Table 1 Abbreviations
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Evidence summary
Population and studies description
This overview of interventional procedures is based on data from 1,098,766 people across multiple studies, including a randomised controlled trial (RCT) (Garweg 2023), 4 systematic reviews with meta-analyses (Inoue 2024, Wu 2023, Mhasseb 2025, Oliveira 2024), 5 registry studies (El-Chami 2024, El-Chami 2024, Shah 2023, Panico 2024 and Ueyama 2024), 4 prospective studies (Tjong 2018, Amrani 2020, Molitor 2024 and Knops 2023) and 2 retrospective studies (Cabanas-Grandio 2020 and Strik 2023). Among these, 70,394 people had LP implantation. There was considerable overlap in studies between the systematic reviews. Most studies were conducted in the US and Europe. This is a rapid review of the literature, and a flow chart of the complete selection process is shown in figure 1. This overview presents 16 studies as the key evidence in table 2 and table 3, and lists other relevant 126 studies in appendix B, table 5.
The RCT (Garweg 2023) compared the outcomes of LP with conventional TVP using single-chamber VP. The study cohort included 51 people with a mean age of 82.5 years, and 61% were male. The study employed standardised echocardiographic assessments conducted at baseline, 6 months, and 12 months, along with NT-proBNP measurements at baseline and 12 months.
The systematic review and meta-analysis by Inoue (2025) synthesised evidence on the safety and optimal timing of LP implantation following the removal of cardiac implantable electronic devices (CIEDs) because of infection. Data from 16 observational studies (n=653) published between 2015 and 2024 were included. The mean age was 77 years, 69% were male, with a mean left ventricular ejection fraction (LVEF) of 56%. The average follow-up was 14 months, ranging from 6 to 47 months across studies. Results were grouped based on LP implantation timing—either during CIED removal, or after a set interval.
The meta-analysis by Mhasseb (2025) compared the safety profile of TVPs and LPs. The study included data from 19 observational studies, comprising 12 retrospective cohort studies and 7 prospective cohort studies, conducted across various regions, including the US, Italy, France, Spain, and Japan. The total sample size was 972,479 people, with 57,974 having LPs. The mean age ranged from 70 to 90 years, and the proportion of males ranged from 52% to 70%. The prevalence of comorbidities varied, with AF (89%), HTN (90%), diabetes mellitus (46%), and coronary artery disease (CAD) (56%). Follow-up durations ranged from 30 days to over 5 years.
The systematic review and meta-analysis by Oliveira (2025) included 21 observational studies, with 47,229 people, of whom 12,199 had LP implantation. The study population had a mean age of 80 years and 56% were male. Among the included studies, 8 were prospective and 13 were retrospective, with no RCTs identified. The mean follow-up periods ranged from 6 to 24 months.
The meta-analysis by Wu (2023) included data from 8 observational studies with a total of 464 people with complete or high-grade AV block and sinus node dysfunction with or without AF. There were 3 multicentre prospective studies, 3 single-centre prospective studies, and 2 single-centre retrospective studies. The study population had a mean age of 76.3 years and 44% were female. The follow-up duration across studies ranged from immediate post-procedure outcomes to a maximum of 12 months, with most studies reporting follow-up durations of less than 3 months.
El-Chami (2024) conducted a multinational, non-randomised, prospective registry study (the Micra VR Post-Approval Registry, PAR) to evaluate the long-term performance of the LP in real-world clinical settings. The study enrolled 1,809 people across 179 centres in 23 countries between July 2015 and March 2018, with a median follow-up duration of 51.1 months and a leading-edge follow-up of 86.7 months. The mean age of the study population was 75.6 years, with a median age of 79 years (IQR 71.0 to 84.0), and 39% were female (701 out of 1,808). There was a high prevalence of comorbidities, including atrial tachyarrhythmias (76%), congestive heart failure (CHF) (15%), chronic obstructive pulmonary disease (COPD) (10%), CAD (22%), HTN (65%), diabetes (27%), renal dysfunction (22%), and dialysis dependency (8%).
A comparative effectiveness analysis conducted by El-Chami (2024) evaluated the long-term outcomes (over a follow-up period of 2 years) of a LP in comparison to a traditional dual-chamber TVP in a large cohort of US Medicare population. A total of 118,110 people were included, of whom 7,552 had a LP and 110,558 had a TVP. The mean age was 79.0 years (range 21 to 105) in the LP group and 78.7 years (range 23 to 106) in the TVP group. The proportion of females was 48% in the LP group and 47% in the TVP group. People in the LP group had a higher burden of comorbidities compared to those in the TVP group.
A multicentre retrospective registry study by Shah (2023) was conducted across 13 centres in the US, 1 in the UK, and 1 in Italy, using data from the Pediatric and Congenital Electrophysiology Society (PACES) registry. A total of 63 people were enrolled, with a mean age of 15 years; standard deviation (SD) 4.1 years and 59% were male. Of the 63 children and young people, 32% had congenital heart disease (CHD), 29% had previous cardiac surgery and 22% had a prior pacemaker implantation. The mean follow-up was 9.5 months, ranging from 2 to 32 months.
The multicentre, retrospective, observational study by Strik (2023) was based in France and included 35 young adult people aged between 18 and 40 years, with 21 males (60%). The cohort had a mean LVEF of 57%. Indications for LP implantation included congenital AV block (n=3), postoperative AV block (n=7), post-heart transplantation (n=2), muscular dystrophy syndrome (n=5), symptomatic paroxysmal AV block (n=8) and symptomatic sinus node dysfunction (n=10). The mean follow-up period was 26 months; SD 15 months.
Amrani (2020) conducted a prospective observational study in Spain on 129 people over 70 years old who had LPs for single-chamber pacing. The outcomes were stratified into 2 groups based on age: 41 people aged 90 years or older and 88 people younger than 90 years. Sex distribution differed between the groups, with 18 males (44%) and 23 females (56%) in the 90 years and older cohort, compared to 32 males (36%) and 56 females (64%) in the younger cohort. Both groups had a high prevalence of comorbidities, and AV block was the main pacing indication. Follow-ups were done at 7 days, and at 1-, 3-, 6-, and 12-months post-implant, then annually.
A retrospective cohort study (Panico 2024) in France compared outcomes of LPs versus single-chamber TVPs implantation in 384 people on haemodialysis. After 1:1 propensity score matching, 178 people were included (89 in each group), with a mean age of 77.9 years and 30% female. Comorbidities were common: chronic heart failure (63%), AF or flutter (67%), ischaemic heart disease (55%), and diabetes (74%). Median follow-up was 24 months (range 7 to 37).
Molitor (2024) conducted a prospective study in Switzerland and the Netherlands comparing internal jugular versus femoral vein approaches for LP implantation in 200 people (mean age 81.2 years, 60% male). In the jugular group, primary indications included AV block (39 people), AF-related conditions (32), and sick sinus syndrome or pauses (29). AF was more common in the femoral group, though detailed indications were not provided. Comorbidities were prevalent, with 73% having AF, 36% CAD, 43% valvular disease, 37% chronic kidney disease, and others including COPD, diabetes, cancer, and prior stroke. Follow-ups were on days 1 and 14 with clinical reviews and device checks.
Knops (2023) conducted a prospective multicentre study across 55 sites in the US, Canada, and Europe to assess the safety and performance of a dual-chamber LP in 300 people (mean age 69.2 years, 62% male). Main pacing indications were sinus node dysfunction (63%) and AV block (33%). The primary safety outcome was freedom from serious device- or procedure-related events within 90 days. Performance was evaluated at 3 months by atrial capture and sensing, and by AV synchrony while seated, targeting at least 70%.
