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During His-Purkinje conduction system (HPS) pacing, it is crucial to confirm capture of the His bundle or left bundle branch versus myocardialonly capture. For this, several methods and criteria for differentiation between non-selective (ns) capture – capture of the HPS and the adjacent myocardium – and myocardial-only capture were developed. HPS capture results in faster and more homogenous depolarisation of the left ventricle than right ventricular septal (RVS) myocardial-only capture. Specifically, the depolarisation of the left ventricle (LV) does not require slow cell-to-cell spread of activation from the right side to the left side of the interventricular septum but begins simultaneously with QRS onset as in native depolarisation. These phenomena greatly influence QRS complex morphology and form the basis of electrocardiographic differentiation between HPS and myocardial paced QRS. Moreover, the HPS and the working myocardium are different tissues within the heart muscle that vary not only in conduction velocities but also in refractoriness and capture thresholds. These last two differences can be exploited for the diagnosis of HPS capture using dynamic pacing manoeuvres, namely differential output pacing, programmed stimulation and burst pacing. This review summarises current knowledge of this subject.

His bundle pacing and left bundle branch pacing are complementary implantation techniques that combine into conduction system pacing, which allows maintaining or recovering physiological activation of the heart. We selected cases from the electrophysiological laboratory of the University Hospital in Krakow to present theoretical and practical aspects of conduction system pacing using fluoroscopy images, ECG and EGM recordings.

Left bundle branch pacing (LBBP) technique is a new method for conduction system pacing that is useful for both bradyarrhythmia and heart failure indications. LBBP, while less physiological than His bundle pacing, offers several practical advantages. Namely, lower and stable pacing thresholds, good sensing of the intrinsic ventricular activity and easiness in localizing the pacing target. The LBBP method more often than His bundle pacing results in engagement of the conduction system distal to the area of the block. A step-by-step approach to LBBP was described. Attention was given to the following phases of the procedure: 1) localization of the target area on the septum, 2) the lead rotation technique with an interpretation of the lead responses (drill effect, screwdriver effect, entanglement effect), 3) methods for monitoring the lead depth in the septum to avoid perforation (fixation beats, continuous pace mapping, impedance), and 4) methods to differentiate between LBBP and left ventricular septal pacing.

Introduction There are several prognostic scores for the assessment of risk of atrial fibrillation (AF) recurrence post ablation procedure. However, the use of these complex scores is difficult and the validation on different populations brought divergent results. Our goal was to compare the performance of these risk scores as the basis for the development of a new, simplified score based only on few universally predictive variables. Methods All cryoballoon‐based AF ablations performed in a single‐center over a 10‐year period were prospectively analyzed with regard to AF recurrence. This served to analyze the performance of APPLE, CAAP‐AF, SCALE‐CryoAF, MB‐LATER, CHADS2, and CHA2DS2‐VASc risk scores. Results A total of 597 patients, mostly (78.1%) with paroxysmal AF were studied. Analyzed risk scores performed poorer than in the original publications because some risk factors were not predictive of AF recurrence. A simplified score named 0‐1‐2 PL, composed of just two universally predictive variables, AF type (1 point for P ersistent AF) and LA dimension (1 point for L A size >45 mm) was developed. The 0‐1‐2 PL score stratified patients into low risk (0 points), intermediate risk (1 point), and high risk categories (2 points) which were related to a 2‐year risk of AF recurrence of 21%, 37%, and 55%, respectively. This score had C‐statistics (0.620) higher/comparable to other investigated much more complex scores. Conclusion The assessment of risk of AF recurrence at the pre‐ablation stage can be simplified without compromising accuracy. This could help to popularize risk assessment and standardization of AF management., This study suggests that despite the significant differences between risk scores in terms of the choice of risk factors and the relative weights assigned to them, their performance for pre‐ablation risk assessment is quite similar, and weaker than originally reported. It seems that the assessment of the risk of AF recurrence at the pre‐ablation stage can be simplified by using the novel 0‐1‐2 PL score instead of more complex scores.

IntroductionOne of the challenges of left bundle branch (LBB) pacing is to place the pacing lead deep enough in the septum to obtain capture of the LBB, yet not too deep to avoid perforation. We hypothesized that the occurrence of the ectopic beats of qR/rsR’ morphology in V1 lead (fixation beats) during the lead fixation would predict that the final desired intraseptal lead depth was just reached, while the lack of fixation beats would indicate too shallow position, and need for more lead rotations.MethodsConsecutive patients during LBB pacing device implantation were analyzed retrospectively and then prospectively with respect to the occurrence of the fixation beats during each episode of lead rotation. We compared the presence of fixation beats during the lead rotation event directly before the LBB capture area depth was reached versus during the events before intermediate/unsuccessful positions.ResultsA total of 339 patients and 1278 lead rotation events were analyzed. In the retrospective phase, the fixation beats were observed in 327/339 of final lead positions and in 9/939 of intermediate lead positions (pConclusionsMonitoring fixation beats during deep septal lead deployment can facilitate the procedure and possibly increase the safety of lead implantation.

Objectives The aim of this study was to assess the feasibility and outcomes of left bundle branch area pacing (LBBAP) in patients eligible for cardiac resynchronization therapy (CRT) in an international, multicenter, collaborative study. Background CRT using biventricular pacing is effective in patients with heart failure and left bundle branch block (LBBB). LBBAP has been reported as an alternative option for CRT. Methods LBBAP was attempted in patients with left ventricular ejection fraction (LVEF) Results LBBAP was attempted in 325 patients, and CRT was successfully achieved in 277 (85%) (mean age 71 ± 12 years, 35% women, ischemic cardiomyopathy in 44%). QRS configuration at baseline was LBBB in 39% and non-LBBB in 46%. Procedure and fluoroscopy duration were 105 ± 54 and 19 ± 15 min, respectively. LBBAP threshold and R-wave amplitudes were 0.6 ± 0.3 V at 0.5 ms and 10.6 ± 6 mV at implantation and remained stable during mean follow-up of 6 ± 5 months. LBBAP resulted in significant QRS narrowing from 152 ± 32 to 137 ± 22 ms (p Conclusions LBBAP is feasible and safe and provides an alternative option for CRT. LBBAP provides remarkably low and stable pacing thresholds and was associated with improved clinical and echocardiographic outcomes.

