Distal His Research Articles

Exploring structural and computational contrasts in Myoglobins: Implications for thermal treatment-induced Sulfmyoglobin formation

Greening of tuna metmyoglobin (MetMb) by thermal treatment (TT) and free cysteine is associated with sulfmyoglobin (SulfMb) production. This greening reaction (GR) was once thought to occur only in tuna species. However, recent research has revealed that not all tuna species exhibit this behavior, and it can also occur in horse MetMb. Thus, the present study aimed to compare the GR-reactive (Katsuwonus pelamis and Equus caballus) and GR-unreactive (Sarda chiliensis and Euthynnus lineatus) MetMb using UV–vis spectrometry during TT (60 °C/30 min and free cysteine) to monitor the GR. We used molecular dynamics (MD) simulation to assess the stability of the heme group during TT. We discovered that using GR-unreactive MetMb resulted in an incomplete GR without producing SulfMb. Additionally, our MD simulations indicated that Met85 presence in the heme cavity from GR-unreactive is responsible for the heme group instability and displacement of distal His during TT.

Single-center experience with His bundle lead implantation: success rate, implantation method optimization, and lessons learned in 426 patients

Abstract Background Conduction system pacing (CSP) is increasingly used to avoid the development of pacing-induced cardiomyopathy in patients who require a high amount of ventricular pacing. His bundle pacing (HBP) is considered as ideal to achieve the narrowest paced QRS and optimal synchronization in patients with intrinsic narrow QRS or right bundle branch block but also as difficult at implantation. Purpose We analyzed our experience with HBP in terms of time and effort, pacing and sensing results, success rate, and lessons learned for optimization over a time period of 7 years. Methods All consecutive patients in whom HBP was attempted between 6/2016 and 11/2023 were included in this analysis. Implantations were performed using a pacing system analyzer (PSA) with high-resolution electrograms (EGMs). Data on implantation success [selective or non-selective HBP, left bundle branch area pacing (LBBAP)], sensing and pacing parameters, achievement of His bundle current of injury (coi), duration of implantation and fluoroscopy were collected prospectively. These results were compared for the 1st, 2nd, 3rd and 4th quartile of implantations and reasons for improvement or deterioration were analyzed. Results HBP was attempted in 426 patients (78±11 years, 38% female, 90% AV block, left ventricular ejection fraction 54±10 %, 81 single-, 286 dual-, 46 triple-chamber pacemakers, 2 dual- and 11 triple-chamber ICDs) and was successful in 404 patients (95%): 182 non-selective HBP, 206 selective HBP, and 16 LBBAP. R wave amplitude was 4.5±3.5 mV, pacing threshold 1.1 ± 0.6V/1.0 ms. In 16% of patients, a ventricular back-up lead was implanted. A His bundle coi was achieved in 61% of patients. The implantation duration was 92±43 min, fluoroscopy duration 10±8 min. Success rate increased from 89% in the 1st to 99% in the 4th quartile. Improved implantation success was associated with using a stiff 3D steerable sheath, implantation site at the distal His bundle, and an increased number of screw-in turns until a His bundle coi was visible. Conclusions Establishing an implantation routine with 1) a PSA and high-resolution EGMs, 2) use of a stiff 3D steerable sheath, 3) implantation at the distal His bundle with myocardial capture (non-selective HBP) as a back-up, and 4) an increased number of screw-in turns of the lead tip until a His bundle coi is achieved, HBP implantation can be facilitated and results optimized to a highly acceptable implantation effort and a success rate >95%.

Dynamic changes of atrioventricular conduction during Covid-19 infection: Does inflammation matter?

BackgroundThe primary manifestation of COVID-19 infection was pulmonary involvement. However, it can also manifest as a cardiovascular problem.MethodsWe report a case of 82-year-old male COVID-19 patient who experienced atrioventricular (AV) conduction disturbance.ResultsThe rhythm was degenerated from sinus rhythm to complete AV block. We observe dynamic AV node dysfunction associated with inflammatory response. His bundle pacing successfully captured distal His region.ConclusionThe severe inflammatory response during COVID-19 infection might permanently damage cardiac conduction system resulted in a complete AV node block.

