Chronic Pacing Research Articles

Cellular calcium handling and electrophysiology are modulated by chronic physiological pacing in human induced pluripotent stem cell-derived cardiomyocytes.

Electric pacing of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) has been increasingly used to simulate cardiac arrhythmias in vitro and to enhance cardiomyocyte maturity. However, the impact of electric pacing on cellular electrophysiology and Ca2+ handling in differentiated hiPSC-CM is less characterized. Here we studied the effects of electric pacing for 24 h or 7 days at a physiological rate of 60 beats/min on cellular electrophysiology and Ca2+ cycling in late-stage, differentiated hiPSC-CM (>90% troponin+, >60 days postdifferentiation). Electric culture pacing for 7 days did not influence cardiomyocyte cell size, apoptosis, or generation of reactive oxygen species in differentiated hiPSC-CM compared with 24-h pacing. However, epifluorescence measurements revealed that electric pacing for 7 days improved systolic Ca2+ transient amplitude and Ca2+ transient upstroke, which could be explained by elevated sarcoplasmic reticulum Ca2+ load and SERCA activity. Diastolic Ca2+ leak was not changed in line-scanning confocal microscopy, suggesting that the improvement in systolic Ca2+ release was not associated with a higher open probability of ryanodine receptor (RyR)2 during diastole. Whereas bulk cytosolic Na+ concentration and Na+/Ca2+ exchanger (NCX) activity were not changed, patch-clamp studies revealed that chronic pacing caused a slight abbreviation of the action potential duration (APD) in hiPSC-CM. We found in whole cell voltage-clamp measurements that chronic pacing for 7 days led to a decrease in late Na+ current, which might explain the changes in APD. In conclusion, our results show that chronic pacing improves systolic Ca2+ handling and modulates the electrophysiology of late-stage, differentiated hiPSC-CM. This study might help to understand the effects of electric pacing and its numerous applications in stem cell research including arrhythmia simulation.NEW & NOTEWORTHY Electric pacing is increasingly used in research with human induced pluripotent stem cell cardiomyocytes (hiPSC-CM), for example to simulate arrhythmias but also to enhance maturity. Therefore, it is mandatory to understand the effects of pacing itself on cellular electrophysiology in late-stage, matured hiPSC-CM. This study provides an electrophysiological characterization of the effects of chronic electric pacing at a physiological rate on differentiated hiPSC-CM.

Real-world evidence of implanting leadless pacemakers after transcatheter aortic valve implantation procedures

Abstract Background Conduction disturbances can be a complication of Transcatheter Aortic Valve Implantation (TAVI) procedures, for which transvenous pacemakers (TVPs) are recommended. Leadless pacemakers (LPs) are a safe alternative to TVPs in a pacemaker-indicated population, but little is known about their use for TAVI-related conduction disturbances. Purpose To examine rates of pacemaker implantation post-TAVI, compare complications, all-cause mortality, and ventricular pacing rates in LP vs. TVP patients, and assess pacemaker deactivations/upgrades in LP patients. Methods Data from Optum’s de-identified Clinformatics Data Mart Database linked to a device registry between 2016 and 2021 were used to identify patients with TAVI procedures that are subsequently implanted with an LP or a TVP. Claims data were used to assess complications and all-cause mortality; device-reported parameters were used to calculate VP rates and deactivations. Complication rates, all-cause mortality, ventricular pacing rates, and device deactivations were calculated for patients with a pacemaker implant between 7 days before and 90 days after TAVI. Chronic complication rates, defined as complications with the potential to occur outside the acute peri- or post-procedural period, were assessed at 1 year. Regressions were used to compare complications and all-cause mortality, adjusting for patient characteristics. Results In a cohort of 18,073 patients with a TAVI procedure, 11.7% were implanted with a pacemaker at 1 year post-TAVI; 76.7% of implants occurred within 7 days. LPs comprised 7.2% of the total pacemaker implants observed. Of those LPs in the registry, around 25% have VDD capability. LP patients were older (avg. 84 LP, 82 TVP, p=0.02) and were more likely to have atrial fibrillation, end-stage or chronic kidney disease, and ventricular arrhythmias. Of patients implanted with a pacemaker within 90 days post-TAVI (LP N=122, TVP N=1,779), there were no differences in 30-day complication rates (12.3% LP, 15.6% TVP, unadj. p=0.33, adj. p=0.27). LP had fewer chronic complications than TVP (0.8% LP, 9.4% TVP, unadj. p=0.02, adj p=0.02) though the sample size was small. LP patients had higher unadjusted 30-day all-cause mortality (4.1% LP, 1.0% TVP, unadj. p=0.01, adj. p=0.06), reflecting the higher acuity of LP patients. At both 30 days and 1 year post-implant, most patients (85.3% LP, 72.7% TVP) continued to receive pacing support (ventricular pacing >10%). TVP patients were more likely than LP patients to be pacing dependent (ventricular pacing ≥90%) at both 30 days (53.8% vs. 29.4%) and 1 year (44.7% vs. 35.7%) post-implant. There were no observed deactivations/upgrades in LP patients at 1 year. Conclusion LPs, when used concomitantly with TAVI procedures, show similar acute and lower chronic complication rates compared to patients treated with TVPs implanted with TAVI. Most patients who received a pacemaker post-TAVI continue to receive pacing support.Acute and Chronic complicationsVentricular pacing

