Atrioventricular Synchrony Research Articles

Left atrial strain is a good predictor of atrio-ventricular synchrony in leadless pacemaker pacing.

The importance of atrio-ventricular synchrony pacing in sinus rhythm patients is known. To identify patients in whom leadless pacemakers are able to guarantee this atrio-ventricular synchrony, we explored correlations among echocardiographic measures of left atrial (LA) size and function (doppler parameter and strain) with A4 amplitude in patients implanted with new generation Micra-AV device. After implantation with Micra-AV system, patients underwent device interrogation to evaluate AV synchrony based on the sensing of atrial mechanics and echocardiographic exam to assess LA morphology and LA function. In the 21 studied patients (14 males, 72 ± 13 years), the A4 wave amplitude values inversely correlated with LA antero-posterior diameter, LA volume, LA contraction strain and LA conduit strain, while they were positively related with LA reservoir strain. Our results indicate a statistically significant relationship between morphological echocardiographic LA parameters and atrial contraction signal (A4), detected by leadless pacemakers and used to synchronize ventricular pacing with the atrium. Instantaneous LA function assessment obtained with LA strain provides incremental information over morphological parameters. LA strain evaluates atrial myocardial deformation during the whole cardiac cycle. We found higher value of A4 in patients that have grater absolute value of LAsr, LAscd and LAsct, that are simple and measurable parameters of LA functional capacity. Preimplant echocardiographic evaluation of the atrial contractility may be useful in predicting adequate A4 sensing and consequently a good atrio-ventricular synchrony pacing. Echocardiography LA strain study seems promising in Micra-AV patient selection.

Conversion to Sinus Rhythm in Refractory Atrial Fibrillation Patients after Atrioventricular Node Ablation with Conduction System Pacing.

"Ablate and pace" strategy is a reasonable treatment option in refractory atrial fibrillation (AF) when sinus rhythm (SR) cannot be achieved with catheter ablation or pharmacological therapy. Atrioventricular node ablation (AVNA) combined with conduction system pacing (CSP), with left bundle branch pacing (LBBP) or His bundle pacing (HBP), is gaining recognition since it offers the most physiological activation of the left ventricle. However, the incidence of conversion to SR after AVNA with CSP is not known. The purpose of the investigation was to determine the incidence of spontaneous conversion to SR and its predicting factors in patients undergoing CSP and AVNA. Consecutive refractory symptomatic AF patients undergoing AVNA with CSP at our institution between June 2018 and December 2022 were retrospectively analyzed. Twelve lead electrocardiogram (ECG) recordings were analyzed at each outpatient follow-up visit. Echocardiographic and clinical parameters were assessed at baseline and six months after the implantation. Sixty-eight patients (male 42.6%, age 71 8 years, left ventricular ejection fraction 40 15%) were included. Thirty-seven patients (54.4%) received HBP and 31 (45.6%) LBBP. During follow-up, spontaneous conversion to SR was registered in 6 patients (8.8%); 3 in the HBP group and 3 in the LBBP group. Baseline characteristics of patients who converted to SR did not differ from non-sinus rhythm (NSR) patients except for left atrial volume index (LAVI), which was significantly smaller in the SR group (45 mL/ (41-51) vs. 60 mL/ (52-75); p = 0.002). Multiple regression model confirmed an inverse association between LAVI and conversion to SR even after considering other clinically relevant covariates (odds ratio 1.273, p = 0.028). At follow-up, LAVI did not change in any group (SR: p = 0.345; NSR: p = 0.508). Improvement in New York Heart Association (NYHA) class was comparable in both groups. Spontaneous conversion to SR after AVNA combined with CSP is not uncommon, especially in patients with smaller left atria. Further studies are warranted to clarify which patients should be considered for initial dual-chamber device implantation to provide atrio-ventricular synchrony in case of SR restoration.

A leadless ventricular pacemaker providing atrioventricular synchronous pacing in the real-world setting: results from the Micra AV post-approval registry

Abstract Introduction Advances in leadless pacemaker technology have enabled accelerometer based atrioventricular synchronous (AVS) pacing by sensing atrial mechanical contraction. However, longer-term performance of these devices in real-world clinical practice has not been assessed. Objectives To report the performance of the Micra AV transcatheter pacemaker from the worldwide Micra AV post-approval registry (PAR) through 1-year post-implant. Methods The Micra AV PAR is an ongoing prospective single-arm observational study designed to assess the safety and effectiveness of the Micra AV system in the real-world setting. Patients enrolled in the Micra AV PAR will be followed for 3 years. For the present interim analysis, baseline characteristics, total AV synchrony index (sum of %AM-VP, %AM-VS, and AV conduction mode switch percentage), major complications, and system revisions through 12-months of implant were summarized and compared to a historical cohort of 2,667 transvenous dual chamber (TV-DC) pacing patients. Results The device was successfully implanted in 797 of 801 patients (99.4%) at 98 centers in 19 countries between February 2020 and April 2022. Mean age was 74.1±15.1 years, 42.2% were female, and 31.3% were precluded from transvenous device therapy. Micra AV patients were on average older (74.1 vs. 71.1 yrs, P<0.0001) and had a significantly higher incidence of renal disease (22.3% vs. 9.8%, P<0.0001) compared with TV-DC patients. Mean follow-up was 7.7±6.4 months. Through 12-months, the major complication rate was 4.2% in Micra AV patients compared to 8.8% TV-DC patients (HR: 0.48, P<0.001, Figure). At 12-months, the system revision rate was 1.9% in Micra AV patients compared to 5.5% for TV-DC patients (HR: 0.28, P<0.001). The reduction in system revisions was largely driven by the absence of lead dislodgements requiring revision. Of the 397 patients with device interrogation files available for analysis, 315 (79.4%) were programmed to VDD mode at last follow-up and had a median AV synchrony index of 86.4% (IQR: 68.8% - 97.4%). Conclusions The Micra AV leadless pacemaker was implanted with a high rate of success in patients with a high co-morbidity burden, with a significantly lower rate of complications and system revisions through 12-months compared to dual-chamber transvenous pacemakers despite patients being older and having a higher incidence of renal disease. Longer-term performance will continue to be assessed in this ongoing trial.Major Complications Through 12-months

