Evolution of ventricular and valve function in patients with right ventricular pacing - A randomized controlled trial comparing leadless and conventional pacing.

BACKGROUND: Leadless pacemakers (PMs) were recently introduced to overcome lead-related complications. They showed high safety and efficacy profiles. Prospective studies assessing long-term safety on cardiac structures are still missing. OBJECTIVE: The purpose of this study was to compare the mechanical impact of Micra with conventional PM on heart function. METHODS: We conducted a non-inferiority trial in patients with an indication for single chamber ventricular pacing. Patients were 1:1 randomized to undergo implantation of either Micra or conventional monochamber ventricular pacemaker (PM). Patients underwent echocardiography at baseline, 6 and 12 months after implantation. Analysis included left ventricular ejection fraction (LVEF), global longitudinal strain (GLS) and valve function. N-terminal-pro hormone B-type natriuretic peptide (NT-pro-BNP) levels were measured at baseline and 12 months. RESULTS: Fifty-one patients (27 in Micra group and 24 in conventional group) were included. Baseline characteristics were similar for both groups. At 12 months, (1) the left ventricular function as assessed by LVEF and GLS worsened similarly in both groups (∆LVEF -10 ± 7.3% and ∆GLS +5.7 ± 6.4 in Micra group vs. -13.4 ± 9.9% and +5.2 ± 3.2 in conventional group) (p = 0.218 and 0.778, respectively), (2) the severity of tricuspid valve regurgitation was significantly lower with Micra than conventional pacing (p = 0.009) and (3) median NT-pro-BNP was lower in Micra group (970 pg/dL in Micra group versus 1394 pg/dL in conventional group, p = 0.041). CONCLUSION: Micra is non inferior to conventional PMs concerning the evolution of left ventricular function at 12-month follow-up. Our data suggest that Micra has a comparable mechanical impact on the ventricular systolic function but resulted in less valvular dysfunction.

The jugular approach for leadless pacing: A novel and safe alternative.

AIMS: To evaluate safety of leadless pacemaker implantation through the internal jugular vein in a larger cohort with longer follow-up. Moreover, feasibility of non-apical pacing as well as relation between pacing site and QRS duration were assessed. METHODS: Eighty Two consecutive patients, who received a leadless pacemaker though the internal jugular vein, were included. Electrical parameters were measured at regular follow-up and any complications were registered. Paced QRS interval was compared for three pacing sites, RVOT, RV mid septum, and RV apical septum. RESULTS: In all patients, the leadless pacemaker was implanted successfully. In 69 patients, the device was implanted in a non-apical position. In 71% of cases, the device could be deployed at first attempt. The median fluoroscopy time was 4.4 min (range 0.9-51) The paced QRS interval was significantly narrower for non-apical pacing sites compared to apical pacing si 156  vs. 179 ms. p = .04, respectively. During mean follow-up of 16 months (range 0-43 months), electrical parameters remained stable. Two complications occurred, which could be resolved during the implant procedure. There were no access site related complications. CONCLUSION: The jugular approach for leadless pacemaker implantation is feasible and may avoid vascular complications. It facilitates non-apical positioning of leadless pacemakers leading to a narrower paced QRS interval. The jugular approach allows for immediate post procedural ambulation.

Conventional single-chamber pacemakers versus transcatheter pacing systems in a "real world" cohort of patients: A comparative prospective single-center study.

