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Cardiac resynchronization therapy (CRT) is an established treatment for heart failure patients with myocardial dysfunction and delayed ventricular activation, but approximately 25% to 40% of patients do not respond to CRT. Left ventricular (LV) multisite pacing (MSP) has been proposed as a tool to improve CRT response. The goal of this study is to examine the safety and efficacy of LV MSP in CRT nonresponders. Between January 2018, and September 2019, the Strategic Management to Improve CRT Using Multi-Site Pacing trial prospectively enrolled 584 CRT-defibrillator recipients for established indications at 52 sites across the United States and evaluated their response at 6 months using the clinical composite score (CCS). Of the nonresponders, 102 patients had the LV MSP feature turned on and 78 patients completed the 12-month CCS evaluation. The LV MSP feature-related complication-free rate was 99.0% with a lower 95% confidence interval limit of 94.9%, which was higher than the performance goal of 90%. The proportion of nonresponders with an improved CCS from 6 to 12 months was 51.3% with a lower 95% confidence interval limit of 41.4%, which was higher than the performance goal of 5%. The estimated mean reduction in battery longevity with the LV MSP feature was about 3.6 months (estimated battery longevity of 8.87 ± 2.08 years at 6 months and 8.07 ± 2.23 years at 12 months). In conclusion, in CRT nonresponders, the use of the LV MSP feature is safe and associated with a ∼50% conversion rate with a small projected reduction in CRT-defibrillator battery longevity. LV MSP should be considered in the management of CRT nonresponders.

Left bundle branch pacing (LBBP) is a novel near-physiological pacing method that still lacks quantitative criteria to guide the selection of lead-implanted sites to enhance the success likelihood of lead deployments. This study aimed to quantitatively analyze the relationships of LBBP success likelihood to the distribution of lead-implanted sites and the lead-localization-pacing electrocardiographic (ECG) features. All the lead-implanted sites in patients with finally successful LBBP were enrolled for analysis, including successful and failed sites. A novel coordinate system was invented to describe the sites’ distribution as longitudinal distance (longit-dist) and lateral distance (lat-dist). Corrected distance parameters were generated to eliminate the cardiac dimension variations. The lead-localization-pacing ECG parameters were also collected, such as paced QRS duration (locat-QRSd), left ventricular activation time (locat-LVAT), LVAT/QRSd ratio (locat-LVAT/QRSd), and QRS directions. A total of 94 patients with 105 successful sites and 93 failed sites were enrolled. Longit-dist and corrected longit-dist of successful sites were significantly longer, while locat-QRSd and locat-LVAT were shorter and locat-LVAT/QRSd was lower than failed sites. There was a positive dose–response relationship between LBBP success likelihood and corrected longit-dist with a cut-off of 26.95 mm, whereas there were negative dose–response relationships of LBBP success likelihood to locat-QRSd, locat-LVAT, and locat-LVAT/QRSd with the cut-offs of 142 ms, 92 ms, and 64.7%, respectively. Downward QRS direction in II/III ECG leads was also associated with successful LBBP. Longit-dist, locat-QRSd, locat-LVAT, and locat-LVAT/QRSd were quantitative parameters to guide the selection of lead-implanted sites during LBBP implantation. Quantitative distance and electrocardiographic parameters for lead-implanted site selection to enhance the success likelihood of left bundle branch pacing. LBBP, left bundle branch pacing; Longit-dist, longitudinal distance; CL-apex-dist, distance from contraction line to apex; LBBB, left bundle branch block; IVCD, intraventricular conduction delay; Locat-QRSd, lead-localization-pacing QRS duration; Locat-LVAT, lead-localization-pacing left ventricular activation time; Locat-LVAT/QRSd, lead-localization-pacing LVAT/QRSd ratio.

BackgroundDiagnosis of cardiac amyloidosis (CA) requires advanced imaging techniques. Typical surface ECG patterns have been described, but their diagnostic abilities are limited.ObjectiveThe aim was to perform a thorough electrophysiological characterisation of patients with CA and derive an easy-to-use tool for diagnosis.MethodsWe applied electrocardiographic imaging (ECGI) to acquire electroanatomical maps in patients with CA and controls. A machine learning approach was then used to decipher the complex data sets obtained and generate a surface ECG-based diagnostic tool.FindingsAreas of low voltage were localised in the basal inferior regions of both ventricles and the remaining right ventricular segments in CA. The earliest epicardial breakthrough of myocardial activation was visualised on the right ventricle. Potential maps revealed an accelerated and diffuse propagation pattern. We correlated the results from ECGI with 12-lead ECG recordings. Ventricular activation correlated best with R-peak timing in leads V1–V3. Epicardial voltage showed a strong positive correlation with R-peak amplitude in the inferior leads II, III and aVF. Respective surface ECG leads showed two characteristic patterns. Ten blinded cardiologists were asked to identify patients with CA by analysing 12-lead ECGs before and after training on the defined ECG patterns. Training led to significant improvements in the detection rate of CA, with an area under the curve of 0.69 before and 0.97 after training.InterpretationUsing a machine learning approach, an ECG-based tool was developed from detailed electroanatomical mapping of patients with CA. The ECG algorithm is simple and has proven helpful to suspect CA without the aid of advanced imaging modalities.

Background: Cardiac resynchronization therapy (CRT) is a treatment for patients with heart failure and electrical dyssynchrony, i.e., left bundle branch block (LBBB) ECG pattern. CRT resynchronizes ventricular contraction with a right ventricle (RV) and a left ventricle (LV) pacemaker lead. Positioning the LV lead in the latest electrically activated region (measured from Q wave onset in the ECG to LV sensing by the left pacemaker electrode [QLV]) is associated with favorable outcome. However, optimal LV lead placement is limited by coronary venous anatomy and the inability to measure QLV non-invasively before implantation. We propose a novel non-invasive method for estimating QLV in sinus-rhythm from the standard 12-lead ECG.Methods: We obtained 12-lead ECG, LV electrograms and LV lead position in a standard LV 17-segment model from procedural recordings from 135 standard CRT recipients. QLV duration was measured post-operatively. Using a generic heart geometry and corresponding forward model for ECG computation, the electrical activation pattern of the heart was fitted to best match the 12-lead ECG in an iterative optimization procedure. This procedure initialized six activation sites associated with the His-Purkinje system. The initial timing of each site was based on the directions of the vectorcardiogram (VCG). Timing and position of the sites were then changed iteratively to improve the match between simulated and measured ECG. Noninvasive estimation of QLV was done by calculating the time difference between Q-onset on the computed ECG and the activation time corresponding to centroidal epicardial activation time of the segment where the LV electrode is positioned. The estimated QLV was compared to the measured QLV. Further, the distance between the actual LV position and the estimated LV position was computed from the generic ventricular model.Results: On average there was no difference between QLV measured from procedural recordings and non-invasive estimation of QLV (ΔQLV=−3.0±22.5 ms, p=0.12). Median distance between actual LV pacing site and the estimated pacing site was 18.6 mm (IQR 17.3 mm).Conclusion: Using the standard 12-lead ECG and a generic heart model it is possible to accurately estimate QLV. This method may potentially be used to support patient selection, optimize implant procedures, and to simulate optimal stimulation parameters prior to pacemaker implantation.

