Background: Signal processing tools are required to efficiently analyze data collected in body-su... more Background: Signal processing tools are required to efficiently analyze data collected in body-surface-potential map (BSPM) recordings. A limited number of such tools exist for studying persistent atrial fibrillation (persAF). We propose two novel, spatiotemporal indices for processing BSPM data and test their clinical applicability through a comparison with the recently proposed non-dipolar component index (NDI) for prediction of single-procedure catheter ablation (CA) success rate in persAF patients.Methods: BSPM recordings were obtained with a 252-lead vest in 13 persAF patients (8 men, 63 ± 8 years, 11 ± 13 months sustained AF duration) before undergoing CA. Each recording was divided into seven 1-min segments of high signal quality. Spatiotemporal ventricular activity (VA) cancellation was applied to each segment to isolate atrial activity (AA). The two novel indices, called error-ratio, normalized root-mean-square error (ERNRMSE) and error-ratio, mean-absolute error (ERABSE), ...
BackgroundStudies suggest that performing an electrophysiological study (EPS) may be useful to id... more BackgroundStudies suggest that performing an electrophysiological study (EPS) may be useful to identify patients with new-onset left bundle branch block (LBBB) post-TAVR at risk of atrioventricular block. However, tools to optimize the yield of such strategy are needed. We therefore aimed to investigate whether 12-lead ECG changes post-TAVR may help identify patients with abnormal EPS findings.Materials and methodsConsecutive patients with new-onset LBBB post-TAVR who underwent EPS were included. PR and QRS intervals were measured on 12-lead ECG pre-TAVR and during EPS. Abnormal EPS was defined as an HV interval > 55 ms.ResultsAmong 61 patients, 28 (46%) had an HV interval > 55 ms after TAVR. Post-TAVR PR interval and ΔPR (PR-post–pre-TAVR) were significantly longer in patients with prolonged HV (PR: 188 ± 38 vs. 228 ± 34 ms, p < 0.001, ΔPR: 10 ± 30 vs. 34 ± 23 ms, p = 0.001), while no difference was found in QRS duration. PR and ΔPR intervals both effectively discriminated...
Background: Consistently successful patient outcomes following catheter ablation (CA) for treatme... more Background: Consistently successful patient outcomes following catheter ablation (CA) for treatment of persistent atrial fibrillation (pers-AF) remain elusive. We propose an electrocardiogram (ECG) analysis designed to (1) refine selection of patients most likely to benefit from ablation, and (2) examine the temporal evolution of AF organization indices that could act as clinical indicators of ongoing ablation effectiveness and completeness.Method: Twelve-lead ECG was continuously recorded in 40 patients (61 ± 8 years) during stepwise CA (step-CA) procedures for treatment of pers-AF (sustained duration 19 ± 11 months). Following standard pre-processing, ECG signals were divided into 10-s epochs and labeled according to their temporal placement: pre-PVI (baseline), dur-PVI (during pulmonary vein isolation), and post-PVI (during complex-fractionated atrial electrograms and linear ablation). Instantaneous frequency (IF), adaptive organization index (AOI), sample entropy (SampEn) and f-...
Introduction: We hypothesized that organization indices based on the analysis of atrial ECG harmo... more Introduction: We hypothesized that organization indices based on the analysis of atrial ECG harmonic components may help identify patients (pts) with persistent AF (pAF) unresponsive to pulmonary vein isolation (PVI) and left atrial (LA) ablation. Using adaptive harmonic frequency tracking schemes, we computed on the atrial ECG: 1) the variance of the phase difference (aPD) between the dominant frequency (DF) and the 1st harmonic (H1), and 2) the organization index (AOI) defined as the ratio of the power of the DF and H1 over the total power of the unprocessed atrial signal as measures of AF regularity. Methods: In 34 consecutive pts (61±7 y, pAF duration: 19±11 m), PVI and LA ablation were performed until AF termination. 40-sec ECG time series devoid of QRST were recorded at baseline (BL), after PVI (end_PVI) and at the end of LA ablation (end_ABL). APD and AOI were estimated on leads V1 and V6b (placed on the pts back). Results: pAF was terminated within the LA in 68% (23/34 LT - ...