Short term outcomes of distal (ventricular) His bundle pacing: A single centre retrospective study

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Chronic right ventricular apical pacing can lead to pacing induced cardiomyopathy in a significant proportion of patients. Conduction system pacing may restore more physiological activation of the heart, and has recently been shown to have favourable outcomes in clinical trials. However there remains concern regarding the long-term outcomes due to lead displacement and high pacing thresholds. The most widely used technique in current practice is to pace the His bundle proximal to the tricuspid valve. Distal His bundle pacing has a number of advantages over proximal His pacing, including, lower capture thresholds, a more stable lead position, less far field atrial sensing and better spacing from the AV node in case ablation of this is required for AF rate control. Despite these, outcomes of distal His bundle pacing from the ventricular aspect are less well defined. Methods We performed a retrospective review of patients who underwent conduction system pacing between January 2020 and October 2021 at our centre. During this period all procedures were performed employing a distal His bundle pacing approach with the lead placed on the ventricular aspect of the tricuspid annulus. Data was collected at implant, follow-up at 1 month and then every 6 months. Results Out of 35 patients, 33 underwent successful His bundle pacing (acute success rate of 94%), 1 patient had left bundle branch pacing and another patient had an unsuccessful procedure. Mean age was 74 years, median LVEF 45% and median pre-implant QRS was 108ms. 80% of the cohort had a history of AF. The indications for pacing were as follows: AF - for pace & ablate (60%); high grade AV block with narrow QRS and mild LVSD (17%); failed LV lead (14%); and other 9%. Mean procedure duration and fluoroscopy time were 78 minutes and 12.05 minutes, respectively. Median threshold at implant was 1.00V (IQR 0.719V). Selective His bundle pacing was achieved in 60% and non-selective in 34%. Mean follow-up duration was 150 days with median threshold at last f/up of 0.75V (IQR 0.750V). There were no acute procedural complications. 1 patient had a significant rise in threshold at follow-up and therefore required upgrade to CRT-P. Discussion Our data shows that distal His bundle pacing is a safe and effective technique for conduction system pacing. Thresholds appear stable at follow-up and failure rate was found to be comparable to biventricular pacing. We noted an initial learning curve for both implanter and physiologists with relatively poorer outcomes for the earlier cases. Longer term follow-up is ongoing, including functional assessment and follow-up to assess for remodelling with echocardiography. Prospective randomised trials are needed to compare conduction system pacing vs RV pacing in AF patients with HFpEF or mild LVSD undergoing AVN ablation, and vs biventricular pacing in the severe LVSD population.

Short term outcome of distal (ventricular) His bundle pacing and atrioventricular node ablation in patients with symptomatic atrial fibrillation - Refining the concept