Right ventriculography to guide left bundle branch pacing in pacing-induced cardiomyopathy: a novel case report

Abstract Background There is emerging evidence for the potential utility of left bundle branch area pacing (LBBAP), as an alternative to conventional cardiac resynchronization therapy (CRT). The utility of right ventriculography by way of power injector to facilitate lead placement has not yet been reported in the literature. Case summary A 79-year-old female, with a background of poorly rate-controlled atrial fibrillation, presented with worsening dyspnoea. She had recently undergone single-chamber pacemaker insertion prior to an atrioventricular nodal (AVN) ablation, owing to failure in achieving successful CRT coronary sinus lead placement. She had clinical evidence of volume overload, and her electrocardiogram demonstrated right ventricular pacing. Echocardiography demonstrated left ventricular (LV) impairment, with an ejection fraction (EF) of 35%, and severe functional mitral regurgitation (MR). Her diagnosis was overall consistent with pacing-induced cardiomyopathy (PIC). In this patient, the use of right ventriculography, using power-injector-delivered contrast, successfully facilitated placement of an LBBAP lead, with confirmation of good threshold and sensing parameters. Following an upgrade to conduction system pacing, the patient recovered well. On recent follow-up, repeat echocardiography (24 months post initial presentation) demonstrated improved LV function (EF 45% from 35%) and only mild-to-moderate MR. Discussion In conclusion, we demonstrate the utility of right ventriculography to facilitate placement of an LBBAP lead, successfully treating a patient who developed PIC from chronic right ventricular pacing following AVN ablation.

Chronic Right Ventricular Pacing Post-Transcatheter Aortic Valve Replacement Attenuates the Benefit on Left Ventricular Function.

Background: Conduction abnormality post-transcatheter aortic valve implantation (TAVI) remains clinically significant and usually requires chronic pacing. The effect of right ventricular (RV) pacing post-TAVI on clinical outcomes warrants further studies. Methods: We identified 147 consecutive patients who required chronic RV pacing after a successful TAVI procedure and propensity-matched these patients according to the Society of Thoracic Surgeons (STS) risk score to a control group of patients that did not require RV pacing post-TAVI. We evaluated routine echocardiographic measurements and performed offline speckle-tracking strain analysis for the purpose of this study on transthoracic echocardiographic (TTE) images performed at 9 to 18 months post-TAVI. Results: The final study population comprised 294 patients (pacing group n = 147 and non-pacing group n = 147), with a mean age of 81 ± 7 years, 59% male; median follow-up was 354 days. There were more baseline conduction abnormalities in the pacing group compared to the non-pacing group (56.5% vs. 41.5%. p = 0.01). Eighty-eight patients (61.6%) in the pacing group required RV pacing due to atrioventricular (AV) conduction block post-TAVI. The mean RV pacing burden was 44% in the pacing group. Left ventricular ejection fraction (LVEF) was similar at follow-up in the pacing vs. non-pacing groups (57 ± 13.0%, 59 ± 11% p = 0.31); however, LV global longitudinal strain (-12.7 ± 3.5% vs. -18.8 ± 2.7%, p < 0.0001), LV apical strain (-12.9 ± 5.5% vs. 23.2 ± 9.2%, p < 0.0001), and mid-LV strain (-12.7 ± 4.6% vs. -18.7 ± 3.4%, p < 0.0001) were significantly worse in the pacing vs. non-pacing groups. Conclusions: Chronic RV pacing after the TAVI procedure is associated with subclinical LV systolic dysfunction within 1.5 years of follow-up.