Personalized models of cardiac electrophysiology (EP) that match clinical observation with high fidelity, referred to as cardiac digital twins (CDTs), show promise as a tool for tailoring cardiac precision therapies. Building CDTs of cardiac EP relies on the ability of models to replicate the ventricular activation sequence under a broad range of conditions. Of pivotal importance is the His–Purkinje system (HPS) within the ventricles. Workflows for the generation and incorporation of HPS models are needed for use in cardiac digital twinning pipelines that aim to minimize the misfit between model predictions and clinical data such as the 12 lead electrocardiogram (ECG). We thus develop an automated two stage approach for HPS personalization. A fascicular-based model is first introduced that modulates the endocardial Purkinje network. Only emergent features of sites of earliest activation within the ventricular myocardium and a fast-conducting sub-endocardial layer are accounted for. It is then replaced by a topologically realistic Purkinje-based representation of the HPS. Feasibility of the approach is demonstrated. Equivalence between both HPS model representations is investigated by comparing activation patterns and 12 lead ECGs under both sinus rhythm and right-ventricular apical pacing. Predominant ECG morphology is preserved by both HPS models under sinus conditions, but elucidates differences during pacing. Supplementary Information The online version contains supplementary material available at 10.1007/s10439-021-02825-9.

It has been suggested that nonselective His bundle pacing (NS-HBP) corrects terminal conduction delay in right bundle branch block by early excitation of the right ventricular free wall. A similar analysis of NS-HBP, in patients with left bundle branch block (LBBB) and left-axis deviation (LAD) has not been done. Therefore, we compared the baseline QRS parameters in LAD and LBBB during NS-HBP and selective HBP (S-HBP). In LAD patients (n = 16), NS-HBP normalized the QRS axis from −35° ± 10° to 30° ± 34° (p < 0.01) and increased the lead 1 voltage (L1V) from 0.55 ± 0.3 mV to 0.88 ± 0.2 mV (p < 0.001) without increasing the peak lateral wall activation time (PLWAT) (p = not significant). In 23 of 41 LBBB patients, NS-HBP decreased the prolonged PLWAT by 73 ms (p < 0.0001), resolved the mid-QRS notch, normalized the QRS axis, and increased the L1V from 0.5 ± 0.3 mV to 1.15 ± 0.3 mV (p < 0.0001). In the remaining 18 LBBB patients, NS-HBP did not resolve the mid-QRS notch; however, the peak septal activation time decreased by 45 ms (p < 0.0001), PLWAT decreased by 53 ms (p < 0.0001), L1V increased from 0.5 ± 0.3 mV to 0.87 ± 0.4 mV (p < 0.0001), and the QRS axis normalized. All patients who developed S-HBP at lower pacing showed uncorrected LBBB (n = 6) or LAD (n = 7). In conclusion, NS-HBP, which causes myocardial activation in advance of simultaneously initiated S-HBP, results in a paced QRS complex with a normal axis and shorter activation times and restores the L1V in patients with LAD and LBBB. In some patients, a mid-QRS notch was seen with NS-HBP, which suggests fusion with S-HBP, which conducts without LBBB correction. A higher L1V in association with a shorter PLWAT and a normal QRS axis suggests that a more organized degree of left ventricular activation occurs with NS-HBP as compared to LBBB.

Cardiac resynchronization therapy (CRT) is an established treatment of patients with medically refractory, mild-to-severe systolic heart failure (HF), impaired left ventricular function, and wide QRS complex. The pathologic activation sequence observed in patients with abnormal QRS duration and morphology results in a dyssynchronous ventricular activation and contraction leading to cardiac remodeling, worsening systolic and diastolic function, and progressive HF. In this article, the authors aim to explore the current CRT literature, focusing their attentions on the promising innovation in this field.

Left bundle branch pacing (LBBP) has been adopted as a new pacing therapy whether in routine pacing or patients with heart failure, but the criteria for a completely captured LBBP are too complicated and have a low success rate in routine clinical practice.Consecutive patients with pacing therapy indications were enrolled. Left bundle branch area pacing (LBBAP) was conducted, and the presence of LBB potential, paced QRS duration, stimulus to left ventricular activation time (Stim-LVAT), and LBB potential to left ventricular activation time (LBB po-LVAT) were determined and utilized to characterize LBBAP modalities. Pacing parameters and safety were assessed at 6-month follow-up. LBBAP succeeded in 95.6% of patients (103/106) who completed the 6-month follow-up. Complete LBBP was achieved in 21 (20%) patients, characterized with a short Stim-LVAT equal to LBB po-LVAT. Incomplete LBBP was achieved in 58 (56%) patients with a short Stim-LVAT equal to LBB po-LVAT at a high pacing output and a relatively longer Stim-LVAT at a low pacing output. Deep septal pacing (DSP) characterized with no LBB potential and a longer Stim-LVAT (83.3 ± 7.7 ms) than that in LBBP (71.37 ± 7.1 ms, P < 0.01 versus DSP) was observed in 24 (23%) patients. Complete LBBP had a longer total procedure time and longer fluoroscopic time than the other two groups.This study describes the similarities and differences in electrophysiological characteristics and the possible mechanisms of the different types of LBBAP, classified into 3 modalities in routine clinical practice, each with narrow paced QRS duration and stable parameters, indicating LBBAP can be a near-physiological pacing modality.

Left ventricular septal pacing (LVSP) and left bundle branch pacing (LBBP) have been introduced to maintain or correct interventricular and intraventricular (dys)synchrony. LVSP is hypothesised to produce a fairly physiological sequence of activation, since in the left ventricle (LV) the working myocardium is activated first at the LV endocardium in the low septal and anterior free-wall regions. Animal studies as well as patient studies have demonstrated that LV function is maintained during LVSP at levels comparable to sinus rhythm with normal conduction. Left ventricular activation is more synchronous during LBBP than LVSP, but LBBP produces a higher level of intraventricular dyssynchrony compared to LVSP. While LVSP is fairly straightforward to perform, targeting the left bundle branch area may be more challenging. Long-term effects of LVSP and LBBP are yet to be determined. This review focuses on the physiology and practicality of LVSP and provides a guide for permanent LVSP implantation.

Background It is generally accepted that bundle branch block (BBB) may be corrected simply by selective His bundle pacing (S-HBP) distal to site of block. However, clinical HBP is often non-selective (NS), the site of block unknown and moving the HB lead is not always an option. Thus, while correction of right (R) BBB in NS-HBP has been reported, its mechanism is unknown. Methods Threshold testing was done during His bundle pacing in 39 patients with RBBB. We compared NS-HBP and S-HBP and analyzed the role of pacing voltage and capture threshold of the parallel pathway, in partially or completely correcting RBBB. Results During NS-HBP, higher pacing voltage completely corrected RBBB in 22/35 patients as compared to 5/18 patients at lower voltage. Remaining patients showed incomplete correction of RBBB. NS-HBP group with lower capture threshold of 1.3 ± 0.5 V completely resolved RBBB in 9/14 vs 3/11 patients in NS-S HBP group with higher capture threshold of 2.4 ± 0.8 V. QRS activation time in NSHBP was 91 ± 8 ms (baseline 97 ± 7 ms p = ns). S-HBP resolved RBBB in only 1/21 patients. Conclusions 1.) Lack of correction with S-HBP suggests that RBBB was distal to site of HBP and yet was corrected with NS-HBP. 2.) Voltage dependent correction of RBBB in NS-HBP suggests that conduction via a specialized parallel pathway maintains normal ventricular activation time. 3.) Correction of RBBB in all patients with NS-HBP, suggests that conduction block was either bypassed or right ventricular free wall pre-excited by conduction via parallel pathway.

Ventricular preexcitation is a depolarization of the ventricles that occurs before the conventional sequence, and the electrocardiogram is the specific test for diagnosis. A Kent bundle is the paradigm of ventricular preexcitation, and it is associated with short PR, wide QRS and delta wave. This finding is not always very evident, as it can have different degrees of pre-eccitazione; therefore great diagnostic care must be taken in this field. If not properly identified, the pattern of ventricular preexcitation may lead to an incorrect diagnosis. The methodology of precision electrocardiology is able to confront all these aspects.