Abstract 13903: Pacemaker Mediated Arrhythmia Following AV Synchronous Leadless Pacemaker Implantation

Background: Leadless pacemakers have gained popularity in providing permanent pacing in select patient populations. Pacemaker mediated tachycardia and arrhythmias have been well described in patients with dual chamber pacemakers, but up to this point not in leadless pacing. Case Description: A 91-year-old female with symptomatic bradycardia and 2:1 AV block underwent implantation of a Micra AV pacemaker programmed VDD 60-100 bpm. Five months later, she presented with decompensated heart failure with a heart rate of 88 bpm and a newly reduced left ventricular ejection fraction of 30%. Device interrogation showed 95% ventricular pacing, with 91% AV synchrony. The Micra was found to be tracking an atrial rhythm between 80-100 bpm more than 80% of the time (Figure 1A). RV pacing induced cardiomyopathy was suspected and she underwent placement of a bi-ventricular pacemaker. During implant, a short VA time was noted and changes in the V-V cycle length predicted changes in the A-A cycle length (Figure 1B). Micra ventricular pacing was held resulting in an AV paced rhythm from the CRT system and a drop in rate to 60 bpm (Figure 1C). These results indicate that the Micra pacemaker was tracking the atrial mechanical contraction (AM) from a retrograde conducted P-wave resulting in elevated heart rates from a pacemaker-driven arrhythmia. Discussion: In patients with poor AV conduction, intact VA conduction, and SA node dysfunction, Micra AV may create pacemaker mediated arrhythmia by tracking the AM of the retrograde conducted P-wave. Careful patient selection to avoid Micra AV placement in patients with SA node dysfunction, and close attention to the rate histogram on device interrogation may prevent development and facilitate recognition of this unique cause of pacemaker-mediated arrhythmia.

Left bundle branch pacing in alternating bundle branch block

We present a case of symptomatic intermittent AV block showing during monitorization alternating bundle branch block. Presuming a high need of pacing, conduction system pacing was considered a more physiological alternative in this patient. Left bundle branch pacing restored a stable atrioventricular synchrony with a paced QRS complex similar to the native one and might be a good alternative in these cases.

Acute lymphocytic myocarditis presenting as complete heart block in an adult: a case report

BackgroundComplete heart block (CHB) as a first presentation of acute viral myocarditis is a rare occurrence associated with increased morbidity and mortality. In such cases, an endomyocardial biopsy is recommended to make a clear histological diagnosis aiding to differentiate from other possible conditions such as sarcoiditic myocarditis, giant cell myocarditis, and eosinophilic myocarditis. Insertion of a permanent pacemaker may be considered on a case-to-case basis.Case presentationA previously healthy 21-year-old female presented to the emergency department after having suffered two episodes of syncope on a background of a few days’ history of myalgias, chills, and rigors. Electrocardiogram showed high-grade Mobitz II block with intermittent periods of CHB. A bedside echocardiogram upon admission demonstrated normal biventricular systolic function. Given the patient’s unstable haemodynamic status and lack of obvious reversible causes for the CHB, a permanent dual-chamber pacemaker was inserted urgently. Initial blood investigations indicated an ongoing inflammatory process highlighting the possibility of myocarditis as a cause of the CHB. Therefore, a troponin level was taken and was noted to be elevated confirming the suspicion of myocarditis. The left ventricular ejection fraction (LVEF) decreased over the following days to approximately 20%, clinically resulting in pulmonary oedema and acute shortness of breath. The patient required aggressive intravenous diuresis and anti-heart failure medication. An endomyocardial biopsy (EMB) confirmed the diagnosis of lymphocytic myocarditis. The patient’s condition improved secondary to an improvement in LVEF and resolution of the heart block. A cardiac magnetic resonance (CMR) imaging performed 6 weeks from admission reported an improved LVEF of 51% with no late gadolinium enhancement (LGE). Based on the reassuring CMR findings and the resolution of CHB on follow-up pacemaker checks, it was deemed safe to explant the pacemaker.ConclusionsAcute myocarditis may be complicated with high-degree AV block and cardiogenic shock necessitating close observation in a critical care unit. A permanent pacemaker may provide atrio-ventricular synchrony which helps stabilise the patient’s condition and protect from a prolonged period of heart block. Early myocardial fibrosis on EMB and degree of LGE on CMR are indicators of persistent atrioventricular block. Guideline-directed treatment of heart failure is essential.

