Output-dependent His bundle pacing: Unexpected His-Purkinje system pathology unmasking.

The anatomy of the His-Purkinje system has been studied, yet there remains a knowledge gap regarding the impact of His bundle pacing and its electrocardiographic implications. This case report highlights the presence of His-Purkinje system pathology without apparent clues on the surface electrocardiogram (EKG). By observing identical QRS morphology with varying HV intervals resulting from different pacing outputs, we demonstrate the presence of an electrical propagation block within the His bundle.

Transient 2:1 Atrioventricular Block with Peri-Conduction System Pacing After Leadless Pacemaker Implantation.

This report discusses a case of transient 2:1 atrioventricular block with conduction system pacing 4 hours after leadless right ventricular pacemaker implantation in a 19-year-old patient with a history of cardioinhibitory syncope and asystole cardiac arrest but without preexisting atrioventricular block. The atrioventricular block was resolved spontaneously. Pacing morphology was suggestive of right bundle branch pacing. Neither 2:1 atrioventricular block nor conduction system pacing has previously been a reported outcome of right ventricular leadless pacemaker implantation. The report demonstrates that conduction system pacing with leadless devices is achievable. Further study of techniques, limitations, and complications related to intentional right ventricular leadless conduction system pacing is warranted.

Pacing Using Cardiac Implantable Electric Device During TAVR: 10-Year Experience of a High-Volume Center.

BACKGROUND: Transcatheter aortic valve replacement (TAVR) is an effective and safe therapy for severe aortic stenosis. Rapid or fast pacing is required for implantation, which can be performed via a pre-existing cardiac implantable electric device (CIED). However, safety data on CIEDs for pacing in TAVR are missing. OBJECTIVES: The aim of this study was to elucidate procedural safety and feasibility of internal pacing with a CIED in TAVR. METHODS: Patients undergoing TAVR with a CIED were included in this analysis. Baseline characteristics, procedural details, and complications according to Valve Academic Research Consortium 3 (VARC-3) criteria after TAVR were compared between both groups. RESULTS: A total of 486 patients were included. Pacing was performed using a CIED in 150 patients and a transient pacemaker in 336 patients. No differences in technical success according to VARC-3 criteria or procedure duration occurred between the groups. The usage of transient pacers for pacing was associated with a significantly higher bleeding rate (bleeding type ≥2 according to VARC-3-criteria; 2.0% vs 13.1%; P < 0.01). Furthermore, impairment of the CIED appeared in 2.3% of patients after TAVR only in the group in which pacing was performed by a transient pacer, leading to surgical revision of the CIED in 1.3% of all patients when transient pacemakers were used. CONCLUSIONS: Internal pacing using a CIED is safe and feasible without differences of procedural time and technical success and might reduce bleeding rates. Furthermore, pacing using a CIED circumvents the risk of lead dislocation. Our data provide an urgent call for the use of a CIED for pacing during a TAVR procedure in general.

Strategies to improve atrioventricular synchrony in patients with a Micra AV leadless pacemaker.

The second generation of transcatheter pacing systems, called Micra AV, can provide atrioventricular (AV) synchronous pacing via a new pacing algorithm relying on sensing mechanical atrial contraction. Several novel programming parameters were introduced to enable AV synchronous pacing, including an A3 window and A4 window as well as a conduction mode switch and an activity mode switch. In addition to several automated features, manual programming optimization of some of the novel parameters is key to improving AV synchrony. A solid knowledge of the features and their programming is essential for electrophysiologists implanting or following patients with Micra AV devices. Differences in programming optimization might partially explain the high variability of AV synchrony published in real-world data reports. This article reviews the key programming parameters of Micra AV. Subsequently, optimal programming recommendations for defined patient profiles are presented. Those were established by consensus within an expert panel comprised of 11 European electrophysiologists from high-volume Micra AV centres. The patient profiles were (1) high degree AV block and slow sinus rhythm; (2) high degree AV block and fast sinus rhythm; and (3) intermittent AV block. The panel recommended to evaluate the mechanical atrial activity on transthoracic echocardiography prior to implant. It was also agreed that Auto A3 Threshold and Tracking Check should be turned off in all patients, AV conduction mode switch should be turned off in all patients with high degree AV block, and the lower rate should be programmed to 50 bpm with exceptions based on individual clinical assessment. Future studies will be useful to evaluate the strength of those recommendations to improve the AV synchrony.