His bundle pacing was presented as the most physiological mode of ventricular pacing. In the article we describe His pacing as an alternative cardiac pacing modality both for classic indications and resynchronization candidates. On the basis of personal experience and literature data a practical, step-by-step approach to direct His bundle pacing was described. With several ECG examples various forms of His bundle pacing were illustrated. Special attention was given to diagnosis of His bundle capture / loss of His bundle capture on the basis of ECG.

His bundle pacing (HBP) is steadily gaining interest for providing physiological cardiac stimulation. Careful analysis of the electrocardiogram (ECG) is crucial to confirm capture of conduction tissue, which is a prerequisite for successful HBP at implantation and follow-up. However, interpretation of the ECG with HBP can be challenging. This review provides the reader with practical guidance on how to best use and troubleshoot the 12-lead ECG for HBP in daily clinical practice.

Background: Several electrocardiographic (ECG) algorithms have been developed for predicting accessory pathway (AP) location in Wolff–Parkinson–White syndrome. However, their accuracy may be related to the manifested degree of preexcitation on ECG. Aims: Our goal was to assess the effect of the degree of preexcitation on the accuracy of 4 traditional AP localization algorithms and to compare them with the algorithm specifically designed for ECGs with maximal preexcitation (Pambrun) Methods: The study included 300 patients who underwent successful ablation of an overt atrioventricular AP. Resting and maximally preexcited ECGs obtained during incremental atrial pacing were assessed using 4 traditional AP localization algorithms: Xie, d’Avila, Iturralde, and Taguchi. Maximally preexcited ECGs were additionally assessed with the Pambrun algorithm. We compared the precision of the algorithms to predict accurate or anatomically adjacent AP location. Results: Theoverall accuracy of traditional AP localization algorithms using resting ECG ranged between 26% and 53.7% and improved to a range of 47.3% to 69.7% when adjacent locations were accepted. When used with maximal preexcitation, all algorithms had significantly higher accuracy, with a mean improvement of 14.3 and 15.6 percentage points for precise and adjacent sites, respectively. The Pambrun algorithm for maximally preexcited ECGs had the highest precision for both accurate and adjacent locations of the APs (89.7% and 97%, respectively). Conclusions: Greater preexcitation on ECG improved the accuracy of the traditional AP localization algorithms. The algorithm designed to use maximally preexcited ECGs has the best accuracy. Maximally preexcited ECG recordings should preferably be used in clinical practice to facilitate the ablation procedure.

BACKGROUND Cardiac resynchronization therapy (CRT) based on the conventional biventricular pacing (BiV-CRT) technique sometimes results in broad QRS complex and suboptimal response. OBJECTIVE We aimed to assess the feasibility and outcomes of CRT based on left bundle branch area pacing (LBBAP, in lieu of the right ventricular lead) combined with coronary venous left ventricular pacing in an international multicenter study. METHODS LBBAP-optimized CRT (LOT-CRT) was attempted in nonconsecutive patients with CRT indications. Addition of the LBBA (or coronary venous) lead was at the discretion of the implanting physician, who was guided by suboptimal paced QRS complex, and/or on clinical grounds. RESULTS LOT-CRT was successful in 91 of 112 patients (81%). The baseline characteristics were as follows: mean age 70 +/- 11 years, female 22 (20%), left ventricular ejection fraction 28.7% +/- 9.8%, left ventricular end-diastolic diameter 62 +/- 9 mm, N-terminal pro-B-type natriuretic peptide level 5821 +/- 8193 pg/mL, left bundle branch block 47 (42%), nonspecific intraventricular conduction delay 25 (22%), right ventricular pacing 26 (23%), and right bundle branch block 14 (12%). The procedure characteristics were as follows: mean fluoroscopy time 27.3 +/- 22 minutes, LBBAP capture threshold 0.8 +/- 0.5 V @ 0.5 ms, and R-wave amplitude 10 mV. LOT-CRT resulted in significantly greater narrowing of QRS complex from 182 +/- 25 ms at baseline to 144 +/- 22 ms (P < .0001) than did BiV-CRT (170 +/- 30 ms; P < .0001) and LBBAP (162 +/- 23 ms; P < .0001). At follow-up of >= 3 months, the ejection fraction improved to 37% +/- 12%, left ventricular end-diastolic diameter decreased to 59 +/- 9 mm, N-terminal pro-B-type natriuretic peptide level decreased to 2514 +/- 3537 pg/mL, pacing parameters were stable, and clinical improvement was noted in 76% of patients (New York Heart Association class 2.9 vs 1.9). CONCLUSION LOT-CRT is feasible and safe and provides greater electrical resynchronization as compared with BiV-CRT and could be an alternative, especially when only suboptimal electrical re synchronization is obtained with BiV-CRT. Randomized controlled trials comparing LOT-CRT and BiV-CRT are needed.

Aims We hypothesized that during left bundle branch (LBB) area pacing, the various possible combinations of direct capture/non-capture of the septal myocardium and the LBB result in distinct patterns of right and left ventricular activation. This could translate into different combinations of R-wave peak time (RWPT) in V1 and V6. Consequently, the V6-V1 interpeak interval could differentiate the three types of LBB area capture: non-selective (ns-)LBB, selective (s-)LBB, and left ventricular septal (LVS). Methods and results Patients with unquestionable evidence of LBB capture were included. The V6-V1 interpeak interval, V6RWPT, and V1RWPT were compared between different types of LBB area capture. A total of 468 patients from two centres were screened, with 124 patients (239 electrocardiograms) included in the analysis. Loss of LVS capture resulted in an increase in V1RWPT by ≥15 ms but did not impact V6RWPT. Loss of LBB capture resulted in an increase in V6RWPT by ≥15 ms but only minimally influenced V1RWPT. Consequently, the V6-V1 interval was longest during s-LBB capture (62.3 ± 21.4 ms), intermediate during ns-LBB capture (41.3 ± 14.0 ms), and shortest during LVS capture (26.5 ± 8.6 ms). The optimal value of the V6-V1 interval value for the differentiation between ns-LBB and LVS capture was 33 ms (area under the receiver operating characteristic curve of 84.7%). A specificity of 100% for the diagnosis of LBB capture was obtained with a cut-off value of >44 ms. Conclusion The V6-V1 interpeak interval is a promising novel criterion for the diagnosis of LBB area capture.

