Ultra-high-frequency ECG volumetric and negative derivative epicardial ventricular electrical activation pattern

From precordial ECG leads, the conventional determination of the negative derivative of the QRS complex (ND-ECG) assesses epicardial activation. Recently we showed that ultra-high-frequency electrocardiography (UHF-ECG) determines the activation of a larger volume of the ventricular wall. We aimed to combine these two methods to investigate the potential of volumetric and epicardial ventricular activation assessment and thereby determine the transmural activation sequence. We retrospectively analyzed 390 ECG records divided into three groups-healthy subjects with normal ECG, left bundle branch block (LBBB), and right bundle branch block (RBBB) patients. Then we created UHF-ECG and ND-ECG-derived depolarization maps and computed interventricular electrical dyssynchrony. Characteristic spatio-temporal differences were found between the volumetric UHF-ECG activation patterns and epicardial ND-ECG in the Normal, LBBB, and RBBB groups, despite the overall high correlations between both methods. Interventricular electrical dyssynchrony values assessed by the ND-ECG were consistently larger than values computed by the UHF-ECG method. Noninvasively obtained UHF-ECG and ND-ECG analyses describe different ventricular dyssynchrony and the general course of ventricular depolarization. Combining both methods based on standard 12-lead ECG electrode positions allows for a more detailed analysis of volumetric and epicardial ventricular electrical activation, including the assessment of the depolarization wave direction propagation in ventricles.

Left bundle branch area pacing results in more physiological ventricular activation than biventricular pacing in patients with left bundle branch block heart failure

Biventricular pacing (Biv) and left bundle branch area pacing (LBBAP) are methods of cardiac resynchronization therapy (CRT). Currently, little is known about how they differ in terms of ventricular activation. This study compared ventricular activation patterns in left bundle branch block (LBBB) heart failure patients using an ultra-high-frequency electrocardiography (UHF-ECG). This was a retrospective analysis including 80 CRT patients from two centres. UHF-ECG data were obtained during LBBB, LBBAP, and Biv. Left bundle branch area pacing patients were divided into non-selective left bundle branch pacing (NSLBBP) or left ventricular septal pacing (LVSP) and into groups with V6 R-wave peak times (V6RWPT) < 90 ms and ≥ 90 ms. Calculated parameters were: e-DYS (time difference between the first and last activation in V1-V8 leads) and Vdmean (average of V1-V8 local depolarization durations). In LBBB patients (n = 80) indicated for CRT, spontaneous rhythms were compared with Biv (39) and LBBAP rhythms (64). Although both Biv and LBBAP significantly reduced QRS duration (QRSd) compared with LBBB (from 172 to 148 and 152 ms, respectively, both P < 0.001), the difference between them was not significant (P = 0.2). Left bundle branch area pacing led to shorter e-DYS (24 ms) than Biv (33 ms; P = 0.008) and shorter Vdmean (53 vs. 59 ms; P = 0.003). No differences in QRSd, e-DYS, or Vdmean were found between NSLBBP, LVSP, and LBBAP with paced V6RWPTs < 90 and ≥ 90 ms. Both Biv CRT and LBBAP significantly reduce ventricular dyssynchrony in CRT patients with LBBB. Left bundle branch area pacing is associated with more physiological ventricular activation.

Bipolar anodal septal pacing with direct LBB capture preserves physiological ventricular activation better than unipolar left bundle branch pacing

Background

Left bundle branch pacing (LBBP) produces delayed, unphysiological activation of the right ventricle. Using ultra-high-frequency electrocardiography (UHF-ECG), we explored how bipolar anodal septal pacing with direct LBB capture (aLBBP) affects the resultant ventricular depolarization pattern.

Methods

In patients with bradycardia, His bundle pacing (HBP), unipolar nonselective LBBP (nsLBBP), aLBBP, and right ventricular septal pacing (RVSP) were performed. Timing of local ventricular activation, in leads V1-V8, was displayed using UHF-ECG, and electrical dyssynchrony (e-DYS) was calculated as the difference between the first and last activation. Durations of local depolarizations were determined as the width of the UHF-QRS complex at 50% of its amplitude.

