The efficacy of adenotonsillectomy for relieving obstructive sleep apnoea symptoms in children ha... more The efficacy of adenotonsillectomy for relieving obstructive sleep apnoea symptoms in children has been firmly established, but its precise effects on cardiorespiratory control are poorly understood. In 375 children enrolled in the Childhood Adenotonsillectomy Trial, randomised to undergo either adenotonsillectomy (n=194) or a strategy of watching waiting (n=181), respiratory rate, respiratory sinus arrhythmia and heart rate were analysed during quiet, non-apnoeic and non-hypopnoeic breathing throughout sleep at baseline and at 7 months using overnight polysomnography. Children who underwent early adenotonsillectomy demonstrated an increase in respiratory rate post-surgery while the watchful waiting group showed no change. Heart rate and respiratory sinus arrhythmia were comparable between both arms. On assessing cardiorespiratory variables with regard to normalisation of clinical polysomnography findings during follow-up, heart rate was reduced in children who had resolution of obstructive sleep apnoea syndrome, while no differences in their respiratory rate or respiratory sinus arrhythmia were observed. Adenotonsillectomy for obstructive sleep apnoea increases baseline respiratory rate during sleep. Normalisation of apnoea–hypopnoea index, spontaneously or via surgery, lowers heart rate. Considering the small average effect size, the clinical significance is uncertain. @ERSpublications Adenotonsillectomy for childhood obstructive sleep apnoea increases respiratory rate during sleep http://ow.ly/Dptd300w9Pp
This consensus guideline discusses the electrocardiographic phenomenon of beat-to-beat QT interva... more This consensus guideline discusses the electrocardiographic phenomenon of beat-to-beat QT interval variability (QTV) on surface electrocar-diograms. The text covers measurement principles, physiological basis, and clinical value of QTV. Technical considerations include QT interval measurement and the relation between QTV and heart rate variability. Research frontiers of QTV include understanding of QTV physiology, systematic evaluation of the link between QTV and direct measures of neural activity, modelling of the QTV dependence on the variability of other physiological variables, distinction between QTV and general T wave shape variability, and assessing of the QTV utility for guiding therapy. Increased QTV appears to be a risk marker of arrhythmic and cardiovascular death. It remains to be established whether it can guide therapy alone or in combination with other risk factors. QT interval variability has a possible role in non-invasive assessment of tonic sympathetic activity.
Beat-to-beat variability of the QT interval (QTV) has been used as a marker of repolarization lab... more Beat-to-beat variability of the QT interval (QTV) has been used as a marker of repolarization lability and sympathetic activation. The aim of this study was to establish ECG sampling rate requirements for reliable QT interval variability measurement. We measured QTV in high resolution simulated (1000 Hz) and real ECG (1600 Hz; in the supine position during rest and during sympathetic activation upon standing), using time and frequency domain metrics as well as measures of symbolic dynamics for complexity assessment. We successively halved the sampling rate and investigated its effect on the QTV metrics. Reduction in sampling rate below 400 Hz and 500 Hz, respectively, resulted in a significant overestima-tion of QTV variability and also affected complexity measurement of QTV. QTV increased during standing compared to the supine measurement. At 100 Hz, the posture related change in QTV was completely masked by the measurement noise introduced by the low sampling rate. In conclusion, ECG sampling rates of 500 Hz yields a reliable QTV measurement, while sampling rates of 200 Hz and below should be avoided.
SUMMARY Hypertrophic cardiomyopathy (HCM) is a common heritable cardiac disorder with diverse cli... more SUMMARY Hypertrophic cardiomyopathy (HCM) is a common heritable cardiac disorder with diverse clinical outcomes including sudden death, heart failure, and stroke. Depressed heart rate variability (HRV), a measure of cardiac autonomic regulation, has been shown to predict mortality in patients with cardiovascular disease. Cardiac autonomic remodelling in animal models of HCM are not well characterised. This study analysed Gly203-Ser cardiac troponin-I transgenic (TG) male mice previously demonstrated to develop hallmarks of HCM by age 21 weeks. 33 mice aged 30 and 50 weeks underwent continuous electro-cardiogram (ECG) recording for 30 min under anaesthesia. TG mice demonstrated prolonged P-wave duration (P < 0.001) and PR intervals (P < 0.001) compared to controls. Additionally, TG mice demonstrated depressed standard deviation of RR intervals (SDRR; P < 0.01), coefficient of variation of RR intervals (CVRR; P < 0.001) and standard deviation of heart rate (SDHR; P < 0.001) compared to controls. Additionally, total power was significantly reduced in TG mice (P < 0.05). No significant age-related difference in either strain was observed in ECG or HRV parameters. Mice with HCM developed slowed atrial and atrioventricular conduction and depressed HRV. These changes were conserved with increasing age. This finding may be indicative of atrial and ventricular hypertrophy or dys-function, and perhaps an indication of worse clinical outcome in heart failure progression in HCM patients.
