Cardiac Pacemaker Research Articles

Comparison of in-hospital outcomes and complications of leadless pacemaker and traditional transvenous pacemaker implantation.

Since their introduction in 1958, traditional cardiac pacemakers have undergone considerable upgrades over the years, but they continue to have a complication rate of ∼3.8%-12.4%. There are no randomized controlled trials comparing outcomes of leadless pacemakers (LPM) with single-chamber transvenous pacemakers (TV-VVI). The aim is to assess the differences in the procedural complications and in-hospital outcomes between LPM and TV-VVI implants. We queried the national inpatient database from 2016 to 2019 to include adult patients undergoing LPM and TV-VVI. Admissions for leadless and single-lead transvenous pacemakers were identified by their appropriate ICD-10 codes. Complications were identified using ICD-10 codes that mostly represent initial encounter. The difference in outcomes was assessed using multivariable logistic regression and 1:1 propensity score matching between the two cohorts. Thirty-five thousand four hundred thirty expanded samples of admissions were retrieved of which 27 650 (78%) underwent TV-VVI with a mean age 81.3 ± 9.4 years and 7780 (22%) underwent LPM with a mean age of 77.1 ± 12.1 years. The LPM group had a higher likelihood of in-hospital mortality [adjusted odds ratio (aOR): 1.63, 95% CI (1.29-2.05), P < 0.001], vascular complications [aOR: 7.54, 95% CI (3.21-17.68), P < 0.001], venous thromboembolism [aOR: 3.67, 95% CI (2.68-5.02), P < 0.001], cardiac complications [aOR: 1.79, 95% CI (1.59-2.03), P < 0.001], device thrombus formation [aOR: 5.03, 95% CI (2.55-9.92), P < 0.001], and need for a blood transfusion [aOR: 1.54, 95% CI (1.14-2.07), P < 0.005]. The TV-VVI group had higher likelihood of in-hospital pulmonary complications [aOR:0.68, 95% CI (0.54-0.87), P < 0.002] and had a need for device revisions [aOR:0.42, 95% CI (0.23-0.76), P < 0.004]. There is a higher likelihood of all-cause in-hospital mortality and complications following LPM implantation in comparison to TV-VVI. This could be related to higher co-morbidities in the LPM group. Clinical trials aimed to accurately compare these two groups should be undertaken.

Resistance of Embryonic Chick Atria to Inhibition of HCN-Channels and Components of the “Ca&lt;sup&gt;2+&lt;/sup&gt;-Clock”

Despite its medical importance, the cellular mechanisms activity and the contribution of various ion channels of embryonic heart automatism are not yet fully understood. In this study we investigated the effects of specific ion-channel inhibitors on the generation of action potentials in pacemaker cells of the right atrium in chicken embryos (HH36). We used microelectrode technique and evaluated the sensitivity of pacemaker cells to ivabradine (inhibitor of HCN-channels, through which the hyperpolarization-activated current, If), ryanodine (agonist of ryanodine receptors) and SN6 (inhibitor of Na+/Ca2+-exchange). It was found that the right atrium cells have a phase of slow diastolic depolarization. However, these cells were not sensitive to ivabradine (3 μM). We did not register significant changes in the electrophysiological parameters of action potentials.When ryanodine (1 μM) and SN6 (10 μM) were added to the perfusion solution, we observed similar effects: spontaneous rate the generation of action potential increased by 15%. Disturbance of rhythmic activity or disruption of the generation of electrical impulses were not observed in right atrial samples of chicken embryos. The obtained results allow us to conclude that, at this of embryonic development stage, HCN4-channels, ryanodine receptors, and the Na+/Ca2+-exchange are not decisive for maintaining the automatism of the right atrial cells in the chick embryo. We assume that the ion currents flowing through these channels are important in electrophysiology in adult animals, but they have a modulating function in the embryonic myocardium.

Overview of the Enteric Nervous System.

Propulsion of contents in the gastrointestinal tract requires coordinated functions of the extrinsic nerves to the gut from the brain and spinal cord, as well as the neuromuscular apparatus within the gut. The latter includes excitatory and inhibitory neurons, pacemaker cells such as the interstitial cells of Cajal and fibroblast-like cells, and smooth muscle cells. Coordination between these extrinsic and enteric neurons results in propulsive functions which include peristaltic reflexes, migrating motor complexes in the small intestine which serve as the housekeeper propelling to the colon the residual content after digestion, and mass movements in the colon which lead to defecation.