Aveir VR real-world performance and chronic pacing threshold prediction using mapping and fixation electrical data.

AIMS: Aveir VR performance and predictors for its pacing threshold (PCT) in a real-world cohort were investigated. METHODS: Electrical measurements at various stages of an Aveir VR implant were prospectively collected. Predictors for 3-month PCT were studied. A retrospective cohort of consecutive 139 Micra implants was used to compare the PCT evolution. High PCT was defined as ≥1.5 V, using a pulse width of 0.4 ms for Aveir and 0.24 ms for Micra. Excellent PCT was defined as ≤0.5 V at the respective pulse width. RESULTS: Among the 123 consecutive Aveir VR implant attempts, 122 (99.2%) were successful. The majority were of advanced age (mean 79.7) and small body size (mean BSA 1.60). Two patients (1.6%) experienced complications, including one pericardial effusion after device reposition and one intraoperative device dislodgement. Eighty-eight patients reached a 3-month follow-up. Aveir 3-month PCT was correlated with impedance at mapping (P = 0.015), tether mode (P < 0.001), end-of-procedure (P < 0.001), and mapping PCT (P = 0.035), but not with PCTs after fixation (P > 0.05). Tether mode impedance >470 ohms had 88% sensitivity and 71% specificity in predicting excellent 3-month PCT. Although it is more common for Aveir to have high PCT at end of procedure (11.5% for Aveir and 2.2% for Micra, P = 0.004), the rate at 3 months was similar (2.3% for Aveir and 3.1% for Micra, P = 1.000). CONCLUSION: Aveir VR demonstrated satisfactory performance in this high-risk cohort. Pacing thresholds tend to improve to a greater extent than Micra after implantation. The PCT after fixation, even after a waiting period, has limited predictive value for the chronic threshold. Low-mapping PCT and high intraoperative impedance predict chronic low PCT.

Atrial Pacing Negatively Affects Left Atrial Morphological and Functional Parameters Similarly to Atrioventricular Dyssynchrony.

Background and Objectives: Atrioventricular (AV) dyssynchrony as well as atrial and ventricular pacing affect left atrial (LA) function. We conducted a study evaluating the effect of atrial and ventricular pacing on LA morphological and functional changes after dual-chamber pacemaker implantation. Materials and Methods: The study prospectively enrolled 121 subjects who had a dual-chamber pacemaker implanted due to sinus node disease (SND) or atrioventricular block (AVB). Subjects were divided into three groups based on indication and pacemaker programming: (1) SND DDDR 60; (2) AVB DDD 60 and (3) AVB DDD 40. Subjects were invited to one- and three-month follow-up visits. Three subsets based on pacing burden were analyzed: (1) high atrial (A) low ventricular (V); (2) high A, high V and (3) low A, high V. LA function was assessed from volumetric parameters and measured strains from echocardiography. Results: The high A, low V group consisted of 38 subjects; while high A, high V had 26 and low A, high V had 23. A significant decrease in reservoir and contractile LA strain parameters were only observed in the high A, low V pacing group after three months (reservoir 25.9 ± 10.3% vs. 21.1 ± 9.9%, p = 0.003, contractile -14.0 ± 9.0% vs. -11.1 ± 7.8, p = 0.018). While the re-established atrioventricular synchrony in the low A, high V group maintained reservoir LA strain at the baseline level after three months (21.4 ± 10.4% vs. 22.5 ± 10.4%, p = 0.975); in the high A, high V group, a further trend to decrease was noted (20.3 ± 8.9% vs. 18.7 ± 8.3%, p = 0.231). Conclusions: High atrial pacing burden independently of atrioventricular dyssynchrony and ventricular pacing impairs LA functional and morphological parameters. Changes appear soon after pacemaker implantation and are maintained.