Calibrated variability of muscle sympathetic nerve activity during graded head-up tilt in humans ... more Calibrated variability of muscle sympathetic nerve activity during graded head-up tilt in humans and its link with noradrenaline data and cardiovascular rhythms..—Muscle sympathetic nerve activity (MSNA) variability is traditionally computed through a low-pass filtering procedure that requires normalization. We proposed a new beat-to-beat MSNA variability computation that preserves dimensionality typical of an integrated neural discharge (i.e., bursts per unit of time). The calibrated MSNA (cMSNA) variability technique is contrasted with the traditional uncalibrated MSNA (ucMSNA) version. The powers of cMSNA and ucMSNA variabili-ties in the low-frequency (LF, from 0.04 to 0.15 Hz) band were computed with those of the heart period (HP) of systolic and diastolic arterial pressure (SAP and DAP, respectively) in seven healthy subjects (age, 20 –28 years; median, 22 years; 5 women) during a graded head-up tilt. Subjects were sequentially tilted at 0°, 20°, 30°, 40°, and 60° table inclinations. The LF powers of ucMSNA and HP variabil-ities were expressed in normalized units (LFnu), whereas all remaining spectral markers were expressed in absolute units. We found that 1) the LF power of cMSNA variability was positively correlated with tilt angle, whereas the LFnu power of the ucMSNA series was uncorrelated; 2) the LF power of cMSNA variability was correlated with LF powers of SAP and DAP, LFnu power of HP and noradren-aline concentration, whereas the relationship of the LFnu power of ucMSNA variability to LF powers of SAP and DAP was weaker and that to LFnu power of HP was absent; and 3) the stronger relationship of cMSNA variability to SAP and DAP spectral markers compared with the ucMSNA series was confirmed individually. The cMSNA variability appears to be more suitable in describing sympathetic control in humans than traditional ucMSNA variability. heart rate variability; arterial pressure variability; MSNA; cat-echolamines; autonomic nervous system; cardiovascular control SPECTRAL ANALYSIS OF SPONTANEOUS cardiovascular variability allows the indirect, noninvasive, inference of the autonomic function in humans (1, 20). The suitability of the spectral indexes derived from the beat-to-beat variations of the heart period (HP), of systolic and diastolic arterial pressure (SAP and DAP, respectively) has been validated by assessing their correlation with spectral indexes derived from direct, invasive, microneurographic recordings of muscle sympathetic nerve activity (MSNA) (5, 11, 28) during sympatho-inhibitory and/or sympatho-excitatory maneuvers (4, 10, 18, 21, 26). The link between MSNA and arterial pressure (AP) is widely recognized with MSNA burst rate increasing when AP falls and MSNA becoming silent when AP rises as a result of an operating baroreflex that inhibits sympathetic drive (29), even though central mechanisms such as the entrainment of a central oscillator by pulse-synchronous baroreceptor nerve activity cannot be excluded (2). Baroreflex-mediated modifications of the sympathetic drive are responsible for the changes in HP, and they partially explain the link between MSNA and HP variations (7). Traditionally, validation of the link between MSNA and modifications of HP and AP (mainly SAP and DAP in cardiovascular variability studies) was carried out after applying a suitable low-pass filtering procedure to the MSNA signal that retains the range of frequencies typical of cardio-vascular variability (i.e., from 0 to 0.5 Hz) (4, 10, 18, 21, 26). Because the power of the MSNA signal in the low-frequency (LF, from 0.04 to 0.15 Hz) band is significantly and positively correlated with the LF power of HP variability when expressed in normalized units and with the LF power of SAP variability when expressed in absolute units, this suggests that HP and SAP spectral indexes, when expressed in suitable units, may provide insight into autonomic regulatory mechanisms (21). Because the spectral indexes that describe MSNA variability are traditionally computed directly from a low-pass-filtered version of the MSNA signal (4, 10, 13, 18, 21, 26, 27, 31), these markers quantify the magnitude of changes in burst amplitude and area about their mean value more than the variations in their rate of occurrence. In other words, the variability series of MSNA, as currently derived from the MSNA signal, has the same physical dimension of the MSNA signal (i.e., mV) and does not have the physical dimension of a neural discharge (i.e., bursts per unit of time). As a consequence, the spectral indexes derived from MSNA variability depend on numerous factors including number of active fibers, proximity to the recording electrode to the bundle, operator's experience in picking the nerve up, acquisition system settings (e.g., the gain of the neural traffic amplifier), and level of noise superimposed on the MSNA signal. These factors increase