Abstract We094: Acute Administration of The Novel Cardiac Sarcomere Modulator EDG-7500, Improves Ventricular Filling While Preserving LVEF In Dogs with Pacing Induced Left-Ventricular Systolic Dysfunction

Introduction: EDG-7500 is a cardiac sarcomere modulator that has been shown to slow early LV contraction and to improve diastolic filling, without directly inhibiting cardiac myosin. To assess the acute hemodynamic effects of EDG-7500 in a model of depressed systolic and diastolic LV function, we studied dogs with pacing-induced LV dysfunction before and after EDG-7500 administration. Methods: Beagle dogs (n = 7) underwent chronic RV pacing (180 to 240 ppm), and were studied, in sinus rhythm, at two levels of induced-dysfunction: mid-range EF (mEF, targeting 50%), and reduced EF (rEF, targeting 40%). At each level, animals were evaluated by echocardiography before and after administration of 0.3 mg/kg IV EDG-7500. Healthy beagle dogs served as disease controls (n = 7). Results: Post-pacing (Paced) dogs had depressed EF (mEF: 50 ± 4 and rEF: 40 ± 4 vs. 74 ± 1%, P &lt; 0.05) and short-axis global circumferential strain (mEF: -23 ± 2 and rEF: -14 ± 2 vs. -33 ± 1%, P &lt; 0.05), and elevated NT-proBNPs (mEF: 1,049 ± 319 and rEF: 4,236 ± 722 vs. 302 ± 27 pmol/L, P &lt; 0.05) when compared vs. healthy dogs. Paced dogs had slower early diastolic mitral annular velocity (mean e’, mEF: 11.0 ± 0.9 and rEF: 8.4 ± 0.8 vs. 14.2 ± 0.7 cm/s, P &lt; 0.05) and elevated E/e’ (mEF: 7.4 ± 0.7 and rEF: 8.4 ± 0.9 vs. 6.0 ± 0.2 n/u, P &lt; 0.05), at similar heart rates. Acute EDG-7500 increased e’ (mean e’, mEF: +9 ± 2 and rEF: +12 ± 3%, P&lt;0.05) and decreased E/e’ (mEF: -7 ± 2% and rEF: -9 ± 2%, P&lt;0.05), with no detectable effects on EF (mEF: +3 ± 6% and rEF: -5 ± 3%, P=NS). There were no adverse clinical observations. Conclusions: Treatment with EDG-7500 was well tolerated in dogs with tachycardia-induced mid-range (mEF) and reduced LV systolic function (rEF). In both cases, EDG-7500 improved echocardiographic indices of early ventricular filling and filling pressures, without observable effect on systolic performance. This data supports exploration of the effects of EDG-7500 in patient populations with LV diastolic dysfunction and mild to moderately reduced cardiac systolic performance.

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.