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Many patients with atrial fibrillation (AF) do not benefit from rhythm control due to failed catheter ablation, advanced left atrial disease and comorbidities. "Pace and AV node (AVN) ablation" strategy is often adopted for rate control but with a substantial risk of pacing-induced cardiomyopathy. His bundle pacing (HBP) enables physiological biventricular activation through the His Purkinje conduction system. However, the proximity of the HBP lead to the site of AV node ablation may potentially compromise lead integrity in patients who undergo conventional HBP and AVN ablation. Therefore, we have modified HBP by placing the HBP lead distally at the ventricular side of the His bundle (D-HBP) before AVN ablation in patients with symptomatic AF. All patients had a backup RV lead. Method Patients who had D-HBP as part of a "Pace and AVN ablation" strategy were retrospectively analysed. Implant and device clinic follow-up data were collected and analysed. Result Twenty-one patients who had "pace and AVN ablation strategy" with D-HBP between 26th February 2020 and 3rd November 2021 were included. They had a mean age of 75 ± 1.4 years (mean ± SEM), NYHA class of 2.1 ± 0.2, QRS duration of 106 ± 5.3ms and 50% had at least moderately impaired LV systolic function. Seventeen patients (81%) had narrow QRS duration. D-HBP was successful in twenty of twenty-one patients (95%). At D-HBP implant, the mean acute threshold of the HBP lead was 0.96 ± 0.12V at 0.5 ± 0.05ms and the mean HBP lead impedance was 548.1 ± 29.5Ω. Selective HBP pacing was observed in thirteen of twenty patients. The mean QRS duration of HBP paced beats was 104.5 ± 4.7ms. Failure to capture the His bundle was observed in one patient. AVN ablation was performed on the same day after D-HBP in eleven patients and as a subsequent procedure in nine patients. The mean duration of procedure and fluoroscopy for D-HBP were 77.4 ± 4.6 minutes and 11.9 ± 1.4 minutes respectively. There were no acute procedural complications with no lead damage, displacement or lead perforation observed. The median follow-up period was 207 days. The mean D-HBP lead threshold following AVN ablation was 1.1 ± 0.2 V at 0.6 ± 0.07 ms and the mean lead impedance was 433.8 ± 20.7Ω, which were similar to before AVN ablation. One patient was reprogrammed with RV pacing only for elevated HBP lead threshold after AVN ablation to 4.2 V at 1ms. The mean D-HBP percentage was 92.3 ± 6.6% and the mean estimated battery longevity of the pacemaker was 7.9 ± 0.6 years at the last follow up. There was improvement in heart failure symptoms in eight patients from previously symptomatic to NYHA class I following D-HBP and AVN ablation. Conclusion D-HBP appear to be safe with potentially more favourable lead parameters than conventional proximal HBP in patients with symptomatic AF offered "Pace and AVN ablation" strategy.

PC-577-01 FASCICULAR ECTOPY FROM THE RIGHT CORONARY SINUS OF VALSALVA

Fascicular ectopic complexes (FEC) can cause symptoms and pseudo atrio-ventricular block (AVB). Ablation is a viable option but carries a risk of AVB. Successful far-field ablation of left anterior fascicular beats from right aortic sinus of Valsalva (RASoV) has been reported. We present a case of FEC with earliest HPS signal and successful ablation from the RASoV. N/A A 60-year-old woman had palpitations and blocked P waves. ECG revealed frequent FEC and occasional blocked P waves (fig. 1a). We postulated this to be due to concealed FEC (pseudo AVB). She failed flecainide and presented for ablation. A decapolar catheter was placed across the right His-Purkinje system (HPS). She had frequent FECs with early activation of the HPS. We observed FECs with complete antegrade block within the HPS but retrograde penetration into the atrium proving this as the mechanism for pseudo AVB (fig. 1b). Activation mapping of the right and left (retroaortic) HPS was performed with the earliest HPS potential on the decapolar catheter as the fiducial reference. Activation progressed retrograde to the proximal His and antegrade to the RBB, both being later than the distal His. Similarly, the left bundle branch and both fascicles were late. Mapping in the RASoV identified a His-like signal in sinus rhythm that was the earliest site in FEC, 7 ms ahead of reference (fig 1c & d). Focal radiofrequency ablation immediately abolished FECs. Monitoring overnight revealed no further FECs or blocked P waves, and patient reported relief of symptoms. Mapping of FEC should include the RASoV. The anatomic basis for such fascicular potential in the RASoV may be the dead-end tract of the conduction axis reported by Kurosawa and Becker.

Interesting phenomenon during positioning of the 3830 lead deep inside the septum by rapid rotations. What is the mechanism?