A multiscale predictive digital twin for neurocardiac modulation.

Cardiac function is tightly regulated by the autonomic nervous system (ANS). Activation of the sympathetic nervous system increases cardiac output by increasing heart rate and stroke volume, while parasympathetic nerve stimulation instantly slows heart rate. Importantly, imbalance in autonomic control of the heart has been implicated in the development of arrhythmias and heart failure. Understanding of the mechanisms and effects of autonomic stimulation is a major challenge because synapses in different regions of the heart result in multiple changes to heart function. For example, nerve synapses on the sinoatrial node (SAN) impact pacemaking, while synapses on contractile cells alter contraction and arrhythmia vulnerability. Here, we present a multiscale neurocardiac modelling and simulator tool that predicts the effect of efferent stimulation of the sympathetic and parasympathetic branches of the ANS on the cardiac SAN and ventricular myocardium. The model includes a layered representation of the ANS and reproduces firing properties measured experimentally. Model parameters are derived from experiments and atomistic simulations. The model is a first prototype of a digital twin that is applied to make predictions across all system scales, from subcellular signalling to pacemaker frequency to tissue level responses. We predict conditions under which autonomic imbalance induces proarrhythmia and can be modified to prevent or inhibit arrhythmia. In summary, the multiscale model constitutes a predictive digital twin framework to test and guide high-throughput prediction of novel neuromodulatory therapy. KEY POINTS: A multi-layered model representation of the autonomic nervous system that includes sympathetic and parasympathetic branches, each with sparse random intralayer connectivity, synaptic dynamics and conductance based integrate-and-fire neurons generates firing patterns in close agreement with experiment. A key feature of the neurocardiac computational model is the connection between the autonomic nervous system and both pacemaker and contractile cells, where modification to pacemaker frequency drives initiation of electrical signals in the contractile cells. We utilized atomic-scale molecular dynamics simulations to predict the association and dissociation rates of noradrenaline with the β-adrenergic receptor. Multiscale predictions demonstrate how autonomic imbalance may increase proclivity to arrhythmias or be used to terminate arrhythmias. The model serves as a first step towards a digital twin for predicting neuromodulation to prevent or reduce disease.

A Sewing Approach to the Fabrication of Eco/bioresorbable Electronics.

Eco/bioresorbable electronics represent an emerging class of technology defined by an ability to dissolve or otherwise harmlessly disappear in environmental or biological surroundings after a period of stable operation. The resulting devices provide unique capabilities as temporary biomedical implants, environmental sensors, and related systems. Recent publications report schemes to overcome challenges in fabrication that follow from the low thermostability and/or high chemical reactivity of the eco/bioresorbable constituent materials. Here, this work reports the use of high-speed sewing machines, as the basis for a high-throughput manufacturing technique that addresses many requirements for these applications, without the need for high temperatures or reactive solvents. Results demonstrate that a range of eco/bioresorbable metal wires and polymer threads can be embroidered into complex, user-defined conductive patterns on eco/bioresorbable substrates. Functional electronic components, such as stretchable interconnects and antennas are possible, along with fully integrated systems. Examples of the latter include wirelessly powered light-emitting diodes, radiofrequency identification tags, and temporary cardiac pacemakers. These advances add to a growing range of options in high-throughput, automated fabrication of eco/bioresorbable electronics.

Temporary pacemaker implantation via median cubital vein: A simple safe and effective technique.