Background Left bundle branch area pacing (LBBAP) has recently been introduced as a physiological pacing technique with a synchronous ventricular activation. Objective To prospectively evaluate the feasibility and learning curve, as well as the electrical characteristics of LBBAP. Methods In 80 consecutive LBBAP pacemaker patients, ECG characteristics during intrinsic rhythm, RV septum pacing (RVSP) and LBBAP were evaluated. From the ECG's QRS duration and LVAT (stimulus to V6 R-wave peak time, RWPT) were measured. Also, the left bundle branch potential (LBBpot) to V6 RWPT interval was measured and compared to the LVAT. After conversion of the ECG into VCG (Kors conversion matrix), QRS area, as measurement for electrical dyssynchrony, was calculated. Results Permanent lead implantation was successful in 77/80 patients (96%) undergoing an attempt at LBBAP. LBBAP lead implantation time as well as fluoroscopy time were significantly shorter during last 25% of implantation compared to first 25% of implantations (17±5 min vs. 33±16 min and 12±7 min vs. 21±13 min, respectively, panel A and B). LBB capture was obtained in 54/80 patients (68%). In 36/45 patients (80%) with intact AV conduction and narrow QRS an LBBpot was present. The mean interval between the LBBpot and the onset of QRS was 22±6 ms. In the patients with narrow QRS (n=45), QRS duration increased significantly during both RVSP (139±24 ms) and LBBAP (123±21 ms), compared to intrinsic rhythm (95±13 ms). QRS area on the other hand, increased during both RVSP (73±20 μVs) but decreased during LBBAP (41±15 μVs), to values close to intrinsic rhythm (32±16 μVs, panel C). For all patients, QRS area was significantly lower in patients with LBB capture compared to patients without capture (43±18 μVs vs 54±21 μVs, respectively). In patients with LBB capture (n=54), LVAT was significantly shorter compared to patients without LBB capture (75±14 vs. 88±9 ms, respectively). In the patients with LBB capture, there was a significant correlation between the LBBpot – V6 RWPT and S – V6 RWPT intervals (Pearson correlation 0.739, P Conclusion LBBAP is a safe and feasible technique, with a clear learning curve that seems obtained after ± 40–60 implantations. LBB capture is obtained in two-thirds of patients. Although QRS duration remains prolonged, LBBAP largely restores ventricular electrical synchrony to values close to intrinsic (narrow QRS) rhythm. Funding Acknowledgement Type of funding sources: None.

Background Strength-duration curves for permanent His bundle (HB) pacing are potentially important for pacemaker programming. Objectives We aimed to calculate strength-duration curves and chronaxies of the HB and of the adjacent right ventricular (RV) working myocardium and to analyze zones of selective HB capture and battery current drain when pacing at different pulse durations (PDs). Methods Consecutive patients with permanent HB pacing were studied. The RV and HB capture thresholds were assessed at several PDs. Battery current drain and zones of selective HB capture at PDs of 0.1, 0.2, 0.4, and 1.0 ms were determined. Results In the whole group (N = 127), the HB chronaxie was shorter than the RV chronaxie. This difference was driven by patients with selective HB pacing (HB chronaxie 0.47 ms vs RV chronaxie 0.79 ms). The strength-duration curve for the HB had a lower rheobase and its steep portion started at shorter PDs, thus creating wider distance—zone of programmable selective HB pacing—between the HB and RV strength-duration curves at shorter PDs. The battery current drain was lower with pacing at PDs of 0.1–0.4 ms vs 1.0 ms. Chronaxie-adjusted PDs offered the lowest current drain. Conclusion For the first time, the strength-duration curves for permanent selective and nonselective HB pacing were determined. Selective HB capture and battery longevity can be promoted by shorter PDs (0.2 ms). Longer PDs (1.0 ms) offer greater safety margin for RV capture and may be preferable if simultaneous RV capture during HB pacing is desired.

Background Brugada phenocopies clinical entities that have indistinguishable electrocardiographic (ECG) patterns from true congenital Brugada syndrome. However, they are induced by other clinical circumstances such as myocardial ischemia. The purpose of our study was to examine the clinical features and pathogenesis of ischemia-induced Brugada phenocopy (BrP). Methods Data from 17 cases of ischemia-induced BrP were collected from the International Registry (www.brugadaphenocopy.com). Data were extracted from these publications and authors were contacted to provide further insight into each case. Results Of the patients included in this study, 71% were male. Mean age was 59 ± 11 years (range: 38-76). Type-1 Brugada ECG pattern occurred in 15/17 (88%) of the cases, while a type-2 Brugada ECG pattern was observed in the other 2/17 (12%). In all cases, the Brugada ECG pattern resolved upon correction of the ischemia, indicating ischemia as the inducing circumstance. No arrhythmic events have been detected acutely or during the follow-up. Reported time to resolution ranged from 2 minutes to 5 hours. Provocative challenges using sodium channel blocking agents were performed in 7/17 cases (41%), and all failed to induce a Brugada ECG pattern (BrP Class A). The remaining 10/17 cases (59%) did not undergo provocative testing due to various clinical reasons. Conclusions Myocardial ischemia is a commonly reported etiology of BrP. Importantly, this study found no association between BrP induced by myocardial ischemia and sudden cardiac death or malignant ventricular arrhythmias.

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.

Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Polish Cardiac Society - Section of Non-invasive Electrocardiology and Telemonitoring (PTK SENIT) Background. Electrocardiographical localization of accessory pathways (AP) in WPW syndrome remains an elusive goal. Despite several, often very complex algorithms that were developed over the last three decades, none of them is very accurate - as demonstrated by several independent validation studies. Moreover, algorithms are difficult to remember, which further limits their usefulness. The accessory pathway regions are arbitrary and transitions between them are smooth, not binary. The same applies to ECG features such as QRS polarity – they are not binary. Moreover, even the most careful ECG lead placement cannot compensate for the variability in heart position within the chest. Therefore, it is unrealistic to expect that any ECG feature or feature set will precisely identify a particular location in a 0 vs. 1 fashion. Aim We intend to create a mobile app / web based localizing application, that would support a novel method for AP localization: a colour density map generator - based on actual distribution of a sizable number of accessory pathway with a particular QRS features. Methods A total of 881 consecutive AP ablation procedures were reviewed and patients with successful ablation of an overt accessory pathway were included. ECG with baseline and full preexcitation obtained during incremental atrial pacing were obtained. AP localization was based on stored fluoroscopic images in several projections and procedure description. Each AP localization, as well as QRS polarity in all 12 leads, separately for full and baseline preexcitation patterns, were coded and introduced into the application database. An application web-based, optimized for mobile devices was developed. This application enabled to graphically show changing localization of AP with regard to the introduced, at each step, QRS polarity in a particular ECG lead. User can choose his/her own steps or criteria; there is no need to adhere to the proposed steps. Results A total of 604 patients/ ECGs were available for density map generation. With each additional lead QRS information introduced into the application the user can appreciate more and more precise localization of the AP. This quickly enables to pinpoint the area of maximum probability, i.e. the most likely/frequent location, followed by the immediate adjacent locations. Representative screen shots of to typical inital steps for left- and right-sided APs are provided below (Figure 1 and Figure 2). Limited prospective assessment was very favourable. Conclusions A novel method, easy to use, not requiring to remember any algorithmic steps, and based on an analysis of by far the largest cohort of over accessory pathways (in comparison with published algorithms) was developed. Prospective validation of the localization application seems warranted. Abstract Figure.

Introduction We aimed to compare the acute differences in left ventricular (LV) function and mechanical synchrony during nonselective His bundle pacing (ns-HBP) versus selective His bundle pacing (s-HBP) using strain echocardiography. Methods and results Consecutive patients with permanent His bundle pacing, in whom it was possible to obtain both s-HBP and ns-HBP, were studied in two centers. In each patient, echocardiography was performed sequentially during s-HBP and ns-HBP. Speckle-tracking echocardiography parameters were analyzed: Global longitudinal strain (GLS), the time delay between peak systolic strain in the basal septal and basal lateral segments (BS-BL delay), peak strain dispersion (PSD) and strain delay index. Right ventricle function was assessed using tricuspid annular plane systolic excursion (TAPSE) and tissue Doppler velocity of the lateral tricuspid annulus (S'). A total of 69 patients (age: 75.6 ± 10.5 years; males: 75%) were enrolled. There were no differences in LV ejection fraction and GLS between s-HBP and ns-HBP modes: 59% versus 60%, and -15.6% versus -15.7%, respectively; as well as no difference in BS-BL delay and strain delay index. The PSD value was higher in the ns-HBP group than in the s-HBP group with the most pronounced difference in the basal LV segments. No differences in right ventricular function parameters (TAPSE and S') were found. Conclusion The ns-HBP and s-HBP modes seem comparable regarding ventricular function. The dyssynchrony parameters were significantly higher during ns-HBP, however, the difference seems modest and clarification of its impact on LV function requires a larger long-term study.

Background: Cardiac resynchronization therapy (CRT) using biventricular pacing (BVP) has limited efficacy in patients with heart failure (HF) and right bundle branch block (RBBB). Left bundle branch area pacing (LBBAP) has been reported as an alternative option for BVP-CRT. The aim of the study was to assess the feasibility and outcomes of LBBAP in patients with RBBB and indication for CRT in an international, multicenter, collaborative study. Methods: LBBAP was attempted in patients with LVEF

Background: Transesophageal echocardiography (TEE) allows detailed characterization of atrial fibrillation (AF) substrate and could be valuable for predicting pulmonary vein isolation (PVI) procedure outcomes. Aims: We aimed at assessing the value of TEE-derived left atrial (LA) and LA appendage (LAA) features as prognostic markers for AF recurrence after cryoballoon-based ablation. Methods: Patients were enrolled using a prospective database of consecutive PVI procedures performed over a 7-year period. The following TEE-derived parameters were investigated: LAA emptying flow velocity (LAA-FV), the presence of patent foramen ovale (PFO), LA spontaneous echo contrast, and mitral regurgitation. Diagnosis of AF recurrence was based on scheduled and symptoms triggered ECG monitoring. The Cox’s regression model and Kaplan-Meier survival curves were applied for statistical analysis. Results: A total of 417 consecutive patients who underwent their first PVI using cryoballoon were analyzed (mean age: 59 years). AF recurrence was noted in 25.7% of patients (median follow-up of 24 months). Four TEE-derived variables had predictive values for AF recurrence: LAA-FV

BackgroundDuring left bundle branch (LBB) area pacing, it is important to confirm that the capture of the LBB is achieved, not just the capture of only the adjacent left ventricular myocardium (LV septal capture). Our aim was to establish ECG criteria for LBB capture by analyzing ECGs with confirmed LBB capture and non-capture. We hypothesized that since LBB pacing results in physiologic depolarization of the left ventricle then the native QRS can serve as a reference for the diagnosis of LBB capture in the same patient.MethodsOnly patients with direct evidence of LBB capture (output-dependent or refractoriness-dependent QRS morphology transition) were included. Several QRS characteristics were compared between the native rhythm and different types of LBB area capture. Receiver-operator characteristics analysis was performed to determine the optimal V6 R-wave peak time (RWPT) cut-off for LBB diagnosis.ResultsA total of 357 ECG tracing (124 patients) were analyzed: 118 with native rhythm, 124 with non-selective LBB capture, 69 with selective LBB capture and 46 with LV septal capture. Our hypotheses that during LBB capture the paced V6 RWPT (measured from QRS onset) equals the native V6 RWPT and that the paced V6 RWPT (measured from the stimulus) equals the LBB potential to V6 R-wave peak interval were positively validated. Criteria based on these rules had sensitivity and specificity of 98.0–88.2% and 85.7–95.4%, respectively. The optimal and 100% specific V6 RWPT values for differentiation between LBB capture and LV septal capture in patients with narrow QRS / right bundle branch block were 83 ms and 74 ms, respectively; while in patients with left bundle branch block/asystole/ventricular escape the optimal and 100% specific V6 RWPT values were 101 ms and 80 ms, respectively.ConclusionsNovel criteria for LBB capture were developed and optimal V6 RWPT cut-offs were determined.What this study addsWe showed that LBB pacing truly reproduce the physiological depolarization of the left ventricle since the paced V6 RWPT equals the native conduction V6 RWPT.Individualized LBB capture criteria, that use the native QRS as a reference, were developed.The optimal V6 RWPT values for differentiation between LBB capture and LV septal capture were determined, separately for patients with healthy and diseased LBB.