Background: His Bundle pacing (HBP) preserves native ventricular activation through His Purkinje. Unfortunately, most current techniques for HBP implants require sheaths, special leads, and an electrophysiology setup for electrogram recording. Methods: We developed an implantation technique guided by a non-invasive assessment of left ventricular electrical delay (LVED) as a measure of intraventricular dyssynchrony. The objective was to evaluate the usefulness and safety of this technique for implants of pacemakers and ICDs with right ventricular septal pacing (RVSP) using conventional screw-in leads and compare it with a reduced group of HBP (n = 32) guided by His potential mapping. 208 patients eligible for ventricular stimulation were implanted. Conventional screw-in leads were used in all cases. To ensure mechanical stability, stylets required a slight reshaping at the tip Results: RVSP normalized electrical activity in patients with conduction disease, producing NS-HBP-like patterns. The parameters evaluated during implantation for the RVSP group were better than those of HBP and remained constant at a twelve months follow-up. In proportion, the number of dislodgments and the need for CRT upgrade was lower for RVSP than for HBP. Additionally, fluoroscopy time was significantly reduced in the RVSP group. Conclusions: This technique successfully guided RVSP implants in a non-invasive way and represents a simple alternative to the implant of a cardiac stimulation device. Fil: Ortega, Daniel. Fundación para Investigaciones Biológicas Aplicadas; Argentina Fil: Logarzo, Emilio. Fundación para Investigaciones Biológicas Aplicadas; Argentina Fil: Barja, Luis. No especifíca; Fil: Paolucci, Analía. Fundación para Investigaciones Biológicas Aplicadas; Argentina Fil: Mangani, Nicolás. Fundación para Investigaciones Biológicas Aplicadas; Argentina Fil: Mazzetti, Eduardo. No especifíca; Fil: Bonomini, Maria Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Argentino de Matemática Alberto Calderón; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Ingeniería Biomédica; Argentina

His-Purkinje conduction system pacing (HPCSP) in the form of His bundle pacing (HBP) and left bundle branch pacing (LBBP) allows normal left ventricular activation, thereby preventing the adverse consequences of right ventricular pacing. HBP has been established for several years with centers from China, Europe, and North America reporting their experience. There is international guidance as to how to implant such systems with the differing patterns of His bundle capture clearly described. LBBP is a more recent innovation with potential advantages including improved pacing parameters. HPCSP has been extensively studied in a variety of indications including cardiac resynchronization therapy, atrioventricular node ablation, and bradycardia pacing. This review will focus on the clinical outcomes of HPCSP including mortality and morbidity of heart failure hospitalization and symptoms.

Background His-bundle pacing (HBP) has emerged as an alternative to conventional ventricular pacing because of its ability to deliver physiological ventricular activation. Pacing at the His bundle produces different electrocardiographic (ECG) responses: selective His-bundle pacing (S-HBP), non-selective His bundle pacing (NS-HBP), and myocardium-only capture (MOC). These 3 capture types must be distinguished from each other, which can be challenging and time-consuming even for experts. Objective The purpose of this study was to use artificial intelligence (AI) in the form of supervised machine learning using a convolutional neural network (CNN) to automate HBP ECG interpretation. Methods We identified patients who had undergone HBP and extracted raw 12-lead ECG data during S-HBP, NS-HBP, and MOC. A CNN was trained, using 3-fold cross-validation, on 75% of the segmented QRS complexes labeled with their capture type. The remaining 25% was kept aside as a testing dataset. Results The CNN was trained with 1297 QRS complexes from 59 patients. Cohen kappa for the neural network’s performance on the 17-patient testing set was 0.59 (95% confidence interval 0.30 to 0.88; P, Graphical abstract

AIM To assess the electrocardiogram patterns of paced QRS narrowing after successful left bundle branch area pacing (LBBAP) and echocardiographic measurements in patients with bradycardia and bundle branch block (BBB). METHODS We prospectively enrolled 55 consecutive bradycardia patients with BBB and left ventricular ejection fraction ≥40% who had attempted LBBAP. Successful LBBAP was defined as paced QRS morphology of a right BBB (RBBB) pattern in lead V1 and a recording of abruptly shortened and then constant stimulus to peak left ventricular activation time with high and low output. Pacing characteristics and echocardiographic measurements were evaluated perioperatively and at 6-month follow-up. RESULTS The success rate of LBBAP was 83.6% in patients with BBB, and median cumulative X-ray dose-area product was 100.5 µGym2 (60.0, 179.3). LBBAP was successful in 19 of 26 patients with left BBB (LBBB) (73.1%) and in 27 of 29 patients with RBBB (93.1%). The QRS duration (QRSd) was significantly shortened in patients with LBBB (QRSd 169.4 ± 22.6 to 119.6 ± 9.5 ms), and five forms of QRSd narrowing were observed in patients with RBBB with the mean QRSd shortened from 143.1 ± 16.6 ms to 119.5 ± 11.7 ms. The thresholds for narrowing of QRSd were higher in RBBB than LBBB (1.74 ± 0.36 V/0.4 ms vs 0.79 ± 0.17 V/0.4 ms, P

We report the case of syncope in a 75-year-old man with known coronary artery disease following complete atrioventricular block, which became symptomatic with the loss of anterograde conduction properties of his left postero-septal accessory pathway. A double chamber pacemaker implantation was decided. There is no indication for radiofrequency ablation in the absence of reentry tachycardia and intermittent conduction. Cardiac pacing offers him an electrophysiologically interesting excitation profile with a quasi-synchronous right and left ventricular activation.

Giriş: Kardiyak sendrom X (KSX) noninvaziv stres testlerinde tespit edilebilen iskemi olmasına rağmen koroner anjiyografide koroner arter stenozu bulgularının olmadığı tipik anjina olarak tanımlanmaktadır. Bozulmuş koroner mikrosirkülasyon, inflamasyon ve endotel disfonksiyonu KSX için kabul edilmiş etyolojik faktörlerdir. Ventriküler aktivasyon zamanının (VAZ) miyokardiyal iskemi durumunda Purkinje liflerinde ve miyositlerdeki iletim yavaşlamasına bağlı olarak uzadığı bildirilmiştir. Bu çalışmada, KSX hastalarında aralarında VAZ’ın da bulunduğu elektrokardiyografik parametrelerin araştırılması amaçlanmıştır. Hastalar ve Yöntem: Çalışmaya KSX tanısı alan 120 hasta (ortalama yaş: 54.7 ± 8.6 yıl , erkek: 53) ile iskemisi olmayan 130 sağlıklı kontrol (ortalama yaş: 53.3 ± 8.9 yıl , erkek: 66) dahil edildi. Tüm hastalar elektrokardiyografi ve transtorasik ekokardiyografi ile değerlendirildi. VAZ elektrokardiyografide QRS kompleksinin başlangıcından R veya R’ dalgasının zirvesine kadar geçen zaman aralığı olarak tanımlandı. Bulgular: KSX hastaları ile kontrol grubu arasında demografik, laboratuvar ve ekokardiyografik parametreler açısından anlamlı bir fark izlenmedi. Elektrokardiyografik parametreler karşılaştırıldığında gruplar arasında kalp hızı, P dalga süresi, PR aralığı, QT ve düzeltilmiş QT aralığı açısından anlamlı fark yok iken, QRS süresi (95.1 ± 13.8 ve 90.4 ± 12.7 msn, p= 0.006) ve VAZ (34.8 ± 5.7 ve 29.2 ± 5.6 msn, p< 0.001) KSX grubunda anlamlı olarak daha uzun olarak tespit edildi. Sonuç: Bu çalışmada KSX hastalarında QRS süresi ve VAZ’ın anlamlı olarak uzadığı gösterilmiştir. Bu uzama KSX hastalarındaki bozulmuş mikrovasküler perfüzyon ve iskemiye bağlı iletim yavaşlamasına bağlı gelişmiş olabilir., Introduction: Cardiac syndrome X (CSX) is defined as typical angina with detectable ischaemia on noninvasive stress tests without any evidence of coronary artery stenosis during coronary angiography. Impaired coronary microcirculation, inflammation and endothelial dysfunction are accepted aetiological factors for CSX. The ventricular activation time (VAT) has been reported to be prolonged in myocardial ischaemia due to the conduction delay in the Purkinje fibres and the myocytes. In this study, we aimed to investigate the electrocardiographic parameters including VAT in patients with CSX. Patients and Methods: This study enrolled 120 patients (mean age, 54.7 ± 8.6 years; male, 53) diagnosed with CSX and 130 healthy controls (mean age, 53.3 ± 8.9; male, 66) without ischaemia. All patients underwent electrocardiography and transthoracic echocardiography. VAT was defined as the interval from the beginning of the QRS complex until the peak of the R or R’ wave. Results: There was no significant difference in terms of demographic, laboratory and echocardiographic parameters between CSX patients and controls. Comparison of electrocardiographic parameters yielded that there was no significant difference in terms of the heart rate, P-wave duration, PR interval, QT and corrected QT intervals between the groups. However, the QRS duration (95.1 ± 13.8 vs. 90.4 ± 12.7 msec; p= 0.006) and VAT (34.8 ± 5.7 vs. 29.2 ± 5.6 msec; p< 0.001) were significantly higher in patients with CSX. Conclusion: The present study demonstrated that QRS duration and VAT were prolonged significantly in patients with CSX. This prolongation may be due to the presence of impaired microvascular perfusion and ischaemia-induced conduction delay.

