Misinterpretation of sleep-induced second-degree atrioventricular block.

A number of publications have claimed that Mobitz type II atrioventricular block (AVB) may occur during sleep. None of the reports defined type II AVB and representative electrocardiograms were either misinterpreted or missing. Relatively benign Wenckebach type I AVB is often misdiagnosed as Mobitz type II which is an indication for a pacemaker. Review of the published reports indicates that Mobitz type II AVB does not occur during sleep when it is absent in the awake state. Conclusion: There is no proof that sleep is associated with Mobitz type II AVB.

Implantable Cardiac Devices in Patients with Brady- and Tachy-Arrhythmias: An Update of the Literature.

Implantable cardiac devices are a vital treatment option in the management of tachy/brady-arrhythmias and heart failure with conduction disease. In the recent years, these devices have become increasingly sophisticated, with high implantation success rates and longevity. However, these devices are not without risks and complications, which need to be carefully considered before implantation. In an era of rapidly evolving cardiac device therapies, this review article will provide an update on the literature and outline some of the emerging technologies that aim to maximise the efficiency of implantable devices and reduce complications. We discuss novel pacing techniques, including alternative pacing sites in anti-bradycardia and biventricular pacing, as well as the latest evidence surrounding leadless device technologies and patient selection for implantable device therapies.

New Insights into Pacing Induced Cardiomyopathy.

Pacing induced cardiomyopathy (PICM) can occur as a complication due to pacing the right ventricle. Its precise definition varies across different studies, leading to uncertainty as to the best approach for managing this entity. More than 10% of patients who undergo chronic right ventricular pacing develop PICM. Risk factors associated with PICM include reduced left ventricular ejection fraction (LVEF), the proportion of right ventricular pacing, and paced QRS duration. The main approach to treating PICM has been upgrading to biventricular pacing cardiac resynchronization therapy when the LVEF decreases. However, emerging evidence suggest that conduction system pacing might provide an opportunity to manage PICM.

Incidence of Coronary Artery Disease After Permanent Pacemaker Implantation: A Hospital-based Study from East India.

Bradyarrhythmias, characterized by heart rates of <60 bpm due to conduction issues, carry risks of sudden cardiac death and falls. Pacemaker implantation is a standard treatment, but the interplay between bradyarrhythmias, coronary artery disease (CAD), and patient attributes requires further exploration. This study was a retrospective hospital record-based study that analyzed data from 699 patients who underwent pacemaker implantation for symptomatic bradyarrhythmias between February 2019 and February 2022. Clinical parameters, coronary angiography (CAG) findings, ejection fraction, and indications for pacemaker implantation were documented. The relationship between CAD severity, specific bradyarrhythmias, and ejection fraction was explored. Statistical analysis included chi-squared tests and t tests. The mean age of the study population (n = 699) was 66.75 years (male:female ratio, 70:30), with 77.2% having type 2 diabetes and 61.6% being hypertensive. The majority of patients had minor or non-obstructive CAD (61.8%), followed by normal CAG findings (25.75%) and obstructive CAD (12.45%). Complete heart block (CHB) was the primary indication for pacemaker implantation (55.2%), followed by sick sinus syndrome (22.3%). The results did not show any association between ejection fraction and CAG findings. Patients who presented with CHB had a higher incidence of obstructive CAD, indicating greater severity. This study sheds light on the intricate interplay between severe bradyarrhythmias, CAD, and patient characteristics. Our analysis revealed no statistical significance between obstructive CAD and the need for a permanent pacemaker. This makes us question our practice of maintaining a low threshold for coronary angiography during pacemaker implantation. The observed low yield and anticoagulation protocol reassure us of the choice to delay this diagnostic intervention. These insights can guide tailored management strategies, enhancing clinical care approaches for patients with severe bradyarrhythmias necessitating pacemaker implantation.

Wireless Device Therapy in Hypertrophic Cardiomyopathy Using the Combination of a Leadless Pacemaker and a Subcutaneous Defibrillator: A Report with 2-year Follow-up of Two Patients.

Cardiac implantable electronic devices (CIEDs) are essential tools in cardiology for tackling rhythm disturbances and have come a long way over the last decades. Technology is shifting toward leadless devices that spare the complications and limitations of traditional intravascular CIEDs. Herein, we report the simultaneous implantation of a leadless pacemaker (LP) and a subcutaneous implantable cardioverter-defibrillator (S-ICD) in two patients with hypertrophic cardiomyopathy, as well as their 2-year follow-up results, while explaining the preventive measures taken to steer around unwanted device interaction. Implantation of an S-ICD with an LP is reserved for unique cases but is a feasible approach when there is a contraindication for intravascular CIED implantation. Furthermore, this technique may be used in younger patients with cardiomyopathies in whom multiple generator replacements are expected, along with their known adverse effects.