Temporary cardiac pacemaker implantation (PM) via the femoral and subclavian veins is widely used in clinics to treat patients with severe bradycardia or tachycardia, but it is technically challenging and potentially associated with various complications. This study investigated the feasibility and safety of a novel method of PM implantation via the median cubital vein. A total of 279 patients of the First Affiliated Hospital of Xiamen University between March 2020 and December 2021 who required no-emergency PM implantation were enrolled. The patients were divided into three groups based on the temporary PM implantation routes: F-control (n = 107), via the femoral vein; S-control (n = 67), via the subclavian vein, and N-group (n = 105), via the median cubital vein. The sheath placement time (SPT), electrode placement time (EPT), electrode arrival rate (EAR), rate of sensing and pacing (RSP), radiation quantity (RD), electrode dislocation rate (EDR) and average electrode retention time (AERT) were recorded and evaluated. In addition, the Hamilton Anxiety Scale (HAMA) and Self-Rating Depression Scale (SDS) were used to evaluate the comfort levels of patients in the three groups. There were no significant differences between the groups with regard to age, EAR, RSP, EPT, RD, and AERT (p > 0.05). However, the N-group had significantly lower SPT than the F-control and S-control groups (67.0 ± 22.0 s vs. 321.7 ± 122.2 s and 307.3 ± 128.5 s, p = 0.000). Additionally, the F-control had significantly higher EDR than the S-control group and the N-group (11 (10.3%) vs. 2 (3.0%) and 3 (2.9%), p = 0.036). Besides, comparison of the HAMA and SDS scores before and after PM implantation showed significant differences in the S-control group (p = 0.010) and the N-group (p = 0.000). Temporary PM implantation via the median cubital vein is safe, effective, and less time-consuming.

An Optogenetics-based Approach to Regulate Colonic Contractions by Modulating the Activity of the Interstitial Cells of Cajal in Mice.

The interstitial cells of Cajal (ICC) are pacemaker cells in the gastrointestinal (GI) tract. We examined whether the activity of ICC could be stimulated to control colonic contractions. An optogenetics-based mouse model in which the light-sensitive protein channelrhodopsin-2 (ChR2) was expressed was used to accomplish cell specific, direct stimulation of ICC. An inducible site-specific Cre-loxP recombination system was used to generate KitCreERT2/+;ROSAChR2(H134R)/tdTomato/+ mice in which ChR2(H134R), a variant of ChR2, was genetically expressed in ICC after tamoxifen administration. Genotyping and immunofluorescence analysis were performed to confirm gene fusion and expression. Isometric force recordings were performed to measure changes in contractions in the colonic muscle strips. ChR2 was specifically expressed in Kit-labeled ICC. The isometric force recordings showed that the contractions of the colonic muscle strips changed under 470 nm blue light. Light stimulation evoked premature low-frequency and high amplitude (LFHA) contractions and enhanced the frequency of the LFHA contractions. The light-evoked contractions were blocked by T16Ainh-A01, an antagonist of anoctamin 1 channels that are expressed selectively in ICC in colonic muscles. Our study demonstrates a potentially feasible approach to stimulate the activity of ICC by optogenetics. The colonic motor patterns of muscle strips, especially LFHA contractions, can be regulated by 470 nm light via ChR2, which is expressed in ICC.

Anesthetic Choice for Cardiovascular Implantable Electronic Device Placement and Lead Removal: A National Anesthesia Clinical Outcomes Registry Analysis

The authors evaluated the anesthetic approach for cardiovascular implantable electronic device (CIED) placement and transvenous lead removal, hypothesizing that monitored anesthesia care is used more frequently than general anesthesia. A retrospective study. National Anesthesia Clinical Outcomes Registry data. Adult patients who underwent CIED (permanent cardiac pacemaker or implantable cardioverter-defibrillator [ICD]) placement or transvenous lead removal between 2010 and 2021. None. Covariates were selected a priori within multivariate models to assess predictors of anesthetic type. A total of 87,530 patients underwent pacemaker placement, 76,140 had ICD placement, 2,568 had pacemaker transvenous lead removal, and 4,861 had ICD transvenous lead extraction; 51.2%, 45.64%, 16.82%, and 45.64% received monitored anesthesia care, respectively. A 2%, 1% (both p < 0.0001), and 2% (p=0.0003) increase in monitored anesthesia care occurred for each 1-year increase in age for pacemaker placement, ICD placement, and pacemaker transvenous lead removal, respectively. American Society of Anesthesiologists (ASA) physical status ≤III for pacemaker placement, ASA ≥IV for ICD placement, and ASA ≤III for pacemaker transvenous lead removal were 7% (p=0.0013), 5% (p=0.0144), and 27% (p = 0.0247) more likely to receive monitored anesthesia care, respectively. Patients treated in the Northeast were more likely to receive monitored anesthesia care than in the West for all groups analyzed (p < 0.0024). Male patients were 24% less likely to receive monitored anesthesia care for pacemaker transvenous lead removal (p=0.0378). For every additional 10 pacemaker or ICD lead removals performed in a year, a 2% decrease in monitored anesthesia care was evident (p=0.0271, p < 0.0001, respectively). General anesthesia still has a strong presence in the anesthetic management of both CIED placement and transvenous lead removal. Anesthetic choice, however, varies with patient demographics, hospital characteristics, and geographic region.