Electrical Synchrony Optimization for Left Bundle Branch Area Pacing in Patients With Bradycardia and Heart Failure

Left bundle branch area pacing (LBBAP) has emerged as a promising physiological pacing modality. This study was designed to investigate the acute impact of the atrioventricular delay (AVD) on cardiac electrical characteristics and identify an optimal range of AVDs for LBBAP to achieve electrical atrioventricular and interventricular synchrony. Patients indicated for ventricular or biventricular pacing were studied during routine follow-ups at least 3months after LBBAP implantation. Patients were excluded if they had a complete AV block or persistent atrial fibrillation. AVD was programed from 40 to 240ms or until intrinsic conduction occurred. Optimal AVD was determined by the electrocardiography criteria, including QRS duration, reduced R-wave in lead V1, reduced notching or slurring in lateral leads, and more desirable precordial QRS transition. A total of 38 patients (age 68.7 ± 10.3years; 16 male (42%); 18 dual-chamber pacemakers and 20 cardiac resynchronization therapy devices; average follow-up period 15.1 ± 10.2months) were included. The fusion of LBBAP and intrinsic right ventricular conduction occurred in 21 patients with corresponding optimal AVD determined. A great proportion (∼85%) of the optimal AVDs ranged from 50% to 80% of the observed atrium-to-left bundle branch-sensing (A-LBBS) intervals. The linear correlation between the optimal AVD and corresponding A-LBBS interval (optimal AVD=0.84×[A-LBSs interval] - 36ms) produced R=0.86 and p <0.0001. In conclusion, AVD selection during LBBAP greatly impacted the ventricular electrical characteristics and the optimal AVD was linearly correlated with the corresponding A-LBBS interval.

Atrial mechanical contraction and ambulatory atrioventricular synchrony: Predictors from the OPTIVALL study.

The role that preprocedural factors have on atrioventricular synchrony (AVS) provided by leadless pacemakers requires investigation. We aimed to assess the correlation between mitral inflow echocardiographic parameters and p-wave morphology with the accelerometer A4 signal amplitude. We also sought to identify clinical and echocardiographic predictors of optimal ambulatory AVS (≥85% of cardiac cycles). Forty-three patients undergoing Micra AV implant from June 2020 to March 2023 were prospectively enrolled. Baseline echocardiogram and 12-lead resting ECG were performed. Device follow-up was scheduled at 24 h, 1, 3, and 6 months and yearly after the implant. Ambulatory AVS was studied with a 24 h Holter monitor performed at 3 months follow-up in 35 patients who remained in VDD mode. A4 signal amplitude at 1 month correlated to peak A wave velocity (r = .376; p = .024) at echocardiogram, but no relationship was found with peak A' wave velocity, E/A, or E'/A' ratio. P-wave amplitude in lead I and aVF correlated to A4 signal amplitude at 1- and 3-months follow-up, respectively. Median AVS during 24 h of daily activities was 85.6 ± 7.6% and remained stable up to 100 bpm. Twenty-three out of 35 patients (65.7%) reached optimal ambulatory AVS. There was no association between mitral inflow echocardiographic parameters and optimal AVS. Diabetes (OR: 0.05, 95% CI: 0.01-0.47; p = .009) and chronic obstructive pulmonary disease (COPD) (OR: 0.06, 95% CI: 0.01-0.63; p = .019) strongly predicted ambulatory AVS<85%. Diabetes and COPD should be considered when selecting candidates for Micra AV. Measurements of pulsed wave Doppler mitral inflow do not systematically reflect the behavior of the A4 signal amplitude.

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.

Feasibility of novel atrial mechanical sensing method for leadless atrioventricular synchronous pacing