Right ventricular myocardial pacing leads to nonphysiological activation of heart ventricles. Contrary to this, His bundle pacing preserves their fast activation. Ultra-high-frequency electrocardiography (UHF-ECG) is a novel tool for ventricular depolarization assessment.The purpose of this study was to describe UHF-ECG depolarization patterns during myocardial and His bundle pacing.Forty-six patients undergoing His bundle pacing to treat bradycardia and spontaneous QRS complexes without bundle branch block were included. UHF-ECG recordings were performed during spontaneous rhythm, pure myocardial para-Hisian capture, and His bundle capture. QRS duration, QRS area, depolarization time in specific leads, and the UHF-ECG-derived ventricular dyssynchrony index were calculated.One hundred thirty-three UHF-ECG recordings were performed in 46 patients (44 spontaneous rhythm, 28 selective His bundle, 43 nonselective His bundle, and 18 myocardial capture). The mean QRS duration was 117 ms for spontaneous rhythm, 118 ms for selective, 135 ms for nonselective, and 166 ms for myocardial capture (P.001 for nonselective and myocardial capture compared to each of the other types of ventricular activation). The calculated dyssynchrony index was shortest during spontaneous rhythm (12 ms; P = .02 compared to selective and P = .09 compared to nonselective), and it did not differ between selective and nonselective His bundle capture (16 vs 15 ms; P.99) and was longest during myocardial capture of the para-Hisian area (37 ms; P.001 compared to each of the other types of ventricular activation).In patients without bundle branch block, both types of His bundle, but not myocardial, capture preserve ventricular electrical synchrony as measured using UHF-ECG.

Background The presence of accessory pathways (APs) is a risk factor for sudden cardiac death and other clinical complications. Aims We aimed to characterize all adverse events likely related to the presence of APs in patients referred for AP ablation and to identify risk factors for malignant arrhythmias. Methods We performed a retrospective analysis of consecutive patients referred for AP ablation from 2002 to 2017. Electrocardiograms, electrophysiological system records, and hospital discharge notes were reviewed. We collected data concerning symptoms before ablation, occurrence of ventricular fibrillation or malignant atrial fibrillation (AF), as well as other complications related to APs. Results We identified 602 patients with APs. Serious AP‑related events were observed in 41 patients, including 14 sudden cardiac arrests (1 death) and 16 pre–cardiac arrest events. Other complications included strokes, pulmonary edema, heart failure, and unnecessary device implantation. The risk of malignant arrhythmias decreased with a longer shortest preexcited RR interval (per 10 ms: odds ratio [OR], 1.3; 95% CI, 1.16–1.47) and increased with age (per 10 years: OR, 1.29; 95% CI, 1.06–1.57). The presence of inducible AF, but not sole atrioventricular reentrant tachycardia, increased the risk for malignant arrhythmias when compared with patients without any inducible arrhythmias. Conclusions Patients with APs referred for ablation commonly present with various adverse events. The predictive value of clinical risk factors for malignant arrhythmias is too low to prevent devastating consequences. When high safety and efficacy of AP ablation are ensured, even a low risk of sudden death is unacceptable and a lower threshold for prophylactic ablation should be used to prevent AP‑related adverse events.

Aims QRS narrowing with initiation of biventricular pacing might be an acute electrocardiographic indicator of correction of left bundle branch block (LBBB)-induced depolarization delay and asynchrony. However, its impact on prognosis remains controversial, especially in non-LBBB patients. Our goal was to evaluate the impact of QRS narrowing on long-term mortality and morbidity in a large cohort of patients undergoing cardiac resynchronization therapy (CRT) with different pre-implantation QRS types: LBBB, non-LBBB, and permanent right ventricular pacing. Methods and results This study included consecutive patients who underwent CRT device implantation. Study endpoints: death from any cause or urgent heart transplantation and death from any cause/urgent heart transplantation or hospital admission for heart failure. All pre- and post-implantation electrocardiograms were analysed using digital callipers, high-amplitude augmentation, 100 mm/s paper speed, and global QRS duration measurement method. A total of 552 CRT patients entered the survival analysis. During the 9 years observation period, 232 (42.0%) and 292 (52.9%) patients met primary and secondary endpoints, respectively. QRS narrowing predicted survival in the Kaplan-Meier analysis only in patients with LBBB. Multivariate Cox regression model showed that QRS narrowing was the major determinant of both study endpoints, with hazard ratios of 0.46 and 0.43, respectively. There was a strong relationship between mortality risk and shortening/widening of the QRS, albeit only in the LBBB group. Patients with non-LBBB morphologies had unfavourable prognosis similar to that in LBBB patients without QRS narrowing. Conclusion Acute QRS narrowing in patients with LBBB might be a desirable endpoint of CRT device implantation.

