Pacing Capture Threshold Research Articles

Regional results of the lead evaluation for defibrillation and reliability (LEADR) trial

Abstract Introduction ICD/CRT-D patients are living longer, and interest in reliable leads with targeted placement is growing. The Lead EvaluAtion for Defibrillation and Reliability (LEADR) trial was designed to assess the novel small-diameter, lumenless, catheter-delivered, defibrillation study lead. The study lead is based on the SelectSecure SureScan MRI Model 3830 lumenless pacing lead delivered by catheter that has a simplified durable construction with improved long-term reliability (97.2% 12-year RV lead survival). Purpose The LEADR trial assessed the efficacy and safety of the novel defibrillation lead. Methods The global LEADR Pivotal trial (NCT04863664) enrolled patients with ACC/AHA/ESC guideline-directed indications for de novo implant of a primary or secondary prevention ICD/CRT-D. The primary efficacy and safety endpoints were defibrillation success at implant and freedom from study lead-related major complications at 6-months, respectively. Results A total of 643 patients were successfully implanted (61.9±12.9 years, 26% female, 28.5±6.4 kg/m2 BMI, and 80.9% NYHA Class II) with the study lead placed in the desired RV location in 99.5%. The estimated freedom from study lead-related major complications was 97.1% at 6- and 12-months. Defibrillation testing was successful in 116/119 (97.5%) patients. The prespecified primary efficacy and safety thresholds (88% and 90%, respectively) were exceeded. There were zero study lead fractures and electrical measurements were stable through 12.7±4.8-month mean follow-up. Approximately 20% of patients were in Asia, 9% in Australia, 21% in Europe, and 50% in North America (Table). The estimated freedom from study lead-related major complications at 6- and 12-months per region were 96.2% in Asia, 100% in Australia, 96.4% in Europe, and 97.2% in North America (Figure), P=0.82 across regions. There were 19 study lead-related major complications (5 in Asia, 0 in Australia, 5 in Europe, 9 in North America), with the most common being lead dislodgement across regions. Defibrillation testing was successful in 116/119 patients with 33/33 in Asia, 32/32 in Australia, 7/8 in Europe, and 44/46 in North America, P=0.11 across regions. Among the 3 patients with unsuccessful testing, 2 (North America) remained in the study at physician discretion after successful conversion outside of protocol requirements, and 1 (Europe) was exited. Pacing capture threshold, pacing impedance, and R-wave amplitude were chronically stable across regions. Conclusion The LEADR Pivotal trial demonstrated the safety, efficacy, and reliability of the novel defibrillation lead, exceeding prespecified efficacy and safety thresholds. There were no notable differences in primary endpoints between regions. The trial has met its endpoints and ongoing follow-up will provide long-term performance. This trial demonstrated the ability to place the lead in targeted RV locations; a study of this lead for conduction system pacing is forthcoming.TableFigure

Electrical performance of a novel extravascular temporary pacing lead system

Abstract Background An investigational extravascular (EV) cardiac temporary pacing system has been developed that includes a parasternally-positioned temporary pacing lead within the anterior mediastinum. The pacing lead is inserted using a custom delivery tool through a parasternal skin incision. This novel system may provide clinical advantages over existing device alternatives that require intravascular, endocardial, or epicardial contact. Objective The purpose of this study was to evaluate electrical performance of an EV temporary pacing lead over 48 hours. Methods In this single-center study, patients who underwent a transvenous (TV) permanent pacemaker implant or replacement were simultaneously implanted with the investigational EV temporary pacing lead. Electrical performance was evaluated through analysis of capture thresholds, impedance, and R-wave amplitudes during multiple times on the day of the procedure and on the subsequent 2 days of follow-up. Results Lead insertions with acute capture were successful in all 8 patients (40% female, 71 ± 8 years, BMI 27 ± 3 kg/m2). Mean acute measurements for pacing capture threshold at 1.5 ms, impedance and R-wave amplitude were 6.2 mA, 1396 Ω, 5.4 mV, respectively. Pacing capture was maintained in 100% of assessments conducted over 3 days (Figure 1). There were no serious complications during insertion, removal or chronic use of the lead. Conclusions Results support that the investigational EV temporary pacing lead is capable of safely providing temporary pacing with thresholds typically well below the maximum output of temporary pacemakers.