Abstract Funding Acknowledgements Type of funding sources: None. Background/Introduction A novel leadless pacemaker enables atrioventricular synchronous pacing. However, there have been still difficulties to obtain high atrioventricular (AV) synchrony due to a mechanical sensing algorithm. We’ve reported a new sensing method for acquiring high AV synchrony regardless of heart rate. Our hypothesis is that this novel sensing method might facilitate better AV synchrony. Purpose The purpose of this study is to investigate the feasibility of our novel sensing method for the patients that ventricular activity completely depends on the ventricular pacing. Methods This study is a retrospective study conducted by 2 centers. From the 1st December, 2021 to the 31th October, 2022, leadless pacemakers with atrioventricular synchronous pacing were implanted to 32 patients in 2 centers. Among the 20 patients with sinus rhythm and complete AV block were analyzed. Two groups were compared in this study. Novel sensing setting was programmed during the hospitalization in Group 1, composed by 9 patients. Auto A3 threshold and auto A3 window end are turned off. An intentionally prolonged A3 window end and a low A3 threshold are programmed in a novel sensing method. Conventional setting (auto A3 threshold, auto A3 window end and auto A4 threshold were turned on) was programmed during the hospitalization in Group 2, composed by 11 patients. Device check was performed at the first outpatient clinic within 3 months after the implantation. Results Overall, 20 patients were analyzed. Baseline characters are described in Table 1. BMI (23.5±0.9 vs 20.4±0.8, p&amp;lt;0.05), BNP at the hospitalization (130.7±143.6 pg/ml vs 686.9±129.9 pg/ml, p&amp;lt;0.05) were different between 2 groups. Mean age, sex, past history of atrial fibrillation, hypertension, diabetes mellitus, dyslipidemia, past history of coronary artery disease, eGFR, previous cardiac surgery, left ventricular ejection fraction, E/A, left atrial diameter were no significant differences between 2 groups. Table 2 shows the comparison of the device parameters between 2 groups. In Group 1, AV synchrony (%AMVp) was significantly higher at the first outpatient clinic (81.0 ± 4.2 % vs 63.0 ± 5.7 %, p=0.03). A3 window end was significantly longer in Group 1 (883.3 ± 34.0 ms vs 757.0 ± 45.5 ms, p&amp;lt;0.05). A3 threshold was significantly lower in Group 1 (2.3 ± 0.5 m/s² vs 5.9 ± 0.7 m/s², p&amp;lt;0.05). There were no significant differences about A4 amplitude (1.8 ± 0.4 m/s² vs 1.0 ± 0.6 m/s², p=0.34) and A4 threshold (2.3 ± 0.3 m/s² vs 1.5 ± 0.4 m/s², p=0.12). Conclusion Novel sensing method might be a feasible sensing method to obtain higher AV synchrony than conventional algorithm. Further prospective studies will be required.

Optimizing atrial sensing parameters in leadless pacemakers: main findings of the OptiVALL study

Abstract Funding Acknowledgements Type of funding sources: None. Backgroung: The MARVEL2 study demonstrated the feasibility of leadless pacemakers in delivering atrioventricular (AV) synchronous pacing with an accelerometer-based algorithm, for up to 5 h. Purpose To assess the AV synchrony (AVS) the device can provide under daily activities and across different heart rate (HR) ranges, and to describe what programming changes are needed to achieve proper atrial tracking and AVS. Methods The OptiVALL study is a single-centre and prospective study of consecutive patients implanted with MICRA AV. Follow-up was routinely performed at 24 hours and at 1, 3, 6 and 12 months. The pacing mode was programmed to VDD in all patients and AV conduction mode switch (VVI +) was deactivated. In each visit a device check was carried out and reprogramming of the atrial sensing parameters was performed according to the manual atrial mechanical tests, as well as information from device counters and rate histograms. A 24-h Holter monitoring was placed at 3-months follow-up and ECG recorded tracings were automatically and blindly analyzed with an ECG delineation system. Cardiac cycles were defined as synchronous if a ventricular event followed the P-wave by ≤300 ms. AVS was calculated by dividing the number of synchronous cycles by the total number of cardiac cycles. The primary efficacy endpoint was defined as AVS≥ 85% of total cardiac cycles during the 24-h Holter-ECG monitor. AVS was also calculated for each HR range of 10 bpm. Results Thirty-two patients (18 males, mean age 78.8 ±15.1, 16 patients with 3rd degree AV block, 15 patients with 2nd degree AV block, 1 patient with bifascicular block) underwent successful Micra AV implant, of whom 31 remained in VDD mode at some visit throughout the follow-up, and 26 remained in VDD mode at 3 months follow-up. Device reprogramming of nominal parameters was needed in all patients at follow-up (table). The automatic A3 window end was disabled, and a fixed and short value was set in 100% of patients. Lower HR was set to 40 bpm in 88.5% (n=23) of patients. Auto A4 threshold and auto A3 threshold were modified in 6 and 3 patients respectively and vector was changed in 3 patients. An ambulatory 24-h Holter monitor was performed 112.8±37.5 days after the implant in the 26 patients who remained in VDD. A comparison between nominal parameters and programming at ambulatory 24-h Holter monitoring is displayed in the table. Total ECG recorded time was 550.8 hours and 2,291,953 cardiac cycles were analyzed. Average ambulatory AVS was 87.3±6.3% (median: 87.6%) and 20 out of 26 patients showed an AVS≥85% of cardiac cycles. AVS across the different heart rate ranges was good and remained ≥85% until 90 bpm (figure) with a substantial drop only with HR over 110 bpm. Conclusions High ambulatory AVS in outpatients with leadless pacemakers can be feasible, although may require manual reprogramming of atrial sensing parameters, especially the A3 window end setting.