Objectives: Rapid pacing of atrial fibrillation (AF) can induce local atrial capture. The present... more Objectives: Rapid pacing of atrial fibrillation (AF) can induce local atrial capture. The present model-based study investigated the impact of atrial tissue conduction velocity on AF capture ability during rapid septal pacing. Methods: The AF model combined a membrane kinetics model with geometry based on computed tomography of AF patients. Conduction velocity was varied ±20% over a baseline AF model based on multiple reentrant wavelets. Rapid pacing of AF was applied from the septum for 50s with pacing cycle length (PCL) computed as percent of mean AFCL. Analysis of 24 electrode pairs evenly distributed on the atrial surface yielded percentage of captured tissue (CL within ±5% of PCL). Capture window was the range of PCL with capture > 50%. Reentrant wavelets quantity (#W) was computed before and during pacing. Optimal PCL was leading to the highest capture. Results were averaged on 10 AF simulations. Results: AFCL did not change significantly with conduction velocity, and optim...
2016 Computing in Cardiology Conference (CinC), 2016
Our study aims at determining whether the efficiency of step-wise catheter ablation (step-CA) of ... more Our study aims at determining whether the efficiency of step-wise catheter ablation (step-CA) of persistent atrial fibrillation (pAF) can be tracked using organization indices based on the harmonic components of atrial ECG signals until pAF termination. ECG time series devoid of QRST were recorded at baseline (pre-ablation), after pulmonary vein isolation and at the end of left atrium (LA) ablation. Using adaptive harmonic frequency tracking schemes, two organisation indices characterizing the relationship between the harmonic components of atrial ECG were computed. Patients in whom the pAF termination was achieved during ablation within the LA displayed greater baseline atrial ECG organization that further increased significantly at the end of LA ablation as opposed to patients in whom the pAF did not terminate. Estimation of the level of atrial ECG organization based on adaptive harmonic schemes appears as promising tool for tracking changes in pAF dynamics during CA and predictio...
The paper presents a detailed analysis of two types of pseudorandom binary sequence generators ob... more The paper presents a detailed analysis of two types of pseudorandom binary sequence generators obtained by using tent map. The test is performed using a NIST statistical test suite which is widely used for testing the randomness of any random number generator. The binary sequences under investigation are obtained either by considering all the successive iterations of the tent map and choosing a threshold equal to the tent map parameter or by applying a periodical sampling on the tent map values and by choosing a threshold equal to 0.5. Additionally, the paper comes up with a new discussion concerning the elements of the secret key for both of the generators. Based upon the results presented in the paper, both generators can be used for designing a new cipher where the pseudorandom binary sequence is the main ingredient of the cipher.
This paper completes recent results obtained by extending the running-key cipher procedure from n... more This paper completes recent results obtained by extending the running-key cipher procedure from natural language to applications over chaotic systems. We apply the new running-key approach on the chaotic tent map and prove its utility in obtaining practically zero-redundant pseudo-random number generators, alongside with the possibility to consider the initial condition and the tent map control parameter as elements in the secret key – a desideratum in chaos-based cryptography. The results are both theoretically and experimentally supported by combining concepts from information theory and statistical methods in the context of the chaotic system. The statistical evaluation includes NIST test suite for testing the randomness of the proposed binary generator. Based upon the results presented in this paper, the provided generator can be used for designing new cryptosystems where the pseudorandom binary sequences can be a chief support.
The electrocardiogram (ECG) of patients with BrS in sinus rhythm might reflect intrinsic atrial e... more The electrocardiogram (ECG) of patients with BrS in sinus rhythm might reflect intrinsic atrial electrical abnormalities independent from any previous atrial fibrillation (AF). Aim of this study is to investigate the presence of P-wave abnormalities in patients with BrS and no history of AF, and to compare them with those displayed by patients with documented paroxysmal AF and by healthy subjects. Continuous 5-min 16-lead ECG recordings in sinus rhythm were obtained from 72 participants: 32 patients with a type 1 Brugada ECG, 20 patients with a history of paroxysmal AF and 20 age-matched healthy subjects. Different ECG-based features were computed on the P-wave first principal component representing the predominant morphology across leads and containing the maximal information on atrial depolarization: duration, full width half maximum (FWHM), area under the curve and number of peaks in the wave. Patients with BrS and no history of AF (mean age: 53±12years; males: 28 pts., spontaneo...