Time-dependent activation and repolarization changes following left bundle branch area pacing versus conventional biventricular pacing in patients with dyssynchronous heart failure

Abstract Background Cardiac Resynchronization Therapy (CRT) is the standard treatment for patients with dyssynchronous heart failure. Despite the effectiveness of conventional biventricular pacing (BiVP), 6-16% of patients develop ventricular tachyarrhythmias (VTAs) within a year of implantation. The relationship between BiVP and the development of VTAs is still under debate. During BiVP, the left-sided epicardium-to-endocardium activation creates a non-physiological activation and hence a non-physiological repolarization, which might trigger VTAs. A novel alternative treatment option to BiVP that on the contrary induces a left ventricular endocardium-to-epicardium activation, is left bundle branch area pacing (LBBAP). We hypothesized that LBBAP leads to a more homogenous repolarization than conventional BiVP. Purpose To compare time-dependent activation and repolarization changes in patients with dyssynchronous heart failure receiving LBBAP versus BiVP. Methods Patients eligible for CRT who underwent LBBAP (n=21) or BiVP (n=94) were retrospectively included. Standard 12-lead electrocardiograms obtained prior to implantation [baseline], shortly following implantation (0-2 days, [acute phase]), and after prolonged pacing during follow-up (31-180 days, [chronic phase]) were analyzed. QRS duration and QRS area were calculated through reconstruction of the vectorcardiogram and further analyzed together with corrected QT (QTc) and corrected Tpeak-Tend (Tp-e,c) intervals using a semi-automatic approach in MATLAB. Differences between LBBAP and BiVP patients were determined using the Mann-Whitney U-test. Time-dependent changes within groups were determined using the Wilcoxon signed-rank tests. Significance was defined as a p-value ≤0.05. Results (see figure): Compared to baseline, QRS duration and QRS area decreased significantly during the acute phase (both p &amp;lt; 0.01) and stabilized during chronic pacing for both BiVP and LBBAP patients. Differences in QRS duration or QRS area between LBBAP and BiVP were not significant at any of the time points. In the acute phase, BiVP resulted in a temporary and significant prolongation of both QTc and Tp-e,c compared to baseline (both p &amp;lt; 0.01). However, there was a subsequent shortening observed between the acute and chronic phases for both QTc and Tp-e,c (both p &amp;lt; 0.01). Compared to baseline, LBBAP acutely shortened Tp-e,c (p = 0.02) and tended to shorten QTc. During chronic pacing, LBBAP shortened QTc and Tp-e,c compared to baseline (p = 0.01 and p &amp;lt; 0.01). The decreases in QTc and Tp-e,c were larger in LBBAP than in BiVP patients in the acute and chronic pacing phase (all p &amp;lt;0.01). Conclusion CRT induces activation changes in both BiVP and LBBAP patients to a comparable extent. While BiVP leads to an acute increase in repolarization dispersions, LBBAP reduces markers of repolarization dispersion compared to baseline. The diminished dispersion of repolarization might contribute to an antiarrhythmic effect with LBBAP.

Left bundle branch area pacing in the setting of cardiac amyloidosis: a case series