Expert opinion on optimal programming strategy to increase AV synchrony in different profiles of patients implanted with leadless ventricular pacemaker

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Medtronic Background Recently published real-world data showed that Micra leadless pacemaker implanted in the right ventricle can provide atrioventricular (AV) synchronous pacing by accelerometer-based mechanically sensing atrial contractions in patients with a high pacing burden (1). Routinely performed programming optimization of several novel parameters (particularly concerning the A3 and A4 windows) is key to improving AV synchrony (AVS). Purpose This project aims to define optimal programming recommendations for defined patient profiles. Methods An Experts Panel (ExpP), made up of 11 electrophysiologists from high-volume centers (37±17 Micra AV procedures/year) contributing to the Medtronic Micra AV prospective Post Approval Registry (PAR), was assembled to share their opinion about the optimal programming strategy to improve AVS in patients with: 1) slow sinus rhythm and high degree AV block, 2) fast sinus rhythm and high degree AV block, 3) intermittent AV-block. The following steps were followed: - Data from Micra AV PAR database were retrospectively analyzed and shared with ExpP. - An online survey was completed by the ExpP to evaluate their current programming strategy, based on PAR data. - After a face-to-face meeting to discuss the survey results, a second survey round was completed to reach consensus on the optimal programming strategy. Agreement was considered reached when &amp;gt;75% of responders did not disagree. Results Specific detailed programming recommendations have been developed for the three different patient profiles (Figure 1). Most importantly, it was agreed that Auto A3 Threshold and tracking check should be turned off in all patients, AV conduction mode switch should be turned off in all patients with high degree AVB, and the lower rate should be programmed in general to 50bpm. In addition, the following general recommendations were agreed on by the ExpP: - A pre-implant echocardiogram with a particular focus on diastolic function should always be performed to identify patients who may benefit from Micra AV implantation. - Micra AV auto-setup should always be performed at implant. - Before discharge, basic adjustments based on results of the Manual Atrial. Mechanical (MAM) test, patient activity level, and age should be performed. - At each follow-up visit, fine-tuning programming based on patient feedback, device data (in particular %AM-VP) and performance of a MAM Test. Conclusions An ExpP of Micra AV implanters agreed on general recommendations for Micra AV patients’ management before implant and during follow-up. Specific programming recommendations for patients with slow sinus rhythm and high degree AV block, fast sinus rhythm and high degree AV block, and intermittent AV block have been developed. A validation phase will show if the application of these indications in clinical practice may improve AVS.

Clinical and echocardiographic predictors of atrioventricular synchrony provided by leadless pacemakers: results from the OptiVALL study

Abstract Funding Acknowledgements Type of funding sources: None. Background: Several clinical parameters and echocardiographic markers of atrial function were associated with A4 signal amplitude and high atrioventricular synchrony (AVS) in the MARVEL 2 study. Purpose To study the correlation between the amplitude of the A4 signal determined by the MICRA AV and, the active filling diastolic waves (A and A´ waves velocity) obtained by a transthoracic echocardiogram (TTE). We also aimed to assess echocardiographic and clinical predictors for optimal AVS. Methods The OptiVALL study is a single-centre and prospective study of consecutive patients implanted with MICRA AV. Baseline and procedure characteristics were obtained at implant and a TTE was performed within 48 h after the implant. Follow-up was routinely performed at 24 hours and at 1, 3, 6 and 12 months. Reprogramming of the atrial sensing parameters was guided by device counters, rate histograms and manual atrial mechanical tests. The pacing mode was programmed to VDD in all patients and AV conduction mode switch (VVI +) was deactivated. AVS was studied by an ambulatory 24-h Holter monitoring placed at 3-months follow-up. ECG recorded tracings were automatically and blindly analyzed with an ECG delineation system. Cardiac cycles were defined as synchronous if a ventricular event followed the P-wave by ≤300 ms. AV synchrony was calculated by dividing the number of synchronous cycles by the total number of cardiac cycles. Optimal AVS was defined as AVS≥ 85% of total cardiac cycles during the 24-h Holter-ECG monitor. Results Twenty-six patients who remained in VDD mode at all follow-up visits were included for analysis. Baseline, echocardiographic and procedure-related data is displayed in table 1. Total ECG recorded time was 550.8 hours and 2,291,953 cardiac cycles were analyzed. Average ambulatory AVS during the 24 h Holter monitoring was 87.3±6.3% and 20 out of 26 patients exhibited optimal AVS (≥85% of cardiac cycles). There was no correlation between the active filling diastolic waves and the A4 signal amplitude (r Pearson=-0.251, p=0.237 for A4 signal Vs A´wave and r Pearson=0.018, p=0.932 for A4 signal vs A wave). We did not find any relationship between several diastolic filling parameters (E, A, E/A ratio, E´, A´) and optimal AVS (table 2). There was also a trend towards better optimal AVS with higher E´/A´ ratios. Optimal AVS was related to patients with smaller right atrium size and with lower body mass index. A trend towards optimal AVS was also found in devices deployed in mid interventricular septum locations. On the other hand, patients with diabetes showed lower rates of optimal AVS. Conclusions The correlation between the echocardiographic diastolic filling parameters and diastolic signals detected by the accelerometer of the MICRA AV is poor, so it seems to be as poor guidance to select proper candidates for MICRA AV.