Pacing sensation with a second generation intercostal extravascular ICD lead

Abstract Background/Introduction An investigational intercostal extravascular ICD lead (EV-ICD Lead) has been developed to provide antitachycardia pacing and shock treatment of ventricular tachyarrhythmias when connected to a commercially available ICD pulse generator. Unlike other available extravascular ICD systems that achieve pacing with ring electrodes which transmit undirected current to cardiac and non-cardiac tissue alike, the intercostal EV-ICD Lead uses button-shaped electrodes backed by an insulative paddle to direct current toward excitable myocytes while minimizing undesired excitation of the adjacent tissues. Purpose The purpose of this analysis was to evaluate pacing sensation with the intercostal EV-ICD Lead connected to a commercially-available ICD pulse generator programmed to the maximum voltage output and pulse width settings. Methods In the STEP ICD Study (n=20), pacing sensation was evaluated at the pre-discharge visit while pacing at the maximum programmable voltage output (7.5 or 8.0 V, depending on manufacturer) and pulse width (1.5 or 2.0 ms). Sensation was reported by the patient as one of four choices: No Sensation, Sensation Only, Tolerable Pain or Intolerable Pain. Results Pacing sensation was assessed in 18 of 20 patients. One (1) patient did not undergo a pacing evaluation due to atrial fibrillation with rapid ventricular response. Responses were as follows: No Sensation in 4 (22%) patients, Sensation Only in 10 (56%) patients, Tolerable Pain in 3 (17%) and Intolerable Pain in 1 (6%). In no patient was the pain so severe that pacing capture threshold testing could not be completed. Of note, the single report of intolerable pain was only reported in the sitting posture. When tested supine, the patient reported sensation only. Conclusion(s) The design of the investigational intercostal EV-ICD Lead, with button-shaped electrodes backed by an insulative paddle, produced low levels of patient sensation at maximum output and pulse width. These sensation levels represent an improvement over designs that employ ring electrodes and indicate that antitachycardia pacing will be well tolerated with the novel EV-ICD Lead. These results corroborate the predictions about patient discomfort from in silico models.

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

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. 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. 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.

Clinical Usefulness of the Active Fixation Quadripolar Left Ventricular Lead Compared With the Passive Fixation Quadripolar Lead in Cardiac Resynchronization Therapy.

This study compared the stability of the Medtronic Attain Stability Quad (ASQ), a novel quadripolar active fixation left ventricular (LV) lead with a side helix, to that of conventional quadripolar leads with passive fixation (non-ASQ) and evaluated their LV lead performance. In all, 183 consecutive patients (69 ASQ, 114 non-ASQ) who underwent cardiac resynchronization therapy (CRT) between January 2018 and June 2021 were enrolled. Complications, including elevated pacing capture threshold (PCT) levels, phrenic nerve stimulation (PNS), and LV lead dislodgement, were analyzed during the postimplantation period until the first outpatient visit after discharge. The frequency of LV lead-related complications was significantly lower in the ASQ than non-ASQ group (14% vs. 30%, respectively; P=0.019). Specifically, LV lead dislodgement occurred only in the non-ASQ group, and elevated PCT levels were significantly lower in the ASQ group (7% vs. 23%; P=0.007). Kaplan-Meier analysis confirmed a significantly lower incidence of LV lead-related complications in the ASQ group (log-rank P=0.005). Cox multivariable regression analysis showed a significant reduction in lead-related complications associated with ASQ (hazard ratio 0.44; 95% confidence interval 0.23-0.83; P=0.011). The ASQ group exhibited fewer LV lead-related complications requiring reintervention and setting changes than the non-ASQ group. Thus, the ASQ may be a favorable choice for CRT device implantation.