Leadless pacemakers at 5-year follow-up: the Micra transcatheter pacing system post-approval registry.

BACKGROUND AND AIMS: Prior reports have demonstrated a favourable safety and efficacy profile of the Micra leadless pacemaker over mid-term follow-up; however, long-term outcomes in real-world clinical practice remain unknown. Updated performance of the Micra VR leadless pacemaker through five years from the worldwide post-approval registry (PAR) was assessed. METHODS: All Micra PAR patients undergoing implant attempts were included. Endpoints included system- or procedure-related major complications and system revision rate for any cause through 60 months post-implant. Rates were compared through 36 months post-implant to a reference dataset of 2667 transvenous pacemaker patients using Fine-Gray competing risk models. RESULTS: 1809 patients were enrolled between July 2015 and March 2018 and underwent implant attempts from 179 centres in 23 countries with a median follow-up period of 51.1 months (IQR: 21.6-64.2). The major complication rate at 60 months was 4.5% [95% confidence interval (CI): 3.6%-5.5%] and was 4.1% at 36 months, which was significantly lower than the 8.5% rate observed for transvenous systems (HR: .47, 95% CI: .36-.61; P < .001). The all-cause system revision rate at 60 months was 4.9% (95% CI: 3.9%-6.1%). System revisions among Micra patients were mostly for device upgrades (41.2%) or elevated thresholds (30.6%). There were no Micra removals due to infection noted over the duration of follow-up. At 36 months, the system revision rate was significantly lower with Micra vs. transvenous systems (3.2% vs. 6.6%, P < .001). CONCLUSIONS: Long-term outcomes with the Micra leadless pacemaker continue to demonstrate low rates of major complications and system revisions and an extremely low incidence of infection.

Bioresorbable molybdenum temporary epicardial pacing wires.

Cardiac pacing with temporary epicardial pacing wires (TEPW) is used to treat rhythm disturbances after cardiac surgery. Occasionally, TEPW cannot be mechanically extracted and remain in the thorax, where they may rarely cause serious complications like migration and infection. We aim to develop bioresorbable TEPW that will dissolve over time even if postoperative removal is unsuccessful. In the present study, we demonstrate a completely bioresorbable design using molybdenum (Mo) as electric conductor and the resorbable polymers poly(D, L-lactic-co-glycolic acid) (PLGA) and polycaprolactone (PCL) for electrically insulating double-coating. We compared the pacing properties of these Mo TEPW demonstrators to conventional steel TEPW in Langendorff-perfused rat hearts and observed similar functionality. In vitro, static immersion tests in simulated body fluid for up to 28 days elucidated the degradation behaviour of uncoated Mo strands and the influence of polymer coating thereon. Degradation was considerably reduced in double-coated Mo TEPW compared to the uncoated and the PLGA-coated condition. Furthermore, we confirmed good biocompatibility of Mo degradation products in the form of low cytotoxicity in cell cultures of human cardiomyocytes and cardiac fibroblasts. STATEMENT OF SIGNIFICANCE: Temporary pacing wires are routinely implanted on the heart surface to treat rhythm disturbances in the days following cardiac surgery. Subsequently, these wires are to be removed. When removal attempts are unsuccessful, wires are cut at skin level and the remainders are left inside the chest. Retained fragments may migrate within the body or become a centre of infection. These complications may be prevented using resorbable pacing wires. We manufactured completely resorbable temporary pacing wires using molybdenum as electrical conductor and assessed their function, degradation and biological compatibility. Our study represents an important step in the development of a safer approach to the treatment of rhythm disturbances after cardiac surgery.