espanolIntroduccion: La terapia de resincronizacion cardiaca presenta una tasa de un 25%-30% de pacientes “no respondedores”. La resincronizacion endocardica, en la que el cateter del ventriculo izquierdo se implanta en el endocardio, seria una alternativa para estos pacientes, aunque su evolucion a largo plazo no ha sido investigada. Objetivos: Evaluacion hemodinamica no invasiva a largo plazo de la resincronizacion endocardica en respondedores clinicos. Metodos: Se incluyeron pacientes implantados segun los criterios para resincronizacion, usando la tecnica Jurdham, con mas de 6 meses desde el implante. Todos eran respondedores clinicos. La respuesta hemodinamica se evaluo con un analizador de la funcion cardiaca, que mide los intervalos sistolicos (periodos preeyectivo y eyectivo) del ventriculo izquierdo y calcula automaticamente un indice de funcion sistolica y estimar la fraccion de eyeccion (Systocor mod IS100). Para determinar la eficacia mecanica de la TRCe se comparo la funcion cardiaca durante el modo biventricular con el bloqueo completo de la rama izquierda, espontaneo o por estimulacion unica del ventriculo derecho; los pacientes fueron sus propios controles. Se promediaron al menos 20 latidos en cada modo de estimulacion y se consideraron solo los cambios >1% con valor p Resultados: Se incluyeron 17 pacientes, con mediana de seguimiento de 43 meses, rango 9 a 78 meses. La resincronizacion endocardica, en comparacion con la activacion ventricular con BCRI, demostro que todos los pacientes acortaron el periodo preeyectivo en un promedio de 31 ms (15%), indicativo de disminucion de la disincronia interventricular causada por el BCRI. En todos aumento el indice de funcion sistolica en 0,3 (23%) y la FE en el 8,3%. En 12/17 (71%) aumento el periodo eyectivo en promedio 8,7 mseg (2,9%), lo que sugiere un aumento del volumen sistolico. En todos los cambios el valor de p fue menor de 0,01. Conclusiones: La TRCe ofrece mejoria hemodinamica significativa a largo plazo, detectada por intervalos sistolicos. EnglishBackground: Cardiac resynchronization therapy has 25% to 30% rate of “non-responder” patients. Endocardial cardiac resynchronization therapy (eCRT), in which the left ventricular catheter is implanted in the endocardium, would be an alternative for these patients; however, its long-term outcome has not been investigated. Objectives: The aim of this study was the long-term non-invasive hemodynamic evaluation of eCRT in clinical responders. Methods: Patients implanted according to the criteria for resynchronization, using the Jurdham technique, with more than 6 months after the implant, were included in the study. All were clinical responders. The hemodynamic response was evaluated with a cardiac function analyzer, which measures the left ventricular systolic intervals (preejection and ejection periods) and automatically calculates an index of systolic function and estimates the ejection fraction (Systocor mod IS100). To assess the mechanical efficacy of eCRT, the cardiac function during biventricular mode was compared with left bundle branch block (LBBB), either spontaneous or by single stimulation of the right ventricle, with patients as their own controls. At least 20 beats were averaged in each stimulation mode and only changes >1% with p Results: Seventeen patients were included, with a median follow-up of 43 months, (9 to 78 months). Endocardial resynchronization, compared with LBBB ventricular activation, showed that all patients shortened the preejection period by an average of 31 ms (15%), indicative of decreased interventricular dyssynchrony caused by LBBB. In all patients, systolic function index increased by 0.3 (23%) and the EF by 8.3%. In 12/17 of cases (71%) the ejective period increased on average 8.7 ms (2.9%), suggesting an increase in systolic volume. In all changes p was Conclusions: Endocardial resynchronization therapy offers significant long-term hemodynamic improvement, detected by systolic intervals.

The identification of the initial ventricular activation sequence is a critical step for the correct personalization of patient‐specific cardiac models. In healthy conditions, the Purkinje network is the main source of the electrical activation, but under pathological conditions the so‐called earliest activation sites (EASs) are possibly sparser and more localized. Yet, their number, location and timing may not be easily inferred from remote recordings, such as the epicardial activation or the 12‐lead electrocardiogram (ECG), due to the underlying complexity of the model. In this work, we introduce GEASI (Geodesic‐based Earliest Activation Sites Identification) as a novel approach to simultaneously identify all EASs. To this end, we start from the anisotropic eikonal equation modeling cardiac electrical activation and exploit its Hamilton–Jacobi formulation to minimize a given objective function, for example, the quadratic mismatch to given activation measurements. This versatile approach can be extended to estimate the number of activation sites by means of the topological gradient, or fitting a given ECG. We conducted various experiments in 2D and 3D for in‐silico models and an in‐vivo intracardiac recording collected from a patient undergoing cardiac resynchronization therapy. The results demonstrate the clinical applicability of GEASI for potential future personalized models and clinical intervention., The identification of the earliest activation sites (EASs) of cardiac activation from the surface electrocardiogram (ECG) constitutes the grand challenge in patient‐specific modeling. To this aim, this work introduces GEASI (Geodesic‐based EASs Identification), an innovative method to identify the number, location, and onset timing of EASs from non‐local activation measurements or even the ECG. The effectiveness and versatility of GEASI is demonstrated through a variety of experiments, strongly supporting its clinical feasibility.

A high-risk left-sided posterolateral manifest accessory pathway (AP) was identified in a 49-year-old man. Two prior ablations had failed. A repeat procedure using 3D electroanatomic mapping demonstrated an extremely oblique AP. The earliest atrial activation site was not amenable to endocardial ablation. The earliest ventricular activation site was identified, demonstrating an AP with an extremely slanted course. Radiofrequency ablation here resulted in sustained bidirectional AP block. In challenging AP ablation cases, recognition of the potential for an oblique AP and the use of electroanatomic mapping may be beneficial.

Ventricular activation via the specialized His Purkinje system results in synchronous bi-ventricular contraction with an endocardial to epicardial activation wavefront. Biventricular (BiV) pacing for cardiac resynchronization therapy (CRT) often results in a non physiological bi-ventricular activation. Furthermore, LV lead implantation may be challenging due to anatomical constraints. Physiological pacing i.e. Permanent His Bundle pacing (HBP)/Left bundle branch pacing (LBBP) provides an alternative to BiV pacing for these patients. In this report, we present the case of CRT with physiological pacing while minimizing hardware using a dual chamber ICD system.

