Impact of lead placement site on right ventricular function: a comparative echocardiographic analysis of apical versus septal pacing in permanent pacemaker recipients

Abstract

Objectives: Permanent pacemaker (PPM) implantation is a standard intervention for bradyarrhythmias, yet the long-term hemodynamic consequences of right ventricular (RV) lead positioning remain underexplored. While apical pacing has traditionally been favored, emerging evidence suggests that septal positioning may offer more physiological activation and better preserve cardiac function. This study aimed to compare the early echocardiographic effects of apical versus septal RV lead placement on right heart structure, function, and tricuspid valve competence in patients undergoing PPM implantation. Methods: In this prospective observational study, 20 patients were divided equally into two groups: apical and septal pacing. Comprehensive echocardiographic evaluations were performed pre- and one month post-implantation. Parameters included RV and right atrial (RA) size, RV fractional area change (RVFAC), tricuspid annular plane systolic excursion (TAPSE), pulmonary artery pressure (PAP), inferior vena cava (IVC) diameter, tissue Doppler indices (E’, A’), and tricuspid regurgitation (TR) severity. Statistical analyses included Mann-Whitney U tests and visualizations using radar plots and p-value heatmaps. Results: Post-implantation, the apical group demonstrated significantly greater RV and RA dilation, elevated PAP, and reduced E’ velocities, indicative of impaired diastolic function and increased right-sided load. In contrast, the septal group exhibited more stable dimensions and preserved diastolic function. Although baseline mild TR was more prevalent in the apical group (P<0.024), no significant intergroup differences in TR severity were observed at follow-up. Other clinical risk factors were comparable between groups. Conclusions: Septal lead positioning is associated with more favorable right heart geometry and hemodynamics than apical pacing in the early post-implantation period. These preliminary findings support septal pacing as a potentially superior strategy for long-term cardiac preservation, but the small sample size limits generalizability and warrants confirmation in larger, randomized trials.

Introduction

Permanent pacemaker (PPM) implantation remains a cornerstone of therapy for symptomatic bradyarrhythmias, with millions of patients worldwide benefiting from the restoration of adequate heart rates and improved hemodynamic stability [1,2]. While the efficacy and safety of PPM therapy are well established, accumulating evidence suggests that the long-term physiological impact of right ventricular (RV) pacing is far from neutral. In particular, chronic RV pacing, especially when delivered from the apical position, has been associated with electrical and mechanical dyssynchrony, adverse ventricular remodeling, and an increased risk of pacing-induced cardiomyopathy. These observations have prompted a growing interest in optimizing lead placement not solely for technical feasibility, but for the preservation of ventricular mechanics and prevention of pacing-related dysfunction [3].

Historically, the right ventricular apex has been the preferred site for lead placement due to its procedural accessibility, stability of the lead, and ease of fluoroscopic confirmation. However, several studies have demonstrated that apical pacing may exert deleterious effects on ventricular strain patterns and intraventricular synchrony, resulting in gradual impairment of both left and right ventricular function [4].

Previous studies have shown that apical pacing, due to its non-physiological activation pattern originating at the right ventricular apex, leads to intraventricular dyssynchrony, increased wall stress, and adverse remodeling characterized by chamber dilation and impaired strain patterns. Functionally, it is associated with reduced diastolic relaxation and elevated filling pressures. In contrast, septal pacing more closely mimics natural conduction pathways, resulting in narrower QRS complexes, more synchronous ventricular activation, and improved preservation of both systolic and diastolic function. Structurally, septal lead positioning has been associated with less right ventricular dilation and better maintenance of tricuspid valve competence, likely due to its more orthogonal lead trajectory and reduced mechanical interference with the valve leaflets. Despite these proposed advantages, direct comparative evidence on the specific right heart consequences of these two pacing sites remains scarce.

In contrast, septal pacing has emerged as a promising alternative, offering a more physiological activation sequence and potentially attenuating the mechanical stress imposed by chronic pacing. Despite this theoretical advantage, direct comparative data on the structural and functional consequences of septal versus apical pacing remain limited, particularly concerning the right heart, a chamber often underrepresented in pacing research despite its central role in cardiovascular performance [5,6].