Pacemaker-induced atrial fibrillation reconsidered-associations with different pacing sites and prevention approaches.

The incidence of atrial fibrillation (AF) is significantly higher in patients with pacemakers than in the general population, which could be due to patient characteristics and the diagnostic tool of the pacemaker in detecting atrial high-rate episodes and subclinical AF, but also to the pacemaker itself providing AF-promoting conditions. It is well known that high ventricular pacemaker burden increases the likelihood of AF occurrence. However, the sites of atrial and ventricular pacing may also influence the risk for AF. The conventional sites for atrial and ventricular pacing are in the right atrial appendage and in the right ventricular apex. However, growing evidence suggests that alternative pacing sites may be superior for the prevention of AF. Bachmann bundle pacing, for example, promotes interatrial excitation conduction, resulting in atrial synchronicity and a shorter total atrial activation time, which may be preventive for the occurrence of AF. Moreover, in recent years, new ventricular pacing sites have come into focus with His bundle and left bundle branch pacing. In addition to the hemodynamic and electrophysiological cardiac benefits, these new options may also offer benefits in the prevention of AF. This review provides an overview of pacing-induced AF mechanisms and the association with different pacing sites, as well as approaches for prevention of pacing-induced AF, highlighting different sites and modes of atrial pacing and the newer sites of ventricular pacing.

Periprocedural Management and Multidisciplinary Care Pathways for Patients With Cardiac Implantable Electronic Devices: A Scientific Statement From the American Heart Association.

The rapid technological advancements in cardiac implantable electronic devices such as pacemakers, implantable cardioverter defibrillators, and loop recorders, coupled with a rise in the number of patients with these devices, necessitate an updated clinical framework for periprocedural management. The introduction of leadless pacemakers, subcutaneous and extravascular defibrillators, and novel device communication protocols underscores the imperative for clinical updates. This scientific statement provides an inclusive framework for the periprocedural management of patients with these devices, encompassing the planning phase, procedure, and subsequent care coordinated with the primary device managing clinic. Expert contributions from anesthesiologists, cardiac electrophysiologists, and cardiac nurses are consolidated to appraise current evidence, offer patient and health system management strategies, and highlight key areas for future research. The statement, pertinent to a wide range of health care professionals, underscores the importance of quality care pathways for patient safety, optimal device function, and minimization of hemodynamic disturbances or arrhythmias during procedures. Our primary objective is to deliver quality care to the expanding patient cohort with cardiac implanted electronic devices, offering direction in the era of evolving technologies and laying a foundation for sustained education and practice enhancement.

Atrioventricular Synchrony Delivered by a Dual-Chamber Leadless Pacemaker System.

BACKGROUND: A dual-chamber leadless pacemaker system has been designed for AV synchronous pacing using wireless, beat-to-beat, implant-to-implant (i2i) communication between distinct atrial and ventricular leadless pacemakers. The AV synchrony achieved across various ambulatory scenarios has yet to be systematically evaluated. METHODS: A prospective, single-arm, unblinded, multicenter, international clinical trial of the leadless pacemaker system was conducted in patients with a conventional dual-chamber pacing indication enrolled from February 2022 to March 2023. Leadless pacemaker systems were implanted, and 12-lead Holter electrocardiographic recordings were collected 3 months after implantation over various postures/activities: sitting, supine, left lateral recumbent, right lateral recumbent, standing, normal walk, and fast walk. An independent Holter core laboratory performed a manual adjudication of the percent of AV synchronous beats using the standard 300-millisecond PR interval limit. Atrium-to-ventricle and ventricle-to-atrium i2i communication success rates were also assessed. Post hoc summary statistics describing the relationships between AV synchrony and i2i success, posture/activity, implantation indication, AV event, and heart rate were calculated. RESULTS: In the evaluable population (n=384 of 464 enrolled [83%]; 61% male; age, 70 years; weight, 82 kg; 60% ejection fraction; 95% of beats evaluable), the mean AV synchrony of 98% of beats observed across all postures using the standard 300-millisecond limit was greater than both atrium-to-ventricle i2i (94%) and ventricle-to-atrium i2i (94%; P<0.001), exceeding both i2i values in 95% of patients. AV synchrony was achieved in >95% of evaluable beats across all postures/activities, implantation indications, AV paced/sensed event combinations, and heart rate ranges (including >100 bpm). CONCLUSIONS: This dual-chamber leadless pacemaker system demonstrated AV synchrony in 98% of evaluable beats at 3 months after implantation. AV synchrony was maintained across postures/activities and remained robust for heart rates >100 bpm.