Safety and performance of conduction system pacing: Real-world experience from a product surveillance registry

BackgroundConduction system pacing (CSP), including His-bundle pacing (HBP) and left bundle branch area pacing (LBBAP), has been used as an alternative for pacemaker indicated patients requiring ventricular pacing. ObjectiveThe purpose of this study was to characterize the safety and performance of HBP and LBBAP among patients enrolled in the Medtronic product surveillance registry (PSR). MethodsThis observational analysis included patients who underwent pacemaker implantations for HBP or LBBAP with a Medtronic Model 3830 lead between January 2019 and December 2023 in the Medtronic PSR. The primary outcomes were lead-related complications and pacing capture threshold. Baseline characteristics, R-wave amplitude, impedance, and all-cause mortality were summarized. ResultsA total of 2342 patients were included across 77 centers (mean age 74 years; 38.9% female). Of the patients implanted with a 3830 lead for CSP, 64.1% (n = 1502) had LBBAP placement and 35.9% (n = 840) had HBP placement. The most commonly reported indications for CSP were sinus node dysfunction (67.0%) and atrioventricular block (57.2%). LBBAP had lower pacing thresholds, higher R-wave sensing, and higher impedance (all P <.001) through 30 months. At 36 months postimplant, the lead complication rate for LBBAP and HBP was 2.5% and 6.3%, ,respectively with no difference in all-cause mortality. ConclusionIn a multicenter cohort of LBBAP and HBP patients treated with the catheter-delivered 3830 lead, lead-related complication rates were low and electrical parameters were stable through 30 months.

Performance of the quadripolar CRT-D system: Five-year results from the Quadripolar Pacing Post-Approval Study

BackgroundCardiac resynchronization therapy (CRT) is associated with challenges such as elevated capture thresholds, diaphragmatic stimulation, and lead instability. ObjectiveThis study aimed to assess the long-term safety and efficacy of the quadripolar CRT-defibrillator (CRT-D) device system with the Quartet 1458Q left ventricular (LV) lead in a CRT-indicated population observed for 5 years and to evaluate all-cause mortality and impact of baseline characteristics on survival through 5 years. MethodsPatients indicated for a CRT-D system were observed every 6 months after implantation for 5 years, and device performance and adverse events were assessed at each visit. The 3 primary end points were freedom from quadripolar CRT-D system-related complications through 5 years, freedom from Quartet 1458Q LV lead-related complications through 5 years, and mean programmed pacing capture threshold at 5 years. ResultsThe study enrolled 1970 participants at 71 sites. The quadripolar CRT-D system was successfully implanted in 97.2% of participants. Freedom from quadripolar CRT-D device system-related complications through 5 years was 89.7%. Freedom from Quartet 1458Q LV lead-related complications through 5 years was 95.7%; 3.49% of participants had LV lead-related complications, and an overall LV lead complication rate was 0.0122 event per patient-year. The mean LV pacing capture threshold was 1.52 ± 1.01 V at 5 years. The 5-year survival rate was 67.4%. ConclusionThe quadripolar CRT-D system with the Quartet 1458Q LV lead exhibited low rates of complications and stable electrical performance through 5 years of follow-up and suggested a higher 5-year survival rate compared with traditional CRT systems.

The Effectiveness and Safety of Leadless Pacemakers: An Updated Meta-Analysis.

Leadless pacemakers (LPs) are promising alternatives to traditional transvenous pacemakers (TVPs), but their comparative effectiveness and safety in clinical outcomes remain uncertain. We systematically searched PubMed, Embase, Scopus, Cochrane, and ClinicalTrials.gov for studies comparing LPs and TVPs. A restricted maximum likelihood random-effects model was used for all outcomes. Heterogeneity was assessed using I2 statistics. We performed a subgroup analysis with studies with multivariate-adjusted data. We included 21 studies involving 47,229 patients, of whom 12,199 (25.8%) underwent LP implantation. Compared with TVPs, LPs were associated with a significantly lower risk of overall complications (OR 0.61; 95% CI 0.45-0.81; p < 0.01), dislodgement (OR 0.34; 95% CI 0.20-0.56; p < 0.01), and pneumothorax (OR 0.27; 95% CI 0.16-0.46; p < 0.01). No significant difference in all-cause mortality was observed in the overall analysis (OR 1.43; 95% CI 0.65-3.15; p = 0.35) and in studies with multivariate-adjusted data (OR 1.34; 95% CI 0.65-2.78; p = 0.43). However, LPs were associated with a higher risk of pericardial effusion (OR 2.47; 95% CI 1.39-4.38; p < 0.01) and cardiac tamponade (OR 3.75; 95% CI 2.41-5.83; p < 0.01). LPs also demonstrated a lower pacing capture threshold (MD -0.19V; 95% CI [-0.23V]-[-0.16V]; p < 0.01), but no significant difference in impedance (MD 32.63 ohms; 95% CI [-22.50 ohms]-[87.76 ohms]; p = 0.25). These findings suggest that LPs were associated with lower overall complication rates and similar effectiveness to TVPs. However, randomized controlled trials are warranted to validate these results.