A 66-year-old lady having complete AV block with narrow QRS escape had undergone left bundle branch pacing (LBB) with 4.1-F diameter 3830 Select SecureTM pacing lead (Medtronic Inc., Minneapolis, MN, USA). The pacing lead was placed with the inter-ventricular septum, 2 cm inferior to the distal His region towards the right ventricular apex, by 5 rapid turns. During the rapid turns, an interesting phenomenon was noted [Fig. 1A & B]. What is the mechanism?

Conduction system pacing following septal myectomy: Insights into site of conduction block.

Septal myectomy for obstructive hypertrophic cardiomyopathy (HCM) is associated with conduction block; however, the electrophysiological characteristics of conduction block have not been well characterized. The aim of study was to assess the feasibility and safety of His bundle pacing (HBP) and left bundle branch area pacing (LBBAP) in patients with septal myectomy-associated conduction block. Patients with HCM and indications for pacing or cardiac resynchronization therapy after septal myectomy were included. Electrophysiological mapping was performed to identify the site of block. The success rates and pacing characteristics of HBP and LBBAP were also recorded. The echocardiographic data and complications were documented and tracked during follow-up. Ten patients with atrioventricular block (AVB) or left bundle branch block (LBBB) post-myectomy were included in the study. The site of block was infranodal in the nine patients with AVB. HBP failed due to the lack of distal His bundle capture (N = 7) or LBBB correction (N = 3). LBBAP was successful in nine patients and failed in one. QRS duration narrowed from 163.3 ± 16.6 ms after surgery to 123.6 ± 15.8 ms during LBBAP (p < .001). The mean depth of the leads was 13.3 ± 4.0 mm (range from 10 to 20 mm). At a mean follow-up of 5.3 ± 3.9 months, pacing parameters and left ventricular ejection fraction remained stable. Electrophysiological mapping revealed that the site of block was infra-Hisian and not correctable with HBP in patients with HCM post-myectomy. LBBAP appears to be a more feasible physiological strategy for these patients.

New safe approach to target symptomatic Hisian ectopy/tachycardia

Although cryoenergy safety profile is appropriate for the ablation of arrhythmogenic foci near the conduction system, mapping using the cryoablation catheter is of limited precision. Combining the safety of cryoenergy and the high precision of a 3D mapping system therefore appears the most appropriate set-up for ablation in the vicinity of the His bundle. A 29-year-old woman with a 3-year history of increasing shorteness of breath and palpitations refractory to medical treatment was sent to the EP laboratory for catheter ablation. Surface ECG showed sinus rhythm and frequent ectopic beats with narrow QRS complexes similar to those of the sinus beats. The left ventricular ejection fraction was impaired (38%) with no other etiology found, apart from frequent ectopies. Detailed intracardiac mapping, using a 3D electroanatomical system, revealed that the ectopy originated from the distal His bundle, which was indicated by both antegrade and reversed His bundle activation sequence during ectopy compared to that during sinus rhythm. Due to the proximity of the conduction system, cryoenergy rather than radiofrequency was chosen to target this Hisian ectopy. A special set-up was made in order to allow the cryoablation catheter to be visualized into the 3D mapping system. Cryoenergy delivered to the site of earliest Hisian ectopy activation completely abolished it ( Fig. 1 ). Such a combined approach may help to improve therapeutic strategy for ablation procedures with a high-risk of injury to the conduction system. It could notably be extended to the ablation of para-Hisian ectopy or accessory pathways.

3D electro-anatomical mapping to guide conduction system pacing in complex cardiac anatomies