Application of Integrated Circuits in Cardiac Pacemakers

This article briefly describes the application of integrated circuits in the medical field, such as wearable and implantable medical devices. The article introduces the development process of integrated circuits used in cardiac pacemakers, explaining how it evolved from bipolar junction transistors integrated circuits in the past to today's complementary metal oxide semiconductor integrated circuits. The basic components of the pacemaker are described from a system level, including the signal amplifier, pulse generator, battery management system, and analog-to-digital converter. This allows for a clear presentation of the working process of the pacemaker. Furthermore, the article explains how analog integrated circuits and digital integrated circuits can be used together to achieve the goal of low power consumption of cardiac pacemakers at a circuit level, with reference to some cutting-edge scientific and technological achievements. The necessity and advantages of integrated circuits in medical applications are demonstrated, and the future development of integrated circuits in related aspects is forecasted based on the current development situation.

Plasticity of colonic enteric nervous system following spinal cord injury in male and female rats.

Neurogenic bowel is a dysmotility disorder following spinal cord injury (SCI) that negatively impacts quality of life, social integration, and physical health. Colonic transit is directly modulated by the enteric nervous system. Interstitial Cells of Cajal (ICC) distributed throughout the small intestine and colon serve as specialized pacemaker cells, generating rhythmic electrical slow waves within intestinal smooth muscle, or serve as an interface between smooth muscle cells and enteric motor neurons of the myenteric plexus. Interstitial Cells of Cajal loss has been reported for other preclinical models of dysmotility, and our previous experimental SCI study provided evidence of reduced excitatory and inhibitory enteric neuronal count and smooth muscle neural control. Immunohistochemistry for the ICC-specific marker c-Kit was utilized to examine neuromuscular remodeling of the distal colon in male and female rats with experimental SCI. Myenteric plexus ICC (ICC-MP) exhibited increased cell counts 3 days following SCI in male rats, but did not significantly increase in females until 3 weeks after SCI. On average, ICC-MP total primary arborization length increased significantly in male rats at 3-day, 3-week, and 6-week time points, whereas in females, this increase occurred most frequently at 6 weeks post-SCI. Conversely, circular muscle ICC (ICC-CM) did not demonstrate post-SCI changes. These data demonstrate resiliency of the ICC-MP in neurogenic bowel following SCI, unlike seen in other related disease states. This plasticity underscores the need to further understand neuromuscular changes driving colonic dysmotility after SCI in order to advance therapeutic targets for neurogenic bowel treatment.

Phrenic nerve stimulation for treatment of central sleep apnea

The prevalence of central sleep apnea (CSA) is rare in general population. However, CSA is prevalent in those with cardiovascular and cerebrovascular disorders. CSA may persist or even worsen with positive airway pressure therapy in some patients and phrenic nerve stimulation (PNS) offers an alternative treatment for patients with CSA. The device is implanted similar to a cardiac pacemaker and typically followed in the sleep clinic. Multiple studies have described the efficacy and safety of PNS. Improvements were seen in apnea hypopnea events, central events, arousals, and daytime sleepiness and maintained through 5 years. Safety demonstrated a 91% freedom from serious adverse events through 1 year. The physiologic approach and improvement in sleep metrics and quality of life with a strong safety profile make this therapy a good option for many patients with central sleep apnea.

Venous access routes for cardiac implantable electronic devices

Various venous access routes in the region of the clavicle are available for cardiac device treatment. After many years of choosing access via the subclavian vein, current data explicitly show that lateral approaches such as preparation of the cephalic vein or puncture of the axillary vein are clearly superior in terms of probe durability and risk of complications. This article describes the preparation and performance of the various access techniques and is intended to provide apractical guide for the work in cardiac pacemaker operations. This work continues aseries of articles designed for advanced training in specialized rhythmology.