PURPOSE: Despite the developments in conventional transvenous pacemakers (VVI-PM), the procedure is still associated with significant complications. Although there are no prospective clinical trials that compared VVI-PM with transcatheter pacemaker systems (TPS). METHODS: This is a prospective, observational, single-center study that included all patients with an indication for a single-chamber pacemaker implant within a 4-year period. All clinical, ECG and echocardiographic characteristics at implant, electrical parameters, associated complications and mortality were analyzed. A Cox survival model and a Bayesian cohort analysis were performed for differences in complication rates between groups. RESULTS: There were 443 patients included (198 TPS and 245 VVI-PM). The mean age was 81.5 years (TPS group, 79.2 ± 6.6 years; VVI-PM group, 83.5 ± 8.9 years). There was a male predominance in TPS group (123, 62.1% vs. 67, 27.3%; p < 0.001). The presence of systolic dysfunction and renal insufficiency were more frequent in VVI-PM group than in TPS patients. Mean follow-up was 22.3 ± 15.9 months. In a multivariable paired data the TPS group presented fewer complications than VVI-PM group (HR = 0.39 [0.15-0.98], p-value 0.013), but major complications were not different (6, 3% vs 14, 5.6% respectively, p = 0.1761). There was no difference in the mortality rate between the groups. The TPS group had less risk than VVI-PM group to have a complication, with a 96% of probability. CONCLUSIONS: TPS patients had a lower overall complication rate than VVI-PM patients including matched-pair samples using a Bayesian analysis. These results confirm the safety profile of TPS in clinical practice.

Very high pacing thresholds during long-term follow-up predicted by a combination of implant pacing threshold and impedance in leadless transcatheter pacemakers.

BACKGROUND: Micra transcatheter pacemaker system (TPS) usually achieves low implant pacing threshold (IPT). However, IPT may increase in some patients during follow-up. AIM: To apply implant parameters in predicting long-term occurrence of very high pacing threshold (VHPT) in patients with Micra-TPS. METHODS: A cohort of 110 consecutive patients implanted with a Micra-TPS from 2014 to 2018 was evaluated at discharge and at 1, 12, 24, 36, and 48 months follow-up. VHPT was defined as greater than 2 V/0.24 ms. VHPT predictors were identified. RESULTS: Micra-TPS was implanted successfully in 108 patients (98.2%). During a mean follow-up of 24 ± 16 months, 18 patients (16.7%) died of causes nonpacemaker-related, and 4 (3.8%) developed VHPT. Patients with VHPT had higher IPT and lower implant impedance than patients with non-VHPT: 1 ± 0.31 vs 0.55 ± 0.29 V/0.24 ms (P = .003) and 580 ± 59 vs 837 ± 232 Ω (P = .03), respectively. IPT and impedance had excellent discriminative power to predict VHPT (area under the curve: 0.85 ± 0.07 and 0.91 ± 0.05, respectively). Negative predictive value (NPV) of IPT ≤ 0.5 V/0.24 ms was 100%; positive predictive value (PPV) was 8% throughout follow-up. Implant impedance ≤ 600 Ω had NPV of 99% throughout follow-up, whereas PPV varied: 16%, 21%, 16%, and 28% at 1, 12, 24, and 36 months, respectively. Sequential combination of IPT greater than 0.5 V/0.24 ms and impedance ≤ 600 Ω improved PPV to 25%, 35%, 27%, and 44%, respectively, whereas NPV remained 99% throughout follow-up. CONCLUSION: Despite favorable long-term electrical performance of Micra-TPS, a small percent of patients developed VHPT during follow-up. A sequential combination of IPT and impedance could allow the implanter to identify patients who will develop VHPT during long-term follow-up.

Leadless pacemaker implant in patients with pre-existing infections: Results from the Micra postapproval registry.

INTRODUCTION: Leadless pacemakers may provide a safe and attractive pacing option to patients with cardiac implantable electronic device (CIED) infection. We describe the characteristics and outcomes of patients with a recent CIED infection undergoing Micra implant attempt. METHODS AND RESULTS: Patients with prior CIED infection and device explant with Micra implant within 30 days, were identified from the Micra post approval registry. Procedure characteristics and outcomes were summarized. A total of 105 patients with prior CIED infection underwent Micra implant attempt ≤30 days from prior system explant (84 [80%] pacemakers and 13 [12%] ICD/CRT-D). All system components were explanted in 93% of patients and explant occurred a median of 6 days before Micra implant, with 37% occurring on the day of Micra implant. Micra was successfully implanted in 99% patients, mean follow-up duration was 8.5 ± 7.1 months (range 0-28.5). The majority of patients (91%) received IV antibiotics preimplant, while 42% of patients received IV antibiotics postprocedure. The median length of hospitalization following Micra implant was 2 days (IQR, 1-7). During follow-up, two patients died from sepsis and four patients required system upgrade, of which two patients received Micra to provide temporary pacing support. There were no Micra devices explanted due to infection. CONCLUSION: Implantation of the Micra transcatheter pacemaker is safe and feasible in patients with a recent CIED infection. No recurrent infections that required Micra device removal were seen. Leadless pacemakers appear to be a safe pacing alternative for patients with CIED infection who undergo extraction.