Early Experience of Left Bundle Branch Pacing with Lumenless Lead in a Single Center: A Case Series.

Left bundle branch pacing (LBBP) has been subject to increasing interest over the last few years due to its capacity for physiological conduction and its advantages compared to His bundle pacing. His bundle pacing has certain limitations, such as a small pacing area for the His bundle, a high threshold that leads to battery depletion, a low R-wave amplitude that may result in atrial or His oversensing, and ventricular signal undersensing. In this case series, four patients (two female and two male) aged 62.2 ± 8.4 years old with symptomatic sick sinus disease and no scar tissue in the interventricular septum underwent LBBP. All LBBPs were done with standard LBBP using a lumenless SelectSecure 3830 lead (Medtronic®, Minneapolis, USA) with a fixed helix. The lead parameters showed a good R-wave amplitudes (13 ± 7.4 mV) and a low threshold  (0.77 ± 0.17 V @ 0.4 ms). All patients were discharged on the next day. During follow-up period of 13.3 ± 12.9 months, all patients were well and no complications were noted. In conclusion, LBBP may be as an alternative of novel conduction pacing techniques and can be done relatively easy and safe, even with limited experience center.

Deactivation of cardiac implantable electronic devices in palliative patients: When and how.

Cardiac implantable electronic devices have transformed medicine as they improve quality of life and prevent premature death. In palliative care settings, deactivation of these devices must be discussed, particularly at end-of-life. In terminally ill patients it is consensual to recommend implantable cardioverter defibrillator deactivation once shocks are frequent and painful. Concerning pacemakers, the decision to deactivate is controversial and it usually is not an option at patients' end-of-life, since in pacing-dependent patients, such low heart rates might induce symptoms of bradycardia, with no impact on survival. Regarding cardiac resynchronization therapy, deactivation is not recommended as it can worsen symptoms. Left ventricular assistance device deactivation at end-of-life is a well-accepted practice, since it has the benefit of ending the physical burden associated with the device. Advance care planning should be encouraged and patients should be informed that deactivation is possible.

Chronic clinical performance of a novel subxiphoidal pacemaker system: Early feasibility study design.

BACKGROUND: Extravascular and leadless pacemakers are a new class of cardiac devices that may reduce the rate of complications common to traditional cardiac pacemakers with intracardiac leads. These devices also have the potential of expanding access to cardiac pacing therapy by simplifying the complexity and cost of implantation. The objective of this study is to evaluate the implantation, chronic safety, and performance of a novel subxiphoidal pacemaker. METHODS: This study is an open-label, non-randomized, early feasibility study. Ten patients indicated for implantation of a single-chamber ventricular pacemaker will be enrolled and implanted with the investigational device. The pacemaker will be inserted underneath the ribcage and clipped to the xiphoid process, with stimulation electrodes positioned on the cardiac pericardium. Patients will be programmed to chronic pacing; pacing capture threshold, sensing amplitude, and lead impedance will be measured at implant and regularly scheduled follow-up visits. 24-h Holter ECG and cardiac troponin will also be periodically measured. Adverse events will be recorded throughout the study period. CONCLUSION: This study is designed to assess the feasibility, safety, and chronic performance of a novel extravascular pacemaker, and will provide valuable data on whether this device has the potential to be a viable alternative to conventional pacemakers.

Leadless pacemakers in patients with different stages of chronic kidney disease: real-world data from the updated i-LEAPER registry.