Of particular relevance is the interaction between RV lead position and tricuspid valve integrity. The transvalvular passage of pacing leads has been implicated in the development and progression of tricuspid regurgitation (TR), which is independently associated with heart failure progression and mortality in device recipients. The anatomical trajectory of apical leads increases the likelihood of leaflet impingement, chordal entrapment, or annular distortion, thereby potentiating functional TR [7]. Septal lead positioning, by contrast, may reduce this mechanical interference and mitigate valve-related complications. However, the comparative impact of both lead positions on TR severity has yet to be definitively established [8].

To address these knowledge gaps, the present study prospectively examines the echocardiographic impact of apical versus septal lead placement in patients undergoing PPM implantation, with a focus on right heart remodeling, hemodynamic parameters, and tricuspid valve competence. By evaluating structural and functional changes both before and after device implantation, this study aims to clarify whether pacing site selection significantly alters right ventricular adaptation and to provide evidence that may inform positioning strategies in clinical practice.

Methods

Study design

This investigation was conducted as a prospective observational study aimed at assessing the impact of right ventricular lead placement site, specifically apical versus septal positioning, on right heart function in patients undergoing permanent pacemaker (PPM) implantation. The study was conducted at the Modarres Heart Center, a tertiary cardiovascular care facility, over a defined enrollment period.

Patient selection and group allocation

A total of twenty patients who were admitted for PPM implantation due to symptomatic bradyarrhythmias, including complete heart block, sick sinus syndrome, or atrial fibrillation with slow ventricular response, were included in the study. Participants were selected using an available sampling strategy. Based on the anatomical location of the right ventricular pacing lead, patients were assigned to either the apical group or the septal group. The assignment was non-randomized and determined intra-procedurally by the implanting physician, based on anatomical accessibility and clinical discretion.

Because group assignment was based on intraoperative physician discretion rather than randomization, the potential for selection bias cannot be excluded. Operator decisions were influenced by procedural feasibility, anatomical constraints, and clinical judgment, which may have introduced unmeasured confounding factors. To minimize observational bias, all echocardiographic measurements were performed by a single experienced cardiologist who remained blinded to the lead position throughout the study. Additionally, baseline demographic and clinical characteristics were comparable between groups, thereby reducing the likelihood that pre-existing comorbidities contributed to the observed differences in outcomes.

Inclusion and exclusion criteria

Eligible participants were adults aged 18 years or older undergoing first-time permanent pacemaker (PPM) implantation for standard clinical indications, including complete atrioventricular (AV) block, sick sinus syndrome, or atrial fibrillation with slow ventricular response. All patients were required to have adequate transthoracic echocardiographic windows to allow for reliable imaging of right heart structures, both before implantation and at one-month follow-up. Only those capable of providing informed written consent and adhering to the planned echocardiographic evaluations were included in the study.

Exclusion criteria were designed to eliminate confounding anatomical or physiological factors that might independently affect right heart remodeling or tricuspid valve function. Patients with prior cardiac device implantation, including temporary or permanent pacemakers, implantable cardioverter-defibrillators (ICDs), or cardiac resynchronization therapy (CRT) systems, were excluded. Additional exclusions included the presence of significant congenital heart disease, prior cardiac surgery involving the right heart, or moderate-to-severe tricuspid regurgitation at baseline from non-pacing-related etiologies (e.g., rheumatic valve disease or carcinoid syndrome). Patients with significant left-sided valvular abnormalities, defined as moderate or greater mitral or aortic regurgitation or stenosis, were also excluded. Other exclusion criteria included known pulmonary hypertension with a pulmonary artery systolic pressure (PASP) exceeding 40 mmHg unrelated to left heart disease, inadequate echocardiographic image quality, and persistent atrial fibrillation with a highly irregular rhythm that interfered with consistent Doppler measurement. Patients who declined follow-up or were unable to comply with study protocols were excluded from the final analysis.

Data collection and echocardiographic assessment

Demographic and clinical information were obtained through structured interviews and a review of hospital records. Key baseline variables included age, sex, history of hypertension, diabetes mellitus, ischemic heart disease, and tobacco use. All patients underwent comprehensive echocardiographic evaluation before pacemaker implantation and again at one-month follow-up using standardized transthoracic imaging protocols. Echocardiographic assessments focused on right ventricular and atrial dimensions, systolic and diastolic function, and tricuspid valve performance.