The prospective multi-centre clinical trial study (Tjong 2018) involved 726 people undergoing Micra transcatheter pacing system (TPS) implantation across 56 centres in 19 countries between December 2013 and May 2015. The cohort had a mean age of 76 years, with 59% being male. The primary outcomes measured included health-related quality of life, patient satisfaction, and activity restrictions post-implantation.
The comparative retrospective study (Cabanas-Grandío 2020) examined 106 people (64 with TVPs and 42 with LPs) undergoing single-chamber pacemaker implantation from December 2016 to March 2018 across four tertiary hospitals in Spain. The participants had an average age of 79.8 years, with significant differences in age and diabetes prevalence between the groups. Quality of life was assessed using the SF-36 questionnaire at baseline and 6 months post-implantation.
The retrospective cohort study by Ueyama (2024) analysed data from 10,338 Medicare fee-for-service beneficiaries aged 65 or above who had transcatheter aortic valve replacement (TAVR) followed by permanent pacemaker implantation between January 2017 and December 2020 in the USA. Among them, 730 people (7%) had LPs and 9,608 (93%) had TVPs. People were identified using procedure codes from national Medicare claims databases. The study aimed to compare short- and midterm outcomes between the 2 pacemaker types using propensity score overlap weighting to adjust for confounding. The primary outcome measures included in-hospital complications, and midterm outcomes up to 2 years, including all-cause mortality, heart failure hospitalisation, infective endocarditis, and device-related complications.
Table 2 presents study details.
Study no. | First author, date country | Characteristics of people in the study (as reported by the study) | Study design | Inclusion criteria | Intervention | Follow up |
|---|---|---|---|---|---|---|
1 | Garweg C, 2023, Belgium | n=51 Mean age: 82.5 years (SD 4.6) Male: 61% Indications:
Comorbidities:
renal impairment (mean eGFR ~60 mL/min) Median CHA2DS2-VASc score around 4. | Prospective, randomised, non-inferiority, single-centre study. | 18 years or older; Class I or II indication for single-chamber VVI pacemaker; LVEF greater than 40%; adequate baseline echocardiographic image quality; no previously implanted cardiac devices or mechanical valves; no pre-existing conditions challenging or precluding conventional pacemaker implantation; capable and willing to provide informed consent. | Intervention group (n=27): LPs (Micra LP) implanted via femoral approach targeting RV mid-septum or basal outflow tract; Control group (n=24): TVP (single-chamber VVI pacemaker, Medtronic Advisa ADSR03) implanted transvenous with RV pacing lead, also targeting mid-septum or basal RV outflow tract initially, apical positioning considered secondary if necessary. | 12 months; echocardiography at baseline, 6 and 12 months; NT-pro-BNP measured at baseline and 12 months; clinical assessments at day 10, 1, 6, and 12 months. |
2 | Inoue N, 2024, Japan | n=653 Mean age: 76.9 years Male: 69%; Mean LVEF: 56% (95% CI: 52% to 59%). Common comorbidities:
| Systematic review and meta-analysis of 16 studies: 1 prospective 7 retrospectives 4 case series 4 unclear designs | Included clinical studies and case series reporting 2 or more cases of CIED removal because of infection followed by LP implantation. Outcomes assessed: all-cause mortality or reinfection after LP implantation. Excluded were reviews, single-case reports, abstracts, indications other than infection, unclear follow-up durations, additional cardiac devices other than LPs, animal studies, and non-English literature. | LP implantation done either simultaneously (immediate strategy: median interval of 0 days) or staged after extraction of infected CIEDs (delayed strategy: median interval of 8 days). | Mean=14 months (SD 9.3); outcomes monitored included mortality rates (all-cause mortality) and occurrences of reinfection. |
3 | Mhasseb C, 2025, Lebanon | n=972,479 People with cardiovascular diseases needing permanent pacemaker implantation. Sample size: ranged from 62 to 580,925, mean age ranged from 70 to 90 years. Common comorbidities included:
| Meta-analysis including 19 observational studies (no RCTs): 7 prospective observational cohort 12 retrospective observational cohort studies or database analyses. High methodological heterogeneity (I² varied from 3% to 99%). | Studies comparing TVP and LP, published between 2018 and 2023, in English, with safety-related outcomes: major complications, reintervention, mortality, device malfunction, thromboembolic events, infections, pneumothorax, and haemothorax. | LP, specifically Micra (Medtronic, Minnesota – 17 studies), versus conventional TVP. | Varied widely among studies: from immediate post-procedure (in-hospital outcomes) up to long-term follow-ups ranging from 6 months to approximately 3.5 years (median follow-up durations ranged from 180 days to 39 months across studies). |
4 | Oliveira VMR, 2025, Brazil | n=47,229 (12,199 LP) Mean age: 80 years (SD 10); 26,646 (56%) males. | Meta-analysis of 21 observational studies: 8 prospective 13 retrospectives No RCTs included. | Studies published up to September 2023 comparing LP with TVP, reporting on effectiveness or safety endpoints; adults needing VP. | LP: primarily Micra (Medtronic, Minnesota) – 15 studies; Nanostim – 2 studies; both Micra and Nanostim – 3 studies; unspecified – 1 study. LP compared to conventional TVP. | Varied widely among studies: from immediate post-procedure (in-hospital outcomes) up to 24 months. Mean follow-up ranged between 6 months to 24 months across studies. |
5 | Wu S, 2023, China | n=464 Mean age: 76.3 years (SD 4.2); Females: 44%. Indications for pacing included:
VP burden varied (from about 10% in sinus node dysfunction to about 100% in complete AV block). | Systematic review and meta-analysis, including 8 observational studies: 3 prospective multicentre 3 prospective single centres 2 retrospective single centre All studies published between 2018 and 2022. | Studies evaluating LP with AV-synchrony algorithm. Reported AV synchrony outcomes post-implantation. Excluded case reports, reviews, non-human studies, duplicated cohorts, studies with combined interventions (ablation or defibrillation) and studies not reporting AV synchrony. | LP, specifically Micra AV (Medtronic, Minneapolis, Minnesota, USA) in 100% of included studies. Accelerometer-based AV synchrony algorithm in VDD pacing mode versus conventional VVI pacing mode. | Immediate post-procedure (in-hospital outcomes) up to a maximum of 12 months follow-up (most studies reported follow-up durations less than 3 months). |
6 | El-Chami MF, 2024, Multinational (23 countries) | n=1,809 LP (2,667 historical controls) Median age: 79 years (IQR: 71 to 84) Female: 39% (701/1808)
Pacing Indication:
| Micra VR PAR, non-randomised, prospective registry study Comparator group: Historical control (2,667 people with TVPs, studies 2000 to 2012) Outcomes adjudicated by Clinical Events Committee Statistical analysis: Fine–Gray competing risk models, propensity score overlaps weights | People having Micra VR LP implantation Class I or II indications for pacing No comorbidity restrictions Enrolment July 2015 to March 2018 Exclusion: previous enrolment in pre-market trials | Micra VR LP Implantation | Median follow-up: 51.1 months (IQR: 21.6 to 64.2) |
7 | El-Chami MF, 2024, USA | n=118,110 (n=7,552 LP, n=110,558 TVP) Mean age: LP AV: 79.0 years (SD 10.2); (range: 21 to 105) TVP: 78.7 years (SD 8); (range: 23 to 106) Female:
Key Comorbidities (LP AV versus TVP):
Charlson Comorbidity Index:
| Comparative effectiveness analysis using Medicare administrative claims linked to device registry data. People identified via device implantation registry and Medicare claims. Adjusted using propensity score overlap-weighted analysis to control for population characteristics. | US Medicare Fee-for-Service (FFS) population undergoing first-time pacemaker implantation (LP AV or TVP) between February 2020 and December 2021. | LP (Micra AV, Medtronic) versus TVP | 2 years post-implantation. |