Right Ventricular Anatomy Can Accommodate Multiple Micra Transcatheter Pacemakers.

BACKGROUND: The introduction of transcatheter pacemaker technology has the potential to significantly reduce if not eliminate a number of complications associated with a traditional leaded pacing system. However, this technology raises new questions regarding how to manage the device at end of service, the number of devices the right ventricle (RV) can accommodate, and what patient age is appropriate for this therapy. In this study, six human cadaver hearts and one reanimated human heart (not deemed viable for transplant) were each implanted with three Micra devices in traditional pacing locations via fluoroscopic imaging. METHODS: A total of six human cadaver hearts were obtained from the University of Minnesota Anatomy Bequest Program; the seventh heart was a heart not deemed viable for transplant obtained from LifeSource and then reanimated using Visible Heart(®) methodologies. Each heart was implanted with multiple Micras using imaging and proper delivery tools; in these, the right ventricular volumes were measured and recorded. The hearts were subsequently dissected to view the right ventricular anatomies and the positions and spacing between devices. RESULTS: Multiple Micra devices could be placed in each heart in traditional, clinically accepted pacing implant locations within the RV and in each case without physical device interactions. This was true even in a human heart considered to be relatively small. CONCLUSIONS: Although this technology is new, it was demonstrated here that within the human heart's RV, three Micra devices could be accommodated within traditional pacing locations: with the potential in some, for even more.

Impact of comorbidity on complication rates and life expectancy in patients with a leadless pacemaker.

BACKGROUND: Knowledge about impact of age and comorbidities on outcome in patients with leadless pacemakers (LPM) is limited. OBJECTIVES: To analyse outcome in LPM patients according to age and comorbidities. METHODS: This Swiss, multi-centre, retrospective analysis includes all patients with LPM implanted between 2015 and 2022. Charlson-Comorbidity-Index (CCI) was determined and patients were divided into a low- (CCI ≤ 5) and high-comorbidity (CCI > 5) group. Peri-procedural complications, in-hospital death, and all-cause mortalities were assessed. Finally, all-cause mortality according to three groups (CCI ≤ 3, 4-5, >5) was compared to age and sex-adjusted mortality in the general Swiss population. RESULTS: 863 patients (median age 81 years, 65% male, 42% with CCI > 5) were included. Peri-procedural/long-term complication rates did not differ between the low- vs. high-comorbidity groups (2.6% vs. 1.7%, p = 0.48 and 1.2% vs. 2.8%, p = 0.12, respectively). In-hospital (3.6% vs. 0.6%, p = 0.002) and all-cause mortality (HR 2.9, 95%CI 2.2-3.8, p < 0.001) were significantly higher in the high-comorbidity group resulting in a three-year mortality of 58% (95%CI 51-65%) vs. 22% (95%CI 17-27%) in the low-comorbidity group. In patients with a CCI ≤ 3, all-cause mortality was comparable to the age- and sex-adjusted mortality of the general Swiss population. CONCLUSIONS: In elderly patients with high comorbidity, LPM implantation was not associated with increased peri-procedural/long-term complications. All-cause mortality in LPM patients with a CCI ≤ 3 was comparable to age- and sex-adjusted mortality in the general Swiss population. Despite a relatively high three-year mortality due to competing risk factors, LPM implantation is safe, even in elderly patients with high comorbidity. CONDENSED ABSTRACT: In this Swiss, multi-centre, retrospective cohort analysis, 863 patients implanted with a leadless pacemaker were included and divided into a high-comorbidity (with a CCI > 5) and low-comorbidity (with a CCI ≤ 5) group. There was no between group difference in terms of implantation outcomes and peri-operative or long-term complications. Furthermore, all-cause mortality during follow-up in patients with a CCI ≤ 3 was comparable to age- and sex-adjusted mortality in the general Swiss population. These data indicate that LPM implantation is a safe procedure, even in elderly patients with high comorbidity.