Introduction: The resting ECG is the most commonly used tool to assess cardiac electrophysiology.... more Introduction: The resting ECG is the most commonly used tool to assess cardiac electrophysiology. Previous studies have estimated heritability of ECG parameters based on these snapshots of the cardiac electrical activity. In this study we set out to determine whether analysis of heart rate specific data from Holter ECGs allows more complete assessment of the heritability of ECG parameters.
Objectives: The inverse relationship between QT interval variability (QTV) and T wave amplitude p... more Objectives: The inverse relationship between QT interval variability (QTV) and T wave amplitude potentially confounds QT variability assessment. We quantified the influence of the T wave amplitude on QTV in a comprehensive dataset and devised a correction formula. Methods: Three ECG datasets of healthy subjects were analyzed to model the relationship between T wave amplitude and QTV. To derive a generally valid correction formula, linear regression analysis was used. The proposed correction formula was applied to patients enrolled in the Evaluation of Defibrillator in Non-Ischemic Cardiomyopathy Treatment Evaluation trial (DEFINITE) to assess the prognostic significance of QTV for all-cause mortality in patients with non-ischemic dilated cardiomyopathy. Results: A strong inverse relationship between T wave amplitude and QTV was demonstrated, both in healthy subjects (R 2 = 0.68, p < 0.001) and DEFINITE patients (R 2 = 0.20, p < 0.001). Applying the T wave amplitude correction to QTV achieved 2.5-times better group discrimination between patients enrolled in the DEFINITE study and healthy subjects. Kaplan-Meier estimator analysis showed that T wave amplitude corrected QTVi is inversely related to survival (p < 0.01) and a significant predictor of all-cause mortality. Conclusion: We have proposed a simple correction formula for improved QTV assessment. Using this correction, predictive value of QTV for all-cause mortality in patients with non-ischemic cardiomyopathy has been demonstrated.
| Atrial fibrillation (AF) is the most common cardiac arrhythmia in humans, with an estimated lif... more | Atrial fibrillation (AF) is the most common cardiac arrhythmia in humans, with an estimated lifetime prevalence of 25%. It is characterized by irregular and disorganized electrical activation of the atria. In the past decade, catheter ablation, i.e., focally burning targeted areas of cardiac muscle, has emerged as a potentially curative therapy for AF. Accompanying this development there has been an increasing interest in quantitative intraprocedural signal analysis to guide the selection of ablation targets. In this review, we provide an overview of quantitative signal processing approaches for mapping and ablation of AF.
Expert Review of Cardiovascular Therapy, Feb 1, 2022
ABSTRACT Introduction Sleep-disordered breathing (SDB) is present in 21–74% of all patients with ... more ABSTRACT Introduction Sleep-disordered breathing (SDB) is present in 21–74% of all patients with atrial fibrillation (AF). Treatment of SDB by positive airway pressure may help to prevent recurrence of AF after electrical cardioversion and help to improve AF ablation success rates in non-randomized studies. Areas covered In this review, the current understanding of the atrial arrhythmogenic pathophysiology of SDB is summarized, and diagnostic and therapeutic challenges in AF patients are discussed. Current international recommendations are presented, and a comprehensive literature search is undertaken. Expert opinion AF patients with SDB rarely report SDB-related symptoms such as daytime sleepiness. Therefore, systematic home sleep testing evaluation should be considered for all patients eligible for rhythm control strategy. A close interdisciplinary collaboration between the electrophysiologist/cardiologist, nurses and sleep-specialists are required for the management of SDB in AF patients. An arrhythmia-orientated assessment of SDB may better quantify SDB-related AF risk in an individual patient and may help to better guide targeted and personalized SDB treatment in AF patients as a component of rhythm and symptom control strategies. Finally, randomized controlled trials are needed to confirm the relationship between SDB and AF, and the benefits of routine testing and treatment of SDB in AF patients.