Background: Signal processing tools are required to efficiently analyze data collected in body-su... more Background: Signal processing tools are required to efficiently analyze data collected in body-surface-potential map (BSPM) recordings. A limited number of such tools exist for studying persistent atrial fibrillation (persAF). We propose two novel, spatiotemporal indices for processing BSPM data and test their clinical applicability through a comparison with the recently proposed non-dipolar component index (NDI) for prediction of single-procedure catheter ablation (CA) success rate in persAF patients.Methods: BSPM recordings were obtained with a 252-lead vest in 13 persAF patients (8 men, 63 ± 8 years, 11 ± 13 months sustained AF duration) before undergoing CA. Each recording was divided into seven 1-min segments of high signal quality. Spatiotemporal ventricular activity (VA) cancellation was applied to each segment to isolate atrial activity (AA). The two novel indices, called error-ratio, normalized root-mean-square error (ERNRMSE) and error-ratio, mean-absolute error (ERABSE), ...
BackgroundStudies suggest that performing an electrophysiological study (EPS) may be useful to id... more BackgroundStudies suggest that performing an electrophysiological study (EPS) may be useful to identify patients with new-onset left bundle branch block (LBBB) post-TAVR at risk of atrioventricular block. However, tools to optimize the yield of such strategy are needed. We therefore aimed to investigate whether 12-lead ECG changes post-TAVR may help identify patients with abnormal EPS findings.Materials and methodsConsecutive patients with new-onset LBBB post-TAVR who underwent EPS were included. PR and QRS intervals were measured on 12-lead ECG pre-TAVR and during EPS. Abnormal EPS was defined as an HV interval > 55 ms.ResultsAmong 61 patients, 28 (46%) had an HV interval > 55 ms after TAVR. Post-TAVR PR interval and ΔPR (PR-post–pre-TAVR) were significantly longer in patients with prolonged HV (PR: 188 ± 38 vs. 228 ± 34 ms, p < 0.001, ΔPR: 10 ± 30 vs. 34 ± 23 ms, p = 0.001), while no difference was found in QRS duration. PR and ΔPR intervals both effectively discriminated...
Background: Consistently successful patient outcomes following catheter ablation (CA) for treatme... more Background: Consistently successful patient outcomes following catheter ablation (CA) for treatment of persistent atrial fibrillation (pers-AF) remain elusive. We propose an electrocardiogram (ECG) analysis designed to (1) refine selection of patients most likely to benefit from ablation, and (2) examine the temporal evolution of AF organization indices that could act as clinical indicators of ongoing ablation effectiveness and completeness.Method: Twelve-lead ECG was continuously recorded in 40 patients (61 ± 8 years) during stepwise CA (step-CA) procedures for treatment of pers-AF (sustained duration 19 ± 11 months). Following standard pre-processing, ECG signals were divided into 10-s epochs and labeled according to their temporal placement: pre-PVI (baseline), dur-PVI (during pulmonary vein isolation), and post-PVI (during complex-fractionated atrial electrograms and linear ablation). Instantaneous frequency (IF), adaptive organization index (AOI), sample entropy (SampEn) and f-...
Introduction: We hypothesized that organization indices based on the analysis of atrial ECG harmo... more Introduction: We hypothesized that organization indices based on the analysis of atrial ECG harmonic components may help identify patients (pts) with persistent AF (pAF) unresponsive to pulmonary vein isolation (PVI) and left atrial (LA) ablation. Using adaptive harmonic frequency tracking schemes, we computed on the atrial ECG: 1) the variance of the phase difference (aPD) between the dominant frequency (DF) and the 1st harmonic (H1), and 2) the organization index (AOI) defined as the ratio of the power of the DF and H1 over the total power of the unprocessed atrial signal as measures of AF regularity. Methods: In 34 consecutive pts (61±7 y, pAF duration: 19±11 m), PVI and LA ablation were performed until AF termination. 40-sec ECG time series devoid of QRST were recorded at baseline (BL), after PVI (end_PVI) and at the end of LA ablation (end_ABL). APD and AOI were estimated on leads V1 and V6b (placed on the pts back). Results: pAF was terminated within the LA in 68% (23/34 LT - ...
