerging as a valuable tool i... more Biophysically detailed and anatomically realistic atrial models are emerging as a valuable tool in the study of atrial arrhythmias, nevertheless clinical use of these models would be favored by a reduction of computational times. This paper introduces a novel adaptive mesh algorithm, based on multiresolution representation (MR), for the efficient integration of cardiac ordinary differential equation (ODE)-partial differential equation (PDE) systems on unstructured triangle meshes. The algorithm applies a dynamically adapted node-centered finite volume method (FVM) scheme for integration of diffusion. The method accuracy and efficiency were evaluated by simulating propagation scenarios of increasing complexity levels (pacing, stable spirals, atrial fibrillation) on tomography-derived three-dimensional monolayer atrial models, based on a monodomain reaction-diffusion formulation coupled with the Courtemanche atrial ionic model. All simulated propagation patterns were accurately reproduced with substantially reduced computational times (10%-30% of the full-resolution simulation time). The proposed algorithm, combining the MR computational efficiency with the geometrical flexibility of unstructured meshes, may favor the development of patient-specific multiscale models of atrial arrhythmias and their application in the clinical setting.
Journal of cardiovascular medicine (Hagerstown, Md.), Jan 21, 2015
Heterozygous p.(Ser64Arg) mutation in the natriuretic peptide precursor A gene has been associate... more Heterozygous p.(Ser64Arg) mutation in the natriuretic peptide precursor A gene has been associated with atrial fibrillation in the presence of common single nucleotide polymorphisms (rs10033464 and rs2200733; 4q25) that would act as modifiers. We screened natriuretic peptide precursor A gene in 583 individuals and identified three unrelated carriers of the p.(Ser64Arg) mutation (0.5%). Only one of the three mutation carriers had episodes of atrial fibrillation. Cascade screening of the three families identified seven additional mutation carriers, none showing atrial fibrillation. The patients with atrial fibrillation also carried the rs2200733, which was however found in four additional nonatrial fibrillation family members and carriers of the p.(Ser64Arg). The prevalence of atrial fibrillation in p.(Ser64Arg) carriers was 10% and in those combining the mutation with the risk single nucleotide polymorphisms was 20%. In the unique mutated patient with atrial fibrillation, the arrhyth...
The quantification of the degree of organization of the electrical activity during atrial fibrill... more The quantification of the degree of organization of the electrical activity during atrial fibrillation and the spatial localization of organization levels in a highly-resolved anatomical context may support the investigation of the electrophysiological mechanisms underlying the arrhythmia and the refinement of therapeutic approaches. A multi-technique methodology for the integration of organization maps with CT anatomical images is presented, which takes advantage of innovative signal and image processing techniques, recently developed by our group. Specifically, organization maps were constructed by quantifying the degree of morphological similarity of endocardial activation waves acquired by an electroanatomic mapping system. Accurate 3D-CT reconstructions of the atrial anatomy were obtained by a semiautomatic segmentation process based on marker controlled watershed segmentation. Sparse-point wave-similarity maps were fused on CT atrial reconstructions by a fully-automated regist...
... In fact several observations, both in animal and human studies (Lammers et al., 1991; Waxman ... more ... In fact several observations, both in animal and human studies (Lammers et al., 1991; Waxman et al., 1991, 1992; Vulliemin et al ... of mathematical models have sensitively evolved, leading to the modern biophysical models of cardiac tissue (Luo and Rudy, 1994; Courtemanche ...
Heterozygous p.(Ser64Arg) mutation in the natriuretic peptide precursor A gene has been associate... more Heterozygous p.(Ser64Arg) mutation in the natriuretic peptide precursor A gene has been associated with atrial fibrillation in the presence of common single nucleotide polymorphisms (rs10033464 and rs2200733; 4q25) that would act as modifiers. We screened natriuretic peptide precursor A gene in 583 individuals and identified three unrelated carriers of the p.(Ser64Arg) mutation (0.5%). Only one of the three mutation carriers had episodes of atrial fibrillation. Cascade screening of the three families identified seven additional mutation carriers, none showing atrial fibrillation. The patients with atrial fibrillation also carried the rs2200733, which was however found in four additional nonatrial fibrillation family members and carriers of the p.(Ser64Arg). The prevalence of atrial fibrillation in p.(Ser64Arg) carriers was 10% and in those combining the mutation with the risk single nucleotide polymorphisms was 20%. In the unique mutated patient with atrial fibrillation, the arrhythmias was refractory to both pharmacological and ablation treatment, during 16 years of follow-up; his electrophysiological phenotype was characterized by short atrial cycle lengths with a median value of 131 ms that suggests shortening of atrial action potential. The prevalence of p.(Ser64Arg) mutation is low in the general population as is the prevalence of atrial fibrillation in mutation carriers (1/10). Atrial fibrillation in the affected mutated patient was lone at onset and progressively evolved with peculiar electrophysiological patterns.