Upgrading a single-chamber leadless pacemaker to a dual-chamber leadless pacemaker system

Abstract Background/Introduction The first global dual-chamber leadless pacemaker (DR-LP) study included a group of subjects with a pre-existing upgradeable ventricular single chamber leadless pacemaker (VR-LP) in whom the addition of an atrial leadless pacemaker (AR-LP) was undertaken to allow upgrading to a dual chamber leadless pacing (DR-LP) system. Purpose Summarize success rates of single to dual chamber leadless pacemaker upgrades, as well as device and i2i throughput measurements, serious adverse device effects (SADEs) and mortality in this cohort. Methods Subjects with a pre-existing VR-LP who were indicated for a dual-chamber pacemaker were included. Upgrade procedures included downloading firmware to existing VR-LP, placing AR-LP, and pairing the devices to operate in a DR-LP mode. Electrical and i2i throughput measurements were collected at implant, pre-discharge, 1-mo, 3-mo, 6-mo, and 12-mo. Upgrade success rate was defined as an AR-LP upgrade procedure that resulted in a functional DR-LP system. SADEs included all reported events that were adjudicated as serious and possibly, probably or causally related to the procedure or system. SADEs and deaths were adjudicated by an independent clinical events committee. Results Out of 36 enrolled subjects (61.1% male, 70.4 ± 13.8 yrs., 55.6% sinus node dysfunction, 38.9% AV block), 35 had an attempted implant, and 32 of these were successful (91.4%). The 3 unsuccessful upgrade attempts were related to unsuccessful placement of the AR-LP due to complications during the procedure (n = 2) or an inability to implant an AR-LP (n = 1). Figure 1 illustrates a declining early mean pacing capture threshold, rising early P-wave amplitudes, and stable impedance for the AR-LP over the 12 months. Mean i2i throughput for communication from the RV to RA and the RA to RV improved from pre-discharge to 3 months and remained stable through the subsequent 9 months (Figure 2). A total of 5 subjects (5 of 36; 13.9%) experienced 7 SADEs (all procedure-related; 2 related to the AR-LP and 2 to the delivery catheter). One non-cardiovascular, non-device, non-procedure related death occurred in the upgrade population. Conclusions The single to dual-chamber upgrade cohort demonstrated a high upgrade success rate (91.4%), stable atrial and ventricular electrical measurements and consistently high i2i communication throughout the 12 months. AV synchrony (AVS) was not specifically measured in this upgrade cohort, but data from the main DR-LP study suggest that i2i throughput correlates with, but significantly underestimates AVS. Further, the rate of complications was acceptable (13.9%) and limited to the procedure. These data confirm the feasibility, safety and longer-term effectiveness of adding an atrial LP in patients with a pre-existing ventricular LP order to achieve effective dual chamber pacing.Fig. 1: Upgrade Electrical measurementsFig. 2: i2i communication for Upgrades

First-in-man clinical implantation and acute pacing performance of a novel subxiphoidal pacemaker system.