Abstract Background Conduction System Pacing (CSP) includes both His Bundle Pacing (HBP) and Left Bundle Branch Pacing (LBBP). It guarantees physiological cardiac activation and it is essential to avoid pacing-induced dyssynchrony. Markedly dilated atria, up-grading to CRT, and congenital cardiopathies still represent complex anatomical scenarios in which the available tools could often result inadequate and graved by suboptimal results. Objective To evaluate the feasibility and effectiveness of 3D electro-anatomical mapping (EAM) to guide CSP (both HBP and LBBP) in patients with characteristics that allows “a priori” classification as complex anatomical scenario with low probability of success using only fluoroscopic guidance and available tools. Left atrium area &amp;gt;40 cm2; post-PICM up-grading and congenital heart disease were considered signs of anatomical complexity. Methods and results The study includes 25 patients (19 males, mean age 76–11 years; mean baseline EF 34.2–12.6%; 17 BBB; 5 post-PICM up-grading), candidates for CSP. 16 and 9 were respectively implanted with PM and ICD (13/12 dual/three-chamber devices). CARTO system was used in 6 ptss and EnsiteTM Precision in 19. EAM involved reconstruction of the right atrium and sub-tricuspid septum with the use of a decapolar catheter. Several “tags” have been placed on the His signals, in order to reconstruct the “His Cloud” and distinguish within it the proximal, medium, and distal area (Fig. 1). The sub-tricuspid septum was always reconstructed so that intra-procedurally operator could easily move from HBP to LBBP based on electrical parameters or paced QRS morphology. The mapping catheter was removed after the mapping phase and replaced with the pacing lead. Both exposed fixed screw 3830 leads and standard stylet-driven leads were used. HBP was achieved in 10 pts and LBBP in 13 pts. Three failures were resolved by CS lead implant. The time spend for His cloud mapping was 18±7 min. The mean threshold was 1.1±0.5 V; sensing 11.6±9.3 mV and impedance 786±339 ohm. Baseline QRS 155±19 ms and paced QRS 119±7 ms. In cases of LBBP we were also able to measure on the EAM map the depth of the catheter within the septum, resulting in 11.5±3.1 mm and the distance of the initial screw site from the His of 26.5±10.3 mm. Conclusions The electro-anatomical mapping allows the accurate reconstruction of “His cloud” by properly distinguishing proximal, middle, distal His. The sub-tricuspid zone of the interventricular septum is also reconstructed in high definition, so that intra-procedurally it is possible to easily move from HBP to LBBP and vice-versa based on the electrical parameters and paced QRS morphology. This method appears safe and effective even in complex cardiac anatomies possibly saving time and fluoroscopy use. The tags on the His cloud and sub-tricuspid septum can satisfactorily guide lead placement with high reproducibly. Funding Acknowledgement Type of funding sources: None. Figure 1. 3D-EAM used to guide HBP implant

Left bundle branch pacing: An evolving site for physiological pacing.

For patients with symptomatic bradyarrhythmia, cardiac pacing is the only appropriate treatment option. Electrical and mechanical dyssynchrony caused by traditional right ventricular apical pacing leads to left ventricular dysfunction and atrial arrhythmias. Physiological pacing stimulates natural cardiac conduction, resulting in synchronized ventricular contraction. Even if His bundle pacing (HBP) is an ideal physiological pacing modality, it is technically not always feasible because of high capture thresholds, disease in the distal His bundle, and follow‐up troubleshooting issues. Left bundle branch pacing (LBBP) has been proposed as a viable alternative to HBP since it provides lead stability, a low and stable pacing threshold, and correction of distal conduction system disease.