8 | Shah MJ, 2023, USA, UK, and Italy | n=63 Weight: 55 kg (SD 19) Sex: 58% male Indications for LP:
24 (38%) had symptomatic bradycardia. Prior pacemaker: 14 (22%) had a prior pacemaker (transvenous: 5, epicardial: 9). | Retrospective registry study, multicentre | Inclusion criteria: People aged 21 years or younger LP implantation (Medtronic) Complete LP procedure documentation Clinical follow-up of 1 week or more Exclusion criteria: People older than 21 years Incomplete procedural data Follow-up less than 1 week | Micra Transcatheter LP (Medtronic), implanted via femoral (87%) or internal jugular (13%) venous access. Micra VR was used in 97% of people, and Micra AV in 4.8%. | Mean follow-up duration of 9.5 months (SD 5.3); range: 2 to 32 months, median: 10 months. Follow-up data categorised in 4-month intervals: |
9 | Strik M, 2023, France | n=35 young adult people, with 21 males (60%) and average age of 34 years (SD 8). People had the following characteristics: height: 165 cm (SD 29) weight: 66 kg (SD 19) LVEF of 57% (SD 14%) Indications:
| Multicentre (4), retrospective, observational study conducted between 2015 and 2021. | People aged between 18 and 40 years who had implantation of a LP for any indication. The protocol was approved by the ethics committee at each of the 4 participating centres, and all the people provided written and informed consent. | Implantation of the Micra VR LP (Medtronic) | The mean follow-up was 26 months (SD 15); range: 6 to 60 months. |
10 | Amrani AE, 2020, Spain | n=129 Age: 41 people aged 90 years or above (mean age 92.9 years; SD 2.4) 88 people aged less than 90 years (mean age 83.9 years; SD 4.1). Gender Distribution: ≥90 Years: 18 males (44%) and 23 females (56%) <90 Years: 32 males (36%), 56 females (64%) Comorbidities: HTN: 36 (86%) in ≥90 years, 73 (83%) in <90 years. Diabetes mellitus: 9 (22%) in ≥90 years, 23 (33%) in <90 years. Chronic kidney disease: 24 (59%) in ≥90 years, 31 (35%) in <90 years Structural heart disease: 14 (34%) in ≥90 years, 49 (56%) in <90 years AF: 9 (22%) in ≥90 years, 10 (11%) in <90 years CHF: 4 (10%) in ≥90 years, 36 (41%) in <90 years. Indications for Pacing: AV block: 29 (71%) in ≥90 years, 61 (69%) in <90 years AF with slow ventricular response: 8 (20%) in ≥90 years, 11 (13%) in <90 years Sinus node dysfunction: 4 (10%) in ≥90 years, 36 (41%) in <90 years. | Prospective observational study: People were divided into 2 groups based on age: 90 and above and younger than 90 years. | People older than 70 years with indications for single-chamber pacing. Specific indications for LP implantation included previous TVP infection, absence of upper vascular access, and clinical need assessed by the treating physician. | Micra LPs implanted via transcatheter approach. The procedure was performed under conscious sedation and local anaesthesia. | At 7 days, and 1, 3, 6, and 12 months after implantation, with subsequent annual follow-ups. Electrical parameters and clinical outcomes were monitored throughout the follow-up period. |
11 | Panico A, 2024, France | n=384 adult people with ongoing haemodialysis implanted with a first-time single-chamber pacemaker between 2017 to 2020. Indications: cardiac conduction disorders Demographics: Age: Mean 77.9 years (SD 8.6), Median: 80 years (IQR 74 to 84). Female: 30% (n=27). Comorbidities:
Vascular Access for Dialysis:
Baseline Health Conditions:
| Retrospective cohort study using propensity score matching (1:1) to balance baseline characteristics. Data was sourced from the French REIN registry and linked to the SNDS national health database. | Inclusion Criteria: Adult (≥18 years) haemodialysis population First-time implantation of a single-chamber TVP or LP between January 2017 - December 2020 Matched from the REIN registry and SNDS database Exclusion Criteria: History of any previous pacemaker or defibrillator implantation | LP group (n=89): Majority implanted with Medtronic Micra LP. TVP group (n=89): Conventional single-chamber TVPs. | Median 24 months (range 7 to 37 months). |
12 | Molitor N, 2024, Switzerland and Netherlands | n=200. 100 jugular approaches (University Hospital Zurich: n=50, Haga Teaching Hospital: n=50) + 100 femoral approach (comparison group, Zurich only) Primary Indications (for the jugular approach group only, n=100):
Comorbidities:
| Prospective study comparing jugular vein approach versus femoral vein approach for LP implantation in 2 tertiary centres. | People with indication for LP implantation No contraindications for standard femoral implantation No severe valvular disease preventing pacemaker implantation No history of superior vena cava obstruction No active infection at the time of implantation | Micra LP implantation via the internal jugular vein. Right internal jugular vein punctured under ultrasound guidance. Standard 9Fr sheath followed by 27Fr introducer. Pacemaker delivered via guidewire-assisted catheter technique. Device positioned at inferior (25%), mid (50%), or high (25%) ventricular septum. Compared to standard femoral implantation group | At day 1 and day 14 post-implantation Monitoring through clinical records, hospital visits, and pacemaker interrogation |
13 | Knops RE, 2023, USA, Canada, Europe (55 centers) | n=300 Male: 62%, Female: 38% Age: 69.2 years (SD 13.5) BMI: 28.1 (SD 5.6)
| Prospective, international, multicentre, single-group study, evaluated safety & performance of dual-chamber LPs. | Inclusion: standard indication for dual-chamber pacing, age 18 or above Exclusion:
| Dual-chamber LP (Aveir DR i2i, Abbott Medical) implanted percutaneously via the femoral vein, with 2 separate LPs (1 in the right atrium and 1 in the right ventricle), using an active fixation helix for endocardial attachment and beat-to-beat wireless communication to maintain AV synchrony. | Primary follow-up period was 90 days |
14 | Tjong FVY, 2018, Multiple countries (56 centers across 19 countries), with notable involvement from the Netherlands (Amsterdam UMC, University of Amsterdam). | n=720 implanted with a LP. Mean age: 76; SD 11 years. Gender: 59% male. Clinical indications aligned with class I or II guidelines for VVIR pacing. | Prospective multicenter clinical trial | People suitable for VVIR pacing as per clinical guidelines. | Implantation of a Micra LPs. | At baseline, and then at 3 and 12 months post-implantation. |
15 | Cabanas-Grandío, 2020, Spain | n=106 (64 TVPs and 42 LPs); average age 79.8 years; baseline characteristics included demographic factors such as sex distribution and prevalence of diabetes. | Comparative retrospective study between LPs and TVPs with follow-up assessments. | Age 18 or more, indication for single-chamber pacemaker implantation, absence of cognitive impairment, ability to complete the SF-36 questionnaire, and ability to provide informed consent. | Single-chamber pacemaker implantation (the research did not specify the brand names of the LPs or TVPs) | 6 months post-implantation, with additional assessments at 1 month for some people. |
16 | Ueyama HA, 2024, USA | n=10,338 (LP=730, TVP=9,608), median age 82 years, male: 434 (60%) in LP group and 5,398 (56%) in TVP group. Conditions (LP versus TVP):
| Retrospective cohort study using Medicare claims data | People aged 65 or above who had TAVR between January 2017 to December 2020 with permanent pacemaker (LP or TVP) implanted during same admission. | Micra VR and Micra AV LPs (Medtronic USA), compared to TVPs. | Median duration of 17.3 months (IQR: 7.4 to 29.5), until the occurrence of an outcome event, death, disenrollment from Medicare Part A and B, or up to 2 years post-procedure, whichever came first. |
Procedure technique
Most procedures were done using femoral vein access, but jugular vein access was also used.