New generation of LCPM and left atrial strain: a promising predictor of atrio-ventricular synchrony in leadless pacemaker pacing

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Leadless cardiac pacemakers (LCPMs) are a new alternative to traditional transvenous pacemaker. They recently have evolved from a single chamber VVI-R pacemaker to devices that can provide atrio-ventricular synchrony (AVS) in patient with sinus rhythm through an 3-axis accelerometer, detecting atrial contractions. To date, Micra AV Transcatheter Pacing System (Medtronic) is the only LCPM on the market that provides AVS. Purpose Many efforts have been made to identify clinical predictors of a good A4 signal amplitude, that determines the ability of the Micra-AV to pace while maintaining AVS (1). Our exploratory study investigates the utility of Left Atrial strain (LAs) for this purpose. Methods Data was extracted from the Cardiac Interventional Registry implemented at our hospital and approved by local ethic committee. Six patients, implanted with Micra-AV (72±13 years), underwent to a complete echocardiography focused on left atrium (LA). Morphological (LA diameters, 2d LA volume and 2d LA area) and functional (EA ratio and LAs study) parameters were assessed. An echocardiography core laboratory studied LAs (Figure A), using a dedicated software (Philips, Epiq 7-Auto Strain Tomtec Application): LA Reservoir Strain (LAsr), LA Conduit Strain (LAscd) and LA Contraction Strain (LAsct) were measured (2). All patients after implantation had a complete electronic control of leadless pacemaker to assess A4 wave amplitude. Results We found that A4 wave amplitude was inversely correlated to 2D-LA volume (Spearman's coefficient rho=-0.96; p=0.003), while it was positively related to LAsr (rho=0.81; p=0.05) and LAsct absolute value (Figure B). In the last years, in addition to the traditional echocardiographic parameters, LA was studied with a new functional parameter, LAs (3). The MARVEL2 study showed that A4 amplitude is fundamental to ensure a high AVS percentage; it was directly related to a parameter defined generically "atrial strain" (4). It is known that LAs is a complex parameter that indicates how the left atrium works overall. Today, thanks to the technological developments of the new echocardiographic software, it can be evaluated more precisely in its components. According to our preliminary data the components that predict A4 amplitude are specifically LAsr and LAsct: we found higher value of A4 in patients that have grater absolute value of these LAs parameters. LAsr is related to the atrial filling and depends on atrial stiffness and fibrosis, LAsct is an indicator of LA ability to empty, thus contributing to the final stage of ventricular diastolic filling. These are simple measurable parameters of LA functional capacity and they seem capable of predicting the possibility of a good AVS in LCPM pacing. Conclusion Patient selection is crucial to obtain good clinical outcomes. In this context, echocardiographic parameters and particularly the LAs study look promising to make a correct choice.

Comparison of 1st and 2nd generation leadless pacemaker in sinus rhythm patients with chronic ventricular pacing for complete atrioventricular block

Abstract Funding Acknowledgements Type of funding sources: None. Background Leadless pacemakers (LPMs) represent a seductive alternative to conventional pacing. First generation of Micra transcatheter pacing system was able to provide single-chamber VVI(R) pacing mode only, with a potential risk of pacemaker syndrome in sinus rhythm patients. A 2nd generation system (AV) now provides atrioventricular synchrony through atrial mechanical sensing capability (VDD mode). Purpose We sought to compare VR and AV systems in patients with sinus rhythm and chronic ventricular pacing for complete atrioventricular block. Methods All consecutive patients implanted with an LPM in our department for complete atrioventricular block were retrospectively screened. Patients with atrial fibrillation, sinus dysfunction, or ventricular pacing burden &amp;lt;20% at 1-month post-implantation were excluded. Results A total of 80 patients – 35 VR (2015-2020) and 45 AV (2020-2021) – were included. VR and AV patients had similar baseline characteristics, except for that VR patients being older (82±8 versus 77±9 years, p=0.01). Mean ventricular pacing burden was 75% in the VR and 79% in the AV group (p=0.63). In AV patients, median atrioventricular synchronous beats rate was 77%, 67% having a &amp;gt;66% rate. An E/A ratio &amp;lt;1 as measured on echocardiography was the only independent predictor of accurate atrial mechanical tracking (adjusted OR=13, p=0.006). One-year survival rate was 86% in the VR group and 95% in the AV group (adjusted p=0.21). Two patients in the VR and 0 in the AV group eventually developed pacemaker syndrome in the 1st year post-implantation (p=0.07). Conclusion In sinus rhythm patients with chronic ventricular pacing for complete atrioventricular block implanted with an LPM, atrial mechanical sensing algorithm allowed significant atrioventricular synchrony in most patients, and was associated with no occurrence of – otherwise rare – pacemaker syndrome.