Spatially resolved multiomics of human cardiac niches

The function of a cell is defined by its intrinsic characteristics and its niche: the tissue microenvironment in which it dwells. Here we combine single-cell and spatial transcriptomics data to discover cellular niches within eight regions of the human heart. We map cells to microanatomical locations and integrate knowledge-based and unsupervised structural annotations. We also profile the cells of the human cardiac conduction system1. The results revealed their distinctive repertoire of ion channels, G-protein-coupled receptors (GPCRs) and regulatory networks, and implicated FOXP2 in the pacemaker phenotype. We show that the sinoatrial node is compartmentalized, with a core of pacemaker cells, fibroblasts and glial cells supporting glutamatergic signalling. Using a custom CellPhoneDB.org module, we identify trans-synaptic pacemaker cell interactions with glia. We introduce a druggable target prediction tool, drug2cell, which leverages single-cell profiles and drug–target interactions to provide mechanistic insights into the chronotropic effects of drugs, including GLP-1 analogues. In the epicardium, we show enrichment of both IgG+ and IgA+ plasma cells forming immune niches that may contribute to infection defence. Overall, we provide new clarity to cardiac electro-anatomy and immunology, and our suite of computational approaches can be applied to other tissues and organs.

Increased KCNN4 Expression Is Correlated With Poor Survival in Lower Grade Glioma.

Networks of glioma cells are linked to small groups of pacemaker cells in which levels of calcium ions pulse periodically, driving a signal through the network that causes tumor growth. Using inhibitors, one study blocked the activity of the Ca2+activated potassium-channel protein KCa3.1 in in vitro models and mice, preventing the proliferation of glioma cells and tumor expansion. Marked reduction of tumor cell viability occurred within the entire network, as well as reduced tumor growth in mice and extended animal survival. KCa3.1 is encoded by the gene potassium calcium-activated channel subfamily N member 4 (KCNN4) on the chromosomal location 19q13.31. We used the Cancer Genome Atlas (TCGA) to evaluate the effect of KCNN4 on human glioma survival in the TCGA Lower Grade Glioma (LGG) dataset. In humans, KCNN4 is prognostic in glioma; high expression is unfavorable. In addition, KCNN4 copy number variations are prognostic. Increased masked copy number segments are unfavorable in lower grade glioma. KCNN4 is lost in gliomas with the 1p 19q co-deletion, which may explain in part the comparatively favorable prognosis of 1p 19q co-deletion tumors. Our finding of increased KCNN4 expression related to poor survival in human lower grade glioma suggests that developing novel therapies, such as KCa3.1-inhibiting drugs, might be worthwhile.

SUSCEPTIBILITY WEIGHTED IMAGING TECHNIQUE UTILITY IN DIVERSE NEUROLOGICAL ENTITIES

Background: Susceptibility Weighted Imaging (SWI) is a novel modality based upon GE (Gradient Echo) sequences that employ differences in susceptibility of various paramagnetic as well as diamagnetic substances that aid in the better diagnosis of various neurological entities such as intracranial tumors, vascular malformations, arterial stroke, venous hemorrhagic infarcts. Objective:To assess utility of SWI in various neurological diseases. Methods: The retrospective observational study was held in a tertiary care medical center in India in 2021. Multiple neurological diseases on SWI were analyzed in 100 patients with neurological complaints. The inclusion criteria included patient of all age group who presented with neurological signs and symptoms. The exclusion criteria included presence of post-operative non-compatible orthopedic hardware and patients with cardiac pacemakers, cochlear implants in situ. Results: The majority were males and &gt; 60 years (23%) in age. Among 100 patients, most had tumors (18%), followed by trauma (16%), arterial stroke (15%), and hemorrhage (14%). Most of 14 patients with hemorrhage have intraparenchymal hemorrhage 9 (64.29%). There were10 patients with venous sinuses thrombosis and 15 cases with arterial stroke amongst whom most had middle cerebral artery thrombosis (46.66%). Most 13 patients with vascular pathologies had amyloid angiopathy 4 (30.77%). The majority of tumors were primary 15 (83.33%) with 10 (66.67%) newly diagnosed tumors, 11 (61.11%) tumors had a hemorrhage, 3 (16.67%) presented with calcification, and 4 (22.22%) had both hemorrhage and calcification. According to SWI grading of the tumor by intratumoral susceptibility score (ITSS), the majority were in grade III. On the correlation of SWI grading with MR Spectroscopy (MRS) and MR perfusion (MRP) study, 6 (100%) grade III patients showed hyperperfusion on MRP with raised choline/Creatinine ratio. SWI was better than CT (P&lt;0.05) in detecting trauma, hemorrhage, cerebral venous sinus thrombosis, vascular pathologies, and tumors. Conclusion: SWI is a helpful imaging tool in neuroradiological practice and should be incorporated into standard procedures. It is beneficial in identifying hemorrhages, low-flow vascular abnormalities, diffuse axonal injury, and neurodegenerative illnesses. In addition, it is a supplementary sequence in the stroke by distinguishing calcium from hemorrhage in the brain and categorizing brain tumors.