Final device positioning differed between groups in the RCT of 51 people (Garweg 2023). None of the LPs were placed at the ventricular apex, whereas 6 out of 24 (25%) TVPs needed apical placement because of inadequate pacing parameters in non-apical positions.
In the systematic review and meta-analysis (Oliveira 2023) of 21 studies, LP devices included the Micra (Medtronic, Minnesota) in 15 studies, Nanostim device in 2 studies, both Micra and Nanostim in 3 studies, while 1 study did not specify the LP device used.
Most studies used single-chamber LPs but the study by Knops (2023) used a dual-chamber LP. Dual-chamber LP may need alternative access strategies compared to single-chamber implantation. The Aveir DR i2i (Abbott Medical) dual-chamber LP system was implanted percutaneously via the femoral vein.
Efficacy
Successful Implantation
This outcome was reported in 10 studies and ranged from 98 to 100% for LPs.
A randomised controlled trial of 51 people reported a 100% implantation success rate in both LP and TVP groups. The first-attempt success rate was statistically significantly higher in the LP group (96%; 26 out of 27) compared to the conventional pacemaker group (63%; 15 out of 24, p<0.001). Despite this difference, the median total implantation time was similar between groups (LP: 35 minutes, IQR: 31 to 45; TVP: 35 minutes, IQR: 20.3 to 47.8, p=0.999). Venous access time was statistically significantly longer in the LP group (17 minutes, IQR: 14 to 19) compared to the TVP group (7 minutes, IQR: 6 to 14, p<0.001), likely due to additional procedural steps needed for LP implantation, such as routine RV angiography and the use of temporary pacing guide wires in 18 people (Garweg 2023).
In the meta-analysis by Mhasseb (2025), the overall rate of successful implantation was 99% (95% CI 98 to 100%) in the LP group and 98% (95% CI 97 to 99%) in the TVP group (p=0.07). The authors noted that TVP implantation was associated with a higher rate of procedural complications, which contributed to early implantation failures.
The 5-year follow-up of the Micra PAR study (El-Chami 2024) reported a 99% implantation success rate, with the Micra VR successfully implanted in 1,792 out of 1,809 people. Similarly, in the PACES registry study by Shah (2023), which included 63 children and young people, the implantation success rate was 98% (62 out of 63).
A retrospective study of young adults (Strik 2023) involving 35 people aged 18 to 40 years reported a 100% successful implantation rate for the Micra VR LP, with no technical failures or abandoned procedures. Similarly, a prospective observational study (Amrani 2020) including 129 elderly people found no statistically significant difference in success rates between age groups, with implantation being successful in 98% (40 out of 41) of people aged 90 or above and 99% (87 out of 88) in people younger than 90 (p=0.58).
A propensity score-matched retrospective cohort study (Panico 2024) of people using haemodialysis reported implantation success rates of 99% for LPs and 100% for TVPs.
In a prospective study of 200 people (Molitor 2024), comparing jugular versus femoral vein approaches, the success rate was 100% (100 out of 100) with jugular vein access. Success rate in the femoral group was not reported.
For dual-chamber LP implantation, a prospective study (Knops 2023) of 300 people reported an implantation success rate of 98% (295 out of 300), based on achieving effective implant-to-implant communication.
In the prospective study of 720 people (Tjong 2018), 99% people had successful LP implantation.
Adequate Pacing Performance
The randomised controlled trial of 51 people comparing LPs with TVPs reported similar VP percentages at 12 months (LP: 58% versus TVP: 62%, p=0.744). However, paced QRS duration was statistically significantly shorter in the LP group (median 158 ms, IQR: 146 to 166) than in the conventional pacemaker group (164 ms, IQR: 158 to 178, p=0.024). Additionally, pacing efficiency was superior in the LP group, with a statistically significant lower mean pacing threshold at 12 months (0.4 V versus 0.7 V, p<0.001) and higher mean R-wave sensing (14.2 mV versus 10.4 mV, p=0.021), (Garweg 2023).
Similarly, a meta-analysis of 21 studies by Oliveira (2025) found that LPs demonstrated a statistically significant lower pacing capture threshold than TVPs, with a mean difference (MD) of -0.2 V (95% CI -0.2 to -0.2 V, p<0.01). No statistically significant difference in impedance was observed (MD 32.6 ohms, 95% CI -22.5 to 87.8 ohms, p=0.25).
The ability of LPs to achieve AV synchrony was specifically assessed in a systematic review and meta-analysis of 8 observational studies by Wu (2023). The pooled AV synchrony proportion across these studies was 79% (95% CI 72 to 86%), with individual study results ranging from 63% to 89%. Additionally, programming optimisation led to an 11% improvement in synchrony (95% CI 7 to 16%, p<0.01), demonstrating the adaptability of LPs in improving pacing performance over time.
Long-term observational studies further support these findings. The Micra PAR 5-year follow-up study (El-Chami 2024), involving 1,809 people, documented stable pacing capture thresholds, with initial values of 0.7 V at 0.2 ms at implant, which remained consistent at 0.7 at 0.2 ms at 60 months. Pacing impedance declined from 727 ohms at implantation to 533 ohms at 60 months, while sensing amplitude improved from 10.7 mV to 13.1 mV over the same period. Additionally, the Micra AV CED registry study (El-Chami 2024), which included 118,110 people, demonstrated that AV synchrony with LP ranged between 80% and 84%, over a 2-year follow-up period.
Findings from paediatric and younger adult populations also indicated stable electrical performance over time. The retrospective PACES study (Shah 2023) involving 63 children and young people reported that capture thresholds decreased over time, with an initial mean of 0.8 V at 0.2 ms, which declined to 0.7 V at 1 to 4 months, and 9 to 12 months. Similarly, in the retrospective study of young adults (aged 18 to 40 years) by Strik (2023), the pacing efficacy endpoint was met in 97% of people at 6 months, with 1 person having a pacing threshold above 2 V. Additionally, mean R-wave amplitude increased from baseline to 6 months (1.4 mV, p<0.01), while impedance decreased (-89 ohms, p<0.01), which was statistically significant. At 2 years, 91% of population maintained a pacing threshold below 1 V.
Among an elderly population, findings were similarly positive. The prospective observational study (Amrani 2020) reported that 99% of people aged 90 or above had a pacing threshold below 1.5 V at 0.2 ms, demonstrating electrical stability with no statistically significant differences compared to the younger cohort. The propensity score-matched retrospective cohort study of people on haemodialysis found that LPs maintained stable electrical parameters, with a mean pacing threshold of 0.5 V at implantation, remaining consistent over a median follow-up of 24 months (Panico 2024).
The impact of venous access approach on pacing performance was evaluated in a prospective study (Molitor 2024) of 200 people, comparing jugular and femoral approaches. Pacing thresholds for the jugular approach remained stable over time, measured at 0.6 V at implantation, Day 1, and Day 14. These values were comparable to those observed with the femoral approach, which showed thresholds of 0.5 V at implantation and Day 1, and 0.61 V at Day 14. Sensed amplitudes in the jugular group increased from 10.0 mV at implantation to 10.9 mV on Day 1 and 11.4 mV on Day 14, closely matching the femoral group, which recorded 9.9 mV, 10.8 mV, and 11.7 mV at the same time points. No deterioration in electrical performance was observed. Lead impedance was initially higher in the jugular group at 772.3 ohms; SD 218.6 ohms at implantation, compared to 705.8 ohms; SD 142.3 ohms in the femoral group (p=0.011), but differences diminished over time, with values of 695.7 ohms (SD 205.6) versus 662.9 ohms (SD 131.4) on Day 1 (p=0.188) and 611.1 ohms (SD 143.7) versus 605.6 ohms (SD 96.7) on Day 14 (p=0.675), indicating comparable long-term electrical performance between the 2 approaches.