Intravascular cardiac pacemakers are an established therapy for bradycardic indications. Recently, a new class of leadless pacemakers have mitigated some of the complications related to pacemaker leads. In this study, we evaluate the implantation and performance of a novel extravascular technology that delivers epicardial pacing through a subxiphoidal approach. Fifteen patients undergoing non-emergent open-heart surgery were enrolled. A midline incision was made just below the xiphoid process, and substernal tunneling was used to create a pocket for the device and to access the anterior pericardium over the right ventricle. The test device (Calyan Technologies, Oakdale, MN) was temporarily inserted underneath the ribcage and clipped to the xiphoid process. The sensing and pacing electrode (FlexArm) was positioned on the anterior pericardium. Ventricular sensing and pacing capture thresholds were measured. The test device was successfully implanted in all 15 patients. There were no device or procedure-related adverse events. The first five implanted patients had no pacing capture at maximum stimulation intensity. Design changes were made to the device, including different electrode size and shape, and successful ventricular capture was achieved in 9 of the subsequent 10 patients. In these patients, pacing threshold was 3.8 ± 1.6mA with a pulse width of 0.5 ms. All devices were successfully explanted at the end of the procedure. In a first-in-human experience with a novel extravascular pacemaker, this study demonstrated the feasibility of pericardial ventricular pacing via a subxiphoidal approach. Further chronic studies are required to evaluate the safety and performance of this novel pacing technology.

Six-month electrical performance of the first dual-chamber leadless pacemaker

BackgroundThe first dual-chamber leadless pacemaker (DC-LP) system consists of 2 separate atrial and ventricular devices that communicate to maintain synchronous atrioventricular pacing and sensing. The initial safety and efficacy were previously reported. ObjectiveThe purpose of this study was to evaluate the chronic electrical performance of the DC-LP system. MethodsPatients meeting standard dual-chamber pacing indications were enrolled and implanted with the DC-LP system (Aveir DR, Abbott), including right atrial and ventricular helix-fixation LPs (atrial leadless pacemaker [ALP], ventricular leadless pacemaker [VLP]). Pacing capture threshold, sensed amplitude, and pacing impedance were collected using the device programmer at prespecified timepoints from 0–6 months postimplant. ResultsDe novo devices were successfully implanted in 381 patients with complete 6-month data (62% male; age 69 ± 14 years; weight 82 ± 20 kg; 65% sinus nodal dysfunction, 30% atrioventricular block). ALPs were implanted predominantly in the right atrial appendage anterior base and VLPs primarily at the mid-to-apical right ventricular septum. From implant to 1 month, pacing capture thresholds (0.4-ms pulse width) improved in both ALPs (2.4 ± 1.5 V to 0.8 ± 0.8 V; P <.001) and VLPs (0.8 ± 0.6 V to 0.6 ± 0.4 V; P <.001). Sensed amplitudes improved in both ALPs (1.8 ± 1.3 mV to 3.4 ± 1.9 mV; P <.001) and VLPs (8.8 ± 4.0 mV to 11.7 ± 4.2 mV; P <.001). Impedances were stable in ALPs (334 ± 68 Ω to 329 ± 52 Ω; P = .17) and reduced in VLPs (789 ± 351 Ω to 646 ± 190 Ω; P <.001). Electrical measurements remained relatively stable from 1–6 months postimplant. No differences in electrical metrics were observed among ALP or VLP implant locations. ConclusionThis first in-human evaluation of the new dual-chamber leadless pacemaker system demonstrated reliable electrical performance throughout the initial 6-month evaluation period.

Impact of omitting the intravenous heparin bolus on outcomes of leadless pacemaker implantation.