Abstract Background Cardiac amyloidosis (CA) is a highly prevalent cause of congestive heart failure. It often requires cardiac pacing due atrioventricular conduction (AV) system disorders, often with cardiac resynchronization (CRT) to prevent development/deterioration of left ventricular (LV) dysfunction. Left bundle branch area pacing (LBBAP) is an emerging alternative to CRT, offering a strict physiological LV activation and very limited use of iodinated contrast. The feasibility of LBBAP in CA is considered limited due to the presence of septal pseudohypertrophy which theoretically limits left-sided conduction system engagement. Purpose To evaluate the feasibility and effectiveness of LBBAP in cardiac amyloidosis. Methods Consecutive patients with CA (both light-chain -AL- or wild-type transtiretin -wtATTr) with a pacing indication for AV conduction disorders were enrolled. Patients underwent baseline echocardiographic examination. LBBAP was achieved by means of stylet-driven leads advanced transeptally (right ventricle (RV) to LV) via dedicated delivery systems, with continuous monitoring of 12-lead electrocardiographic morphology and impedance until a typical QRS morphology in V1 was obtained (usually rSr’ or Sr’). Standard measures for left bundle (LB) capture were used (stimulus to peak R in V6 – S-RV6, V6-V1 interpeak interval, presence of transition in these measures during threshold testing, presence of fascicular signal during spontaneous QRS). Results Between January 2022 and June 2023, among 63 patients undergoing LBBAP, 7 patients (11%) had CA, 2 AL (28%) and 5 (72%) wtATTR. Patients were prevalently old (78±7 y) males (6, 85%); LV mean septal thickness was 17±2 mm (min 16, max 20 mm) and mean LV ejection fraction (LVEF) was 45±6%. Indications were PR prolongation in 3, bradycardic atrial fibrillation and LB branch block (LBBB) in 2, primary LBBB in 1 and chronic RV pacing in 1. Baseline QRS duration was 145±47 ms (QRS&amp;lt;120 ms: 97±15 ms, QRS&amp;gt;120 ms: 182±13 ms). LBBAP success was 100%. Fascicular electrograms were observed in ¾ of patients without LBBB; S-RV6 interval was 74 ±11 ms (³70 ms in 3), RV6-RV1 interpeak interval was 47±9 ms (³ 30 ms in 6 patients). DQRS in baseline broad QRS was -52 ms and +32 ms in narrow. No complications were observed. Over a short follow up of 6 months, an increase in average LVEF was observed (LVEF at 6 months: 51±3%, p&amp;lt;0.05). Conclusions In patients with CA, LBBAP is easily achievable with stylet-driven systems with frequent selective engagement of conduction system. QRS narrowing in baseline broad QRS is significant while QRS broadening in baseline narrow QRS is limited. Early results regarding follow-up of surrogate endpoint such as LVEF are promising.

Left ventricular global longitudinal strain is a long-term predictor of pacemaker-associated cardiomyopathy

Abstract Background Implantation of a permanent pacemaker is an effective treatment for symptomatic bradycardia. However, chronic right ventricular pacing (RVP) may lead to compromised left ventricular (LV) function, atrial fibrillation, heart failure, and increased mortality via pacing induced electrical and mechanical dyssynchrony. A decrease in LV ejection fraction (LVEF) of ≥ 10% with a baseline LVEF &amp;gt; 50% prior to RVP and no alternative explanation for the decline in LVEF is termed pacing-induced cardiomyopathy (PICM). Predictive clinical and imaging-derived measures to identify patients at high risk for pacemaker induced cardiomyopathy (PMIC) are lacking, but essential. Objective The study is a prospective, single center, double-blinded trial evaluating the impact of right ventricular pacing on left ventricular function and clinical outcome. Methods In 105 patients (59 male / 46 female), who underwent a dual-chamber pacemaker implantation at the Charité Campus Virchow Klinikum, RVP burden, LVEF and left ventricular global longitudinal strain (LV-GLS) were obtained. Mean follow-up per patient was 29.6 ±13.9 months. We used a stepwise analytic approach including ROC analysis, univariate testing, binary regression as well as Cox-regression models and Kaplan-Meier analysis to compare low RVP burden (&amp;lt; 30%) and high RVP burden (≥ 30%) cohorts according to change in echocardiographic parameters and clinical outcome (all-cause mortality). Results Mean LVEF was 61 ± 6% and mean LV-GLS was 18 ± 4% at baseline. We identified 7 patients with a LVEF decline in the course of the study. In Pearson’s Chi-squared test, patients with a high RVP burden were more likely to develop LVEF and LV-GLS deterioration (6 patients versus 1 patient for LVEF, p&amp;lt;0.05; 28 versus 16 patients for LV-GLS, p&amp;lt;0.001). In multivariable binary logistic regression, LV-GLS (OR: 1.410, 95% CI: 1.201-1.610, p&amp;lt;0.001) deterioration was significantly associated with a LVEF decline and a high RVP burden ≥ 30% (OR: 1.358, 95% CI: 1.160-1.534, p&amp;lt;0.01). In a log-rank test, time to LVEF decline was significantly shorter in patients with a RVP burden ≥ 30% compared to a RVP burden &amp;lt; 30% (45.2±2.9 versus 55.7±1.0 months, p&amp;lt;0.05). In the Cox-regression analysis, LV-strain decline within 12 months (HR: 7.210, 95% CI: 4.239-9.516, p&amp;lt;0.05) was a significant predictor for a later LVEF decline. In a log-rank test, time to LVEF deterioration was significantly shorter in patients with LV-strain decline within 12 months compared to those without (34.7 ± 4.2 versus 53.7 ± 1.4 months, p&amp;lt;0.001). No significant difference in all-cause mortality between patients with a high RVP burden compared to those with low RVP burden (log-rank test, p=0.2). Conclusion A decline in LV-GLS is a sensitive long-term parameter of subsequent LVEF deterioration in patients with normal preimplant LVEF, who require RVP ≥ 30%. and is associated with a poor clinical outcome.