The performance of dual-chamber LPs was assessed in a prospective single-group study (Knops 2023) of 300 people, evaluating atrial capture threshold and sensing amplitude. At 3 months, 90% of population met predefined criteria for adequate atrial capture threshold (less than or equal to 3.0 V at 0.4 ms) and atrial sensing amplitude (P-wave more than or equal to 1 mV) (95% CI 86.8 to 93.6, p<0.001). The mean atrial capture threshold was 0.8 V (SD 0.7), and mean P-wave amplitude was 3.6 mV (SD 1.9), indicating stable pacing function.
6 minute Walk Test (6MWT)
In the randomised controlled trial of 51 people, there was no significant decline in 6MWT distance over 12 months in either group (p=0.577), and the difference between LP and TVP groups at 12 months was also not statistically significant (p=0.088) (Garweg 2023).
Cardiac Function
A key finding from the RCT study (Garweg 2023) was the preservation of tricuspid valve function in LP population. Over the study period, tricuspid regurgitation statistically significantly worsened in the TVP group (p=0.001), whereas it remained stable in the LP group (p=0.195). By 12 months, there was no progression of tricuspid regurgitation in 58% of those in the LP group compared with 13% of those in the TVP group (p=0.009). Additionally, at 12 months, tricuspid regurgitation worsened in 70% of the TVP population but in only 31% of the LP group (p=0.009). The difference for mitral regurgitation was not statistically significant (p=0.304).
A notable difference was observed in NT-proBNP levels, a biomarker for heart failure progression. At baseline, levels were comparable between groups (LP: 1176 pg/dl, IQR: 603 to 2357; TVP: 907 pg/dl, IQR: 410.5 to 2345.8, p=0.355). By 12 months, NT-proBNP levels had increased in the TVP group but had decreased in the LP group. The final median NT-proBNP level was 970.0 pg/dl (IQR: 536.0 to 1453.5) in the LP group compared to 1394.0 pg/dl (IQR: 1030.0 to 2245.5) in the TVP group (p=0.041). Interaction analysis confirmed a statistically significant overall difference between groups (p=0.013).
Length of Hospital Stay
In the prospective study of 129 elderly individuals (Amrani 2020), hospital stay was similar across age groups, with a median of 3.0 days in both the people aged 90 and more and less than 90 years. The IQR was 2 to 5.5 and 1 to 9 days, respectively, with no significant difference (p=0.95).
In the propensity score-matched study of people on haemodialysis (Panico 2024), those who had LPs had a statistically significantly shorter hospital stay (mean: 6.8 days) compared to those with TVPs (mean: 11.2 days, p=0.0014).
The retrospective cohort study by Ueyama (2024) including 10,338 people who had TAVR reported that the median length of stay was 4 days for both LP and TVP groups. The IQR was slightly wider for LPs (2 to 8 days) compared to TVPs (2 to 7 days). The length of stay was significantly longer with leadless pacemakers compared to transvenous pacemakers (adjusted mean difference 0.8 days; 95% CI: 0.2 to 1.4; p=0.005).
Device Durability
The RCT by Garweg (2023), reported higher impedance values in the LP group suggesting lower current drain and potentially extended battery longevity. At 12 months, pacing impedance was 661.2 ohms (SD 133.1) in the LP group versus 447.4 ohms (SD 121.8) in the TVP group (p<0.001). Furthermore, pacing thresholds remained statistically significantly lower in the LP group at all time points (p<0.001).
The meta-analysis by Mhasseb (2025) reported that LPs had a lower incidence of generator malfunction than TVPs (LogOR=-0.5, p=0.13). Battery longevity was also evaluated, with a median projected lifespan of 6.8 years, and a 12.1-year median battery life. Battery depletion was reported in less than 1% of LPs, indicating a high degree of durability.
Long-term observational data further support these findings. The Micra PAR 5-year follow-up study (El-Chami 2024) reported that at 5 years, the projected median battery longevity was 6.8 years, with 84% of people having at least 5 additional years of battery life remaining. Device durability remained high, with only 2% of devices needing replacement because of elevated pacing thresholds or battery depletion.
Among paediatric and younger populations, LPs also demonstrated favourable long-term performance. The Children PACES registry study (Shah 2023), which included 63 people, projected battery longevity using Monte Carlo methods, estimating that 90% of the 55 people with available follow-up data would exceed 8 years of battery life. The retrospective study (Strik 2023) of young adults undergoing LP implantation, with an average follow-up of 26 months; SD 15 months (range: 6 to 60 months), indicated stable device performance, with no reported instances of pacemaker failure, extraction, or retrieval during the study period.
The prospective study of 129 elderly individuals (Amrani 2020) reported that LPs had optimal electrical performance, with no reported device failures, dislodgements, migrations, or malfunctions over a 2-year follow-up period. During the 3-month follow-up after implantation, 93% of people aged less than 90 years and all people aged 90 or above maintained stable pacing thresholds of less than 1.5 V.
Safety
Cardiac perforation
The meta-analysis by Mhasseb (2025) reported that cardiac perforation was statistically significantly higher in the LP group than the TVP group. Among the 10 studies included in the analysis, 8 studies documented a greater risk of perforation in LPs (LogOR=1, p<0.001). However, Oliveira (2025), in a separate meta-analysis, found no statistically significant difference in myocardial perforation rates between LPs and TVPs (OR=1.8, 95% CI 0.5 to 6.5, p=0.39).
Findings from large observational studies support the low absolute incidence of cardiac perforation. The Micra PAR 5-year follow-up study (El-Chami 2024) reported 1 case of cardiac perforation among 1,809 people. Similarly, the retrospective PACES registry study (Shah 2023) recorded 1 case of cardiac perforation with pericardial effusion in a 7-year-old, 19 kg child, where the device had been deployed at the RV apex. This complication led to cardiac tamponade, which was successfully managed with pericardiocentesis, allowing the device to remain in place without further issues.
In elderly populations, the prospective study of 129 people (Amrani 2020) documented 1 case of cardiac perforation occurring in a person aged under 90 years. This complication was observed early in the implantation experience of the clinical team, suggesting that operator experience may play a role in procedural safety.
The propensity score-matched retrospective cohort study (Panico 2024) of people on haemodialysis found that cardiac perforation was not commonly reported in either LP or TVP groups. 1 case of haemopericardium was recorded in the LP group, potentially due to perforation, though no statistically significant difference was observed compared to the TVP group (0% incidence, p=0.07).
Cardiac tamponade
The meta-analysis by Mhasseb (2025) reported a 0.33% cumulative incidence of cardiac tamponade in those who had LPs, consistent with findings (0.33% cumulative incidence) from the Oliveira (2025) study, which found a statistically significantly increased risk in the LP group compared to the TVP group (OR 3.8, 95% CI 2.4 to 5.8, p<0.01). Observational data from the Micra PAR follow-up study (El-Chami 2024), included 6 cases of cardiac tamponade (less than 1%) among 1,809 people.