Early guidance recommended a bolus of intravenous heparin at the beginning of leadless pacemaker (LP) implantation procedures. However, due to concern about bleeding complications, more recent practice has tended toward omitting the bolus and only running a continuous heparin infusion through the introducer sheath. The impact of omitting the heparin bolus on procedural outcomes is not clear. We reviewed all Medtronic Micra LP implants at our institution from 9/2014 to 9/2022. The decision to bolus with heparin was at operator discretion. Among 621 LP implants, 326 received an intravenous heparin bolus, 243 did not, and 52 patients were excluded because heparin bolus status could not be confirmed. There was a trend toward more frequent omission of the heparin bolus with more recent implants. Median follow-up after LP implant was 14.3 (interquartile range [IQR]: 8.4-27.9) months. There was no difference between heparin bolus and no bolus groups in the number of device deployments/recaptures (1.42 ± 0.81 vs. 1.31 ± 0.66, p = .15). Implant-related adverse events were also similar between heparin bolus and no bolus groups: access-site hematoma requiring intervention (7 vs. 5, p = .99), pseudoaneurysm (1 vs. 1, p = .99), cardiac perforation (1 vs. 1, p = .99), intraprocedural device thrombus formation (2 vs. 4, p = .41), 30-day rehospitalization (21 vs. 15, p = .98), and 30-day all-cause mortality (16 vs. 14, p = .70). There was one additional nonfatal cardiac perforation in a patient who was excluded due to unknown heparin bolus status. Regarding device electrical parameters between heparin bolus and no bolus groups, there were no significant differences at the time of implant: pacing capture threshold 0.5 ± 0.4 vs. 0.5 ± 0.3, p = .10; pacing impedance 739.9 ± 226.4 vs. 719.1 ± 215.4, p = .52; R wave sensing 11.7 ± 5.7 vs. 12.0 ± 5.4, p = .34). Long-term device performance was also similar between groups. Omission of the systemic heparin bolus at the time of LP implantation appears safe in appropriately selected patients. Heparin bolus may still be considered in long cases requiring multiple device deployments or in patients at high risk for thrombotic complications.

Permanent Cardiac Pacing of the Right Ventricular Outflow Tract Guided by Real-time Assessment of Electromechanical Synchrony.

Permanent right ventricular apical pacing deteriorates cardiac systolic function in some patients. We investigated an alternative site for permanent pacemaker (PPM) lead positioning with the goal of achieving more physiological pacing. A total of 132 patients with bradyarrhythmias underwent PPM implantation at the right ventricular outflow tract (RVOT) with conventional active-fixation leads. A real-time cross-correlation analysis (CCA) was performed using the Synchromax® software (EXO Health, Seattle, WA, USA) to determine the optimal site for ventricular lead implantation based on the cardiac synchrony index. The follow-up period ranged from 6-36 months, and the following parameters were assessed: pacing capture threshold, lead stability, and the need for lead repositioning. Adequate parameters were achieved in 129 patients (98%), and there were no procedure-related complications. At follow-up, no leads were dislodged, pacing thresholds remained stable, and no lead required repositioning. Using real-time CCA as an intraoperative parameter during PPM implantation at the septal RVOT helps to achieve cardiac synchrony in the vast majority of cases. This technique is a simple, effective, and safe way to simplify and standardize PPM implantation at the RVOT.

Early real-world implant experience with a helix-fixation ventricular leadless pacemaker.

Roughly one in six patients receiving conventional transvenous pacemaker systems experience significant complications within 1year of implant, mainly due to the transvenous lead and subcutaneous pocket. A new helix-fixation single-chamber ventricular leadless pacemaker (LP) system capable of pre-deployment exploratory electrical mapping is commercially available. Such an LP may mitigate complications while streamlining the implantation. In this study, the initial real-world implant experience of the helix-fixation LP was evaluated following its commercial release. In patients indicated for single-chamber right ventricular pacing, helix-fixation Aveir VR LPs (Abbott, Abbott Park, IL) were implanted using the dedicated loading tool, introducer, and delivery catheter. Implant procedural characteristics, electrical parameters, and any 30-day procedure-related adverse events of consecutive implant attempts were retrospectively evaluated. A total of 167 patients with Class I indication for permanent pacing received implants in four North American centers (57% male, 70years old). Pre-fixation electrical mapping of potential sites allowed repositioning to be avoided in 95.7% of patients. Median [interquartile range] LP procedure and fluoroscopy durations were 25.5min [20.0, 35.0] and 5.7min [4.0, 9.2], respectively. Pacing capture threshold, sensed R-wave amplitude, and impedance were 0.8V [0.5, 1.3], 9.0mV [6.0, 12.0], and 705 Ω [550, 910], respectively. Implantation was successful in 98.8% of patients, with 98.2% free from acute adverse events. The initial, real-world experience of the helix-fixation ventricular leadless pacemaker demonstrated safe and efficient implantation with minimal repositioning, viable electrical metrics, and limited acute complications.

Safety and performance of a novel subxiphoidal pacemaker system.