Prediction of pacemaker-induced cardiomyopathy using a convolutional neural network based on clinical findings prior to pacemaker implantation.

Risk factors for pacemaker-induced cardiomyopathy (PICM) have been previously reported, including a high burden of right ventricular pacing, lower left ventricular ejection fraction, a wide QRS duration, and left bundle branch block before pacemaker implantation (PMI). However, predicting the development of PICM remains challenging. This study aimed to use a convolutional neural network (CNN) model, based on clinical findings before PMI, to predict the development of PICM. Out of a total of 561 patients with dual-chamber PMI, 165 (mean age 71.6 years, 89 men [53.9%]) who underwent echocardiography both before and after dual-chamber PMI were enrolled. During a mean follow-up period of 1.7 years, 47 patients developed PICM. A CNN algorithm for prediction of the development of PICM was constructed based on a dataset prior to PMI that included 31 variables such as age, sex, body mass index, left ventricular ejection fraction, left ventricular end-diastolic diameter, left ventricular end-systolic diameter, left atrial diameter, severity of mitral regurgitation, severity of tricuspid regurgitation, ischemic heart disease, diabetes mellitus, hypertension, heart failure, New York Heart Association class, atrial fibrillation, the etiology of bradycardia (sick sinus syndrome or atrioventricular block) , right ventricular (RV) lead tip position (apex, septum, left bundle, His bundle, RV outflow tract), left bundle branch block, QRS duration, white blood cell count, haemoglobin, platelet count, serum total protein, albumin, aspartate transaminase, alanine transaminase, estimated glomerular filtration rate, sodium, potassium, C-reactive protein, and brain natriuretic peptide. The accuracy, sensitivity, specificity, and area under the curve of the CNN model were 75.8%, 55.6%, 83.3% and 0.78 respectively. The CNN model could accurately predict the development of PICM using clinical findings before PMI. This model could be useful for screening patients at risk of developing PICM, ensuring timely upgrades to physiological pacing to avoid missing the optimal intervention window.

Flecainide causing elevated capture thresholds on pacemaker implantation.

Flecainide is a Vaughan Williams class 1c antiarrhythmic used to treat supraventricular and ventricular arrhythmias. It has been described as a rare cause for increased pacemaker capture thresholds. We describe a report of a patient, in her early 80s, presenting with tachy-brady syndrome on a background of permanent atrial fibrillation. She was treated with metoprolol and flecainide by her private cardiologist. Permanent right ventricular chamber pacing was recommended for her slow heart rate. At insertion of her single chamber pacemaker, she was noted to have elevated capture thresholds despite appropriate lead positioning. A flecainide level was elevated at 1.1 µg/mL, and it was subsequently ceased. This was associated with a rapid improvement in her capture threshold. Flecainide should be considered as a cause for elevated pacing thresholds at the time of implant. Particular care should be taken for at-risk groups such as the elderly and patients with renal impairment.

Paced QRS morphology mimicking complete left bundle branch block induced by right ventricular pacing is associated with pacing-induced cardiomyopathy.