Pericardial effusion
The meta-analysis of 21 studies by Oliveira (2025) reported a statistically significantly higher risk of pericardial effusion in the LP group compared to the TVP group (OR 2.5; 95% CI 1.4 to 4.4, p<0.01). The systematic review and meta-analysis by Wu (2023) reported 4 cases of pericardial effusion in their study cohort (n=464).
The occurrence of pericardial effusion was consistently low across studies, with 1 case reported in each of the Micra PAR 5-year follow-up study (El-Chami 2024), the children PACES registry (Shah 2023), and both the jugular and femoral approach groups in a prospective study of 200 people (Molitor 2024). These findings suggest that pericardial effusion remains a rare complication, regardless of population or venous access approach.
In the prospective single-group study (Knops 2023) of 300 people who had dual-chamber LPs, pericardial effusion was reported in 2 people (1%), with 1 needing pericardiocentesis, while the other was managed conservatively.
Pulmonary oedema
In the Micra PAR 5-year follow-up study including 1,809 people (El-Chami 2024), there was 1 report of pulmonary oedema during the follow-up period.
Atrial Fibrillation (AF)
The Micra PAR 5-year follow-up study (El-Chami 2024) reported that AF was more common in people who had LPs compared to historical TVP cohorts, though precise incidence rates were not reported.
In a prospective study (Knops 2023) involving 300 people implanted with dual-chamber LPs, AF was the most common arrhythmic complication, occurring in 9 people (3%). Of these, 5 people had a prior history of atrial arrhythmias. In 8 people, AF occurred either during or immediately after implantation of the atrial LPs. All AF cases were successfully managed with pharmacological or electrical cardioversion.
Device failure (dislodgement, migration, embolisation, malfunction, battery issues)
The meta-analysis by Mhasseb (2025) reported that device dislodgement was lower in the LP group than in the TVP group. Among the 10 studies assessing this outcome, 8 documented a statistically significantly higher risk of dislodgement in TVPs (LogOR=-1.1, p<0.001). Lead dislodgement was less common in the LP group (0.1%) compared to the TVP group (1%, p<0.001) and there were a 70% lower odds of pacing failure due to lead dislodgement in the LP group compared to the TVP group (OR=0.3, 95% CI: 0.2 to 0.4). Additionally, generator malfunction was more frequent in TVPs (LogOR=-0.5, p=0.13), though this difference was not statistically significant. Similarly, a meta-analysis by Oliveira (2025) found that people who had LPs were at lower risk of lead dislodgement compared to those with TVPs (OR 0.3, 95% CI 0.2 to 0.6, p<0.01), a finding attributed to the absence of transvenous leads in LPs. 1 case of device dislodgement was reported in the systematic review by Wu (2023).
The Micra PAR 5-year follow-up study (El-Chami 2024) of 1,809 people documented 2 cases of device dislocation without embolisation (less than 1%) and 1 case of embolisation during implantation. Additionally, battery depletion in the presence of elevated thresholds was reported in 12 people. In the larger Micra AV CED registry study (El-Chami 2024) of 118,110 people, device-related complications were statistically significantly lower in LP population (219 out of 7,552; 3%) compared to TVP population (7,518 out of 110,558; 7%, p<0.0001). Dislodgement was observed in 1% (38 out of 7,552) of LP population versus 3% (3,095 out of 110,558) of TVP population (p<0.0001), and mechanical failure occurred in 1% (60 out of 7,552) versus 2% (1,658 out of 110,558) (p<0.0001).
The propensity score-matched retrospective study of people on haemodialysis found that lead-related complications were higher in the TVP population (Panico 2024). Lead fractures and dislodgements were observed exclusively in those who had TVPs (9%), whereas no cases of lead dislodgement, migration, embolisation, or battery malfunction were reported in the LP group (HR 0.4, 95% CI 0.2 to 0.9, p=0.0093). The prospective study (Molitor 2024) of 200 people comparing venous access sites reported only 1 case of device dislocation in the jugular approach group, which was the only device-related complication documented in that study. In the retrospective cohort study of 10,338 people who had TAVR as well as pacemaker implantation (Ueyama 2024), in-hospital device-related complications were 1% for LPs and 2% for TVPs (p=0.015), with fewer long-term device-related complications (sdHR 0.4; 95% CI: 0.2 to 0.6; p<0.001) and the differences in groups were statistically significant. In the AF cohort, device-related complications were not statistically significant between LPs and TVPs (sdHR 1; 95% CI: 0.4–2.4; p=0.97). The non-AF cohort showed fewer complications with LPs compared to TVPs (sdHR 0.2; 95% CI: 0.1 to 0.7; p=0.017) and the difference was statistically significant.
In the prospective single-group study of 300 people evaluating the safety and performance of dual-chamber LPs, there were 6 cases of intraprocedural dislodgement (5 atrial and 1 ventricular pacemaker) (Knops 2023). Additionally, postprocedural dislodgement was observed in 5 cases, all involving the atrial LPs, at an average of 26 days: SD 17 days (range, 0 to 40 days) after implantation. In 4 of these cases, the device migrated outside the right atrium to the right ventricle (n=3) or the right pulmonary artery (n=1). All dislodged devices were successfully retrieved, and in 3 cases, reimplanted.
Repeat surgery (for device retrieval and revisions)
The meta-analysis by Mhasseb (2025) found that reintervention rates were significantly lower in the people who had LPs than in those with TVPs. Among the 19 included studies, 7 specifically examined reintervention outcomes, all of which reported a higher likelihood of device revision or extraction in the TVP group (LogOR=-0.7, p<0.001). The primary reasons for reintervention in TVPs included lead-related complications and system failures.
The Micra PAR 5-year follow-up study (El-Chami 2024) of 1,809 people reported an all-cause system revision rate of 5% (95% CI: 4% to 6%) over 5 years. The primary drivers of system revision were device upgrades (41%) and elevated pacing thresholds (31%). Similarly, the Micra AC CED study (El-Chami 2024), which included 118,110 people, found that device-related reinterventions were lower in LP population (264 out of 7,552; 4%) compared to TVP population (6,191 out of 110,558; 6%) (p<0.0001), which was statistically significant. Furthermore, device removals occurred in 53 out of 7,552 LP population (less than 1%), while the rate of upgrade from LP to a TVP pacemaker was 1% (106 out of 7,552), indicating that while LPs need fewer system revisions overall, device upgrades still occur in a small proportion.
The retrospective study of 63 children and young people (aged 21 and under; Shah 2023) reported 1 case of device retrieval and replacement due to high pacing thresholds at 1-month post-implantation. The retrospective cohort study of people on haemodialysis (Panico 2024) found that repeat procedures were more common in those who had TVP because of lead-related complications. Reinterventions for lead dysfunction occurred in 9% of people with TVPs compared to 0% of those with LPs (HR 0.4, 95% CI 0.2 to 0.9, p=0.0093).
The prospective single-group study of 300 people implanted with dual-chamber LPs, reported 8 revision procedures within 90 days (Knops 2023). Of these, 6 involved successful percutaneous retrieval followed by new pacemaker implantation, while 2 people did not have a replacement atrial pacemaker at the investigator's discretion.
Venous thromboembolism
The meta-analysis by Mhasseb (2025) indicated a higher risk of thromboembolic events in people who had LPs with a LogOR of 0.5 (95% CI: -0.3 to 1.2; 6 studies; I2=97%). However, this association did not reach statistical significance. The Micra PAR study (El-Chami 2024) reported 2 cases of venous thrombosis (less than 1%) among 1,809 people, comprising 1 case of deep vein thrombosis (DVT) and 1 case of pulmonary embolism (PE). The Micra AV CED registry study (El-Chami 2024), which included 118,110 people, found comparable rates of embolism and thrombosis between LP recipients (15 out of 7,552; 0.2%) and TVP population (221 out of 110,558; 0.2%), with no statistically significant difference between the groups (p=0.9015).