Traditional cardiac pacemakers commonly have a range of complications related to the presence of intracardiac leads. A new class of extravascular and leadless pacemakers has recently emerged with the potential to mitigate these complications and expand access to cardiac pacing. The objective of this study is to evaluate the implantation, short-term chronic safety, and performance of a novel subxiphoidal extracardiac pacemaker. Normal Yorkshire Cross swine (n = 16) were implanted with the subxiphoidal pacemaker. The pacemaker was inserted through a midline chest incision and clipped to the underside of the sternum, with the stimulation electrode placed on the anterior pericardium. Animals were chronically paced and followed for 90days post-implant, with periodic measurement of pacing capture threshold (PCT) and electrode impedance. All 16 animals were successfully implanted with the study device. At implant, a consistent average PCT of 2.2 ± 0.4V at a pulse width of 1.0ms was observed in all animals, with an average implant impedance of 648 ± 44 Ω. Chronic pacing was programmed at a rate of 60bpm, an amplitude of 3.4 ± 0.7V, and a pulse width of 1.0ms. PCT rose to 4.6 ± 0.8V at 14days and stabilized; at 90days, PCT was 3.8 ± 1.2V and electrode impedance was 533 ± 105 Ω. All implanted animals completed the study with no clinically significant findings, no clinically significant abnormalities, and with no adverse events that affected animal welfare. This study demonstrated the safety and feasibility of a novel subxiphoidal extracardiac pacemaker to deliver short-term chronic extravascular therapy. Further studies are required to assess the safety, feasibility, and long-term chronic pacing performance in human subjects.

Efficacy and safety of novel left ventricular pacing leads: 1-year analysis of the NAVIGATOR trial

ObjectivesAssess safety and performance of novel quadripolar preshaped left ventricular (LV) leads: NAVIGO 4LV 2D (‘S shaped’) and NAVIGO 4LV ARC (‘U shaped’).MethodsPatients indicated for cardiac resynchronisation therapy were enrolled...

Multicenter retrospective evaluation of magnetic resonance imaging in pediatric and congenital heart disease patients with cardiac implantable electronic devices

Guidelines addressing magnetic resonance imaging (MRI) in patients with cardiac implantable electronic devices (CIEDs) provide algorithms for imaging pediatric and congenital heart disease (CHD) patients. Guideline acceptance varies by institution. Guidelines also do not support routine MRI scans in patients with epicardial or abandoned leads, common in pediatric and CHD patients. The purpose of this study was to determine the incidence of MRI-related complications in pediatric and CHD patients with CIEDs, including epicardial and/or abandoned leads. A multicenter retrospective review included patients with CIEDs who underwent any MRI between 2007 and 2022 at congenital cardiac centers. The primary outcome was any patient adverse event or clinically significant CIED change after MRI, defined as pacing lead capture threshold increase >0.5 V with output change, P- or R- wave amplitude decrease >50% with sensitivity change, or impedance change >50%. Across 14 institutions, 314 patients (median age 18.8 [1.3; 31.4] years) underwent 389 MRIs. There were 288 pacemakers (74%) and 87 implantable cardioverter-defibrillators (22%); 52% contained epicardial leads, and 14 (4%) were abandoned leads only. Symptoms or CIED changes occurred in 4.9% of MRI scans (6.1% of patients). On 9 occasions (2%), warmth or pain occurred. Pacing capture threshold or lead impedance changes occurred in 1.4% and 2.0% of CIEDs post-MRI and at follow-up. Our data provide evidence that MRIs can be performed in pediatric and CHD patients with CIEDs, including non-MRI-conditional CIEDs and epicardial and/or abandoned leads, with rare minor symptoms or CIED changes but no other complications.

Predictors of Pacing Capture Threshold Exacerbation After Leadless Pacemaker Implantation.

The predictors of pacing capture threshold (PCT) exacerbation after leadless pacemaker implantation remain unknown. We analyzed the predictors of poor PCT by identifying risk factors using multivariate logistic regression analysis for 211 patients with leadless pacemaker implantation. Twenty patients met the criteria for elevated PCT levels and were categorized in the poor PCT group. Multivariate analyses revealed that PCT (P < 0.0001) and pacing impedance (P = 0.03) were independent predictors of PCT exacerbation. Elevated PCT levels and low pacing impedance during leadless pacemaker implantation were potential risk factors for the replacement of leadless pacemakers after the procedure.