Electrocardiographic predictors of atrial mechanical sensing in patients with leadless VDD pacemakers

Abstract Funding Acknowledgements Type of funding sources: None. Background Leadless pacemakers (LP) capable of VDD function are a cornerstone of modern pacemaker therapy reducing complications in elderly patients while enabling atrioventricular synchrony through mechanical sensing of atrial contraction. Because mechanical sensing is less reliable than electrical sensing, the reliability of VDD function in LP varies. We evaluated the p-wave amplitude from patient ECGs as a predictor for successful VDD function in LP. Materials and methods Consecutive patients undergoing LP implantation capable of VDD function were included in this multi-center retrospective cohort study. As VDD function is mainly dependent on the A4 signal amplitude in the current generation of the device, ECG parameters pre-implantation were evaluated separately and in combination for association with A4 signal amplitude post-implantation. Results 122 Patients (mean age 81, female 44%, mean BMI 25.9 kg/m2) were included. Main indication for LP implantation was AV-Block (70%). BMI-adjusted P-wave amplitude demonstrated a statistically significant positive correlation with A4 signal amplitude in leads I, II, aVL, aVF, aVR, V1 and V2 (all p&amp;lt;0.05). A p-wave amplitude of at least 0.1mV had a specificity of 72% (95%-CI 50%-89%) for a good A4 signal. A sum of at least 0.2mV of p-wave amplitudes in V1 and aVL predicts a specificity of 83% (95%-CI 67-100%) for a good A4 signal. Conclusions P-wave amplitudes in selected ECG leads can predict A4 signal amplitude and therefore the reliability of VDD function in LP.

Atrial fibrillation is an independent risk factor for heart failure progression and pump failure mortality in HFpEF:: a propensity score matched analysis of the TOPCAT Americas study

Abstract Funding Acknowledgements Type of funding sources: None. Background Atrial fibrillation (AF) is associated with excess mortality and cardiovascular (CV) hospitalizations in HF patients (pts) with preserved systolic function (pEF) but the contributing factors to these outcomes are not known.. Purpose To analyze the independent impact of AF on clinical outcomes of HFpEF pts in the TOPCAT AMERICAS study using propensity score matched (PSM) cohorts to account for confounding by other comorbidities. Methods Study cohorts were PSM matched for 20 clinical, demographic &amp; ECG variables. 3 matched cohorts based on baseline rhythm status at study entry were compared viz. subjects in sinus rhythm (SR), subjects in AF on baseline ECG &amp; subjects with Any AF event by history or ECG. We analyzed CV mortality, adjudicated modes of death &amp; morbidity during a mean follow up period of 2.9 yrs. Results 418 subjects in SR (SR cohort) were PSM with 418 subjects in AF on baseline ECG (AF on ECG cohort) &amp; 418 pts with any AF event by history or ECG (Any AF cohort) at study entry. Any AF increased the risk of CV death (D), pump failure death (PFD), CV and HF hospitalization (H) and HF progression. AF on ECG increased risk of CVD, CVH, HFH and PFD (Tables). Neither AF cohort increased risk of sudden death (SD) {Figure}. Conclusion 1. AF is an independent risk factor for worsening CV outcomes in HFpEF. 2. This increased risk is due to a selective increase in symptomatic HF progression from early to advanced HF, HFH and PFD in advanced HF rather than SD. 3. Loss of AV synchrony &amp; rate control in AF can independently impact HF progression in HFpEF with consequent HFH and PFD. Restoration of SR may offer benefits for CV outcomes in HFpEF &amp; warrants evaluation.

A leadless ventricular pacemaker providing atrioventricular synchronous pacing in the real-world setting: acute results from the Micra AV post-approval registry

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Medtronic, inc. Introduction Advances in leadless pacemaker technology have enabled accelerometer based atrioventricular synchronous (AVS) pacing by sensing atrial mechanical contraction. However, acute safety performance of these devices in real-world clinical practice has not been assessed. Objectives To report the acute performance of the Micra AV transcatheter pacemaker from the worldwide Micra AV post-approval registry (PAR). Methods The Micra AV PAR is an ongoing prospective single-arm observational study designed to assess the safety and effectiveness of the Micra AV system in the real-world setting. Patients enrolled in the Micra AV PAR will be followed for 3 years. For the present interim analysis, baseline characteristics, total AV synchrony index (sum of %AM-VP, %AM-VS, and AV conduction mode switch percentage), and major complications occurring within 30-days of implant were summarized and compared to a historical cohort of 2,667 transvenous dual chamber (TV-DC) pacing patients. Results The device was successfully implanted in 797 of 802 patients (99.4%) at 99 centers. Mean age was 74.1±15.1 years and 42.3% were female. The most common pacing indication was AV block (55.7%). Comorbidities included diabetes (29.7%), CAD (22.8%), and heart failure (12.1%), with 31.3% precluded from transvenous device therapy. Micra AV patients were on average older (74.1 vs. 71.1 yrs, P&amp;lt;0.0001) and had a significantly higher incidence of renal disease (22.3% vs. 9.8%, P&amp;lt;0.0001). Major complications occurred in 2.6% of Micra AV patients and in 7.1% TV-DC patients (P&amp;lt;0.001, Figure). The reduction in major complications was largely driven by the absence of pneumothoraces and lead dislodgements among Micra AV patients. Of the 309 patients programmed to VDD mode with at least 30 days of device follow-up, the median AV synchrony index was 86.0% (IQR: 69.2% - 97.2%). Mean A4 amplitude was 2.1±1.6 m/s2 post-implant and 2.2±1.7 m/s2 at follow-up (P=0.57) in 308 patients with paired assessments. Conclusions The Micra AV leadless pacemaker was implanted with a high rate of success in patients with a high co-morbidity burden, with a significantly lower rate of acute complications relative to dual-chamber transvenous pacemakers despite patients being older and having a higher incidence of renal disease. Longer-term performance will continue to be assessed in this ongoing trial.