In recent years, machine learning algorithms have become increasingly popular for analyzing biome... more In recent years, machine learning algorithms have become increasingly popular for analyzing biomedical signals. This includes the detection of cyclic alternating pattern (CAP) in electroencephalography recordings. Here, we investigate the performance gain of a recurrent neural network (RNN) for CAP scoring in comparison to standard classification methods. We analyzed 15 recordings (n1-n15) from the publicly available CAP Sleep Database on Physionet to evaluate each machine learning method. A long short-term memory (LSTM) network increases the accuracy and F1-score by 0.5-3.5% and 3.5-8%, respectively, compared to commonly used classification algorithms such as linear discriminant analysis, k-nearest neighbour or feed-forward neural network. Our results show that by using a LSTM classifier the quantity of correctly detected CAP events can be increased and the number of wrongly classified periods reduced. RNNs significantly improve the precision in CAP scoring by taking advantage of available information from the past for deciding current classification.
The efficacy of adenotonsillectomy for relieving obstructive sleep apnoea symptoms in children ha... more The efficacy of adenotonsillectomy for relieving obstructive sleep apnoea symptoms in children has been firmly established, but its precise effects on cardiorespiratory control are poorly understood. In 375 children enrolled in the Childhood Adenotonsillectomy Trial, randomised to undergo either adenotonsillectomy (n=194) or a strategy of watching waiting (n=181), respiratory rate, respiratory sinus arrhythmia and heart rate were analysed during quiet, non-apnoeic and non-hypopnoeic breathing throughout sleep at baseline and at 7 months using overnight polysomnography. Children who underwent early adenotonsillectomy demonstrated an increase in respiratory rate post-surgery while the watchful waiting group showed no change. Heart rate and respiratory sinus arrhythmia were comparable between both arms. On assessing cardiorespiratory variables with regard to normalisation of clinical polysomnography findings during follow-up, heart rate was reduced in children who had resolution of obstructive sleep apnoea syndrome, while no differences in their respiratory rate or respiratory sinus arrhythmia were observed. Adenotonsillectomy for obstructive sleep apnoea increases baseline respiratory rate during sleep. Normalisation of apnoea–hypopnoea index, spontaneously or via surgery, lowers heart rate. Considering the small average effect size, the clinical significance is uncertain. @ERSpublications Adenotonsillectomy for childhood obstructive sleep apnoea increases respiratory rate during sleep http://ow.ly/Dptd300w9Pp
This consensus guideline discusses the electrocardiographic phenomenon of beat-to-beat QT interva... more This consensus guideline discusses the electrocardiographic phenomenon of beat-to-beat QT interval variability (QTV) on surface electrocar-diograms. The text covers measurement principles, physiological basis, and clinical value of QTV. Technical considerations include QT interval measurement and the relation between QTV and heart rate variability. Research frontiers of QTV include understanding of QTV physiology, systematic evaluation of the link between QTV and direct measures of neural activity, modelling of the QTV dependence on the variability of other physiological variables, distinction between QTV and general T wave shape variability, and assessing of the QTV utility for guiding therapy. Increased QTV appears to be a risk marker of arrhythmic and cardiovascular death. It remains to be established whether it can guide therapy alone or in combination with other risk factors. QT interval variability has a possible role in non-invasive assessment of tonic sympathetic activity.