B-AB10-05 PERMANENT DISTAL HIS BUNDLE PACING VIA PERSISTENT LEFT SUPERIOR VENA CAVA

His-purkinje conduction system pacing is widely used as a physiological pacing. Persistent left superior vena cava (PLSVC) is a relatively rare anatomic variation in clinic. Due to the distortion of its venous access, it is a challenge for operator to achieve precise His bundle pacing. Our study aimed to evaluate the feasibility of His bundle pacing in patients with PLSVC. N/A A 57-year-old female who had the indication of pacemaker implantation with sick sinus syndrome and paroxysmal atrial tachycardia was performed with His bundle pacing. PLSVC was found during the operation. The 3830-69 lead was used through C315HIS sheath (Medtronic Inc, Minneapolis, MN, USA) at first. However, either His bundle pacing or left bundle branch area pacing failed. Then we tried the 5076-58 active helix lead by adjusting the steel wire to double-curve shape in reverse and precisely located to His bundle. After electrode fixation, His potential and R wave with current of injury could be recorded, unipolar pacing at 0.5V/0.5ms captured only ventricular endocardium, and increased output at 1.0V/0.5ms captured His (in Fig). The R wave amplitude was 5.6mV and impedance was 570 Ω. The intraoperative electrophysiological characteristics, pacing parameters, UCG and CTA 3D reconstruction all indicated that the electrode was fixed to the ventricular side across the tricuspid valve. The threshold of His bundle was 0.5V/0.5ms on the first day after operation, and increased to 1.5V/0.5ms at two months follow-up. His bundle pacing was successfully achieved by 5076 active lead in the patient, which showed the conventional lead can achieve distal His bundle pacing via PLSVC.

How Electrode Position Affects Selective His Bundle Capture: A Modelling Study.

We investigated the properties which affect the capture thresholds in order to improve selective pacing. We performed biophysically detailed, computer simulations of a His fibre running through a septal wedge preparation to compute capture thresholds under various configurations of electrode polarity and orientation. The myocardial capture threshold was close to that of the His bundle. The His fibre needed to intersect with the electrode tip to favor its activation. Inserting the electrode fully within the septum increased the myocardial capture threshold. Reversing polarity, to rely on anode break excitation, also increased the ease of selective pacing. Model results were consistent with clinical observations. For selective pacing, the tip needs to be in contact with the His fibre and anodal stimulation is preferable. This study provides insight into helping establish electrode and stimulation parameters for selective His bundle pacing in patients.

Safety of Distal His Bundle Pacing Via the Right Ventricle Backed Up by AdjacentVentricularCapture.

This study investigated the differences between distal His bundle pacing (HBP) via the right ventricle and proximal HBP via the right atrium with regard to pacing and sensing parameters. HBP preserves physiological ventricular activation. The capture threshold of the adjacent ventricle accompanying HBP has not been evaluated after implantation. Fifty patients with bradycardia (58% with atrioventricular block) underwent successful HBP and were followed for 1 year. Precise locations of the lead tips were confirmed using follow-up echocardiography. HBP leads were fixed via the right atrium or right ventricle (25 patients each). Overall, the local ventricle and HBP thresholds were elevated during follow-up. The distal HBP thresholds did not significantly differ from the proximal HBP thresholds, although local ventricular thresholds of distal HBP were markedly lower than those of proximal HBP. At 6months, the accepted ventricular threshold (≤2.5 V) was maintained in 39 patients (78%). An amplitude of ventricular electrogram post-fixation of≥2.0mV and a capture threshold of≤1.1V at implantation were determined to be optimal values for predicting the accepted threshold at 6months, with areas under the curve of 0.86 and 0.84, respectively. Atrial oversensing was often detected in proximal HBP but not distal HBP. Distal HBP via the right ventricle captured the His bundle, similar to proximal HBP via the right atrium, with a superior local ventricular threshold during follow-up. Anatomy and electrophysiological ventricular properties at implantation may be critical for maintaining adjacent ventricle capture to prevent lead revision (Evaluation of Electrophysiological Parameters related to His Bundle Pacing in Patients With Bradyarrhythmias; UMIN000031364).

Hemoglobins from Scapharca subcrenata (Bivalvia: Arcidae) likely play an bactericidal role through their peroxidase activity.