Results

aLBBP was feasible in 63 of 75 consecutive patients with successful nsLBBP. aLBBP significantly improved ventricular dyssynchrony (mean -9 ms; 95% CI (-12;-6) vs. -24 ms (-27;-21), ), p < 0.001) and shortened local depolarization durations in V1-V4 (mean differences -7 ms to -5 ms (-11;-1), p < 0.05) compared to nsLBBP. aLBBP resulted in e-DYS -9 ms (-12; -6) vs. e-DYS 10 ms (7;14), p < 0.001 during HBP. Local depolarization durations in V1-V2 during aLBBP were longer than HBP (differences 5-9 ms (1;14), p < 0.05, with local depolarization duration in V1 during aLBBP being the same as during RVSP (difference 2 ms (-2;6), p = 0.52).

Conclusion

Although aLBBP improved ventricular synchrony and depolarization duration of the septum and RV compared to unipolar nsLBBP, the resultant ventricular depolarization was still less physiological than during HBP.

Ventricular Dyssynchrony and Pacing-induced Cardiomyopathy in Patients with Pacemakers, the Utility of Ultra-high-frequency ECG and Other Dyssynchrony Assessment Tools

The majority of patients tolerate right ventricular pacing well; however, some patients manifest signs of heart failure after pacemaker implantation and develop pacing-induced cardiomyopathy. This is a consequence of non-physiological ventricular activation bypassing the conduction system. Ventricular dyssynchrony was identified as one of the main factors responsible for pacing-induced cardiomyopathy development. Currently, methods that would allow rapid and reliable ventricular dyssynchrony assessment, ideally during the implant procedure, are lacking. Paced QRS duration is an imperfect marker of dyssynchrony, and methods based on body surface mapping, electrocardiographic imaging or echocardiography are laborious and time-consuming, and can be difficult to use during the implantation procedure. However, the ventricular activation sequence can be readily displayed from the chest leads using an ultra-high-frequency ECG. It can be performed during the implantation procedure to visualise ventricular depolarisation and resultant ventricular dyssynchrony during pacing. This information can assist the electrophysiologist in selecting a pacing location that avoids dyssynchronous ventricular activation.

Left bundle branch pacing with normal paced QRS axis produce more physiological left ventricular lateral wall depolarization than its pacing resulting in heart axis deviation

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Ministry of Health of the Czech Republic

Background

Left bundle branch pacing is defined as the pacing of the trunk or its proximal fascicles, usually with septal myocardial pacing at low output. It preserves physiological left ventricular activation; however, it is unknown if there is a difference between captures with normal or deviated axes and pacing in proximal vs. distal locations.

Objective

To study ventricular activation during nonselective LBB pacing (nsLBBp) resulting in different paced QRS axes and proximal vs. distal pacing positions using ultra-high-frequency ECG (UHF-ECG).

Methods

This was a retrospective analysis of patients with bradycardia in which nsLBBp was archived during an implant procedure, and UHF-ECG analysis of ventricular activation was performed. nsLBBp captures were classified according to paced QRS axis as with superior (-30°;-90°), normal (-29°;60°), or inferior (61°;120°) axis deviation and proximal (LBbpo to ventricular EGM signal distance ≥ 26 ms) vs. distal (LBBpo to ventricular EGM signal distance &lt; 26 ms). UHF-ECG electrical dyssynchrony parameters – e-DYS (difference between the first and last ventricular activation), local depolarization durations in precordial leads (V1-V8d), and their mean value (Vdmean) were calculated.

Results

We have studied 79 nsLBBp, of which 35 had superior, 28 normal, and 16 had inferior paced QRS axes. There was no difference in LBBpo to V distance, QRSduration, V5 RWPT, or e-DYS (-27 ms vs. – 22 ms vs. -25 ms for superior vs. normal vs. inferior axes; p = NS) between them. However, nsLBBp with normal paced QRS axis had shorter Vdmean (43 ±6 ms) compared to captures with superior (48 ± 7 ms) and inferior axis deviation (48 ± 6 ms); p &lt; 0.05. It was mainly due to shorter V7-8d during nsLBBp with normal axis (mean difference of - 10 ms; p &lt; 0.05) than in captures with superior or inferior axes. No difference in any of the studied parameters was noted when comparing proximal vs. distal pacing locations.