The retrospective multicentre study of 63 children and young people (Shah 2023) reported 1 case of a non-occlusive femoral venous thrombus identified post-implantation. This was successfully treated with enoxaparin for 2 months, with complete resolution confirmed on follow-up imaging.
A propensity score-matched retrospective cohort study (Panico 2024) of people on haemodialysis reported that VTE incidence was slightly higher in the people who had TVPs (13%) compared to those who had LPs (8%). This difference was not statistically significant (HR 1, 95% CI 0.4 to 2.2, p=0.92).
In the prospective study of 300 people who had dual-chamber LP implantation, a single case of pulmonary embolism occurred 28 days post-implantation. This event was excluded from the primary safety analysis as it was attributed to COVID-19 rather than the pacemaker itself.
Vascular complications
The Micra PAR 5-year follow-up study (El-Chami 2024) reported a low incidence of vascular complications, with 12 cases (0.7%) of groin puncture-related issues, including AVF (less than 1%), vascular pseudoaneurysm (less than 1%), and vessel puncture site haematoma (less than 1%). Similarly, the retrospective study of young adult population by Strik (2023) found minimal vascular complications, with no major adverse events reported.
The prospective observational study (Amrani 2020) of an elderly population reported a 2% incidence of vascular complications (n=2), comprising a single case of femoral pseudoaneurysm and 1 haematoma, both of which were deemed unrelated to the LP device itself. Similarly, the retrospective cohort study of a propensity score-matched haemodialysis population (n=384) found that vascular complications were more common in TVP population than in LP population, with 8 cases (9%) occurring in the people who had TVP implantation compared to 2 cases (2%) in the LP population (HR 4.25, 95% CI 0.88 to 20.39, p=0.07).
The prospective study of 200 individuals reported that the femoral approach was associated with a higher rate of complications, with 2 people having femoral artery injury (2%) and 13 major groin haematomas (13%). No vascular complications were observed in the jugular approach group (Molitor 2024).
In the prospective single-arm study of 300 people with dual-chamber LPs, there was 1 report each of vascular access site bleeding and retroperitoneal haematoma (Knops 2023).
Bleeding
The RCT of 51 people by Garweg (2023) reported a single case of pocket haematoma in the TVP group, which led to prolonged hospitalisation. The Micra PAR study of 1,809 people (El-Chami 2024), reported 1 case of retroperitoneal haemorrhage. The Children PACES registry study (Shah 2023) reported minor bleeding at the femoral venous access site in 3 people (5%), all of which resolved with manual compression. 1 person developed a femoral haematoma that needed no further intervention.
The retrospective propensity score-matched study of people on haemodialysis (Panico 2024) reported similar rates of bleeding events in both LP and TVP groups. 6 cases (7%) were recorded in the people who had TVPs, compared to 4 cases (5%) in the LP population (HR 0.7, 95% CI 0.2 to 2.4, p=0.52). In the prospective study of 300 individuals implanted with dual-chamber LPs, bleeding-related complications were minimal, with 1 case of access site bleeding and 1 case of retroperitoneal haematoma (Knops 2023).
Infections
The meta-analysis by Mhasseb (2025) assessed infection rates across 11 studies and found that while infection risk was lower in those who had LPs compared to those with TVPs, the difference did not reach statistical significance (LogOR=-0.6, p=0.27). Similarly, Oliveira (2025) conducted a separate meta-analysis evaluating infection rates and found no statistically significant difference between LPs and TVPs (OR 0.5, 95% CI 0.2 to 1.4, p=0.18).
In the Micra PAR 5-year follow-up study (El-Chami 2024), infection rates remained low, with 9 cases reported among 1,809 people. Of these, 5 were classified as major complications, including sepsis, abdominal wall infection, and catheter site infection, all of which were managed successfully with antibiotic therapy. No cases needed device removal because of infection. In the Micra AV CED study (El-Chami 2024), which analysed data from 7,552 LP recipients, 45 device-related infections were documented (1%). This rate was lower than that observed in the dual-chamber TVP cohort (p<0.0001). Furthermore, device-related infections were statistically significantly lower in the LP group (1%; 45 out of 7,552, p<0.0001). The impact of pacemaker type on infection risk has also been examined in high-risk populations. In a retrospective propensity score-matched study of people on haemodialysis, Panico (2024) reported a statistically significantly higher infection rate among the people who had TVP implantation. Device-related infections occurred in 9% of TVP population, whereas no infections were documented in the LP population (HR 0.4, 95% CI 0.2 to 0.9, p=0.0093).
Mortality
The RCT by Garweg (2023) reported 3 deaths during the study period between 9 and 11 months after implantation—1 in the LP group and 2 in the TVP group. These deaths were attributed to non-cardiac causes (2 due to cancer and 1 due to pulmonary infection) and were not related to the device itself.
The systematic review and meta-analysis by Inoue (2024) demonstrated a statistically significantly higher pooled mortality rate among people who had simultaneous LP implantation and CIED removal (23%, 95% CI: 16% to 32%, I²=0%, p=0.72) compared to post-extraction LP implantation (9%, 95% CI: 4% to 16%, I²=21%, p=0.27), with a statistically significant difference between these groups (p=0.008). Temporal trends indicated an estimated 1-month mortality rate of 3%, which was lower than the 7% observed in the simultaneous implantation population. By 186 days, mortality increased to 9% in the post-extraction implantation group, compared to 21% in the simultaneous implantation population.
The impact of pacemaker type on all-cause mortality has also been evaluated in meta-analyses. The meta-analysis by Mhasseb (2025), analysing 13 of 19 included studies, found a higher risk of mortality associated with TVPs, but this did not reach statistical significance (Cohen's d=-0.1, 95% CI: -0.2 to 0.01). Similarly, found no statistically significant difference in overall mortality between the people who had LPs and TVPs, with ORs and HRs consistently non-significant across different analytical approaches: overall analysis (OR 1.4, 95% CI 0.7 to 3.2, p=0.35), multivariate-adjusted analysis (OR 1.3, 95% CI 0.7 to 2.8, p=0.43), and time-to-event analysis (HR 1.1, 95% CI 0.9 to 1.3, p=0.53). This review also documented 1 death following LP implantation; however, the cause was not specified, making it unclear whether the event was device- or procedure-related.
The Micra PAR 5-year follow-up study (El-Chami 2024) reported 676 deaths among 1,809 people, corresponding to a 5-year mortality rate of 40%. Notably, 5 procedure-related deaths were identified, including 2 attributed to cardiac perforation. In a broader cohort analysis, the Micra AV CED study (El-Chami 2024) involving 118,110 people reported statistically significant higher all-cause mortality in LP population (2,567 of 7,552; 34%) compared to TVP population (26,305 of 110,558; 24%), yielding a HR of 1.5 (95% CI: 1.4 to 1.6, p<0.0001). A sensitivity analysis adjusting for 6-month survival confirmed persistence of this increased mortality risk (adjusted HR: 1.4, 95% CI: 1.3 to1.5).
The retrospective study of young adult people (n=35) recorded 3 deaths over a mean follow-up of 26 months, however none were related to LP implantation or the device (Strik 2023). There were 2 deaths in people with severe pre-existing conditions needing intubation and sedation, while the third resulted from malignancy. In the prospective observational study of an elderly population (Amrani 2020), 29 deaths were reported, with a mortality rate of 32% among those aged more than 90 years (n=13) compared to 18% in those younger than 90 years (n=16). Importantly, all deaths in this cohort were attributed to non-cardiovascular causes, with no device-related mortality reported.