The para-Hisian pacing maneuver is useful in determining whether retrograde conduction is dependent on atrioventricular (AV) nodal conduction. Loss of direct His bundle capture results in a longer route for the depolarization wave to reach the AV node and the atrium, as it has to travel through the working myocardium to engage the distal Purkinje fibers. Thus, loss of direct His bundle capture results in obligatory ventriculoatrial (VA) interval prolongation unless a nonphysiological retrograde conduction route (an accessory pathway [AP]) is present. Consequently, a stable VA interval with loss of His bundle capture is considered diagnostic of the presence of an AP. This concept has been regarded as useful, especially when concentric retrograde atrial activation is present.1 Subsequently, however, potential important pitfalls in the interpretation of this differentiating maneuver were described. These include the recognition of inadvertent atrial capture, pure His bundle capture, the presence of fasciculoventricular pathways, and the impact of retrograde dual AV nodal physiology

Background: The CHADS2 and CHA2DS2-VASc scores were shown to predict mortality in patients with atrial fibrillation. However, pathophysiology and treatment outcomes of atrial fibrillation and typical atrial flutter (AFL) differ. Consequently, the prognosis of patients with AFL can also be different. Aims: The aim of the study was to assess CHADS2 and CHA2DS2‑VASc scores as mortality predictors in patients with typical AFL. Methods: Large cohort of consecutive patients with typical AFL who underwent catheter ablation was retrospectively analyzed. The CHADS2 and CHA2DS2‑VASc were calculated using hospital record data. All-cause mortality data was obtained from the registry of national personal identification numbers. The Kaplan–Meier method and multivariable Cox proportional hazard models were applied for survival and hazard ratio analyses, respectively. Results: A total of 469 patients hospitalized for typical AFL ablation were enrolled (mean [SD] age, 63.7 [12.2] years; male sex, 69.1%). Patients were followed from 2 to 12 years resulting in 2974 patient‑years of follow‑up. The Kaplan–Meier survival analysis revealed a negative impact of each component of the CHADS2 and CHA2DS2‑VASc scores on survival with the exception of stroke (not significant) and female sex (related to abetter survival). Consequently, higher scores were predictive of higher all‑cause mortality rates (2.7%–54% at 10 years); the CHA2DS2‑VASc score was equally predictive as the CHADS2 score. Conclusions: In patients referred for typical AFL ablation, the CHADS2 score can be applied for prognostic assessment. A successful AFL ablation procedure should not divert the attention from recognizing and addressing other medical issues that have an impact on long‑term mortality, which remains very high in this population of patients.

Aims The recently introduced technique of direct transseptal pacing of the left bundle branch is poorly characterized with many questions with regard to the optimal implantation strategy and safety concerns largely left unanswered. We developed a cadaver model for deep septal lead deployment in order to investigate the depth of penetration in relation to lead behaviour, lead tip position, and the number of rotations. Methods and results Five fresh human hearts and five lumenless, 4.1-Fr pacing leads were used for deep septal deployment simulations. The leads were positioned with the use of a dedicated delivery sheath and screwed into the interventricular septum at several sites progressively more distal from the atrioventricular ring with a predetermined number of lead rotations. During each lead deployment, the depth of tip penetration was measured and the lead behaviour was noted. Four distinct lead behaviours were observed: (i) helix only penetration, no matter how many rotations were performed, due to the ‘endocardial entanglement effect’ (43.1% cases) or (ii) ‘endocardial barrier effect’ (19.6% cases), (iii) shallow/moderate penetration, with ensuing ‘drill effect’ when more rotations were added (9.8% cases), and (iv) deep progressive penetration with each additional rotation, occurring when the ‘screwdriver effect’ was present (27.4% cases, including three septal perforations). These different lead behaviours seemed to be determined by the lead position—mainly the strength of the initial endocardial layer—and the number of fully transmitted rotations. Conclusion New insights into deep septal lead deployment technique were gained with regard to safe and successful implantation.

Introduction Permanent deep septal stimulation with capture of the left bundle branch (LBB) enables maintenance/restoration of the physiological activation of the left ventricle. However, it is almost always accompanied by the simultaneous engagement of the local septal myocardium, resulting in a fused (nonselective) QRS complex, therefore, confirmation of LBB capture remains difficult. Methods We hypothesized that programmed extrastimulus technique can differentiate nonselective LBB capture from myocardial-only capture as the effective refractory period (ERP) of the myocardium is different from the ERP of the LBB. Consecutive patients undergoing pacemaker implantation underwent programmed stimulation delivered from the lead implanted in a deep septal position. Responses to programmed stimulation were categorized on the basis of sudden change in the QRS morphology of the extrastimuli, observed when ERP of LBB or myocardium was encroached upon, as: "myocardial," "selective LBB," or nondiagnostic (unequivocal change of QRS morphology). Results Programmed deep septal stimulation was performed 269 times in 143 patients; in every patient with the use of a basic drive train of 600 milliseconds and in 126 patients also during intrinsic rhythm. The average septal-myocardial refractory period was shorter than the LBB refractory period: 263.0 ± 34.4 vs 318.0 ± 37.4 milliseconds. Responses diagnostic for LBB capture ("myocardial" or "selective LBB") were observed in 114 (79.7%) of patients. Conclusions A novel maneuver for the confirmation of LBB capture during deep septal stimulation was developed and found to enable definitive diagnosis by visualization of both components of the paced QRS complex: selective paced LBB QRS and myocardial-only paced QRS.

Introduction His-Purkinje system pacing preserves or restores physiologic depolarization of the left ventricle during permanent pacing. It consists of two complementary techniques: His bundle pacing (HB-P) and the recently introduced left bundle branch pacing (LBB-P). There is limited data on HB-P outcomes and only a few reports of LBB-P results. Purpose Our aim was to investigate success rate, complications, acute and early pacing parameters in patients undergoing HB-P and LBB-P in the setting of a cardiology tertiary centre that routinely implants HB-P and LBB-P pacemakers. Methods On the basis of a prospective database we performed a longitudinal cohort study of all consecutive patients with His-Purkinje system devices implanted in the years 2014–2019. In all cases, model 3830 lumen-less 4.1 Fr pacing lead was used. HB-P was achieved via HB mapping or pace mapping, LBB-P was achieved via deep septal lead deployment under electrophysiological and 12-lead ECG guidance. Results Since 2014 there were 324 implantations of His-Purkinje system pacemakers. Baseline patients' characteristics are presented in Table. The overall success rate was 81.5%. Selective HB-P, non-selective HB-P and LBB-P were achieved in 53%, 19% and 28% of successful cases. The mean fluoroscopy time was 11±9 min. The lead delivery was performed using single sheath (C315His) in 83% cases, while in 17% extra steerable sheath was necessary (C304XL). The acute mean LBB-P capture threshold @0.5 ms was significantly lower than in HB-P (0.65±0.43V vs. 1.47±0.8V). The mean chronic LBB-P capture threshold @1.0 ms was also lower than in HB-P (0.45±0.3V vs. 0.95±0.7V, p Baseline characteristics Age; sex 73±12 years (19–95 years); 64% males Mean EF; mean QRS duration; Presence of heart failuire or ischemic heart disease 47±15%; 128±32 ms; 48%; 37.5% Pacing indication AV block 31%; sinus node disease 12%; atrial fibrillation with bradycardia 37%; CRT 20% QRS morphology narrow QRS 61%; LBBB 20%; other 14%; IVCD 6% CRT, Cardiac Resynchronization Therapy; IVCD, Interventricular Conduction Delay. Conclusion His-Purkinje system pacing in routine practice has an acceptable success rate, pacing parameters and complication rate; the LBB-P provides better pacing parameters than HB-P. We believe that such single-centre experience paves the way for a large randomized trial of physiologic pacing.