Beat-to-beat variability of the QT interval (QTV) has been used as a marker of repolarization lab... more Beat-to-beat variability of the QT interval (QTV) has been used as a marker of repolarization lability and sympathetic activation. The aim of this study was to establish ECG sampling rate requirements for reliable QT interval variability measurement. We measured QTV in high resolution simulated (1000 Hz) and real ECG (1600 Hz; in the supine position during rest and during sympathetic activation upon standing), using time and frequency domain metrics as well as measures of symbolic dynamics for complexity assessment. We successively halved the sampling rate and investigated its effect on the QTV metrics. Reduction in sampling rate below 400 Hz and 500 Hz, respectively, resulted in a significant overestima-tion of QTV variability and also affected complexity measurement of QTV. QTV increased during standing compared to the supine measurement. At 100 Hz, the posture related change in QTV was completely masked by the measurement noise introduced by the low sampling rate. In conclusion, ECG sampling rates of 500 Hz yields a reliable QTV measurement, while sampling rates of 200 Hz and below should be avoided.
SUMMARY Hypertrophic cardiomyopathy (HCM) is a common heritable cardiac disorder with diverse cli... more SUMMARY Hypertrophic cardiomyopathy (HCM) is a common heritable cardiac disorder with diverse clinical outcomes including sudden death, heart failure, and stroke. Depressed heart rate variability (HRV), a measure of cardiac autonomic regulation, has been shown to predict mortality in patients with cardiovascular disease. Cardiac autonomic remodelling in animal models of HCM are not well characterised. This study analysed Gly203-Ser cardiac troponin-I transgenic (TG) male mice previously demonstrated to develop hallmarks of HCM by age 21 weeks. 33 mice aged 30 and 50 weeks underwent continuous electro-cardiogram (ECG) recording for 30 min under anaesthesia. TG mice demonstrated prolonged P-wave duration (P < 0.001) and PR intervals (P < 0.001) compared to controls. Additionally, TG mice demonstrated depressed standard deviation of RR intervals (SDRR; P < 0.01), coefficient of variation of RR intervals (CVRR; P < 0.001) and standard deviation of heart rate (SDHR; P < 0.001) compared to controls. Additionally, total power was significantly reduced in TG mice (P < 0.05). No significant age-related difference in either strain was observed in ECG or HRV parameters. Mice with HCM developed slowed atrial and atrioventricular conduction and depressed HRV. These changes were conserved with increasing age. This finding may be indicative of atrial and ventricular hypertrophy or dys-function, and perhaps an indication of worse clinical outcome in heart failure progression in HCM patients.
Calibrated variability of muscle sympathetic nerve activity during graded head-up tilt in humans ... more Calibrated variability of muscle sympathetic nerve activity during graded head-up tilt in humans and its link with noradrenaline data and cardiovascular rhythms..—Muscle sympathetic nerve activity (MSNA) variability is traditionally computed through a low-pass filtering procedure that requires normalization. We proposed a new beat-to-beat MSNA variability computation that preserves dimensionality typical of an integrated neural discharge (i.e., bursts per unit of time). The calibrated MSNA (cMSNA) variability technique is contrasted with the traditional uncalibrated MSNA (ucMSNA) version. The powers of cMSNA and ucMSNA variabili-ties in the low-frequency (LF, from 0.04 to 0.15 Hz) band were computed with those of the heart period (HP) of systolic and diastolic arterial pressure (SAP and DAP, respectively) in seven healthy subjects (age, 20 –28 years; median, 22 years; 5 women) during a graded head-up tilt. Subjects were sequentially tilted at 0°, 20°, 30°, 40°, and 60° table inclinations. The LF powers of ucMSNA and HP variabil-ities were expressed in normalized units (LFnu), whereas all remaining spectral markers were expressed in absolute units. We found that 1) the LF power of cMSNA variability was positively correlated with tilt angle, whereas the LFnu power of the ucMSNA series was uncorrelated; 2) the LF power of cMSNA variability was correlated with LF powers of SAP and DAP, LFnu power of HP and noradren-aline concentration, whereas the relationship of the LFnu power of ucMSNA variability to LF powers of SAP and DAP was weaker and that to LFnu power of HP was absent; and 3) the stronger relationship of cMSNA variability to SAP and DAP spectral markers compared with the ucMSNA series was confirmed individually. The cMSNA variability appears to be more suitable in describing sympathetic control in humans than traditional ucMSNA variability. heart rate variability; arterial pressure variability; MSNA; cat-echolamines; autonomic nervous system; cardiovascular control SPECTRAL ANALYSIS OF SPONTANEOUS