Conclusion

Nonselective capture of the left bundle branch resulting in normal paced QRS axis produces more physiological LV activation compared to captures with superior or inferior axes deviations.

Left ventricular septal pacing: how deep is enough?

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): Charles University Research Program

Background

When pacing in the left septal area, it is not clear where the pacing lead needs to be implanted to obtain the most physiological ventricular activation during pure myocardial pacing.

Objective

To use UHF-ECG to compare ventricular activation between myocardial pacing of the left septum with and without the possibility to capture the left bundle branch by high output pacing.

Methods

This was a retrospective study of patients with bradycardia and deep septal myocardial pacing close to LBB (paraLBBP) or deep septal pacing more distant from LBB (DSTP), which both produced a pseudo-right bundle branch morphology in V1. During paraLBBP, left bundle branch capture was feasible during increasing pacing output up to 5V at 0.5 ms, but during DSTP, LBB capture was not possible during high output pacing. Only patients with both paraLBBP and DSTP were analyzed. Paced QRS morphology, presence of LBBpotential, QRSduration, R wave peak time (RWPT) in V5, lead depth in the septum and UHF-ECG parameters of dyssynchrony, i.e., e-DYS as the difference between the first and last ventricular activation and local depolarization durations in precordial leads (V1-V8d) were compared between them.

Results

From 119 consecutive bradycardia patients enrolled, we identified 23 with both paraLBBP and DSTP during an implant procedure. On X-ray, a lead tip was placed shallower during DSTP than paraLBBP (12 ± 3 vs. 15 ± 3 mm, p &lt; 0.001). A pseudo right bundle branch block morphology was present in all cases, but LBB potential was more frequently present in paraLBBP (17 of 23) than in DSTP (4 of 36; p &lt; 0.0001). QRSd was not significantly different (146 ± 14 vs. 142 ± 14 ms, p = 0.08), but DSTP had longer V5RWPT (86 ± 11 vs. 83 ± 9 ms; p = 0.03). paraLBBP resulted in larger interventricular dyssynchrony, e-DYS (-20 ± 15 vs. -12 ± 18 ms; p = 0.046), the same V1-6d, but its local depolarization durations in V7 and V8 (V7 and V8d) were shorter compared to DSTP (-5 and -7 ms; p &lt; 0.05).

Conclusion

Interventricular dyssynchrony and LV lateral wall depolarization during myocardial pacing of the left septum are dependent on the relation of the leads´ tip to the LBB. Pacing positions closer to the LBB are responsible for bigger interventricular dyssynchrony and more physiological LV lateral wall depolarization.

Bilateral bundle branch capture during deep septal myocardial and nonselective left bundle branch pacing preserves interventricular synchrony

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Ministry of Health of the Czech Republic

Background

Both left bundle branch pacing (LBBP) and deep septal myocardial pacing (LVSP) are less physiological than His bundle pacing. However, pacing both anode and cathode of the lead that is positioned in the interventricular septum may provide bilateral bundle branch capture, which may result in better interventricular synchrony.

Objective

To use UHF-ECG to compare ventricular activation between HBp and bilateral bundle branch capture during left bundle branch (LBBPbi) and deep septal myocardial pacing (LVSPbi).

Methods

Studies were performed in consecutive bradycardia patients. Bipolar pacing was performed with the lead in the LBBP (pseudo right bundle branch block morphology in V1 + proved LBB capture) and LVSP (pseudo right bundle branch block morphology in V1 without proved LBB capture) positions, with the pacing output leading to bilateral bundle branch capture. QRS duration was measured from the first to the last deflection of the QRS in any lead. UHF-ECG electrical dyssynchrony parameters – e-DYS (difference between the first and last ventricular activation) and local depolarization durations in precordial leads (V1-V8d) were calculated.

Results

In 94 consecutive patients, measurements were performed during HBp (n = 75) and LVSPbi (n = 37) and LBBPbi (n = 64). The average pacing threshold leading to bilateral bundle branch capture was 2.6 V at 0.5 ms. nsHBp led to the shortest QRSd compared to sLBBPbi and LVSPbi (98 vs. 103 vs. 110 ms; p &lt; 0.01). LVSPbi showed smallest e-DYS -2 ms vs. -8 ms during LBBPbi and 11 ms during nsHBp; p &lt; 0.05, but V5-8d were during LVSPbi longer than during nsHBp and LBBPbi (absolute difference 4-9 ms); p &lt; 0.05. No statistical difference in V5-V8d were observed between LBBPbi and nsHBp.