Building a data-driven model to localize the origin of ventricular activation from 12-lead electrocardiograms (ECG) requires addressing the challenge of large anatomical and physiological variations across individuals. The alternative of a patient-specific model is, however, difficult to implement in clinical practice because the training data must be obtained through invasive procedures. In this paper, we present a novel approach that overcomes this problem of the scarcity of clinical data by transferring the knowledge from a large set of patient-specific simulation data while utilizing domain adaptation to address the discrepancy between the simulation and clinical data. The method that we have developed quantifies non-uniformly distributed simulation errors, which are then incorporated into the process of domain adaptation in the context of both classification and regression. This yields a quantitative model that, with the addition of 12-lead ECG data from each patient, provides progressively improved patient-specific localizations of the origin of ventricular activation. We evaluated the performance of the presented method in localizing 75 pacing sites on three in-vivo premature ventricular contraction (PVC) patients. We found that the presented model showed an improvement in localization accuracy relative to a model trained on clinical ECG data alone or a model trained on combined simulation and clinical data without considering domain shift. Furthermore, we demonstrated the ability of the presented model to improve the real-time prediction of the origin of ventricular activation with each added clinical ECG data, progressively guiding the clinician towards the target site.

Cardiac resynchronization therapy (CRT) is an electrical therapy to resolve an electrical problem. Any method to predict CRT response must specifically reflect the electrical substrate. Time-to-peak dyssynchrony is too unspecific for prediction of response because dyssynchrony by this approach may reflect the presence of scar or fibrosis even in the absence of conduction delay. New methods are based on the actual physiology of activation delay–induced heart failure (HF) and are superior to time-to-peak methods in predicting CRT response. Time-to-peak dyssynchrony may be used for prognosis in HF patients without signs of delayed ventricular activation and for monitoring CRT response.

Experimental and clinical studies have shown that after myocardial infarction (MI), increases the risk to develop cardiac arrhythmias. We have evaluated the ventricular activation during healing (MI7) and healed (MI60) stages after MI. We carried out a comparative study between the QRS spectral variance (QRSSV) index and late potentials (LPs) obtained by the Signal-averaged (SaECG) technique. The electrocardiograms of 48 healthy subjects (CTRL); 84 patients in MI7 and 41 in MI60 without VT/VF; and also 7 patients in MI7 and 6 in MI60 with VT/VF, were analysed utilizing the Frank leads. The QRSSV has increased (p < 0.05) in patients without VT/VF for all leads during MI7 and MI60 with respect to CTRL, and just in a few leads in patients with VT/VF. Conversely, we have only found significant proportion of LPs in MI7 with respect to CTRL in patients with VT/VF and none without VT/VF. This investigation might help to comprehend the influence of time in patients with and without VT/VF. We conclude that SaECG could be restricted to locate stable and delayed depolarization, while the QRSSV index could detect both stable and unstable activation disorders in whole depolarization. Fil: Valverde, Esteban Raul. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Ingeniería Biomédica; Argentina Fil: Arini, Pedro David. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Ingeniería Biomédica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Saavedra 15. Instituto Argentino de Matemática Alberto Calderón; Argentina

His-bundle pacing has recently emerged as a means to maintain a physiological ventricular activation and eliminate the risk of pacing-induced myopathy associated with traditional right ventricular pacing. With His-bundle pacing, the exact stimulated structure and resulting excitation wavefront may be highly dependent on the pacing output, dimensions of the stimulatory electrodes, and orientation of the cathode and anode relative to the approximated conduction tissue and surrounding myocardium, owing to the juxtaposition of tissues with very different conduction properties. We herein present an 89-year-old woman with an infra-Hisian conduction disease in whom lower output pacing resulted in pure His-bundle pacing, and higher output pacing resulted in para-Hisian pacing that recruited diseased portions of the conduction system, narrowing the QRS complex.

AimsDuring non-selective His bundle (HB) pacing, it is clinically important to confirm His bundle capture vs. right ventricular septal (RVS) capture. The present study aimed to validate the hypothesis that during HB capture left ventricular lateral wall activation time, approximated by the V6R-wave peak time (V6RWPT), will not be longer than the corresponding activation time during native conduction.MethodsConsecutive patients with permanent HB pacing were recruited; cases with abnormal His-ventricle interval or left bundle branch block were excluded. Two corresponding intervals were compared: stimulus-V6RWPT and native HBpotential-V6RWPT. Difference between these two intervals (delta V6RWPT), diagnostic of lack of HB capture, was identified using receiver operating characteristic (ROC) curve analysis.ResultsA total of 723 ECGs (219 with native rhythm, 172 with selective HB, 215 with non-selective HB, and 117 with RVS capture) were obtained from 219 patients. The native HB-V6RWPT, non-selective-, and selective-HB paced V6RWPT were nearly equal, while RVS V6RWPT was 32.0 (±9.5) ms longer. The ROC curve analysis indicated delta V6RWPT > 12 ms as diagnostic of lack of HB capture (specificity of 99.1% and sensitivity of 100%). A blinded observer correctly diagnosed 96.7% (321/332) of ECGs using this criterion.ConclusionWe validated a novel criterion for HB capture that is based on the physiological left ventricular activation time as an individualized reference. HB capture can be diagnosed when paced V6RWPT does not exceed the value obtained during native conduction by more than 12 ms, while longer paced V6RWPT indicates RVS capture.

Biventricular pacing (BiV) is a conventional form of cardiac resynchronization therapy (CRT) setting. Unfortunately, about 30% of patients undergoing CRT do not show clinical improvements. Direct His-Purkinje system stimulation (HPS) is a promising method to restore the physiological sequence of ventricular activation and synchronize contraction. In this study, we evaluate the effects of HPS on several indices of ventricular activation and electrical dyssynchrony in 27 patientspecific computer models of ventricles utilizing the CT imaging and ECG data from the patients. We compared simulation results of HPS pacing with standard BiV pacing using CT data on the location of ventricular leads (BiV CRT ). Moreover, using personalized ventricular models we predicted an optimal position of LV lead in terms of minimization of QRS complex durations (QRSd) and compared outputs of this BiV opt model with other modes of ventricular pacing. We showed that the majority of indices demonstrated that HPS is superior to both BiV pacing.

PURPOSE: The potential of pacing and capturing the His-Purkinje system (HPS) to synchronize VF wavefronts is not known even though the HPS is thought to be electrically linked during VF. In this study the effect of selective His Bundle (HB) pacing was compared with nearby working myocardial (WM) pacing on the left ventricular (LV) endocardial activation rates. METHODS: Rabbit hearts (n=9) were explanted and Langendorff perfused. Electrodes directly on the HB were identified and paced subsequently using an electrode array. The WM was paced through a silver wire inserted in the right ventricular septal wall. After VF was induced, the HB was paced at rates faster than the intrinsic HB activation rate (n=18 episodes) and also at rates faster than the LV activation rate (n=16). A basket array inserted in the LV was used to record electrograms before and during each pacing episode. Activation rates at five LV electrodes each from the earliest and latest activating sinus rhythm regions were analyzed before and during pacing. RESULTS: Both HB and WM pacing reduced LV activation rates during pacing, but WM pacing was more effective (P