cardiovascular variability allows the indirect, noninvasive, inference of the autonomic function in humans (1, 20). The suitability of the spectral indexes derived from the beat-to-beat variations of the heart period (HP), of systolic and diastolic arterial pressure (SAP and DAP, respectively) has been validated by assessing their correlation with spectral indexes derived from direct, invasive, microneurographic recordings of muscle sympathetic nerve activity (MSNA) (5, 11, 28) during sympatho-inhibitory and/or sympatho-excitatory maneuvers (4, 10, 18, 21, 26). The link between MSNA and arterial pressure (AP) is widely recognized with MSNA burst rate increasing when AP falls and MSNA becoming silent when AP rises as a result of an operating baroreflex that inhibits sympathetic drive (29), even though central mechanisms such as the entrainment of a central oscillator by pulse-synchronous baroreceptor nerve activity cannot be excluded (2). Baroreflex-mediated modifications of the sympathetic drive are responsible for the changes in HP, and they partially explain the link between MSNA and HP variations (7). Traditionally, validation of the link between MSNA and modifications of HP and AP (mainly SAP and DAP in cardiovascular variability studies) was carried out after applying a suitable low-pass filtering procedure to the MSNA signal that retains the range of frequencies typical of cardio-vascular variability (i.e., from 0 to 0.5 Hz) (4, 10, 18, 21, 26). Because the power of the MSNA signal in the low-frequency (LF, from 0.04 to 0.15 Hz) band is significantly and positively correlated with the LF power of HP variability when expressed in normalized units and with the LF power of SAP variability when expressed in absolute units, this suggests that HP and SAP spectral indexes, when expressed in suitable units, may provide insight into autonomic regulatory mechanisms (21). Because the spectral indexes that describe MSNA variability are traditionally computed directly from a low-pass-filtered version of the MSNA signal (4, 10, 13, 18, 21, 26, 27, 31), these markers quantify the magnitude of changes in burst amplitude and area about their mean value more than the variations in their rate of occurrence. In other words, the variability series of MSNA, as currently derived from the MSNA signal, has the same physical dimension of the MSNA signal (i.e., mV) and does not have the physical dimension of a neural discharge (i.e., bursts per unit of time). As a consequence, the spectral indexes derived from MSNA variability depend on numerous factors including number of active fibers, proximity to the recording electrode to the bundle, operator's experience in picking the nerve up, acquisition system settings (e.g., the gain of the neural traffic amplifier), and level of noise superimposed on the MSNA signal. These factors increase
Introduction: The resting ECG is the most commonly used tool to assess cardiac electrophysiology.... more Introduction: The resting ECG is the most commonly used tool to assess cardiac electrophysiology. Previous studies have estimated heritability of ECG parameters based on these snapshots of the cardiac electrical activity. In this study we set out to determine whether analysis of heart rate specific data from Holter ECGs allows more complete assessment of the heritability of ECG parameters.
Objectives: The inverse relationship between QT interval variability (QTV) and T wave amplitude p... more Objectives: The inverse relationship between QT interval variability (QTV) and T wave amplitude potentially confounds QT variability assessment. We quantified the influence of the T wave amplitude on QTV in a comprehensive dataset and devised a correction formula. Methods: Three ECG datasets of healthy subjects were analyzed to model the relationship between T wave amplitude and QTV. To derive a generally valid correction formula, linear regression analysis was used. The proposed correction formula was applied to patients enrolled in the Evaluation of Defibrillator in Non-Ischemic Cardiomyopathy Treatment Evaluation trial (DEFINITE) to assess the prognostic significance of QTV for all-cause mortality in patients with non-ischemic dilated cardiomyopathy. Results: A strong inverse relationship between T wave amplitude and QTV was demonstrated, both in healthy subjects (R 2 = 0.68, p < 0.001) and DEFINITE patients (R 2 = 0.20, p < 0.001). Applying the T wave amplitude correction to QTV achieved 2.5-times better group discrimination between patients enrolled in the DEFINITE study and healthy subjects. Kaplan-Meier estimator analysis showed that T wave amplitude corrected QTVi is inversely related to survival (p < 0.01) and a significant predictor of all-cause mortality. Conclusion: We have proposed a simple correction formula for improved QTV assessment. Using this correction, predictive value of QTV for all-cause mortality in patients with non-ischemic cardiomyopathy has been demonstrated.