American journal of physiology. Heart and circulatory physiology, Jan 24, 2015
The causal relationship between atrial and ventricular activities during human atrial fibrillatio... more The causal relationship between atrial and ventricular activities during human atrial fibrillation (AF) is poorly understood. This study analyzed the effects of an increase in atrial rate on the link between atrial and ventricular activities during AF. Atrial and ventricular time series were determined in fourteen patients during the spontaneous acceleration of the atrial rhythm at AF onset. The dynamical relationship between atrial and ventricular activities was quantified in terms of atrioventricular (AV) coupling by AV synchrogram analysis. The technique identified n:m coupling patterns (n atrial beats in m ventricular cycles), quantifying their percentage (pc), maximal length (lmax) and conduction ratio (CR=m/n). Simulations with a difference-equations AV model were performed to correlate the observed dynamics to specific atrial/nodal properties. The atrial rate increase significantly affected AV coupling and ventricular response during AF. The shortening of atrial intervals fro...
Progress in biophysics and molecular biology, 2014
The identification of suitable markers for critical patterns during atrial fibrillation (AF) may ... more The identification of suitable markers for critical patterns during atrial fibrillation (AF) may be crucial to guide an effective ablation treatment. Single parameter maps, based on dominant frequency and complex fractionated electrograms, have been proposed as a tool for electrogram-guided ablation, however the specificity of these markers is debated. Experimental studies suggest that AF critical patterns may be identified on the basis of specific rate and organization features, where rapid organized and rapid fragmented activities characterize respectively localized sources and critical substrates. In this paper we introduce the logical operator map, a novel mapping tool for a point-by-point identification and localization of AF critical sites. Based on advanced signal and image processing techniques, the approach combines in a single map electrogram-derived rate and organization features with tomographic anatomical detail. The construction of the anatomically-detailed logical ope...
2010 Annual International Conference of the IEEE Engineering in Medicine and Biology, 2010
Although atrial fibrillation (AF) is a common complication of cardiac surgery, its pathophysiolog... more Although atrial fibrillation (AF) is a common complication of cardiac surgery, its pathophysiology remains unclear. The study of post-operative AF demands for the recording of cardiac electrical activity in correspondence of AF onset and progression. Long-term recordings in post-surgery patients could provide this information, but, to date, have been limited to surface signals, which precludes a characterization of the arrhythmic
2014 8th Conference of the European Study Group on Cardiovascular Oscillations (ESGCO), 2014
ABSTRACT The mechanisms underlying the onset of postoperative atrial fibrillation (POAF) are stil... more ABSTRACT The mechanisms underlying the onset of postoperative atrial fibrillation (POAF) are still poorly understood. Enhanced atrial automaticity and alterations in autonomic tone following surgery have been suggested as critical predisposing factors. This paper proposes an unified framework for the combined analysis of ectopic activity and autonomic function preceding POAF. Atrial intervals series were automatically extracted from long-term atrial signal recordings in postoperative patients, and processed with an adaptive filter to separate normal from abnormal beats. Normal intervals were addressed to classical frequency-domain heart rate variability analysis, while ectopic beats were further processed to characterize their occurrence, coupling interval distribution and type. Preliminary application of the analysis showed concurrent changes in autonomic function and ectopic activity in the three hours preceding POAF onset. These results suggest the potential of the combined analysis to disclose interaction patterns between autonomic tone and automaticity leading to the onset of post-operative arrhythmias.