Funding Acknowledgements Type of funding sources: None. Background Left bundle branch area pacing (LBBAP) has recently been introduced as a novel physiological pacing strategy. Within LBBAP, distinction is made between left bundle branch pacing (LBBP) and left ventricular septal pacing (LVSP, no left bundle capture). Objective To compare acute electrocardiographic (ECG) and vectorcardiographic (VCG) effects of LBBP and LVSP as compared to intrinsic conduction. Methods In 50 patients with normal cardiac function and pacemaker indication for bradycardia, ECG characteristics of LBBP and LVSP were evaluated during RVSP and pacing at various depths in the septum: starting at the RV side of the septum: the last position with QS morphology, the first position with r’ morphology, LVSP and – in patients where LBB capture was achieved – LBBP. From the ECG’s QRS duration and QRS morphology in V1, and the stimulus-LVAT interval were measured. After conversion of the ECG into VCG (Kors conversion matrix), QRS area was calculated. Results In LVSP, QRS area significantly decreased from 82 ± 29 µVs during RVSP to 46 ± 12 µVs during LVSP. In patients where LBB capture was achieved QRS area significantly decreased from 78 ± 23 µVs to 38 ± 15 µVs in LBBP. In patients with LBB capture, QRS area was significantly smaller during LBBP compared to LVSP (figure A), but LVAT was not significantly different (figure B, p = 0.138). In patients with normal ventricular activation where LBBP was achieved (n = 20), QRS area was significantly larger during LVSP (48 ± 17) compared to LBBP (37 ± 16), the latter being not significantly different from normal intrinsic ventricular activation (35 ± 19 µVs). Conclusions ECG and VCG indices demonstrate that ventricular dyssynchrony is comparable but slightly more synchronous during LBBP compared to LVSP. Abstract Figure. QRS area and S-LVAT in LVSP and LBBP

Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): British Heart Foundation Background: His bundle pacing can be achieved in two ways selective His bundle pacing, where the His bundle is captured alone, and non-selective His bundle pacing, where local myocardium is also captured resulting a pre-excited ECG appearance. We assessed the impact of this ventricular pre-excitation on left and right ventricular dys-synchrony. Methods We recruited patients who displayed both selective and non-selective His bundle pacing. We performed non-invasive epicardial electrical mapping to determine left and right ventricular activation times and patterns. Results In the primary analysis (n = 20, all patients), non-selective His bundle pacing did not prolong LVAT compared to select His bundle pacing by a pre-specified non-inferiority margin of 10ms (LVAT prolongation: -5.5ms, 95% confidence interval (CI): -0.6 to -10.4, non-inferiority p In patients with narrow intrinsic QRS (n = 6), non-selective His bundle pacing preserved left ventricular activation time (-2.9ms, 95%CI: -9.7 to 4.0, p = 0.331) but prolonged QRS duration (31.4ms, 95%CI: 22.0 to 40.7, p = 0.0003) and mean right ventricular activation time (16.8ms, 95%CI: -5.3 to 38.9, p = 0.108) compared to selective His bundle pacing. Activation pattern of the left ventricular surface was unchanged between selective and non-selective His bundle pacing. Non-selective His bundle pacing produced early basal right ventricular activation, which was not observed with selective His bundle pacing. Conclusions Compared to selective His bundle pacing, local myocardial capture during non-selective His bundle pacing produces right ventricular pre-excitation resulting in prolongation of QRS duration. However, non-selective His bundle pacing preserves the left ventricular activation time and pattern of selective His bundle pacing. When choosing between selective and non-selective His bundle pacing, left ventricular dyssynchrony is not an important factor. Abstract Figure: Selective vs Non-Selective HBP

Background: Left bundle branch area pacing (LBBAP) is a novel physiological pacing approach.Objective: To assess learning curve for LBBAP and compare the procedure and fluoroscopy time between LBBAP and right ventricular pacing (RVP).Methods: Consecutive bradycardia patients who underwent LBBAP or RVP were prospectively recruited from June 2018 to June 2020. The procedure and fluoroscopy time for ventricular lead placement, pacing parameters, and periprocedural complications were recorded. Restricted cubic splines were used to fit learning curves for LBBAP.Results: Left bundle branch area pacing was successful in 376 of 406 (92.6%) patients while 313 patients received RVP. Learning curve for LBBAP illustrated initial (1–50 cases), improved (51–150 cases), and stable stages (151–406 cases) with gradually increased success rates (88.0 vs. 90.0 vs. 94.5%, P = 0.106), steeply decreased median procedure (26.5 vs. 14.0 vs. 9.0min, P < 0.001) and fluoroscopy time (16.0 vs. 6.0 vs. 4.0min, P < 0.001), and shortened stimulus to left ventricular activation time (Sti-LVAT; 78.7 vs. 78.1 vs. 71.2 ms, P < 0.001). LBBAP at the stable stage showed longer but close median procedure (9.0 vs. 6.9min, P < 0.001) and fluoroscopy time (4.0 vs. 2.8min, P < 0.001) compared with RVP.Conclusion: The procedure and fluoroscopy time of LBBAP could be reduced significantly with increasing procedure volume and close to that of RVP for an experienced operator.

Pace mapping is commonly used to locate the origin of ventricular arrhythmias, especially premature ventricular contraction (PVC). However, this technique relies on clinicians’ ability to rapidly interpret ECG data. To avoid time-consuming interpretation of ECG morphology, some automated algorithms or computational models have been explored to guide the ablation. Inspired by these studies, we propose a novel model based on spatial and morphological domains. The purpose of this study is to assess this model and compare it with three existing models. The data are available from the Experimental Data and Geometric Analysis Repository database in which three in vivo PVC patients are included. To measure the hit rate (A hit occurs when the predicted site is within 15 mm of the target) of different algorithms, 47 target sites are tested. Moreover, to evaluate the efficiency of different models in narrowing down the target range, 54 targets are verified. As a result, the proposed algorithm achieves the most hits (37/47) and fewest misses (9/47), and it narrows down the target range most, from 27.62 ± 3.47 mm to 10.72 ± 9.58 mm among 54 target sites. It is expected to be applied in the real-time prediction of the origin of ventricular activation to guide the clinician toward the target site.

Introduction Polymorphic ventricular tachycardia (VT) is defined as a rapid rhythm with continuously changing ventricular activation. In the absence of QT interval prolongation, its evaluation is a challenging activity with a series of differential diagnoses. The present study reports on a case of a young man who had an out-of-hospital cardiac arrest and and who later presented an episode of exercise-induced polymorphic VT. A rational investigation is discussed based on the patient’s clinical findings and baseline ECG. […] Cardiac Arrest [...]

Cardiac resynchronization therapy (CRT) can substantially improve dyssynchronous heart failure and reduce mortality. However, about one-third of patients who are implanted, derive no measurable benefit from CRT. Non-response may partly be due to suboptimal activation of the left ventricle (LV) caused by electrophysiological heterogeneities. The goal of this study is to investigate the performance of a newly developed method used to analyze electrical wavefront propagation in a heart model including myocardial scar and compare this to clinical benchmark studies. We used computational models to measure the maximum activation front (MAF) in the LV during different pacing scenarios. Different heart geometries and scars were created based on cardiac MR images of three patients. The right ventricle (RV) was paced from the apex and the LV was paced from 12 different sites, single site, dual-site and triple site. Our results showed that for single LV site pacing, the pacing site with the largest MAF corresponded with the latest activated regions of the LV demonstrated during RV pacing, which also agrees with previous markers used for predicting optimal single-site pacing location. We then demonstrated the utility of MAF in predicting optimal electrode placements in more complex scenarios including scar and multi-site LV pacing. This study demonstrates the potential value of computational simulations in understanding and planning CRT.