The parameters measured included right ventricular size, right atrial size, right ventricular fractional area change (RVFAC), tricuspid annular plane systolic excursion (TAPSE), pulmonary artery pressure (PAP), inferior vena cava (IVC) diameter, and tissue Doppler imaging indices (E’ and A’ velocities). A blinded cardiologist semi-quantitatively graded tricuspid regurgitation (TR) into five categories: none, trivial, mild, moderate, and severe. All measurements were performed by a single experienced operator who remained blinded to lead position throughout the study to minimize observer bias.

Tricuspid regurgitation classification

Tricuspid regurgitation (TR) severity was assessed semi-quantitatively by a single blinded cardiologist by the 2017 American Society of Echocardiography (ASE) guidelines. Classification was based on an integrated evaluation of color Doppler jet characteristics, including jet area, vena contracta width, hepatic vein flow reversal, and right atrial/ventricular enlargement. TR was categorized into five grades: none (no visible regurgitation), trivial (small central jet, <1 cm²), mild (jet area <5 cm² or <20% of right atrium), moderate (jet area 5-10 cm² or 20-40% of right atrium), and severe (jet area >10 cm² or >40% of right atrium with systolic flow reversal in hepatic veins). Measurements were made at end-systole from the apical four-chamber and subcostal views, ensuring consistency in acquisition. All evaluations were performed by the same experienced echocardiographer who remained blinded to the pacing site throughout the study.

Allocation strategy

Lead positioning, whether apical or septal, was determined intra-procedurally by the implanting cardiologist based on real-time anatomical considerations and procedural feasibility. This approach reflects standard clinical practice, where lead location is influenced by factors such as right ventricular anatomy, trabeculation patterns, fluoroscopic orientation, and the angle of venous access. Operators attempted septal positioning when feasible, particularly in patients with favorable septal anatomy and adequate sheath control. In cases where septal fixation could not be achieved securely or when fluoroscopic landmarks were ambiguous, apical pacing was selected to ensure procedural safety and lead stability. Although not randomized, this pragmatic allocation strategy reflects real-world decision-making and supports the generalizability of the findings. All operators were board-certified electrophysiologists with experience in both techniques.

Statistical analysis

All statistical analyses were conducted using SPSS software version 16. Continuous variables were summarized as mean ± standard deviation. Between-group comparisons were made using the Mann-Whitney U test, given the small sample size and the anticipated non-parametric distribution of the data. Categorical variables were reported as frequencies and compared using chi-square or Fisher’s exact test, depending on expected cell counts. A p-value of less than 0.05 was interpreted as statistically significant.

To enhance the interpretability of echocardiographic outcomes and intergroup comparisons, two advanced visualizations were generated. A radar plot (spider chart) was used to depict the normalized post-implantation functional profiles of apical versus septal pacing groups across eight key echocardiographic parameters, including chamber dimensions, systolic function indices, and diastolic velocities. Values were normalized to the highest value per parameter across groups to ensure uniform scaling and facilitate direct visual comparison. In addition, a heatmap of p-values was constructed to summarize the statistical significance of between-group differences before and after implantation. Raw p-values were categorized and visually encoded using a color gradient, highlighting the most clinically meaningful differences. All visualizations were created using Python (version 3.10) with Matplotlib and Seaborn libraries. These plots served to complement traditional tabular data presentation and underscore functional divergence between pacing sites.

Ethical considerations

The study protocol was approved by the institutional ethics review board and adhered to the principles of the Declaration of Helsinki. Participation in the study was voluntary, and all patients provided written informed consent before their involvement. The study did not involve any experimental procedures beyond routine clinical care. Echocardiographic assessments were performed as part of standard follow-up, and the patients incurred no additional financial costs. Patient confidentiality was strictly maintained, and no identifiable data were disclosed in the reporting of results.