Conclusion

Bilateral bundle branch capture during LVSP and nsLBBp preserves interventricular synchrony at the same level as HBp and thus leads to more physiological ventricular activation in patients with bradycardia.

Reliable P wave detection in pathological ECG signals

Accurate automated detection of P waves in ECG allows to provide fast correct diagnosis of various cardiac arrhythmias and select suitable strategy for patients’ treatment. However, P waves detection is a still challenging task, especially in long-term ECGs with manifested cardiac pathologies. Software tools used in medical practice usually fail to detect P waves under pathological conditions. Most of recently published approaches have not been tested on such the signals at all. Here we introduce a novel method for accurate and reliable P wave detection, which is success in both normal and pathological cases. Our method uses phasor transform of ECG and innovative decision rules in order to improve P waves detection in pathological signals. The rules are based on a deep knowledge of heart manifestation during various arrhythmias, such as atrial fibrillation, premature ventricular contraction, etc. By involving the rules into the decision process, we are able to find the P wave in the correct location or, alternatively, not to search for it at all. In contrast to another studies, we use three, highly variable annotated ECG databases, which contain both normal and pathological records, to objectively validate our algorithm. The results for physiological records are Se = 98.56% and PP = 99.82% for MIT-BIH Arrhythmia Database (MITDP, with MITDB P-Wave Annotations) and Se = 99.23% and PP = 99.12% for QT database. These results are comparable with other published methods. For pathological signals, the proposed method reaches Se = 96.40% and PP = 91.56% for MITDB and Se = 93.07% and PP = 88.60% for Brno University of Technology ECG Signal Database with Annotations of P wave (BUT PDB). In these signals, the proposed detector greatly outperforms other methods and, thus, represents a huge step towards effective use of fully automated ECG analysis in a real medical practice.

Classification of ECG using ensemble of residual CNNs with or without attention mechanism

This paper introduces a winning solution (team ISIBrno-AIMT) to the official round of PhysioNet Challenge 2021. The main goal of the challenge was a classification of ECG recordings into 26 multi-label pathological classes with variable number of leads (e.g., 12,6,4,3,2). We introduced an ECG classification method based on the ResNet architecture with a multi-head attention mechanism for the official round of the challenge. However, empirical findings collected during model development suggested that the multi-head attention layer might not significantly impact the final classification performance. For this reason, during the follow-up round, we removed a multi-head attention layer to test the influence on model performance. Like the official round, the model is optimized using a mixture of loss functions, i.e., binary cross-entropy, custom challenge score loss function, and custom sparsity loss function. Probability thresholds for each classification class are estimated using the evolutionary optimization method. The final architecture consists of three submodels forming a majority voting classification ensemble. Our findings from the follow- up submission support the fact that the multi-head attention layer in the proposed architecture does not significantly affect the classification performance. The modified model without the multi-head attention layer increased the overall challenge score to 0.59 compared to the 0.58 from the official round.

Left Ventricular Myocardial Septal Pacing in Close Proximity to LBB Does Not Prolong the Duration of the Left Ventricular Lateral Wall Depolarization Compared to LBB Pacing

Background: Three different ventricular capture types are observed during left bundle branch pacing (LBBp). They are selective LBB pacing (sLBBp), non-selective LBB pacing (nsLBBp), and myocardial left septal pacing transiting from nsLBBp while decreasing the pacing output (LVSP). Study aimed to compare differences in ventricular depolarization between these captures using ultra-high-frequency electrocardiography (UHF-ECG).

Methods: Using decremental pacing voltage output, we identified and studied nsLBBp, sLBBp, and LVSP in patients with bradycardia. Timing of ventricular activations in precordial leads was displayed using UHF-ECGs, and electrical dyssynchrony (e-DYS) was calculated as the difference between the first and last activation. The durations of local depolarizations (Vd) were determined as the width of the UHF-QRS complex at 50% of its amplitude.