Hemoglobin (Hb) is an iron-containing respiratory protein present in all vertebrates and some invertebrates. The blood clam Scapharca subcrenata is one of the few invertebrates that have Hb-containing red hemocytes. In this study, we purified Hb (Ss-Hb), including Ss-HbI and Ss-HbII, from S. subcrenata hemocytes using gel chromatography with a recovery rate of 70.71%, and then characterized their peroxidase activities. Both Ss-Hbs possessed peroxidase activity with high affinity to the substrates guaiacol and H2O2. Moreover, both Ss-Hbs had structural similarities, such as type b heme, proximal histidine (His), distal His, and heme pocket arginine (Arg), with other peroxidases. The optimal peroxidase activity of both Ss-Hbs was at pH5 and 35°C, but this was inhibited in the presence of Cu2+ and Fe2+. Ss-Hbs produced [Formula: see text] in the presence of H2O2. β-phenylethylamine, a substrate of peroxidase, increased the [Formula: see text] generation, while Cu2+, an inhibitor of peroxidase, inhibited this reaction. These results indicated that the peroxidase cycle of Ss-Hb was involved in the production of [Formula: see text] . A large amount of [Formula: see text] may be generated by the peroxidase cycle if the substrate is sufficient. During the incubation of Ss-Hbs with Bacillus subtilis, it was speculated that trace H2O2, probably from autoxidation of Ss-Hbs or generated by B. subtilis, started the peroxidase cycle of Ss-Hb. and produced a large amount of [Formula: see text] in the presence of sufficient substrate in the culture medium. It is therefore reasonable to assume that Ss-Hbs played an antibacterial role owing to their peroxidase activity, which produced [Formula: see text] .

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

Abstract Background Nonselective pacing of the distal His bundle is practically just another way of right ventricular septal pacing. It leads to the concomitant activation of the His bundle and septal myocytes with unknown impact on ventricular synchrony. Ultra-high frequency ECG (UHF-ECG) is a novel tool for ventricular depolarization imaging. Purpose To describe ventricular depolarization patterns during nonselective pacing of a ventricular aspect of His bundle and myocardial captures from different locations in the right ventricle by using the UHF-ECG. Methods Consecutive patients with an indication for permanent pacing due to bradycardia were included. During pacemaker implantation, the pacing lead was temporarily placed in prespecified locations of the right ventricle (mid-septum, anterior, lateral wall, and the para-hisian area of the RV). When pacing from mentioned locations, myocardial activation time under each specific lead (Vd), and ventricular dyssynchrony (e-DYS) indexes were calculated from UHF-ECG maps, for each particular type of pacing. The demonstration of UHF-ECG maps during pacing from different locations of the right ventricle is shown in the figure. Results Two hundred and fifty UHF ECG recordings were performed in forty-six patients. The calculated mean e-DYS parameter was significantly shorter during non-selective capture of the distal His bundle (14±8 ms) compared to each of myocardial captures of the right ventricle (pure myocardial para-hisian; 35±12 ms, mid-septal; 28±11 ms, anterior wall; 51±16 ms and lateral wall; 62±19 ms (p&amp;lt;0.001). The Vd was also shortest during non-selective capture of the distal His bundle (39±5 ms) compared to each of the others (pure myocardial para-hisian; 52±11 ms, RV mid-septal; 57±11 ms, RV anterior wall; 68±12 ms and RV lateral wall pacing; 85±14 ms (p&amp;lt;0.001). Conclusion Pacing of the basal interventricular septum with the engagement of the His bundle produced a superior depolarization pattern in both heart ventricles compared to other types of right ventricular myocardial capture, as assessed using UHF-ECG. Figure 1. Examples of UHF-ECG depolarization maps of different types of ventricular activation in the same patient. Funding Acknowledgement Type of funding source: Public Institution(s). Main funding source(s): Charles University in Prague

Takashi Yonetani: A stellar biochemist, a man with dignity. The Roman connection

Takashi Yonetani: A stellar biochemist, a man with dignity. The Roman connection

Left bundle branch pacing.