BACKGROUND: Limited data are available on leadless pacemaker (LPM) outcomes according to different stages of chronic kidney disease (CKD). OBJECTIVE: To investigate differences regarding safety and efficacy in LPMs patients stratified per different stages of renal function. METHODS: Consecutive patients enrolled in the multicenter, international i-LEAPER registry were analyzed. Patients were divided into three groups according to CKD stage. The primary endpoint was the comparison of LPM-related major complication rate at implant and during follow-up. Differences in electrical performance were deemed secondary outcomes. RESULTS: Among 1748 patients enrolled, 33% were CKD stage G3a/G3b and 9.4% were CKD stage G4/G5. CKD patients presented cardiovascular comorbidities more frequently. During a median follow-up of 39 [interquartile range (IQR) 18-59] months, major complications rate did not differ between groups (normal kidney function, NKF=1.8% vs CKD stage-G3a/G3b 2.9% vs CKD stage-G4/G5 2.4%, p=0.418). All-cause mortality resulted higher in CKD stage-G4/G5 when compared with NKF group (19.5% vs 9.8%, aHR:1.9, 95%CI 1.25-2.89, p=0.003). LPM electrical performance was comparable between groups, except for CKD patients who showed a slightly higher pacing threshold during the 1-month follow-up (NKF group 0.50 [IQR 0.35-0.70]V vs G3a/G3b group 0.56 [IQR 0.38-0.81]V vs G4/G5 group, 0.51 [0.38-0.84]V @0.24 msec, p<.001). CONCLUSION: In a real-world setting, advanced CKD patients who underwent LPM implantation were underrepresented. Although all-cause mortality was higher in end-stage CKD, periprocedural complications and LPM performance were overall comparable between NKF and different stages of CKD, except for higher values of pacing threshold in CKD patients up to first-month follow-up.

A hazardous collateral pathway following asymptomatic lead-related venous occlusion?

Routine venography should be performed before the device upgrade. Clinicians should not be unconcerned because of the lack of symptoms following lead-related venous occlusion. Knowledge of collateral anatomy is essential for future interventional plans. The venous pathway's return to the right atrium may entail risks to patient outcomes.

Thyroid hormone receptors in control of heart rate.

Thyroid hormone has profound effects on cardiovascular functions, including heart rate. These effects can be mediated directly, e.g. by changing the expression of target genes in the heart through nuclear thyroid hormone receptors, or indirectly by altering the autonomic nervous systems output of the brain. The underlying molecular mechanisms as well as the cellular substrates, however, are far from being understood. In this review, we summarize the recent key findings on the individual contributions of the two thyroid hormone receptor isoforms on the regulation of heart rate, challenging the role of the pacemaker channel genes Hcn2 and Hcn4 as sole mediators of the hormone's effect. Furthermore, we discuss the possible actions of thyroid hormone on the autonomic nervous system affecting heart rate distribution, and highlight the possibility of permanent alterations in heart and brain by impaired thyroid hormone action during development as important factors to consider when analyzing or designing experiments.

Multi-functional adhesive hydrogel as bio-interface for wireless transient pacemaker.

Traditional temporary cardiac pacemakers (TCPs), which employ transcutaneous leads and external wired power systems are battery-dependent and generally non-absorbable with rigidity, thereby necessitating surgical retrieval after therapy and resulting in potentially severe complications. Wireless and bioresorbable transient pacemakers have, hence, emerged recently, though hitting a bottleneck of unfavorable tissue-device bonding interface subject to mismatched mechanical modulus, low adhesive strength, inferior electrical performances, and infection risks. Here, to address such crux, we develop a multifunctional interface hydrogel (MIH) with superior electrical performance to facilitate efficient electrical exchange, comparable mechanical strength to natural heart tissue, robust adhesion property to enable stable device-tissue fixation (tensile strength: ∼30 kPa, shear strength of ∼30 kPa, and peel-off strength: ∼85 kPa), and good bactericidal effect to suppress bacterial growth. Through delicate integration of this versatile MIH with a leadless, battery-free, wireless, and transient pacemaker, the entire system exhibits stable and conformal adhesion to the beating heart while enabling precise and constant electrical stimulation to modulate the cardiac rhythm. It is envisioned that this versatile MIH and the proposed integration framework will have immense potential in overcoming key limitations of traditional TCPs, and may inspire the design of novel bioelectronic-tissue interfaces for next-generation implantable medical devices.

Stem cell-derived cardiomyocytes expressing a dominant negative pacemaker HCN4 channel do not reduce the risk of graft-related arrhythmias.