BackgroundDuring permanent deep septal pacing, it is important to confirm left bundle branch (LBB) capture.ObjectiveThe effective refractory period (ERP) of the working myocardium is different than the ERP of the LBB; we hypothesized that it should be possible to differentiate LBB capture from septal myocardial capture using programmed extra-stimulus technique.MethodsIn consecutive patients undergoing pacemaker implantation who received pacing lead in a deep septal position programmed pacing was delivered from this lead. Responses to programmed pacing were categorized on the basis of QRS morphology of the extrastimuli as: myocardial (broader QRS, often slurred), selective (narrower QRS, preceded by an isoelectric interval) or non-diagnostic (unequivocal change).ResultsProgrammed deep septal pacing was performed 269 times in 143 patients; in every patient with the use of an 8-beat basic drive train of 600 ms and when possible also during supraventricular rhythm. Responses diagnostic for LBB capture were observed in 114 (79.7%) of patients. Selective LBB paced QRS was more often seen when premature beats were introduced during the intrinsic rhythm rather than after the basic drive train. The average septal-myocardial refractory period was significantly shorter than the LBB refractory period: 263.0±34.4 ms vs. 318.0±37.4 ms.ConclusionsA novel maneuver for the diagnosis of LBB capture during deep septal pacing, was formulated, assessed and found as diagnostically valuable. This method, based on the differences in refractoriness between LBB and the septal myocardium is unique in enabling the visualization of components of the usually fused, non-selective LBB paced QRS complex.Graphical abstract

Background Due to limited data, implantable loop recorders (ILR) are not currently recommended by the guidelines to routinely monitor patients after atrial fibrillation (AF) ablation. Aims To validate the diagnostic value of ILR after AF ablation, modern generation ILRs (LINQ) were implanted in patients scheduled for cryoballoon ablation of AF (CBA). Methods We included 29 patients with frequent and symptomatic episodes of paroxysmal AF. ILR was implanted 3 months prior to CBA, and data were collected before and for 6 months after the procedure. The device was programmed to maximize sensitivity of AF/ atrial tachycardia (AT) detection. All EGM recordings were "manually" assessed and annotated as true AF, pseudo AF, unrecognized AF, and episodes with no EGM available. Duration and episode-based standard performance metrics were evaluated. Results A total number of 5,842 episodes were recorded. A total of 4,403 episodes were true AF, 453 episodes were pseudo AF, and 986 episodes had no EGM available. The device did not recognize 144 episodes of AF. Duration-based sensitivity was 95.2%, duration-based specificity 99.9%, duration-based PPV 99.2%, duration-based NPV 99.9%, episode-based sensitivity 98.0%, and episode-based PPV 91.0%. Misdiagnosis happened in 1 in 10 episodes. Total data review time was 166 hr. Conclusions Implantable loop recorders is a valuable tool in evaluation of AF episodes in patients undergoing CBA. However, for high precision all recorded episodes need to be evaluated "manually." The memory storage space is too low for frequent AF episodes, resulting in overwriting of stored EGMs and data loss.

AimsPermanent His bundle (HB) pacing is usually accompanied by simultaneous capture of the adjacent right ventricular (RV) myocardium - this is described as a non-selective (ns)-HB pacing. Our aim was to identify ECG criteria for loss of HB capture during ns-HB pacing.MethodsConsecutive patients with permanent HB pacing were recruited. Surface 12-lead ECGs during ns-HB pacing and loss of HB capture (RV-only capture) were obtained. ECG criteria for loss/presence of HB capture were identified. In the validation phase these criteria and the “HB ECG algorithm” were tested by two blinded observers using a separate, sizable set of ECGs.ResultsA total of 353 ECG (226 ns-HB and 128 RV-only) were obtained from 226 patients with permanent HB pacing devices. QRS notch/slur in left ventricular leads and R-wave peak time in lead V6 were identified as the best features for differentiation. The 2-step HB ECG algorithm based on these features correctly classified 87.1% of cases with sensitivity and specificity of 93.2% and 83.9%, respectively. Moreover, the proposed criteria for definitive diagnosis of ns-HB capture (no QRS slur/notch in leads I, V1, V4-V6 and the R-wave peak time in V6 ≤ 100 ms) presented 100% specificity.ConclusionA novel ECG algorithm for the diagnosis of loss of HB capture and novel criteria for definitive confirmation of HB capture were formulated and validated. Practical application of these criteria during implant and follow-up of patients with HB pacing devices is feasible.Condensed AbstractThe 2-step ECG algorithm for loss of His bundle capture based on surface ECG analysis is proposed and validated. This method correctly classified 87.1% of cases with a sensitivity and specificity of 93.2% and 83.9%, respectively.What’s NewThis is the first study that analyzes QRS characteristics during non-selective His bundle pacing in a sizable cohort of patients.Precise criteria and a novel algorithm for electrocardiographic diagnosis of loss of HB capture during presumed non-selective HB pacing were validated.QRS notch/slur in left ventricular leads was identified as a simple and reproducible feature indicating loss of HB capture or lack/loss of correction of intraventricular conduction disturbances.Assessment of R-wave peak time in lead V6 rather than QRS duration for diagnosis of ns-HB pacing was validated.