In the propensity score-matched cohort study of people on haemodialysis (Panico 2024), the HR for mortality in the LP population compared to TVP was 0.7 (95% CI: 0.5 to 1, p=0.045), indicating a statistically significant reduction in mortality risk.
The prospective study of 300 people with dual-chamber LPs reported 4 deaths during follow-up, occurring between 46- and 86-days post-implantation (Knops 2023). The mean age of these people was 74 years. Causes of death included cardiac arrest (n=2), malignancy (n=1), and sepsis (n=1), with none attributed to the device or implantation procedure. In the retrospective cohort study of 10,338 people who had TAVR as well as pacemaker implantation (Ueyama 2024), there were no statistically significant differences in groups regarding all-cause death, with an adjusted HR of 1.1 (95% CI: 1 to 1.3; p=0.15) and in-hospital death (2% versus 1%; p=0.17). In the AF cohort, there was no statistically significant difference in all-cause death between LPs and TVPs (HR 0.9; 95% CI: 0.7 to 1.2; p=0.57). Similarly, in the non-AF cohort, LPs and TVPs showed no statistically significant difference in all-cause death (HR 1.2; 95% CI: 0.9 to 1.6; p=0.23).
Pacemaker syndrome
In the large prospective registry study, El-Chami (2024) followed 1,809 people with LPs over 5 years and reported pacemaker syndrome incidence of less than 1% (n=7). Similarly, in a retrospective study of 35 young adults by Strik (2023), 1 person experienced pacemaker syndrome, presenting with intermittent chest discomfort and light-headedness, attributed to retrograde P-wave conduction during VP. This issue was managed successfully by lowering the lower rate limit of the pacemaker without necessitating device removal or replacement.
Cardiomyopathy
In the large prospective registry study of 1,809 people by El-Chami (2024) pacing-induced cardiomyopathy occurred in 5 people over 5 years.
Pericarditis
The Micra AV CED study, also led by El-Chami (2024), evaluated a larger cohort of 7,552 LP population compared to 110,558 TVP population. Pericarditis was reported in 2% of LP population and 2% of TVP population (p=0.6876), indicating no significant difference.
Overall complication rate
The systematic review and meta-analysis by Oliveira (2025) reported overall complications were significantly lower in the comparison group, with an OR of 0.6 (95% CI: 0.5 to 0.8; p<0.01). Procedure-related adverse events were assessed in a systematic review by Wu (2023), which included 7 studies and reported an overall complication rate of 6%. The Micra AV CED study by El-Chami (2024), evaluated a larger cohort of 7,552 LP population compared to 110,558 TVP population. In this study, overall complication rates were statistically significantly lower in the LP population (5% versus 10%, p<0.0001), with fewer device-related complications such as dislodgement and infections. The retrospective cohort study of 10,338 people who had TAVR and pacemaker implantation (Ueyama 2024) reported that overall complication rates were statistically significant between LP and TVP groups (7% versus 10%; p=0.014).
In the prospective multi-centre clinical trial of 720 people (Tjong 2018), it is reported that 49% of people rated them as less restrictive compared to TVPs. Additionally, 47% of people felt that the discharge instructions were equally restrictive, while only a small minority of 4% found them to be more restrictive.
At six months post-implantation in the retrospective study of 106 people (Cabanas-Grandio 2020), only 11% of people in the LP group reported restrictions in physical activities due to chest discomfort, compared to 37% in the TVP group. This difference (p=.004) was statistically significant.
Anecdotal and theoretical adverse events
Expert advice was sought from consultants who have been nominated or ratified by their professional society or royal college. They were asked if they knew of any other adverse events for this procedure that they had heard about (anecdotal), which were not reported in the literature. They were also asked if they thought there were other adverse events that might possibly occur, even if they had never happened (theoretical).
They listed the following theoretical adverse events:
Rapid battery depletion due to high pacing thresholds or exit block
Long-term difficulty or inability to extract chronically implanted devices
10 professional expert questionnaires for this procedure were submitted. Find full details of what the professional experts said about the procedure in the specialist advice questionnaires for this procedure.
Validity and generalisability
Sample sizes varied widely, from small studies like Garweg's RCT (n=51) and a young adult study (n=35) to large analyses such as Oliveira's meta-analysis (n=47,229). Smaller studies lacked statistical power, while larger ones included heterogeneous populations.
Only the 5-year Micra PAR study includes UK data (El-Chami 2024). The rest are from the US, France, Switzerland, the Netherlands, or other non-UK European and North American centres.
Follow-up durations ranged from 90 days (dual-chamber LP study) to over 5 years (Micra PAR), providing some insight into long-term outcomes. Long-term data are particularly valuable for this procedure.
Bias was common, with most studies being observational. Meta-analyses by Inoue and Mhasseb found publication bias, especially regarding adverse events. Many studies, such as the Micra AV CED and Micra PAR, were industry-funded, raising concerns about conflict of interest despite transparency in methodology.
Procedural variation was also notable. While Garweg's RCT used standard protocols, others, like the jugular vs femoral study, tested alternative access routes. Device differences (Micra, Nanostim, Abbott dual-chamber LP) made direct comparisons difficult due to varying algorithms and fixation methods.
Results were often conflicting—LPs were associated with reduced infection risk in some studies, but not consistently across pooled data. Reported AV synchrony for LP also varied, with lower rates in real-world settings than in trials, likely due to differences in programming and population selection.
Key evidence gaps remain in long-term outcomes beyond 5 years, LP retrieval and replacement, and patient-reported outcomes. Ongoing trials may help address these gaps, particularly for new dual-chamber LPs and alternative implantation techniques, focusing different subgroups.
Any ongoing trials
Danish Randomized Trial on Leadless vs Transvenous Pacing (DANVERS) (NCT05856799); RCT; Denmark; n=80; completion date August 2025
The leadless MICRA AV versus DDD pacing study (LEAVE DDD) (NCT05498376); RCT (open label); Switzerland; n=100; completion date December 2027
Aveir VR coverage with evidence development post-approval study (CED) (NCT05336877); observational (case-control); US; n=8,744; completion date January 2028
Aveir DR i2i Study (NCT05252702); interventional (single group assignment); worldwide; n=550; completion date November 2025
The leadless II IDE Study for the Aveir VR leadless pacemaker system (NCT04559945); interventional (single group assignment); worldwide; n=326; completion date August 2023
Longitudinal coverage with evidence development study on Micra leadless pacemakers (Micra CED) (NCT03039712); observational (cohort); US; n=37,000; completion date June 2027
Key factors of leadless pacemaker implantation with implantation site, complications and prognosis (NCT05761821); observational (cohort); China; n=300; completion date December 2024
Micra transcatheter pacing system post-approval registry (NCT02536118); observational (cohort, patient registry); worldwide; n=3100; completion date August 2025
International leadless pacemaker registry (i-LEAPER) (NCT05528029); observational; Belgium, Italy, Switzerland; n= 2000; completion date December 2024
Aveir AR coverage with evidence development (CED) study (ARRIVE) (NCT06100770); observational; US; n=586; completion date January 2031
A Safety and Effectiveness Monitoring in France for AVEIR VR LP and AVEIR AR LP (France LEADLES) (NCT06262295); observational (patient registry); France; n=600; completion date September 2028
Aveir dual-chamber leadless pacemaker real-world evidence post-approval study; observational; USA; n= 1805; completion date January 2030
Aveir single-chamber leadless pacemaker real-world evidence post-approval study (NCT05270499); observational (patient registry); US; n= 2100; completion date February 2034
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