Development of chronic thresholds in His bundle pacing: single-center experience over 7 years in 426 patients

Abstract Background Conduction system pacing (CSP), e. g. by His bundle pacing (HBP) has the potential to perform highly synchronized ventricular pacing in patients with AV block and narrow QRS complex or right bundle branch block. Therefore, CSP is recommended in these patients to prevent pacing-induced cardioomyopathy. However, there have been reports about an acute and chronic threshold increase in HBP that may cause asystole in pacemaker-dependent patients. Purpose We checked the development of chronic pacing thresholds, the incidence of dislodgements and of consecutive asystole in patients with HBP. Methods All consecutive patients with HBP attempted in our center between 6/2016 and 11/2023 were enrolled. Pacing and sensing parameters over 36 months together with the follwing events were collected and analyzed: His bundle lead dislodgement, loss of capture, threshold increase to ≥3.0V/1.0 ms, emergency admission due to syncope with loss of HBP and asystole. Results In 426 patients (78±11 years, 38% female, 90% AV block, left ventricular ejection fraction 54±10%), HBP was attempted and in 388 patients successful (47% non-selective, 53% selective HBP), 16 patients were converted to left bundle branch area pacing, 22 implantations attemps were unsuccessful. Pacing and sensing performance during follow-up are listed in the Fig. There were 3 lead dislodgements (2 patients with Twiddler syndrome), 1 loss of capture (patient with sinus node disease), and 13 increases of pacing thresholds to ≥3.0V/1.0 ms, summing up to 17 events over 3 years (4.3%). No patient had a clinical event due to threshold increase or loss of HBP capture. All His bundle threshold increases were clinically silent because patients were not pacemaker-dependent, had non-selective HBP with myocardial capture serving as a "back-up" or due to a previously implanted right ventricular back-up lead. Conclusions There is a modest pacing threshold increase in His bundle thresholds from 1.1 to 1.8V@1.0 ms over a period of 3 years. However, this did not cause clinically relevant events in our patient cohort.Chronic pacing and sensing parameters

Abnormal conduction-induced cardiomyopathy: a poorly explored entity.

A dyssynchronous biventricular activation, which can be determined by left bundle branch block, chronic right ventricular pacing, frequent premature ventricular complexes, or pre-excitation, can cause a global abnormal contractility, thus leading to systolic dysfunction and left ventricular remodelling in a unique nosological entities: abnormal conduction-induced cardiomyopathies. In this clinical scenario, the mainstay therapy is eliminating or improving LV dyssynchrony, removing the trigger. This usually ensures the improvement and even recovery of cardiac geometry and left ventricular function, especially in the absence of genetic background. A multidisciplinary approach, integrating advanced multimodal imaging, is essential for the systematic aetiological definition and the subsequent evaluation and aetiology-guided therapies of patients and their families. This review aims to describe mechanisms, prevalence, risk factors, and diagnostic and therapeutic approach to the various abnormal conduction-induced cardiomyopathies, starting from reasonable certainties and then analysing the grey areas requiring further studies.

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.

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.