| Atrial fibrillation (AF) is the most common cardiac arrhythmia in humans, with an estimated lif... more | Atrial fibrillation (AF) is the most common cardiac arrhythmia in humans, with an estimated lifetime prevalence of 25%. It is characterized by irregular and disorganized electrical activation of the atria. In the past decade, catheter ablation, i.e., focally burning targeted areas of cardiac muscle, has emerged as a potentially curative therapy for AF. Accompanying this development there has been an increasing interest in quantitative intraprocedural signal analysis to guide the selection of ablation targets. In this review, we provide an overview of quantitative signal processing approaches for mapping and ablation of AF.
Expert Review of Cardiovascular Therapy, Feb 1, 2022
ABSTRACT Introduction Sleep-disordered breathing (SDB) is present in 21–74% of all patients with ... more ABSTRACT Introduction Sleep-disordered breathing (SDB) is present in 21–74% of all patients with atrial fibrillation (AF). Treatment of SDB by positive airway pressure may help to prevent recurrence of AF after electrical cardioversion and help to improve AF ablation success rates in non-randomized studies. Areas covered In this review, the current understanding of the atrial arrhythmogenic pathophysiology of SDB is summarized, and diagnostic and therapeutic challenges in AF patients are discussed. Current international recommendations are presented, and a comprehensive literature search is undertaken. Expert opinion AF patients with SDB rarely report SDB-related symptoms such as daytime sleepiness. Therefore, systematic home sleep testing evaluation should be considered for all patients eligible for rhythm control strategy. A close interdisciplinary collaboration between the electrophysiologist/cardiologist, nurses and sleep-specialists are required for the management of SDB in AF patients. An arrhythmia-orientated assessment of SDB may better quantify SDB-related AF risk in an individual patient and may help to better guide targeted and personalized SDB treatment in AF patients as a component of rhythm and symptom control strategies. Finally, randomized controlled trials are needed to confirm the relationship between SDB and AF, and the benefits of routine testing and treatment of SDB in AF patients.
In recent years, machine learning algorithms have become increasingly popular for analyzing biome... more In recent years, machine learning algorithms have become increasingly popular for analyzing biomedical signals. This includes the detection of cyclic alternating pattern (CAP) in electroencephalography recordings. Here, we investigate the performance gain of a recurrent neural network (RNN) for CAP scoring in comparison to standard classification methods. We analyzed 15 recordings (n1-n15) from the publicly available CAP Sleep Database on Physionet to evaluate each machine learning method. A long short-term memory (LSTM) network increases the accuracy and F1-score by 0.5-3.5% and 3.5-8%, respectively, compared to commonly used classification algorithms such as linear discriminant analysis, k-nearest neighbour or feed-forward neural network. Our results show that by using a LSTM classifier the quantity of correctly detected CAP events can be increased and the number of wrongly classified periods reduced. RNNs significantly improve the precision in CAP scoring by taking advantage of available information from the past for deciding current classification.
Bipolar electrograms (EGM) are widely used to assess intracardiac electrical activity and to find... more Bipolar electrograms (EGM) are widely used to assess intracardiac electrical activity and to find the atrial fibrillation-related sources. However, the interpretation of bipolar EGM is not straightforward. Variables including bipolar lead (vector) orientation relative to the wave propagation dynamics significantly impact the EGM and EGM-derived measures, which are clinically used to select target sources for catheter ablation. In this study, left atrial unipolar EGM were recorded using a 4 × 4 grid of 16 unipolar electrodes. A set (node) of 4 unipolar EGM were used to construct possible 6 bipolar EGM to evaluate the measurement uncertainty within a particular node. A novel beamforming-inspired spatial filtering (BiSF) method is proposed to reduce the potential measurement uncertainty inevitable in bipolar EGM. A set of three bipolar lead orientations that were constructed using a common unipolar electrode towards three different directions at 45°s, were added to form beamforming EGM. Finally, two beamforming EGM were intertwined to acquire BiSF EGM for a node. Results show greater signal power gain (at least around 10dB) for all BiSF EGM with better or similar signal-to-noise ratio as compared to their respective bipolar counterparts. In conclusion, reduced uncertainty in BiSF EGM improve the interpretation of EGM and EGM-derived measures used in clinical practice after further validation on a larger dataset.