Results: In 57 consecutive patients, data were collected during nsLBBp (n = 57), LVSP (n = 34), and sLBBp (n = 23). Interventricular dyssynchrony (e-DYS) was significantly lower during LVSP −16 ms (−21; −11), than nsLBBp −24 ms (−28; −20) and sLBBp −31 ms (−36; −25). LVSP had the same V1d-V8d as nsLBBp and sLBBp except for V3d, which during LVSP was shorter than sLBBp; the mean difference −9 ms (−16; −1), p = 0.01. LVSP caused less interventricular dyssynchrony and the same or better local depolarization durations than nsLBBp and sLBBp irrespective of QRS morphology during spontaneous rhythm or paced QRS axis.

Conclusions: In patients with bradycardia, LVSP in close proximity to LBB resulted in better interventricular synchrony than nsLBBp and sLBBp and did not significantly prolong depolarization of the left ventricular lateral wall.

Brno University of Technology Smartphone PPG Database (BUT PPG): Annotated Dataset for PPG Quality Assessment and Heart Rate Estimation

To the best of our knowledge, there is no annotated database of PPG signals recorded by smartphone publicly available. This article introduces Brno University of Technology Smartphone PPG Database (BUT PPG) which is an original database created by the cardiology team at the Department of Biomedical Engineering, Brno University of Technology, for the purpose of evaluating photoplethysmographic (PPG) signal quality and estimation of heart rate (HR). The data comprises 48 10-second recordings of PPGs and associated electrocardiographic (ECG) signals used for determination of reference HR. The data were collected from 12 subjects (6 female, 6 male) aged between 21 and 61. PPG data were collected by smartphone Xiaomi Mi9 with sampling frequency of 30 Hz. Reference ECG signals were recorded using a mobile ECG recorder (Bittium Faros 360) with a sampling frequency of 1,000 Hz. Each PPG signal includes annotation of quality created manually by biomedical experts and reference HR. PPG signal quality is indicated binary: 1 indicates good quality for HR estimation, 0 indicates signals where HR cannot be detected reliably, and thus, these signals are unsuitable for further analysis. As the only available database containing PPG signals recorded by smartphone, BUT PPG is a unique tool for the development of smart, user-friendly, cheap, on-the-spot, self-home-monitoring of heart rate with the potential of widespread using.

Di-4-ANEPPS Modulates Electrical Activity and Progress of Myocardial Ischemia in Rabbit Isolated Heart

Aims

Although voltage-sensitive dye di-4-ANEPPS is a common tool for mapping cardiac electrical activity, reported effects on electrophysiological parameters are rather. The main goals of the study were to reveal effects of the dye on rabbit isolated heart and to verify, whether rabbit isolated heart stained with di-4-ANEPPS is a suitable tool for myocardial ischemia investigation.

Methods and Results

Study involved experiments on stained (n = 9) and non-stained (n = 11) Langendorff perfused rabbit isolated hearts. Electrophysiological effects of the dye were evaluated by analysis of various electrogram (EG) parameters using common paired and unpaired statistical tests. It was shown that staining the hearts with di-4-ANEPPS leads to only short-term sporadic prolongation of impulse conduction through atria and atrioventricular node. On the other hand, significant irreversible slowing of heart rate and ventricular conduction were found in stained hearts as compared to controls. In patch clamp experiments, significant inhibition of sodium current density was observed in differentiated NG108-15 cells stained by the dye. Although no significant differences in mean number of ventricular premature beats were found between the stained and the non-stained hearts in ischemia as well as in reperfusion, all abovementioned results indicate increased arrhythmogenicity. In isolated hearts during ischemia, prominent ischemic patterns appeared in the stained hearts with 3–4 min delay as compared to the non-stained ones. Moreover, the ischemic changes did not achieve the same magnitude as in controls even after 10 min of ischemia. It resulted in poor performance of ischemia detection by proposed EG parameters, as was quantified by receiver operating characteristics analysis.

Conclusion

Our results demonstrate significant direct irreversible effect of di-4-ANEPPS on spontaneous heart rate and ventricular impulse conduction in rabbit isolated heart model. Particularly, this should be considered when di-4-ANEPPS is used in ischemia studies in rabbit. Delayed attenuated response of such hearts to ischemia might lead to misinterpretation of obtained results.