Chronic right ventricular (RV) pacing has been associated with significant electrical and mechanical dyssynchrony leading to increased risk for recurrent heart failure hospitalizations and atrial arrhythmias. His bundle pacing (HBP) is an effective alternative to RV pacing as it is physiological and provides synchronized contraction of both ventricles. But there are limitations to HBP, which include lead stability, rise in threshold, early battery depletion and longer learning curve. Huang etal. recently reported anovel technique to directly capture the left bundle branch (LBB) by deep septal pacing. Subsequently, many studies have demonstrated the feasibility, safety and efficacy of left bundle branch pacing (LBBP). This has the potential to overcome the limitations of HBP and provide asafe technique to capture the conduction system in patients with distal His bundle and proximal bundle branch disease. The criteria for LBB capture and the methodology to perform LBBP are discussed in detail in this review. The Medtronic SelectSecure®3830 pacing lead is used along with afixed-curve C315His® or adeflectable C304His® sheath. LBBP providessafe and low threshold compared to HBP. Left bundle potential should be demonstrable in all patients except in those with infrahisian complete heart block (CHB) and complete left bundle branch block (LBBB), wherein antegrade activation of the left bundle will not occur. LBBP has the potential to be an effective alternative to biventricular pacing or HBP in patients with left ventricular dysfunction, LBBB and recurrent heart failure. Long-term safety and clinical outcomes compared to traditional pacing need to be carefully studied in randomized clinical trials.

Permanent conduction system pacing for congenitally corrected transposition of the great arteries: A Pediatric and Congenital Electrophysiology Society (PACES)/International Society for Adult Congenital Heart Disease (ISACHD) Collaborative Study

Congenitally corrected transposition of the great arteries (CCTGA) is associated with spontaneous atrioventricular block and pacing-induced cardiomyopathy. Conduction system pacing is a potential alternative to conventional cardiac resynchronization therapy (CRT). The purpose of this study was to determine the outcomes of conduction system pacing for CCTGA. Retrospective data were collected from 10 international centers. His bundle (HBP) or left bundle branch pacing (LBBP) was attempted in 15 CCTGA patients (median age 23 years; 87% male). Previous surgery had been performed in 8 and chronic ventricular pacing in 7. Conduction system pacing (11 HBP, 2 LBBP 2; nonselective in 10, selective in 3) was acutely successful in 13 (86%) without complication. In 9 cases, electroanatomic mapping was available and identified the distal His bundle and proximal left bundle branches within the morphologic left ventricle below the pulmonary valve separate from the mitral annulus. Median implant HV interval was 42 ms (interquartile range [IQR] 35-48), R wave 6 mV (IQR 5-18), and threshold 0.5 V (IQR 0.5-1.2) at median 0.5 ms. QRSd was unchanged compared to junctional escape rhythm (124 vs 110 ms; P = .17) and decreased significantly compared to baseline ventricular pacing (112 vs 164 ms; P <.01). At a median of 8 months, all patients were alive without significant change in pacing threshold or lead dysfunction. New York Heart Association functional class improved in 5 patients. Permanent conduction system pacing is feasible in CCTGA by either HBP or proximal LBBP. Narrow paced QRS and stable lead thresholds were observed at intermediate follow-up. Unique anatomic characteristics may favor this approach over conventional CRT.

The unique structural features of carbonmonoxy hemoglobin from the sub-Antarctic fish Eleginops maclovinus

Tetrameric hemoglobins (Hbs) are prototypical systems for the investigations of fundamental properties of proteins. Although the structure of these proteins has been known for nearly sixty years, there are many aspects related to their function/structure that are still obscure. Here, we report the crystal structure of a carbonmonoxy form of the Hb isolated from the sub-Antarctic notothenioid fish Eleginops maclovinus characterised by either rare or unique features. In particular, the distal site of the α chain results to be very unusual since the distal His is displaced from its canonical position. This displacement is coupled with a shortening of the highly conserved E helix and the formation of novel interactions at tertiary structure level. Interestingly, the quaternary structure is closer to the T-deoxy state of Hbs than to the R-state despite the full coordination of all chains. Notably, these peculiar structural features provide a rationale for some spectroscopic properties exhibited by the protein in solution. Finally, this unexpected structural plasticity of the heme distal side has been associated with specific sequence signatures of various Hbs.