Results

The echocardiographic findings of the study revealed distinct differences between the two patient groups, those receiving apical versus septal permanent pacemaker (PPM) implantation, both before and after the procedure. These differences shed light on the physiological implications of lead positioning on right heart function and hemodynamics (Tables 1, 2, 3, 4, 5 and 6; Figures 1, 2).

Table 1.

Echocardiographic parameters before pacemaker implantation

Parameter	Septal (Mean ± SD)	Apical (Mean ± SD)	P-value
RV size	29.8 ± 3.6	33 ± 5.6	NS
RA size	29.7 ± 5.1	37.3 ± 6.4	<0.007
RVFAC	44.2 ± 10.8	43 ± 11.8	NS
TAPS	26.6 ± 3.7	21.4 ± 4.8	NS
PAP	15.4 ± 15.7	23.4 ± 8.8	<0.007
IVC	15.5 ± 2	15.7 ± 2.3	NS
E’	13.8 ± 2.4	12.8 ± 3.3	NS
A’	10.8 ± 1	11.3 ± 1.8	NS

Table 2.

Echocardiographic parameters after pacemaker implantation

Parameter	Septal (Mean ± SD)	Apical (Mean ± SD)	P-value
RV size	30 ± 3.7	34 ± 5.4	<0.052
RA size	31 ± 5.3	38 ± 6.2	<0.009
RVFAC	42 ± 10	37 ± 11	NS
TAPS	20 ± 3.7	18 ± 3.6	NS
PAP	16 ± 15	27 ± 9	<0.009
IVC	15 ± 1.8	17 ± 1.5	<0.043
E’	12 ± 1.9	9 ± 1.6	<0.002
A’	10 ± 1.4	11 ± 1.8	NS

Table 3.

Tricuspid regurgitation severity before implantation

TR Severity	Septal	Apical	P-value
No TR	2	0	NS
Trivial TR	5	5	NS
Mild TR	1	3	<0.024
Moderate TR	0	2	NS
Severe TR	2	0	NS

Table 4.

Clinical risk factor distribution

Risk Factor	Septal	Apical	P-value
HTN	0	1	NS
DM	0	0	NS
IHD	2	1	NS
SM	2	0	NS

Table 5.

Tricuspid regurgitation severity after implantation

TR Severity	Septal	Apical	P-value
No TR	1	0	NS
Trivial TR	5	2	NS
Mild TR	2	6	NS
Moderate TR	0	2	NS
Severe TR	2	2	NS

Table 6.

Variable definitions and measurement characteristics

Variable	Measurement Unit	Measurement Method	Status
Apical Pacing	Qualitative	Medical Record	Independent
Septal Pacing	Qualitative	Medical Record	Independent
Age	Years	Interview	Interventional
Sex	Male/Female	Interview	Interventional
Smoking	Pack Years	Interview	Interventional
Diabetes	Type 1/2	Interview	Interventional
IHD	Yes/No	Interview	Interventional
RVFAC	Percent	Echo	Dependent
TAPSE	Percent	Echo	Dependent
RV size	mm	Echo	Dependent
RA size	mm	Echo	Dependent
TDI E’	cm/s	Echo	Dependent
TDI A’	cm/s	Echo	Dependent
PAP	mmHg	Echo	Dependent
IVC	mm	Echo	Dependent
TR	None-Severe	Echo	Dependent

Figure 1.

Heatmap of statistical significance (P-values) for key echocardiographic parameters comparing apical versus septal right ventricular pacing, both before and after pacemaker implantation. Darker shades represent more significant intergroup differences. Notably, post-implantation differences were observed in right atrial size, pulmonary artery pressure (PAP), inferior vena cava (IVC) diameter, and early diastolic velocity (E’), favoring septal pacing.

Figure 2.

Comparative functional echocardiographic profile following septal vs. apical right ventricular pacing. Radar plot displaying normalized post-implantation echocardiographic parameters for patients with septal and apical lead placement. Each axis represents a distinct functional or structural metric, including right ventricular (RV) size, right atrial (RA) size, RV fractional area change (RVFAC), tricuspid annular plane systolic excursion (TAPSE), pulmonary artery pressure (PAP), inferior vena cava (IVC) diameter, and tissue Doppler velocities (E’ and A’). Septal pacing is characterized by a more compact profile, reflecting reduced chamber dilation, lower PAP, and preserved diastolic function (higher E’), in contrast to the maladaptive remodeling and hemodynamic stress observed in the apical group. All values were normalized to the highest group-specific value per parameter to allow uniform comparison across dimensions.