Design and rationale of the MODULAR ATP global clinical trial: A novel intercommunicative leadless pacing system and the subcutaneous implantable cardioverter-defibrillator.

Background: The subcutaneous implantable cardioverter-defibrillator (S-ICD) has demonstrated safety and efficacy for the treatment of malignant ventricular arrhythmias. However, a limitation of the S-ICD lies in the inability to either pace-terminate ventricular tachycardia or provide prolonged bradycardia pacing support. Objective: The rationale and design of a prospective, single-arm, multinational trial of an intercommunicative leadless pacing system integrated with the S-ICD will be presented. Methods: A technical description of the modular cardiac rhythm management (mCRM) system (EMPOWER leadless pacemaker and EMBLEM S-ICD) and the implantation procedure is provided. MODULAR ATP (Effectiveness of the EMPOWER™ Modular Pacing System and EMBLEM™ Subcutaneous ICD to Communicate Antitachycardia Pacing) is a multicenter, international trial enrolling up to 300 patients at risk of sudden cardiac death at up to 60 centers trial design. The safety endpoint of freedom from major complications related to the mCRM system or implantation procedure at 6 months and 2 years are significantly higher than 86% and 81%, respectively, and all-cause survival is significantly >85% at 2 years. Results: Efficacy endpoints are that at 6 months mCRM communication success is significantly higher than 88% and the percentage of subjects with low and stable thresholds is significantly higher than 80%. Substudies to evaluate rate-responsive features and performance of the pacing module are also described. Conclusion: The MODULAR ATP global clinical trial will prospectively test the safety and efficacy of the first intercommunicating leadless pacing system with the S-ICD. This trial will allow for robust validation of device-device communication, pacing performance, rate responsiveness, and system safety.

Lost but Not Lost-Embolization of a Leadless Pacemaker to the Pulmonary Artery with Consecutive Endovascular Recovery.

BACKGROUND: Leadless transcatheter pacemaker systems (TPS) have become a valuable alternative to transvenous pacemakers in selected indications. With the steadily increasing amount of TPS implantations performed worldwide, reports of periprocedural complications are likewise increasingly found in the literature but are still underreported. CASE PRESENTATION: We report a case of a 75 year old male undergoing TPS implantation due to cardioinhibitory vasovagal syncope. The implantation was primarily uneventful; adequate pacing parameters and fixation of the device were achieved. Unfortunately, dislocation of the leadless pacemaker occurred at the end of the procedure and the device embolized into a primary side branch of the right pulmonary artery. Endovascular retrieval was performed by using a single snare technique without any further complications. CONCLUSIONS: Although challenging, endovascular recovery of embolized TPS from the pulmonary artery is feasible and may be successfully accomplished by experienced implanters.

Predictors of atrial mechanical sensing and atrioventricular synchrony with a leadless ventricular pacemaker: Results from the MARVEL 2 Study.