Atrial fibrillation (AF), a cardiac arrhythmia classically described as completely desynchronized... more Atrial fibrillation (AF), a cardiac arrhythmia classically described as completely desynchronized, is now known to show a certain amount of synchronized electrical activity. In the present work a new method for quantifying the level of synchronization of the electrical activity recorded in pairs of atrial sites during atrial fibrillation is presented. A synchronization index (Sy) was defined by quantifying the degree of complexity of the distribution of the time delays between sites by Shannon entropy estimation. The capability of Sy to discriminate different AF types in patients was assessed on a database of 60 pairs of endocardial recordings from a multipolar basket catheter. The analysis showed a progressive and significant decrease of Sy with increasing AF complexity classes as defined by Wells (AF type I Sy = 0.73 ± 0.07, type II Sy = 0.56 ± 0.07, type III Sy = 0.36 ± 0.04, p < 0.001). The extension of Sy calculation to the whole right atrium showed the existence of spatial heterogeneities in the synchronization level. Moreover, experiments simulated by a computer model of atrial arrhythmias showed that propagation patterns with different complexity could be the basis of different synchronization levels found in patients. In conclusion the quantification of synchronization by Shannon entropy estimation of time delay dispersion may facilitate the identification of different propagation patterns associated with AF, thus enhancing our understanding of AF mechanisms and helping in its treatment.
We validated a prototype cuff-free device for noninvasive estimation of blood pressure (BP). The ... more We validated a prototype cuff-free device for noninvasive estimation of blood pressure (BP). The system assumed a linear relation between BP values and the inverse of arterial blood pulse transit time, measured as time interval between the R wave on the electrocardiograph and the onset of the peripheral pulse wave on a finger plethysmogram. Thirty-three healthy subjects were analyzed at rest and during increasing stress exercise. To estimate subject-specific linear model parameters, the system was calibrated ad personam with reference to BP measures obtained by a cuff sphygmomanometer. High correlation values (R(2) = 0.89 and 0.78 for systolic and diastolic BP, respectively) and differences consistent with clinical requirements (mean discrepancy of -0.058 and -0.25 mm Hg; 95% confidence interval of -13.0 to +12.9 mm Hg and -11.3 to +10.8 mm Hg, for systolic and diastolic BP, respectively) were observed between device and reference measurements. Calibration parameter stability and accuracy level were confirmed in a midterm evaluation, 30 days after calibration. These findings suggest the suitability of the device for noninvasive BP monitoring and its potentiality for clinical applications. Improvements can be achieved by further investigation of the calibration procedure and sensor placement.
It has been recently suggested that many episodes of atrial fibrillation (AF) may be partially or... more It has been recently suggested that many episodes of atrial fibrillation (AF) may be partially organized at the onset and thus more suitable for antitachycardia pacing therapy. Nevertheless, the time course of organization in the first minutes of AF has not been quantified yet. Twenty episodes of paroxysmal AF were studied. Electrograms were recorded from the right atrium (RA), distal (CSd), and proximal coronary sinus (CSp). The time course of AF cycle length (AFCL) and the regularity of wave morphology (similarity index S) were beat-to-beat measured at each recording site during the first 7 minutes of AF. AFCL and S showed a decreasing trend after the onset of AF. AFCL decreased from 208 +/- 31 to 171 +/- 21 msec (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001), from 206 +/- 40 to 169 +/- 23 msec (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001) and from 190 +/- 42 to 152 +/- 18 msec (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05), respectively, in RA, CSd, and CSp. Similarly, the similarity index decreased in CSd from 0.37 +/- 0.27 to 0.12 +/- 0.09 (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01) and in RA from 0.40 +/- 0.18 to 0.17 +/- 0.16 (P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001). The 80% of the decrease occurred during the first 3 minutes of the arrhythmia, while after this time both cycle length and similarity index did not change significantly anymore. Conversely, the electrical activity in CSp was highly disorganized (S = 0.05 +/- 0.03) even in the first minute of AF, and no decreasing temporal trend was observed. Higher levels of organization and longer fibrillation intervals exist at the onset of AF. The degree of organization of the electrical activity decays within less than 3 minutes. Since antitachycardia pacing success rate increases with high levels of organization, these results suggest an early delivery of pacing treatment.
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