Direct capture of the left bundle branch compared to left bundle branch area pacing deteriorates interventricular synchrony but improves left ventricular lateral wall depolarization duration

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): This paper was supported by the Charles University Research Centre program No. UNCE/MED/002 and 260530/SVV/2020

Background

Direct and indirect pacing of the left bundle branch are novel pacing techniques preserving LV synchrony. Aim of the study was to compare differences in ventricular activation between them using an UHF-ECG.

Methods

The left septal lead placement was done in 68 patients with bradycardia. Four distinct ventricular captures were described; nonselective LBBp (nsLBBp), selective LBBp (sLBBp), paraLBBp and left bundle branch area capture (LBBap). The timings of local ventricular activations and local depolarization durations were displayed by the UHF-ECG. e-DYS was calculated as a difference between the first and last activation.

Results

There were 35 nsLBBp, 21 paraLBBp, 12 sLBBp and 96 LBBap obtained in 68 patients.  The nsLBBp compared to LBBap caused worse interventricular synchrony (e-DYS -23 ms (-28;-18) vs -12 ms (-17;-8), p &lt; 0.001), but improved LV lateral wall depolarization duration. The sLBBp, nsLBBp and paraLBBp differed in e-DYS; -31 ms (-38;-24) vs -23 ms (-28;-17) vs -13 ms (-20;-7), p &lt; 0.01 between each of them. Their left ventricular depolarization durations were the same, but they were longer when pacing resulted in the left axis deviation. If the direct capture of the LBB was not confirmed (LBBap), LV depolarization duration was deteriorated irrespective of the QSR morphology in the V1 or RWPT in the V5. Examples of UHF-ECG maps during LBBap, paraLBBp and nsLBBp are shown in Figure 1.

Conclusions

The direct capture of the left bundle branch deteriorates interventriclar synchrony but improves the depolarization duration of the left ventricular lateral wall compared to left ventricular myocardial septal pacing. Abstract Figure 1

Pathologies affect the performance of ECG signals compression

The performance of ECG signals compression is influenced by many things. However, there is not a single study primarily focused on the possible effects of ECG pathologies on the performance of compression algorithms. This study evaluates whether the pathologies present in ECG signals affect the efficiency and quality of compression. Single-cycle fractal-based compression algorithm and compression algorithm based on combination of wavelet transform and set partitioning in hierarchical trees are used to compress 125 15-leads ECG signals from CSE database. Rhythm and morphology of these signals are newly annotated as physiological or pathological. The compression performance results are statistically evaluated. Using both compression algorithms, physiological signals are compressed with better quality than pathological signals according to 8 and 9 out of 12 quality metrics, respectively. Moreover, it was statistically proven that pathological signals were compressed with lower efficiency than physiological signals. Signals with physiological rhythm and physiological morphology were compressed with the best quality. The worst results reported the group of signals with pathological rhythm and pathological morphology. This study is the first one which deals with effects of ECG pathologies on the performance of compression algorithms. Signal-by-signal rhythm and morphology annotations (physiological/pathological) for the CSE database are newly published.

Pacing of the interventricular septum with His bundle engagement, unlike myocardial pacings of the right ventricle, does not lead to ventricular dyssynchrony, as assessed by ultra-high frequency ECG

Background

Nonselective pacing of the distal His bundle is practically just another way of right ventricular septal pacing. It leads to the concomitant activation of the His bundle and septal myocytes with unknown impact on ventricular synchrony. Ultra-high frequency ECG (UHF-ECG) is a novel tool for ventricular depolarization imaging.

Purpose

To describe ventricular depolarization patterns during nonselective pacing of a ventricular aspect of His bundle and myocardial captures from different locations in the right ventricle by using the UHF-ECG.

Methods

Consecutive patients with an indication for permanent pacing due to bradycardia were included. During pacemaker implantation, the pacing lead was temporarily placed in prespecified locations of the right ventricle (mid-septum, anterior, lateral wall, and the para-hisian area of the RV). When pacing from mentioned locations, myocardial activation time under each specific lead (Vd), and ventricular dyssynchrony (e-DYS) indexes were calculated from UHF-ECG maps, for each particular type of pacing. The demonstration of UHF-ECG maps during pacing from different locations of the right ventricle is shown in the figure.