We have reported that non-selective but not selective His-bundle pacing (HBP) resolves bundle branch block (BBB) pattern. Characterized by ventricular pre-excitation, the mechanism by which nonselective-HBP resolves BBB is unknown. As A-V delays may determine both duration and timing of ventricular pre-excitation, it was hypothesized that an analysis of P-wave to HBP interval in relation to P-wave to His-bundle electrogram (HBE), may yield further insights into resolution of BBB pattern in NS-HBP. Methods: In 27 patients with RBBB+LAD (n=11) and LBBB (n=16), QRS parameters at AV delays resulting in P-HBP interval P-HBE. Results: At P-33 HBP< P-HBE, the pre-excitation duration was longest (63±13ms), and a more normal pre-excited complex replaced the RBBB, LAD, or LBBB pattern. In addition, the QRS-voltage in L1 was restored (LAD and LBBB), QRS-axis normalized (LAD), ventricular activation times decreased (LBBB) and rightward delay (S wave in L1) resolved (RBBB) (p

Background: Diagnosis of cardiac amyloidosis (CA) requires advanced imaging techniques. Typical surface ECG patterns have been described, but their diagnostic abilities are limited. Objectives: The aim was to perform a thorough electrophysiological characterization in CA patients and derive an easy-to-use tool for diagnosis. Methods: We applied electrocardiographic imaging (ECGI) to acquire electroanatomical maps in CA patients and controls. A machine learning approach was then utilized to decipher the complex data sets obtained and generate a surface ECG-based diagnostic tool. Findings: Areas of low-voltage were localized in the basal inferior regions of both ventricles and the remaining right ventricular segments in CA. The earliest epicardial breakthrough of myocardial activation was visualized on the right ventricle. Potential maps revealed an accelerated and diffuse propagation pattern. We correlated the results from ECGI with 12-lead ECG recordings. Ventricular activation correlated best with R-peak timing in leads V1 to V3. Epicardial voltage showed a strong positive correlation with R-peak amplitude in the inferior leads II, III, aVF. Respective surface ECG leads showed two characteristic patterns. Ten blinded cardiologists were asked to identify CA patients by analyzing 12-lead ECGs before and after training on the defined ECG patterns. Training led to significant improvements in the detection rate of CA with an AUC of 0.69 before and 0.97 after training. Interpretation: Using a machine learning approach, an ECG-based tool was developed from detailed electroanatomical mapping of CA patients. The ECG algorithm is simple and has proven helpful to suspect CA without the aid of advanced imaging modalities.. Funding Information: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Declaration of Interests: None to declare. Ethics Approval Statement: The study was part of a registry approved by the local ethics committee (EK #796/2010) and conducted according to good clinical practice as outlined in the declaration of Helsinki. All patients gave written informed consent.

Fiber structure governs the spread of excitation in the heart, however, little is known about the effects of physiological variability in the fiber orientation on epicardial activation. To investigate these effects, we used computer simulation to compare ventricular activation sequences initiated from stimulus sites at regularly spaced depths within the myocardium under varying rule-based fiber ranges. We compared the effects using four characteristics of epicardial breakthrough (BKT): location, area, shape (calculated via the axis ratio of a fitted ellipse), and orientation. Our results showed changes in the BKT characteristics as pacing depth increased, e.g., the area increased, the shape became more circular, and the orientation rotated counterclockwise, regardless of the fiber orientation. Furthermore, the maximal differences in epicardial activation from a single pacing site for location, area, axis ratio, and orientation were 1.2 mm, 74 mm(2), 0.16, and 26°, respectively. Our results suggest that variability in fiber orientation has a negligible effect on the location, area, and shape of the BKT, while fluctuations were observed in the BKT orientation in response to the fiber fields, especially for epicardial stimulation sites. Our results suggest the fiber field orientation plays only a minor role in activation simulations of ectopic beats.

Non-invasive estimation of the cardiac activation sequence through inverse electrocardiography (iECG) based on the equivalent double layer becomes increasingly difficult for multiple activation waves through the myocardium. Earlier studies simulated the effect of the His-Purkinje system through a multi-focal search, which does not completely take into account the effect of multiple near simultaneous activation waves initiated by the His-Purkinje system. In this study, the iECG initial estimation of the cardiac activation sequence was modified to include electro-anatomical structures associated with the His-Purkinje system to provide a physiologically robust initial estimate. The performance of two iECG techniques for the estimation of different His-Purkinje mediated ventricular activation sequences were tested, i. e. normal activation and left and right bundle branch block activation.

Background Ventricular arrhythmias (VAs) originating from ventricular outflow tracts can possess a high similarity of QRS configuration resulting in an inaccurate localization, while the reminder of mapping or ablation in the lower right ventricular outflow tract (RVOT) commonly provide the preferred transformation strategy. Methods We retrospectively analyzed the total of 958 patients who were referred for radiofrequency (RF) ablation of VAs in our center. VAs with the sinus of valsalva (SoV) origins were enrolled. Results A total of 120 consecutive patients (mean age 45.0 ± 15.5 years) undergoing the ablation of VAs arising from the left-sided ventricular outflow tracts were included, with 55 (45.8%) female. All patients had a QRS morphology of the LBBB pattern and an inferior axis, with the mean earliest ventricular activation (EVA) of target site of 34.9 ± 8.8ms. 37 (30.8%), 60 (50.0%), and 23 (19.2%) patients obtained the successful RF ablation at the right sinus cusp (RCC), left sinus cusp (LCC), and the commissure of RCC and LCC (R-LCC), respectively. 62 (51.7%) target sites of SoV could record a high-frequency potential. Moreover, 25 (20.8%) patients were continuously recorded an early ventricular activation in the lower RVOT and achieved the elimination of VAs in SoV. Conclusions VAs originating from the SoV could show a low specificity of QRS morphology mimicking the RVOT-like ECG feature. An early ventricular activation mapped in the lower RVOT or RF ablation with poor response likely demonstrated the VAs originating from the SoV, especially the RCC.

Despite advances in the field of cardiac resynchronisation therapy (CRT), response rates and durability of therapy remain relatively static. Optimising device timing intervals may be the most common modifiable factor influencing CRT efficacy after implantation. This review addresses the concept of fusion pacing as a method for improving patient outcomes with CRT. Fusion pacing describes the delivery of CRT pacing with a programming strategy to preserve intrinsic atrioventricular (AV) conduction and ventricular activation via the right bundle branch. Several methods have been assessed to achieve fusion pacing. QRS complex duration (QRSd) shortening with CRT is associated with improved clinical response. Dynamic algorithm-based optimisation targeting narrowest QRSd in patients with intact AV conduction has shown promise in people with heart failure with left bundle branch block. Individualised dynamic programming achieving fusion may achieve the greatest magnitude of electrical synchrony, measured by QRSd narrowing.

Background: Right ventricular (RV) pacing causes delayed activation of remote ventricular segments. We used the UHF-ECG to describe ventricular depolarization when pacing different RV locations. Methods: In 51 consecutive patients, temporary pacing was performed at the RV apex, anterior and lateral wall, and at the RV septum with (cSp) and without direct conductive tissue engagement (mSp) (further subclassified as RVIT and RVOT for septal inflow and outflow positions). The timing of UHF-ECG electrical activations were quantified as: left ventricular lateral wall delay (LVLWd; V8 activation delay), RV lateral wall delay (RVLWd; V1 activation delay), and LV lateral wall depolarization duration (V5-8d). Results: The LVLWd was shortest for cSp (11 ms (95% CI; 5;17), followed by the RVIT (19 ms (11;26) and the RVOT (33 ms (27;40), (p

Aims Ventricular activation patterns can aid clinical decision-making directly by providing spatial information on cardiac electrical activation or indirectly through derived clinical indices. The aim of this work was to derive an atlas of the major modes of variation of ventricular activation from model-predicted 3D bi-ventricular activation time distributions and to relate these modes to corresponding vectorcardiograms (VCGs). We investigated how the resulting dimensionality reduction can improve and accelerate the estimation of activation patterns from surface electrogram measurements. Methods and results Atlases of activation time (AT) and VCGs were derived using principal component analysis on a dataset of simulated electrophysiology simulations computed on eight patient-specific bi-ventricular geometries. The atlases provided significant dimensionality reduction, and the modes of variation in the two atlases described similar features. Utility of the atlases was assessed by resolving clinical waveforms against them and the VCG atlas was able to accurately reconstruct the patient VCGs with fewer than 10 modes. A sensitivity analysis between the two atlases was performed by calculating a compact Jacobian. Finally, VCGs generated by varying AT atlas modes were compared with clinical VCGs to estimate patient-specific activation maps, and the resulting errors between the clinical and atlas-based VCGs were less than those from more computationally expensive method. Conclusion Atlases of activation and VCGs represent a new method of identifying and relating the features of these high-dimensional signals that capture the major sources of variation between patients and may aid in identifying novel clinical indices of arrhythmia risk or therapeutic outcome.