Extra-Thoracic Subclavian Vein Access: The Tips And Tricks

The success of any trans-venous procedure involves the rate liming step, which is the access. The procedure cannot be performed without the access site. It is the key that open the success of the procedure. There are many procedures that require extra-thoracic subclavian vein. These procedures may include: central venous pressure monitoring, administration of multiple medications and drips, high volume/flow resuscitation, emergency venous access, inability to obtain peripheral venous access, repetitive blood sampling, administering hyperalimentation, vasopressors, caustic agents, or other concentrated fluids; insertion of transvenous cardiac pacemakers, hemodialysis or plasmapheresis and insertion of pulmonary artery catheters. In this review, we discuss the various techniques of accessing the vein and it tips and tricks..

Effect of preoperative ivabradine on hemodynamics during elective off-pump CABG.

Ivabradine is a specific heart rate (HR)-lowering agent which blocks the cardiac pacemaker If channels. It reduces the HR without causing a negative inotropic or lusitropic effect, thus preserving ventricular contractility. The authors hypothesized that its usefulness in lowering HR can be utilized in patients undergoing off-pump coronary artery bypass (OPCAB) surgery. To study the effects of preoperative ivabradine on hemodynamics (during surgery) in patients undergoing elective OPCAB surgery. Fifty patients, New York Heart Association (NYHA) class I and II, were randomized into group I (control, n = 25) and group II (ivabradine group, n = 25). In group I, patients received the usual anti-anginal medications in the preoperative period, as per the institutional protocol. In group II, patients received ivabradine 5 mg twice daily for 3 days before surgery, in addition to the usual anti-anginal medications. Anesthesia was induced with fentanyl, thiopentone sodium, and pancuronium bromide as a muscle relaxant and maintained with fentanyl, midazolam, pancuronium bromide, and isoflurane. The hemodynamic parameters [HR and mean arterial pressure (MAP)] and pulmonary artery (PA) catheter-derived data were recorded at the baseline (before induction), 3 min after the induction of anesthesia at 1 min and 3 min after intubation and at 5 min and 30 min after protamine administration. Intraoperatively, hemodynamic data (HR and MAP) were recorded every 10 min, except during distal anastomosis of the coronary arteries when it was recorded every 5 min. Post-operatively, at 24 hours, the levels of troponin T and brain natriuretic peptide (BNP) were measured. This trial's CTRI registration number is CTRI/005858. The HR in group II was lower when compared to group I (range 59.6-72.4 beats/min and 65.8-80.2 beats/min, respectively) throughout the study period. MAP was comparable [range (78.5-87.8 mm Hg) vs. (78.9-88.5 mm Hg) in group II vs. group I, respectively] throughout the study period. Intraoperatively, 5 patients received metoprolol in group I to control the HR, whereas none of the patients in group II required metoprolol. The incidence of preoperative bradycardia (HR <60 beats/min) was higher in group II (20%) vs. group I (8%). There was no difference in both the groups in terms of troponin T and BNP level after 24 hours, time to extubation, requirement of inotropes, incidence of arrhythmias, in-hospital morbidity, and 30-day mortality. Ivabradine can be safely used along with other anti-anginal agents during the preoperative period in patients undergoing OPCAB surgery. It helps to maintain a lower HR during surgery and reduces the need for beta-blockers in the intraoperative period, a desirable and beneficial effect in situations where the use of beta-blockers may be potentially harmful. Further studies are needed to evaluate the beneficial effects of perioperative Ivabradine in patients with moderate-to-severe left ventricular dysfunction.