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

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

Loss of capture of conduction system pacemaker caused by fibrosis surrounding the lead: a case report

BackgroundConduction system pacing (CSP) is a novel technique that involves pacing the His-Purkinje system instead of the traditional right ventricular (RV) apex. This technique aims to avoid the adverse effects of RV apical pacing, which can lead to ventricular dyssynchrony and heart failure over time. CSP is gaining popularity but its long-term efficacy and challenges remain uncertain. This report discusses a case where CSP was initially successful but faced complications due to an increasing pacing threshold.Case presentationA 65-year-old female with total atrioventricular block was referred for brady-pacing. Due to the potential for chronic RV pacing, CSP was chosen. The CSP implantation involved subcutaneous device placement, with a CSP lead in the left bundle branch area (LBBA) and an RV backup lead. A year after successful implantation, the LBBA pacing threshold progressively increased. Subsequent efforts to correct it led to anodal capture and battery depletion. Cardiac magnetic resonance imaging (CMR) revealed mid-septal fibrosis at the area of LBBA lead placement and suggested cardiac sarcoidosis as a possible cause.ConclusionCSP is a promising technique for treating bradyarrhythmias, but this case underscores the need for vigilance in monitoring pacing thresholds. Increasing thresholds can render CSP ineffective, necessitating alternative pacing methods. The CMR findings of mid-septal fibrosis and the potential diagnosis of cardiac sarcoidosis emphasize the importance of pre-implantation assessment, as CSP may be compromised by underlying structural abnormalities. This report highlights the complexities of pacing strategy selection and the significance of comprehensive evaluation before adopting CSP.

Conduction System Pacing for Patients with Congenital Heart Disease.

For patients with congenital heart disease (CHD), chronic ventricular pacing may lead to progressive cardiomyopathy owing to electromechanical dyssynchrony. Cardiac conduction system pacing (CSP) has been proposed as a physiologic pacing strategy-directly engaging the His-Purkinje system and preserving electromechanical synchrony. CSP may be indicated for a wide variety of children and adults with CHD and has emerged as an important tool in the armamentarium for cardiac implantable electronic device operators. This review provides the rationale, background, and supportive evidence for CSP in patients with CHD and discusses implant strategies and outcomes in the context of dominant ventricular morphologic categories.

Pacemaker-induced cardiomyopathy.

Chronic right ventricular (RV) pacing is an often-unrecognized cause of cardiomyopathy, despite research that has revealed that chronic RV pacing can cause significant cardiomyopathy and heart failure, leading causes of hospitalization in the United States. Studies have found that chronic RV apical pacing results in ventricular dyssynchrony, reduced cardiac function, and heart failure. This article describes the deleterious effects of permanent cardiac pacemakers and their association with cardiomyopathy and heart failure. More research is needed to investigate other forms of pacing and treatment to prevent ventricular dyssynchrony and myocardial remodeling.

Conduction system pacing on track to replace CRT? Review of current evidence and prospects of conduction system pacing.

Conduction system pacing (CSP) has been emerging over the last decade as a pacing option instead of conventional right ventricular (RV) pacing and biventricular (BiV) pacing. Numerous case reports, some observational studies and a few randomized control trials have looked at optimum pacing strategies for heart failure (HF) with left bundle branch block (LBBB) or cases where left ventricular (LV) dysfunction is anticipated due to chronic RV pacing (RVP). Evolution of pacing strategies from standard RVP to septal RVP, BiV pacing and now CSP have shown improving hemodynamic responses and possible ease of implantation of CSP systems. In this review article, we review the literature on the evolution of CSP and common scenarios where it might be beneficial.

Pacing of Specialized Conduction System.

Right ventricular pacing for bradycardia remains the mainstay of pacing therapy. Chronic right ventricular pacing may lead to pacing-induced cardiomyopathy. We focus on the anatomy of the conduction system and the clinical feasibility of pacing the His bundle and/or left bundle conduction system. We review the hemodynamics of conduction system pacing, the techniques to capture the conduction system and the electrocardiogram and pacing definitions of conduction system capture. Clinical studies of conduction system pacing in the setting of atrioventricular block and after AV junction ablation are reviewed and the evolving role of conduction system pacing is compared with biventricular pacing.

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.