Results

Two hundred and fifty UHF ECG recordings were performed in forty-six patients. The calculated mean e-DYS parameter was significantly shorter during non-selective capture of the distal His bundle (14±8 ms) compared to each of myocardial captures of the right ventricle (pure myocardial para-hisian; 35±12 ms, mid-septal; 28±11 ms, anterior wall; 51±16 ms and lateral wall; 62±19 ms (p&lt;0.001). The Vd was also shortest during non-selective capture of the distal His bundle (39±5 ms) compared to each of the others (pure myocardial para-hisian; 52±11 ms, RV mid-septal; 57±11 ms, RV anterior wall; 68±12 ms and RV lateral wall pacing; 85±14 ms (p&lt;0.001).

Conclusion

Pacing of the basal interventricular septum with the engagement of the His bundle produced a superior depolarization pattern in both heart ventricles compared to other types of right ventricular myocardial capture, as assessed using UHF-ECG.

Figure 1. Examples of UHF-ECG depolarization maps of different types of ventricular activation in the same patient.

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): Charles University in Prague

Real-Time Quality Assessment of Long-Term ECG Signals Recorded by Wearables in Free-Living Conditions

OBJECTIVE

Nowadays, methods for ECG quality assessment are mostly designed to binary distinguish between good/bad quality of the whole signal. Such classification is not suitable to long-term data collected by wearable devices. In this paper, a novel approach to estimate long-term ECG signal quality is proposed.

METHODS

The real-time quality estimation is performed in a local time window by calculation of continuous signal-to-noise ratio (SNR) curve. The layout of the data quality segments is determined by analysis of SNR waveform. It is distinguished between three levels of ECG signal quality: signal suitable for full wave ECG analysis, signal suitable only for QRS detection, and signal unsuitable for further processing.

RESULTS

The SNR limits for reliable QRS detection and full ECG waveform analysis are 5 and 18 dB respectively. The method was developed and tested using synthetic data and validated on real data from wearable device.

CONCLUSION

The proposed solution is a robust, accurate and computationally efficient algorithm for annotation of ECG signal quality that will facilitate the subsequent tailored analysis of ECG signals recorded in free-living conditions.

SIGNIFICANCE

The field of long-term ECG signals self-monitoring by wearable devices is swiftly developing. The analysis of massive amount of collected data is time consuming. It is advantageous to characterize data quality in advance and thereby limit consequent analysis to useable signals.

The relationship between ECG predictors of cardiac resynchronization therapy benefit

INTRODUCTION

Cardiac resynchronization therapy (CRT) is an effective treatment that reduces mortality and improves cardiac function in patients with left bundle branch block (LBBB). However, about 30% of patients passing the current criteria do not benefit or benefit only a little from CRT. Three predictors of benefit based on different ECG properties were compared: 1) "strict" left bundle branch block classification (SLBBB); 2) QRS area; 3) ventricular electrical delay (VED) which defines the septal-lateral conduction delay. These predictors have never been analyzed concurrently. We analyzed the relationship between them on a subset of 602 records from the MADIT-CRT trial.

METHODS & RESULTS

SLBBB classification was performed by two experts; QRS area and VED were computed fully automatically. High-frequency QRS (HFQRS) maps were used to inspect conduction abnormalities. The correlation between SLBBB and other predictors was R = 0.613, 0.523 and 0.390 for VED, QRS area in Z lead, and QRS duration, respectively. Scatter plots were used to pick up disagreement between the predictors. The majority of SLBBB subjects- 295 of 330 (89%)-are supposed to respond positively to CRT according to the VED and QRS area, though 93 of 272 (34%) non-SLBBB should also benefit from CRT according to the VED and QRS area.

CONCLUSION

SLBBB classification is limited by the proper setting of cut-off values. In addition, it is too "strict" and excludes patients that may benefit from CRT therapy. QRS area and VED are clearly defined parameters. They may be used to optimize biventricular stimulation. Detailed analysis of conduction irregularities with CRT optimization should be based on HFQRS maps.