Increased beat-to-beat QT interval variability in electrocardiograms is a robust descriptor of ve... more Increased beat-to-beat QT interval variability in electrocardiograms is a robust descriptor of ventricular depolarization and repolarization lability. Variability analysis of the depolarization and repolarization intervals in vectorcardiogram has indicated potential diagnostic abilities. Here, we describe an inhomogeneous signal adaptation technique for vectorcardiogram. We propose a novel global-to-local adaptation method that yields robust results even when dealing with noisy vectorcardiogram signals. We evaluated several vectorcardiogram features using the proposed adaptation technique on the PTB database to demonstrate its potential diagnostic prowess for myocardial infarction.
Objective. Closed loop cardiovascular (CV) and cerebrovascular (CBV) variability interactions are... more Objective. Closed loop cardiovascular (CV) and cerebrovascular (CBV) variability interactions are assessed via transfer entropy (TE) from systolic arterial pressure (SAP) to heart period (HP) and vice versa and from mean arterial pressure (MAP) to mean cerebral blood velocity (MCBv) and vice versa. This analysis is exploited to assess the efficiency of baroreflex and cerebral autoregulation. This study aims at characterizing CV and CBV controls in postural orthostatic tachycardiac syndrome (POTS) subjects experiencing exaggerated sympathetic response during orthostatic challenge via unconditional TE and TE conditioned on respiratory activity (R). Approach. In 18 healthy controls (age: 28 ± 13 yrs; 5 males, 13 females) and 15 POTS individuals (age: 29 ± 11 yrs; 3 males, 12 females) we acquired beat-to-beat variability of HP, SAP, MAP and MCBv and two R signals, namely respiratory chest movement (RCM) and capnogram (CAP). Recordings were made at sitting rest and during active standing (STAND). TE was computed via vector autoregressive approach. Main results. We found that: (i) when assessing CV interactions, the increase of the TE from SAP to HP during STAND, indicating baroreflex activation, is detected solely when conditioning on RCM; (ii) when assessing CBV interactions, the impact of R on the TE computation is negligible; (iii) POTS shows baroreflex impairment during STAND; (iv) POTS exhibits a normal CBV response to STAND. Significance. TE is useful for detecting the impairment of specific regulatory mechanisms in POTS. Moreover, using different R signals highlights the sensitivity of CV and CBV controls to specific R aspects.
SummarySleep problems are common among veterans with post‐traumatic stress disorder and closely a... more SummarySleep problems are common among veterans with post‐traumatic stress disorder and closely associated with hyperarousal symptoms. Transcutaneous vagus nerve stimulation (tVNS) may have potential to improve sleep quality in veterans with PTSD through effects on brain systems relevant to hyperarousal and sleep–wake regulation. The current pilot study examines the effect of 1 h of tVNS administered at “lights out” on sleep architecture, microstructure, and autonomic activity. Thirteen veterans with PTSD completed two nights of laboratory‐based polysomnography during which they received 1 h of either active tVNS (tragus) or sham stimulation (earlobe) at “lights out” with randomised order. Sleep staging and stability metrics were derived from polysomnography data. Autonomic activity during sleep was assessed using the Porges‐Bohrer method for calculating respiratory sinus arrhythmia (RSAP‐B). Paired t‐tests revealed a small decrease in the total sleep time (d = −0.31), increase in N3 sleep (d = 0.23), and a small‐to‐moderate decrease in REM sleep (d = −0.48) on nights of active tVNS relative to sham stimulation. tVNS was also associated with a moderate reduction in cyclic alternating pattern (CAP) rate (d = −0.65) and small‐to‐moderate increase in RSAP‐B during NREM sleep. Greater NREM RSAP‐B was associated with a reduced CAP rate and NREM alpha power. This pilot study provides preliminary evidence that tVNS may improve sleep depth and stability in veterans with PTSD, as well as increase parasympathetically mediated nocturnal autonomic activity. These results warrant continued investigation into tVNS as a potential tool for treating sleep disturbance in veterans with PTSD.
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