BACKGROUND: The MARVEL (Micra Atrial TRacking Using a Ventricular AccELerometer) 2 study assessed the efficacy of atrioventricular (AV) synchronous pacing with a Micra leadless pacemaker. Average atrioventricular synchrony (AVS) was 89.2%. Previously, low amplitude of the Micra-sensed atrial signal (A4) was observed to be a factor of low AVS. OBJECTIVE: The purpose of this study was to identify predictors of A4 amplitude and high AVS. METHODS: We analyzed 64 patients enrolled in MARVEL 2 who had visible P waves on electrocardiogram for assessing A4 amplitude and 40 patients with third-degree AV block for assessing AVS at rest. High AVS was defined as >90% correct atrial-triggered ventricular pacing. The association between clinical factors and echocardiographic parameters with A4 amplitude was investigated using a multivariable model with lasso variable selection. Variables associated with A4 amplitude together with premature ventricular contraction burden, sinus rate, and sinus rate variability (standard deviation of successive differences of P-P intervals [SDSD]) were assessed for association with AVS. RESULTS: In univariate analysis, low A4 amplitude was inversely related to atrial function assessed by E/A ratio and e'/a' ratio, and was directly related to atrial contraction excursion (ACE) and atrial strain (Ɛa) on echocardiography (all P ≤.05). The multivariable lasso regression model found coronary artery bypass graft history, E/A ratio, ACE, and Ɛa were associated with low A4 amplitude. E/A ratio and SDSD were multivariable predictors of high AVS, with >90% probability if E/A <0.94 and SDSD <5 bpm. CONCLUSION: Clinical parameters and echocardiographic markers of atrial function are associated with A4 signal amplitude. High AVS can be predicted by E/A ratio <0.94 and low sinus rate variability at rest.

Updated performance of the Micra transcatheter pacemaker in the real-world setting: A comparison to the investigational study and a transvenous historical control.

BACKGROUND: Early results of the Micra Investigational Device Exemption (IDE) study and Micra Post-Approval Registry (PAR) demonstrated excellent safety and efficacy performance; however, intermediate-term results across a large patient population in the real-world setting have not been evaluated. OBJECTIVES: We report updated performance of the Micra transcatheter pacemaker from a worldwide PAR and compare it with the IDE study as well as a transvenous historical control. METHODS: The safety objective of the analysis was system- or procedure-related major complications through 12 months postimplantation. We compared the major complication rate with that of the 726 patients from the IDE and with a reference data set of 2667 patients with transvenous pacemakers by using a Fine-Gray competing risk model. RESULTS: The Micra device was successfully implanted in 1801 of 1817 patients (99.1%). The mean follow-up period was 6.8 ± 6.9 months. Through 12 months, the major complication rate was 2.7% (95% confidence interval [CI] 2.0%-3.7%). The risk of major complications for Micra PAR patients was 63% lower than that for patients with transvenous pacemakers through 12 months postimplantation (hazard ratio 0.37; 95% CI 0.27-0.52; P < .001). The major complication rate trended lower in the PAR than in the IDE study (hazard ratio 0.71; 95% CI 0.44-1.1; P = .160), driven by the lower pericardial effusion rate in the PAR. There were 3 cases of infection associated with the procedure, but none required device removal and there were no battery or telemetry issues. Pacing thresholds were low and stable through 12 months postimplantation. CONCLUSION: Performance of the Micra transcatheter pacemaker in international clinical practice remains consistent with previously reported data. Major complications were infrequent and occurred 63% less often compared to transvenous systems. CLINICAL TRIAL REGISTRATION: Micra Transcatheter Pacing System Post-Approval Registry ClinicalTrials.gov identifier: NCT02536118; Micra Transcatheter Pacing Study ClinicalTrials.gov identifier: NCT02004873.

To retrieve, or not to retrieve: System revisions with the Micra transcatheter pacemaker.