Five-year safety and efficacy of leadless pacemakers in a Dutch cohort

Adequate real-world safety and efficacy of leadless pacemakers (LPs) have been demonstrated up to 3 years after implantation. Longer-term data are warranted to assess the net clinical benefit of leadless pacing. The purpose of this study was to evaluate the long-term safety and efficacy of LP therapy in a real-world cohort. In this retrospective cohort study, all consecutive patients with a first LP implantation from December 21, 2012, to December 13, 2016, in 6 Dutch high-volume centers were included. The primary safety endpoint was the rate of major procedure- or device-related complications (ie, requiring surgery) at 5-year follow-up. Analyses were performed with and without Nanostim battery advisory-related complications. The primary efficacy endpoint was the percentage of patients with a pacing capture threshold ≤2.0 V at implantation and without ≥1.5-V increase at the last follow-up visit. A total of 179 patients were included (mean age 79 ± 9 years), 93 (52%) with a Nanostim and 86 (48%) with a Micra VR LP. Mean follow-up duration was 44 ± 26 months. Forty-one major complications occurred, of which 7 were not advisory related. The 5-year major complication rate was 4% without advisory-related complications and 27% including advisory-related complications. No advisory-related major complications occurred a median 10 days (range 0-88 days) postimplantation. The pacing capture threshold was low in 163 of 167 patients (98%) and stable in 157 of 160 (98%). The long-term major complication rate without advisory-related complications was low with LPs. No complications occurred after the acute phase and no infections occurred, which may be a specific benefit of LPs. The performance was adequate with a stable pacing capture threshold.

Safety and performance of MR-conditional pacing systems with automated MRI mode at 1.5 and 3 Tesla

ObjectivesTo evaluate at 1.5 and 3 T MRI the safety and performance of trademarked ENO®, TEO®, or OTO® pacing systems with automated MRI Mode and the image quality of non-enhanced MR examinations.MethodsA total of 267 implanted patients underwent MRI examination (brain, cardiac, shoulder, cervical spine) at 1.5 (n = 126) or 3 T (n = 141). MRI-related device complications, lead electrical performances stability at 1-month post-MRI, proper functioning of the automated MRI mode and image quality were evaluated.ResultsFreedom from MRI-related complications at 1 month post-MRI was 100% in both 1.5 and 3 T arms (both p < 0.0001). The stability of pacing capture threshold was respectively at 1.5 and 3 T (atrial:: 98.9% (p = 0.001) and 100% (p < 0.0001); ventricular: both 100% (p < 0001)). The stability of sensing was respectively at 1.5 and 3 T (atrial: 100% (p = 0.0001) and 96.9% (p = 0.01); ventricular: 100% (p < 0.0001) and 99.1% (p = 0.0001)). All devices switched automatically to the programmed asynchronous mode in the MRI environment and to initially programmed mode after the MRI exam. While all MR examinations were assessed as interpretable, artifacts deteriorated a subset of examinations including mostly cardiac and shoulder ones.ConclusionThis study demonstrates the safety and electrical stability of ENO®, TEO®, or OTO® pacing systems at 1 month post-MRI at 1.5 and 3 T. Even if artifacts were noticed in a subset of examinations, overall interpretability was preserved.Clinical relevance statementENO®, TEO®, and OTO® pacing systems switch to MR-mode when detecting magnetic field and switch back on conventional mode after MRI. Their safety and electrical stability at 1 month post MRI were shown at 1.5 and 3 T. Overall interpretability was preserved.Key Points• Patients implanted with an MRI conditional cardiac pacemaker can be safely scanned under 1.5 or 3 Tesla MRI with preserved interpretability.• Electrical parameters of the MRI conditional pacing system remain stable after a 1.5 or 3 Tesla MRI scan.• The automated MRI mode enabled the automatic switch to asynchronous mode in the MRI environment and to initial settings after the MRI scan in all patients.