Correct-by-Construction Reinforcement Learning of Cardiac Pacemakers from Duration Calculus Requirements

Correct-by-Construction Reinforcement Learning of Cardiac Pacemakers from Duration Calculus Requirements

Comparison of first- and second-generation leadless pacemakers in patients with sinus rhythm and complete atrioventricular block.

The efficacy and safety of leadless cardiac pacemakers (LPMs) as an alternative to conventional transvenous cardiac pacing have been largely reported. The first generation of the MicraTM transcatheter pacing system (VR; Medtronic) was able to provide single-chamber VVI(R) pacing mode only, with a potential risk of pacemaker syndrome in sinus rhythm patients. A second-generation system (AV) now provides atrioventricular synchrony through atrial mechanical (Am) sensing capability (VDD mode). We sought to compare VR and AV systems in sinus rhythm patients with chronic ventricular pacing (Vp) for complete atrioventricular block. All consecutive patients implanted with an LPM in our department for complete atrioventricular block were retrospectively screened. Patients with atrial fibrillation, sinus dysfunction, or Vp burden <20% at 1 month postimplantation were excluded. Patients were systematically followed with a visit at 1 month, and then at least once a year. A total of 93 patients-45 VR (2015-2020) and 48 AV (2020-2021)-were included. VR and AV patients had similar baseline characteristics, except for VR patients being older (80 ± 8 vs. 77 ± 9 years, p = 0.049). The mean Vp burden was 77% in the VR and 82% in the AV group (p = 0.38). In AV patients, the median AV synchronous beats rate was 78%, with 65% having a >66% rate. An E/A ratio <1.2 as measured on echocardiography was the only independent predictor of accurate atrial mechanical tracking (p = 0.01). One-year survival rate was similar in both groups. Five patients in the VR and 0 in the AV group eventually developed pacemaker syndrome within 1 year post-implantation (p = 0.02). In sinus rhythm patients with chronic Vp for complete atrioventricular block implanted with an LPM, the atrial mechanical sensing algorithm allowed significant atrioventricular synchrony in most patients and was associated with no occurrence of-otherwise rare-pacemaker syndrome.

Initial studies on the implanting sites of high and low ventricular septa using leadless cardiac pacemakers.

To study the safety and electrical characteristics of various implanting sites of the Micra pacemaker. A total of 15 patients from Beijing Anzhen Hospital, Capital Medical University, were included, who were implanted with Micra leadless pacemakers and allocated to either the high ventricular septum group (eight patients) or the low ventricular septum group (seven patients) based on their individual patient factors and clinical conditions. The baseline of the patients, the implanting area, the electrocardiogram change after implantation, the implantation data, the threshold, R wave, impedance, and the date of the 1-month follow-up were then analyzed. With all of the data, the characteristics of different implantation sites of the Micra pacemaker were determined. Overall, the thresholds were low at implantation and remained stable over the 1-, 3-, 6-month, 1-, 2-, 3-, and 4-year follow-ups. On comparing the two groups, there was no difference in QRS duration at pacing (140.00 [40.00] ms vs. 179.00 [50.00] ms), threshold at implantation (0.38 [0.22] mV vs. 0.63 [1.00] mV), R wave at implantation ([10.85 ± 4.71] V vs. [7.26 ± 2.98] V), or impedance at implantation ([906.25 ± 162.39] Ω vs. [750.00 ± 173.40] Ω). While the difference in QRS duration between the two groups was not significant, the QRS duration of the high ventricular septum group exhibited a reduced tendency compared with that of the low ventricular group. The corrected QT interval during pacing exhibited a significant difference (440.00 [80.00] ms vs. 520.00 [100.00] ms; p < .05). For the 1-, 3-, 6-month, 1-, 2-, 3-, and 4-year follow-ups, there was no difference between the threshold of the high ventricular septum group and that of the low ventricular septum group (p > .05). High ventricular septum pacing appears to be a safe site for implantation of the Micra pacemaker. It could entail a shorter QRS duration at pacing and could be more physiological than low ventricular septum pacing.