BackgroundStrength-duration curves for permanent His bundle (HB) pacing are potentially important for pacemaker programming.ObjectiveWe aimed to calculate strength-duration curve and chronaxie of the His bundle (HB) and of the adjacent right ventricular (RV) working myocardium and to analyze zones of selective HB capture and battery current drain when pacing at different pulse durations (PDs).MethodsConsecutive patients with permanent HB pacing were studied. The RV and HB capture thresholds were assessed at several PDs. Battery current drain and zones of selective HB capture at PDs of 0.1, 0.2, 0.4 and 1.0 ms were determined.ResultsIn the whole group (n =127) the HB chronaxie was shorter than the RV chronaxie. This difference was driven by patients with selective HB pacing (HB chronaxie of 0.47 vs RV chronaxie of 0.79 ms). Strength-duration curve for HB had lower rheobase and its steep portion started at shorter PDs thus creating wider distance - zone of programmable selective HB pacing - between the HB and RV strength-duration curves at shorter PDs. The battery current drain was lower with pacing at PDs of 0.1 - 0.4 ms vs 1.0 ms. Chronaxie adjusted PDs offered lowest current drain.ConclusionFor the first time the strength-duration curves for permanent selective and non-selective HB pacing were determined. Selective HB capture and battery longevity can be promoted by shorter PDs (0.2 ms). Longer PDs (1.0 ms) offer bigger safety margin for RV capture and may be preferable if simultaneous RV capture during HB pacing is desired.

Background: Left bundle branch block (LBBB) is an important qualification criterion and determinant of prognosis in cardiac resynchronisation therapy (CRT) patients. Aims: Our goal was to investigate the long-term mortality and morbidity in a sizable cohort of patients with CRT with regard to the new strict LBBB definition proposed by Perrin. Methods: We performed a longitudinal cohort study that included consecutive CRT patients. Primary endpoint (all-cause death) and secondary endpoint (all-cause death and hospitalisation for heart failure) were analysed. All preimplantation elec- trocardiograms were categorised as LBBB or non-LBBB according to the new definitions/criteria analysed. Results: The survival analysis comprised 552 patients with CRT. The Perrin criteria, CRT guidelines class I indication criteria, and Strauss criteria were fulfilled in 38.9%, 79.4%, and 62.3% of all LBBB patients, respectively. During the nine-year study period, 232 patients died and the combined endpoint was met by 292 patients. The Perrin “true LBBB” definition criteria were inferior to the Strauss “complete” LBBB definition criteria in predicting survival as reflected by Kaplan-Meier survival curves (C-statistics). Multivariate Cox regression models showed that both LBBB definitions predicted mortality, however, the Perrin definition had a higher hazard ratio (HR 0.67) compared to the Strauss definition (HR 0.51). Conclusions: It seems that the Perrin “true LBBB” criteria are not well-suited for the selection of CRT candidates. Perhaps they do not reflect the presence of a true/complete LBBB or exclude too many patients who, despite some residual conduction in the left bundle branch, responded well to CRT.

Background His-bundle pacing (HBP) provides physiological ventricular activation. Observational studies have demonstrated the techniques' feasibility; however, data have come from a limited number of centers. Objectives We set out to explore the contemporary global practice in HBP focusing on the learning curve, procedural characteristics, and outcomes. Methods This is a retrospective, multicenter observational study of patients undergoing attempted HBP at seven centers. Pacing indication, fluoroscopy time, HBP thresholds, and lead reintervention and deactivation rates were recorded. Where centers had systematically recorded implant success rates from the outset, these were collated. Results A total of 529 patients underwent attempted HBP during the study period (2014-19) with a mean follow-up of 217 ± 303 days. Most implants were for bradycardia indications. In the three centers with the systematic collation of all attempts, the overall implant success rate was 81%, which improved to 87% after completion of 40 cases. All seven centers reported data on successful implants. The mean fluoroscopy time was 11.7 ± 12.0 minutes, the His-bundle capture threshold at implant was 1.4 ± 0.9 V at 0.8 ± 0.3 ms, and it was 1.3 ± 1.2 V at 0.9 ± 0.2 ms at last device check. HBP lead reintervention or deactivation (for lead displacement or rise in threshold) occurred in 7.5% of successful implants. There was evidence of a learning curve: fluoroscopy time and HBP capture threshold reduced with greater experience, plateauing after approximately 30-50 cases. Conclusion We found that it is feasible to establish a successful HBP program, using the currently available implantation tools. For physicians who are experienced at pacemaker implantation, the steepest part of the learning curve appears to be over the first 30-50 cases.

We present the case of a young patient with significant left ventricular hypertrophy as a common representation of the hypertrophic cardiomyopathy (HCM) phenotype. The clinical presentation and diagnostic route of the disease (despite negative genotype), which can be found in everyday cardiology practice, are shown. Despite the presence of guidelines on this topic, each clinical case is demanding, especially during qualification for invasive procedures. Limited data about the periprocedural risk of catheter ablation and success rate in HCM makes physician decisions for this type of patient challenging. The importance of informed consent and how the patient’s decisions affet further progress are also shown. JRCD 2018; 4 (1): 18-21.

Background Acquired long QT syndrome (a-LQTS) is associated with life-threatening ventricular arrhythmias, mainly torsades de pointes (TdP). ECG parameters predicting evolving into ventricular fibrillation (VF) are ill defined. Aims To determine ECG parameters preceding and during TdP associated with higher risk of developing VF. Methods We analyzed 151 episodes of TdP, recorded in 28 patients with a-LQTS (mean QTc 638 ms ± 57). Results All 28 patients had prolonged QT interval, (mean QTc 638 ms ± 57) ranging from 502 ms to 858 ms correcting by Bazett's formula. The mean TdP heart rate was 218 bpm ± 38 (mean cycle length of TdP 274 ± 47 ms). We classified TdPs episodes into “slower”-TdP (s-TdP) 1. Macro T wave alternans was observed in 4 patients. The QT interval was not different in patients with VF(+) and VF(−) episodes, 633 ± 60 and 639 ± 57, respectively. Conclusions Some electrocardiographic parameters can be helpful in determining the risk of TdP evolving into VF. The slower ventricular rate ( 30 ms) and the short episodes < 20 beats could predict benign evolution.