Marked first-degree AV block may lead to complete AV block development

Abstract Funding Acknowledgements Type of funding sources: None. Background First-degree atrioventricular (AV) block (PR interval &amp;gt;200 ms) is considered a benign condition with rare progression to a higher degree AV block. The site of block is determined with electrophysiological (EP) study and measurement of His-ventricular (HV) interval, with normal values below 55 ms. Prolonged HV interval &amp;gt; 70 ms is predictive of higher-grade AV block development. Marked first-degree AV block with a PR &amp;gt; 300 ms may lead to symptoms such as fatigue, poor exercise tolerance and palpitations. When symptoms are correlated to the conduction delay, permanent pacemaker (PPM) implantation to restore AV synchrony should be considered. In the Framingham heart study, patients with first-degree AV block had a threefold higher risk of PPM implantation. However, there is no data on the HV intervals and the rate of progression of conduction disorder in patients with marked first-degree AV block. Purpose To assess the predictive value of HV interval measurement in patients with marked first-degree AV block for progression to a higher-degree conduction disorder. Methods We prospectively evaluated consecutive patients with symptomatic marked first-degree AV block that underwent a PPM implantation. His electrograms were recorded during the implantation, and HV intervals were measured from the first deflection of the His signal to the earliest onset of ventricular activation on a 12-lead surface ECG. Patients were followed for 6 months with three out-patient visits, during which the PPM was temporarily inhibited to check for intrinsic AV conduction. Results Seventeen patients were evaluated between January 2020 and September 2022. Ten patients (59%) were male, and 7 (41%) were female, with an average age of 61 ± 19 years. All patients had markedly prolonged PR interval (383 ± 47 ms) and narrow QRS complex (100 ± 16 ms). Three patients (17%) had intermittent type 1 second-degree AV block, right bundle branch block was recorded in two (12%) and left anterior fascicular block in four (24%) patients. Except for one patient with a corrected atrial septal defect, there were no echocardiographic signs of structural heart disease with a left ventricular ejection fraction of 61 ± 5%. The HV intervals were on the upper limit of normal values at 54 ± 6ms and no patient had an HV interval above 70 ms. Two patients (12%) developed complete AV block during follow-up: one female, and one male, 28 and 83 years old, respectively, with a PR interval 392 and 363 ms, QRS 104 and 94 ms, and HV 57 and 48 ms. None of the two had any additional conduction blocks at the time of PPM implant. Conclusion In our cohort of patients with symptomatic first-degree AV block (PR&amp;gt;300 ms), two patients (12%) developed complete AV block despite normal HV intervals at the time of implant. Closer monitoring, beyond only EP measurements, of patients with markedly prolonged PR intervals is warranted for the potential progression of conduction disorder.

A Dual-Chamber Leadless Pacemaker

BackgroundSingle-chamber ventricular leadless pacemakers do not support atrial pacing or consistent atrioventricular synchrony. A dual-chamber leadless pacemaker system consisting of two devices implanted percutaneously, one in the right atrium and one in the right ventricle, would make leadless pacemaker therapy a treatment option for a wider range of indications.MethodsWe conducted a prospective, multicenter, single-group study to evaluate the safety and performance of a dual-chamber leadless pacemaker system. Patients with a conventional indication for dual-chamber pacing were eligible for participation. The primary safety end point was freedom from complications (i.e., device- or procedure-related serious adverse events) at 90 days. The first primary performance end point was a combination of adequate atrial capture threshold and sensing amplitude at 3 months. The second primary performance end point was at least 70% atrioventricular synchrony at 3 months while the patient was sitting.ResultsAmong the 300 patients enrolled, 190 (63.3%) had sinus-node dysfunction and 100 (33.3%) had atrioventricular block as the primary pacing indication. The implantation procedure was successful (i.e., two functioning leadless pacemakers were implanted and had established implant-to-implant communication) in 295 patients (98.3%). A total of 35 device- or procedure-related serious adverse events occurred in 29 patients. The primary safety end point was met in 271 patients (90.3%; 95% confidence interval [CI], 87.0 to 93.7), which exceeded the performance goal of 78% (P<0.001). The first primary performance end point was met in 90.2% of the patients (95% CI, 86.8 to 93.6), which exceeded the performance goal of 82.5% (P<0.001). The mean (±SD) atrial capture threshold was 0.82±0.70 V, and the mean P-wave amplitude was 3.58±1.88 mV. Of the 21 patients (7%) with a P-wave amplitude of less than 1.0 mV, none required device revision for inadequate sensing. At least 70% atrioventricular synchrony was achieved in 97.3% of the patients (95% CI, 95.4 to 99.3), which exceeded the performance goal of 83% (P<0.001).ConclusionsThe dual-chamber leadless pacemaker system met the primary safety end point and provided atrial pacing and reliable atrioventricular synchrony for 3 months after implantation. (Funded by Abbott Medical; Aveir DR i2i ClinicalTrials.gov number, NCT05252702.)