INTRODUCTION: Right ventricular (RV) pacing sometimes causes left ventricular (LV) systolic dysfunction, also known as pacing-induced cardiomyopathy (PICM). However, the association between specifically paced QRS morphology and PICM development has not been elucidated. This study aimed to investigate the association between paced QRS mimicking a complete left bundle branch block (CLBBB) and PICM development. METHODS: We retrospectively screened 2009 patients who underwent pacemaker implantation from 2010 to 2020 in seven institutions. Patients who received pacemakers for an advanced atrioventricular block or bradycardia with atrial fibrillation, baseline LV ejection fraction (LVEF) ≥ 50%, and echocardiogram recorded at least 6 months postimplantation were included. The paced QRS recorded immediately after implantation was analyzed. A CLBBB-like paced QRS was defined as meeting the CLBBB criteria of the American Heart Association/American College of Cardiology Foundation/Heart Rhythm Society in 2009. PICM was defined as a ≥10% LVEF decrease, resulting in an LVEF of <50%. RESULTS: Among the 270 patients analyzed, PICM was observed in 38. Baseline LVEF was lower in patients with PICM, and CLBBB-like paced QRS was frequently observed in PICM. Multivariate analysis revealed that low baseline LVEF (odds ratio [OR]: 0.93 per 1% increase, 95% confidence interval [CI]: 0.89-0.98, p = 0.006) and CLBBB-like paced QRS (OR: 2.69, 95% CI: 1.25-5.76, p = 0.011) were significantly associated with PICM development. CONCLUSION: CLBBB-like paced QRS may be a novel risk factor for PICM. RV pacing, which causes CLBBB-like QRS morphology, may need to be avoided, and patients with CLBBB-like paced QRS should be followed-up carefully.

First-in-man report of transsubclavian venous implantation of the Aveir leadless cardiac pacing system.

INTRODUCTION: Transsubclavian venous implantation of the Aveir leadless cardiac pacemaker (LCP) has not been previously reported. METHODS AND RESULTS: Three cases of transsubclavian implantation of the Aveir LCP are reported. Two cases were postbilateral orthotopic lung transplant, without appropriate femoral or jugular access due to recent ECMO cannulation and jugular central venous catheters. In one case, there was strong patient preference for same-day discharge. Stability testing confirmed adequate fixation and electrical testing confirmed stable parameters in all cases. All patients tolerated the procedure well without significant immediate complications. CONCLUSIONS: We demonstrate the feasibility of transsubclavian implantation of the Aveir LCP.

Endocardial repolarization dispersion in BrS: A novel automatic algorithm for mapping activation recovery interval.

INTRODUCTION: Repolarization dispersion in the right ventricular outflow tract (RVOT) contributes to the type-1 electrocardiographic (ECG) phenotype of Brugada syndrome (BrS), while data on the significance and feasibility of mapping repolarization dispersion in BrS patients are scarce. Moreover, the role of endocardial repolarization dispersion in BrS is poorly investigated. We aimed to assess endocardial repolarization patterns through an automated calculation of activation recovery interval (ARI) estimated on unipolar electrograms (UEGs) in spontaneous type-1 BrS patients and controls; we also investigated the relation between ARI and right ventricle activation time (RVAT), and T-wave peak-to-end interval (Tpe) in BrS patients. METHODS: Patients underwent endocardial high-density electroanatomical mapping (HDEAM); BrS showing an overt type-1 ECG were defined as OType1, while those without (latent type-1 ECG and LType1) received ajmaline infusion. BrS patients only underwent programmed ventricular stimulation (PVS). Data were elaborated to obtain ARI corrected with the Bazett formula (ARIc), while RVAT was derived from activation maps. RESULTS: 39 BrS subjects (24 OType1 and 15 LTtype1) and 4 controls were enrolled. OType1 and post-ajmaline LType1 showed longer mean ARIc than controls (306 ± 27.3 ms and 333.3 ± 16.3 ms vs. 281.7 ± 10.3 ms, p = .05 and p < .001, respectively). Ajmaline induced a significant prolongation of ARIc compared to pre-ajmaline LTtype1 (333.3 ± 16.3 vs. 303.4 ± 20.7 ms, p < .001) and OType1 (306 ± 27.3 ms, p < .001). In patients with type-1 ECG (OTtype1 and post-ajmaline LType1) ARIc correlated with RVAT (r = .34, p = .04) and Tpec (r = .60, p < .001), especially in OType1 subjects (r = .55, p = .008 and r = .65 p < .001, respectively). CONCLUSION: ARIc mapping demonstrates increased endocardial repolarization dispersion in RVOT in BrS. Endocardial ARIc positively correlates with RVAT and Tpec, especially in OType1.