BACKGROUND: Early experience with leadless pacemakers has shown a low rate of complications. However, little is known about system revision in patients with these devices. OBJECTIVE: The purpose of this study was to describe the system revision experience with the Micra Transcatheter Pacing System (TPS). METHODS: Patients with implants from the Pre-market Micra Transcatheter Pacing Study and the Micra Transcatheter Pacing System Continued Access Study (N = 989) were analyzed and compared with 2667 patients with transvenous pacemakers (TVPs). Revisions included TPS retrieval/explant, repositioning, replacement, or electrical deactivation (with or without prior attempt at retrieval, generally followed by TVP implant) for any reason. Kaplan-Meier revision rates were calculated to account for varying follow-up duration and were compared using a Fine-Gray competing risk model. RESULTS: The actuarial rate for revision at 24 months postimplant was 1.4% for the TPS group (11 revisions in 10 patients), 75% (95% confidence interval 53%-87%; P < .001) lower than the 5.3% for the TVP group (123 revisions in 117 patients). TPS revisions occurred 5-430 days postimplant for elevated pacing thresholds, need for alternate therapy, pacemaker syndrome, and prosthetic valve endocarditis; none were due to device dislodgment or device-related infection. TPS was disabled and left in situ in 7 cases, 3 were retrieved percutaneously (range 9-406 days postimplant), and 1 was surgically removed during aortic valve surgery. CONCLUSION: The overall system revision rate for patients with TPS at 24 months was 1.4%, 75% lower than that for patients with TVPs. TPS was disabled and left in situ in 64% of revisions, and percutaneous retrieval was successful as late as 14 months postimplant.

Long-term performance of a transcatheter pacing system: 12-Month results from the Micra Transcatheter Pacing Study.

BACKGROUND: Early performance of the Micra transcatheter pacemaker from the global clinical trial reported a 99.2% implant success rate, low and stable pacing capture thresholds, and a low (4.0%) rate of major complications up to 6 months. OBJECTIVE: The purpose of this report was to describe the prespecified long-term safety objective of Micra at 12 months and electrical performance through 24 months. METHODS: The Micra Transcatheter Pacing Study was a prospective single-arm study designed to assess the safety and efficacy of the Micra VVIR leadless/intracardiac pacemaker. Enrolled patients met class I or II guideline recommendations for de novo ventricular pacing. The long-term safety objective was freedom from a system- or procedure-related major complication at 12 months. A predefined historical control group of 2667 patients with transvenous pacemakers was used to compare major complication rates. RESULTS: The long-term safety objective was achieved with a freedom from major complication rate of 96.0% at 12 months (95% confidence interval 94.2%-97.2%; P < .0001 vs performance goal). The risk of major complications for patients with Micra (N = 726) was 48% lower than that for patients with transvenous systems through 12 months postimplant (hazard ratio 0.52; 95% confidence interval 0.35-0.77; P = .001). Across subgroups of age, sex, and comorbidities, Micra reduced the risk of major complications compared to transvenous systems. Electrical performance was excellent through 24 months, with a projected battery longevity of 12.1 years. CONCLUSION: Long-term performance of the Micra transcatheter pacemaker remains consistent with previously reported data. Few patients experienced major complications through 12 months of follow-up, and all patient subgroups benefited as compared to transvenous pacemaker historical control group.

Safety evaluation of a leadless transcatheter pacemaker for magnetic resonance imaging use.

BACKGROUND: Increased magnetic resonance imaging (MRI) adoption and demand are driving the need for device patients to have safe access to MRI. OBJECTIVE: The aim of this study was to address the interactions of MRI with the Micra transcatheter pacemaker system. METHODS: A strategy was developed to evaluate potential MRI risks including device heating, unintended cardiac stimulation, force, torque, vibration, and device malfunction. Assessment of MRI-induced device heating was conducted using a phantom containing gelled saline, and Monte Carlo simulations incorporating these results were conducted to simulate numerous combinations of human body models, position locations in the MRI scanner bore, and a variety of coil designs. Lastly, a patient with a Micra pacemaker who underwent a clinically indicated MRI scan is presented. RESULTS: Compared to traditional MRI conditional pacemakers, the overall risk with Micra was greatly reduced because of the small size of the device and the absence of a lead. The modeling results predicted that the nonperfused temperature rise of the device would be less than 0.4°C at 1.5 T and 0.5°C at 3 T and that the risk of device heating with multiple device implants was not increased as compared with a single device. The clinical case study revealed no MRI-related complications. CONCLUSION: The MRI safety assessment tests conducted for the Micra pacemaker demonstrate that patients with a single device or multiple devices can safely undergo MRI scans in both 1.5- and 3-T MRI scanners. No MRI-related complications were observed in a patient implanted with a Micra pacemaker undergoing a clinically indicated scan.