Background: Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) show tremendous promise for cardiac regeneration following myocardial infarction (MI), but their transplantation gives rise to transient ventricular tachycardia (VT) in large-animal MI models, representing a major hurdle to translation. Our group previously reported that these arrhythmias arise from a focal mechanism whereby graft tissue functions as an ectopic pacemaker; therefore, we hypothesized that hPSC-CMs engineered with a dominant negative form of the pacemaker ion channel HCN4 (dnHCN4) would exhibit reduced automaticity and arrhythmogenic risk following transplantation. Methods: We used CRISPR/Cas9-mediated gene-editing to create transgenic dnHCN4 hPSC-CMs, and their electrophysiological behavior was evaluated in vitro by patch-clamp recordings and optical mapping. Next, we transplanted WT and homozygous dnHCN4 hPSC-CMs in a pig MI model and compared post-transplantation outcomes including the incidence of spontaneous arrhythmias and graft structure by immunohistochemistry. Results: In vitro dnHCN4 hPSC-CMs exhibited significantly reduced automaticity and pacemaker funny current (I f ) density relative to wildtype (WT) cardiomyocytes. Following transplantation with either dnHCN4 or WT hPSC-CMs, all recipient hearts showed transmural infarct scar that was partially remuscularized by scattered islands of human myocardium. However, in contrast to our hypothesis, both dnHCN4 and WT hPSC-CM recipients exhibited frequent episodes of ventricular tachycardia (VT). Conclusions: While genetic silencing of the pacemaker ion channel HCN4 suppresses the automaticity of hPSC-CMs in vitro, this intervention is insufficient to reduce VT risk post-transplantation in the pig MI model, implying more complex mechanism(s) are operational in vivo.

Permanent pacemaker reduction using temporary-permanent pacemaker as a 1-month bridge after transcatheter aortic valve replacement: a prospective, multicentre, single-arm, observational study.

Background: The permanent pacemaker (PPM) implantation and pacemaker dependency rates after transcatheter aortic valve replacement (TAVR) are highly variable as some of the conduction disturbances are reversible. It remains poorly investigated how to optimise temporary pacing in these patients. This study aimed to explore the potential reduction in the PPM implantation rate using temporary-permanent pacemaker (TPPM) as a 1-month bridge. Methods: This is a prospective, multicentre, single-arm, observational study. Consecutive patients undergoing TAVR from March 1, 2022 to March 1, 2023 in 13 tertiary hospitals in China were screened. Patients who developed high-degree atrioventricular block, complete heart block, or first-degree atrioventricular block plus new onset left bundle branch block during the TAVR procedure or within 1 month after TAVR were included to receive TPPM. Patients with pre-existing PPM implantation or indications for PPM implantation before the TAVR procedure were excluded. Patients with TPPM were monitored to determine whether the conduction disturbances persisted or recovered. The primary endpoint was the rate of freedom from indications for PPM implantation 1 month after TAVR. This study is registered with ChiCTR, ChiCTR2200057931. Findings: Of 688 patients who have undergone TAVR, 71 developed conduction disturbance and met the inclusion criteria, 1 patient withdrew due to noncompliance, 70 patients received TPPM and completed follow-up. There were 41 (58.6%) men and 29 (41.4%) women in the study, with a mean age of 74.3 ± 7.3 years. At 1 month follow-up, 75.7% (53/70) of the patients with TPPM did not require PPM implantation. For 688 patients who have undergone TAVR, the rate of PPM implantation at 1 month was 2.47% (17/688, 95% CI 1.55%-3.92%), representing a significant reduction in self-comparison with the rate at 48 h after TPPM (2.47% vs. 8.28% [95% CI 6.45%-10.58%], P < 0.0001). Similar results were obtained in the subgroup analysis of patients with HAVB/CHB. Multivariate analysis revealed the baseline PR interval, difference between the membranous septum length and implantation depth, and timing of postprocedural conduction disturbance occurrence were independent predictors of freedom from indications for PPM implantation at 1 month after TAVR. Interpretation: Using TPPM as a 1-month bridge allows for a buffer period to distinguish whether conduction disturbances are reversible or persistent, resulting in a significant reduction in the PPM implantation rate after TAVR when compared with the current strategy. However, this is an observational study, the results need to be confirmed in a randomized trial. Funding: Beijing Science and Technology Plan 2022 from Beijing Municipal Science & Technology Commission.

Epicardial Pacemaker Causing Cardiac Strangulation.

Cardiac strangulation is a rare but potentially lethal complication of epicardial pacemaker insertion. We present the case of a 9-year-old girl who was identified as having cardiac strangulation on routine follow-up for an epicardial pacemaker inserted on day 1 of life for congenital complete heart block (CCHB). The potential clinical presentations and risk factors for pacemaker strangulation are then discussed.