Objectives: Rapid pacing of atrial fibrillation (AF) can induce local atrial capture. The present... more Objectives: Rapid pacing of atrial fibrillation (AF) can induce local atrial capture. The present model-based study investigated the impact of atrial tissue conduction velocity on AF capture ability during rapid septal pacing. Methods: The AF model combined a membrane kinetics model with geometry based on computed tomography of AF patients. Conduction velocity was varied ±20% over a baseline AF model based on multiple reentrant wavelets. Rapid pacing of AF was applied from the septum for 50s with pacing cycle length (PCL) computed as percent of mean AFCL. Analysis of 24 electrode pairs evenly distributed on the atrial surface yielded percentage of captured tissue (CL within ±5% of PCL). Capture window was the range of PCL with capture > 50%. Reentrant wavelets quantity (#W) was computed before and during pacing. Optimal PCL was leading to the highest capture. Results were averaged on 10 AF simulations. Results: AFCL did not change significantly with conduction velocity, and optim...
2016 Computing in Cardiology Conference (CinC), 2016
Our study aims at determining whether the efficiency of step-wise catheter ablation (step-CA) of ... more Our study aims at determining whether the efficiency of step-wise catheter ablation (step-CA) of persistent atrial fibrillation (pAF) can be tracked using organization indices based on the harmonic components of atrial ECG signals until pAF termination. ECG time series devoid of QRST were recorded at baseline (pre-ablation), after pulmonary vein isolation and at the end of left atrium (LA) ablation. Using adaptive harmonic frequency tracking schemes, two organisation indices characterizing the relationship between the harmonic components of atrial ECG were computed. Patients in whom the pAF termination was achieved during ablation within the LA displayed greater baseline atrial ECG organization that further increased significantly at the end of LA ablation as opposed to patients in whom the pAF did not terminate. Estimation of the level of atrial ECG organization based on adaptive harmonic schemes appears as promising tool for tracking changes in pAF dynamics during CA and predictio...
The paper presents a detailed analysis of two types of pseudorandom binary sequence generators ob... more The paper presents a detailed analysis of two types of pseudorandom binary sequence generators obtained by using tent map. The test is performed using a NIST statistical test suite which is widely used for testing the randomness of any random number generator. The binary sequences under investigation are obtained either by considering all the successive iterations of the tent map and choosing a threshold equal to the tent map parameter or by applying a periodical sampling on the tent map values and by choosing a threshold equal to 0.5. Additionally, the paper comes up with a new discussion concerning the elements of the secret key for both of the generators. Based upon the results presented in the paper, both generators can be used for designing a new cipher where the pseudorandom binary sequence is the main ingredient of the cipher.
This paper completes recent results obtained by extending the running-key cipher procedure from n... more This paper completes recent results obtained by extending the running-key cipher procedure from natural language to applications over chaotic systems. We apply the new running-key approach on the chaotic tent map and prove its utility in obtaining practically zero-redundant pseudo-random number generators, alongside with the possibility to consider the initial condition and the tent map control parameter as elements in the secret key – a desideratum in chaos-based cryptography. The results are both theoretically and experimentally supported by combining concepts from information theory and statistical methods in the context of the chaotic system. The statistical evaluation includes NIST test suite for testing the randomness of the proposed binary generator. Based upon the results presented in this paper, the provided generator can be used for designing new cryptosystems where the pseudorandom binary sequences can be a chief support.
The electrocardiogram (ECG) of patients with BrS in sinus rhythm might reflect intrinsic atrial e... more The electrocardiogram (ECG) of patients with BrS in sinus rhythm might reflect intrinsic atrial electrical abnormalities independent from any previous atrial fibrillation (AF). Aim of this study is to investigate the presence of P-wave abnormalities in patients with BrS and no history of AF, and to compare them with those displayed by patients with documented paroxysmal AF and by healthy subjects. Continuous 5-min 16-lead ECG recordings in sinus rhythm were obtained from 72 participants: 32 patients with a type 1 Brugada ECG, 20 patients with a history of paroxysmal AF and 20 age-matched healthy subjects. Different ECG-based features were computed on the P-wave first principal component representing the predominant morphology across leads and containing the maximal information on atrial depolarization: duration, full width half maximum (FWHM), area under the curve and number of peaks in the wave. Patients with BrS and no history of AF (mean age: 53±12years; males: 28 pts., spontaneo...
Uploads
Papers by Adrian Luca