This study sought to evaluate the effectiveness of His-optimized cardiac resynchronization therapy (HOT-CRT) for reducing left ventricular activation time (LVAT) compared to His bundle pacing (HBP) and biventricular (BiV) pacing (including multipoint pacing [MPP]), using electrocardiographic (ECG) imaging.HBP may correct bundle branch block (BBB) and has shown encouraging results for providing CRT. However, HBP does not correct BBB in all patients and may be combined with univentricular or BiV fusion pacing to deliver HOT-CRT to maximize resynchronization.Nineteen patients with a standard indication for CRT, implanted with HBP without correction of BBB and BiV (n = 14) or right ventricular (n = 5) leads, were prospectively enrolled. Patients underwent ECG imaging while pacing in different configurations using different LV electrodes and at different HBP ventricular pacing (VP) delays. The primary endpoint was reduction in LVAT with HOT-CRT, and the secondary endpoints included various other dys-synchrony measurements including right ventricular activation time (RVAT).Compared to HBP, HOT-CRT reduced LVAT by 21% (-17 ms [95% confidence interval [CI]: -25 to -9 ms]; p 0.001) and outperformed BiV by 24% (-22 ms [95% CI: -33 to -10 ms]; p = 0.002) and MPP by 13% (-11 ms [95% CI: -21 to -1 ms]; p = 0.035). Relative to HBP, HOT-CRT also reduced RVAT by 7% (-5 ms [95% CI: -9 to -1 ms; p = 0.035) in patients with right BBB, whereas RVAT was increased by BiV. The other electrical dyssynchrony measurements also improved with HOT-CRT.HOT-CRT acutely improves ventricular electrical synchrony beyond BiV and MPP. The impact of this finding needs to be evaluated further in studies with clinical follow-up. (Electrical Resynchronization and Acute Hemodynamic Effects of Direct His Bundle Pacing Compared to Biventricular Pacing; NCT03452462).

Introduction: The relationship between conduction time of a sinus impulse and a paced impulse from His bundle to peak of left ventricular activation (HVAT) has not been systematically studied. Hypothesis: To perform a comparative analysis of HVAT of sinus and paced impulse in non-selective (NS) His bundle pacing (HBP) and selective (S)-HBP. Furthermore, to determine if pacing voltage and presence of His Purkinje system (HPS) disease affects HVAT. Methods: In 102 consecutive patients a comparative analysis of native HVAT and paced HVAT at higher (5-volt) and lower voltage (1-volt) was done in all patients and in groups subdivided into NS-HBP, S-HBP, with and without HPS disease. Results: Compared to sinus HVAT (105.9 ± 24.0 ms), paced HVAT was shorter at 5-volt (97.2 ± 17.9 ms) ( p ) and longer at 1-volt ( p ). This voltage effect was significant only in NS-HBP (-15.8 ± 15.7 ms, p ) but not in selective-HBP (-6.2± 13.6 ms p=0.16 ). In NS-HBP, decrease in HVAT caused by 5-volt was the same in normal vs diseased HPS (-14.5 ± 12.8 vs-13.2 ±16.3 ms). Conclusions: 1) Compared to sinus HVAT, NS-HBP HVAT is significantly shorter at 5-volt, however, tends to prolong at 1-volt.2) The 1-volt to 5-volt HVAT decrease appears to be similar both normal and diseased NS-HBP thus not related to correction of HPS delay. 3) The voltage related decrease in HVAT is significant in presence of pre-excitation wave seen in NS-HBP and is not significant in S-HBP.

Background: To facilitate ablation of ventricular tachycardia (VT), an automated localization system to identify the site of origin of left ventricular activation in real time using the 12-lead ECG was developed. The objective of this study was to prospectively assess its accuracy. Methods: The automated site of origin localization system consists of 3 steps: (1) localization of ventricular segment based on population templates, (2) population-based localization within a segment, and (3) patient-specific site localization. Localization error was assessed by the distance between the known reference site and the estimated site. Results: In 19 patients undergoing 21 catheter ablation procedures of scar-related VT, site of origin localization accuracy was estimated using 552 left ventricular endocardial pacing sites pooled together and 25 VT-exit sites identified by contact mapping. For the 25 VT-exit sites, localization error of the population-based localization steps was within 10 mm. Patient-specific site localization achieved accuracy of within 3.5 mm after including up to 11 pacing (training) sites. Using 3 remotes (67.8±17.0 mm from the reference VT-exit site), and then 5 close pacing sites, resulted in localization error of 7.2±4.1 mm for the 25 identified VT-exit sites. In 2 emulated clinical procedure with 2 induced VTs, the site of origin localization system achieved accuracy within 4 mm. Conclusions: In this prospective validation study, the automated localization system achieved estimated accuracy within 10 mm and could thus provide clinical utility.

Introduction. The treatment of congenital complete AV block (CCAVB) is burdened by RV-associated ventricular dysfunction at long-term in a subgroup of patients. Methods and Results. Two CCAVB adolescents with mild systolic dysfunction associated to VVIR pacing reached elective pacemaker replacement after 10±1 years. They were upgraded to physiologic stimulation by restoring AV synchrony and ventricular activation via His bundle pacing (HBP). At 9-months follow-up both had reverse left ventricular (LV) remodeling: LV end-diastolic volume index decreased from 89±4 to 70±7 ml/m2, LV end-systolic volume index decreased from 49±1 to 32 ml/m2, LVEF increased from 43±1% to 53±4%. Conclusions. HBP can improve LV function in CCAVB adolescents. It should be considered in the setting of LV dysfunction associated to RV pacing, and should be explored as first-choice treatment from late childhood onward.

Complete heart block (CHB) results from dysfunction of the cardiac conduction system, which results in complete electrical dissociation. The ventricular escape rhythm can have its origin anywhere from the atrioventricular node to the bundle branch-Purkinje system. CHB typically results in bradycardia, hypotension, fatigue, hemodynamic instability, syncope, or even Stokes-Adams syndrome. Escape rhythm originating above the bifurcation of the His bundle (HB) produces narrow QRSs with relatively rapid heart rate (HR) (except in cases of His system disease). We present a middle-aged man with an HR of 34 bpm, progressive fatigue, in whom a temporary pacemaker was implanted in the subtricuspid region. The post-intervention electrocardiogram had unusual features.

The activation sequence of the ventricular myocardium in ectotherms is a matter of debate. We studied the correlation between the ventricular activation sequence and the pattern of local stretches in 13 toads (Bufo bufo). Epicardial potential mapping was done with 56-lead sock array. Activation times were determined as dV/dt min in each lead. Initial epicardial foci of activation were found on the left side of the ventricular base, whereas regions on the apex and the right side of the base demonstrated late activation. Video recordings (50 frames/s) showed that a median presystolic stretch in left-side ventricular regions were greater than in right-side regions [4.70 (interquartile range 3.25-8.85)% vs 1.45 (interquartile range 0.38-3.05)%, p=0.028, respectively]. Intracardiac bolus injection elicited ventricular activation with a similar sequence and duration. Thus, ventricular areas of earliest activation were associated with greater presystolic stretch, implying the existence of stretch-excitation relationship in ectotherms’ hearts.