Before PPM implantation, the only statistically significant difference between the two groups was observed in the size of the right atrium (RA), which was larger in the apical group compared to the septal group (P<0.007). The pulmonary artery pressure (PAP) also showed a significant elevation in the apical group before the procedure (P<0.007). At the same time, all other echocardiographic parameters, including right ventricular (RV) size, RV fractional area change (RVFAC), tricuspid annular plane systolic excursion (TAPS), inferior vena cava diameter (IVC), and early (E’) and late (A’) diastolic velocities, did not differ significantly between the groups. These pre-implantation findings suggest that while overall right ventricular systolic and diastolic function may be comparable before pacemaker placement, the apical lead group already demonstrated early signs of elevated atrial and pulmonary pressures.

After PPM implantation, the echocardiographic parameters showed more pronounced differences. Patients in the apical pacing group had significantly larger right ventricular and right atrial sizes than those in the septal group, with RV size averaging 34 ± 5.4 mm in the apical group versus 30 ± 3.7 mm in the septal group (P<0.052), and RA size 38 ± 6.2 mm compared to 31 ± 5.3 mm (P<0.009). PAP remained significantly higher in the apical group post-implantation (27 ± 9 mmHg vs. 16 ± 15 mmHg, P<0.009), reinforcing the suggestion of increased afterload or impaired pulmonary vascular adaptation. Similarly, IVC diameter was higher in the apical group (17 ± 1.5 mm) compared to the septal group (15 ± 1.8 mm), with a P-value of less than 0.043. Moreover, early diastolic velocity (E’), a key indicator of diastolic relaxation, was significantly lower in the apical group (9 ± 1.6 mm) versus the septal group (12 ± 1.9 mm), with a P-value below 0.002, suggesting impaired diastolic function. Other variables, such as RVFAC, TAPS, and A’, remained statistically unchanged between the two pacing sites, indicating that while gross systolic performance may be preserved, more subtle diastolic alterations could be induced by apical pacing.

Assessment of tricuspid regurgitation (TR) before and after PPM placement further complemented these findings. Before implantation, the only statistically significant disparity was in the frequency of mild TR, which was more common among patients with apical leads (P<0.024). However, this difference did not persist post-implantation, as the distribution of TR severity, including trivial, mild, moderate, and severe, did not show a statistically significant divergence between groups. This suggests that although apical pacing may contribute to the development or worsening of TR, the limited sample size or variability in baseline characteristics may have obscured the statistical signal after implantation.

Regarding clinical risk factors, including hypertension (HTN), diabetes mellitus (DM), ischemic heart disease (IHD), and smoking, no statistically significant differences were found between the two groups. This suggests that the observed echocardiographic differences are less likely to be attributed to baseline comorbidities and more plausibly explained by the anatomical positioning of the pacemaker lead itself.

Generally, the results demonstrate that patients with apical lead placement experienced more unfavorable changes in right heart structure and pressures compared to those with septal lead placement. These include increases in right atrial and ventricular dimensions, elevated pulmonary artery pressures, and signs of impaired diastolic function. While gross right ventricular systolic function remained statistically similar between groups, the findings support the hypothesis that apical pacing may exert a more deleterious effect on right heart hemodynamics. This highlights the clinical significance of optimal lead positioning in maintaining right ventricular function and preventing long-term complications in patients requiring permanent pacemakers.

Discussion

In this prospective echocardiographic study, we examined the anatomical and functional consequences of right ventricular lead positioning, comparing apical versus septal implantation, in patients undergoing permanent pacemaker (PPM) placement. Our results provide compelling evidence that septal lead placement is associated with more favorable right heart structural remodeling and hemodynamic performance in the early post-implantation period, compared to the traditional apical approach. These findings add to the growing body of literature questioning the long-standing dominance of apical pacing, highlighting the potential for septal positioning to serve as a more physiologically attuned strategy in modern pacing practice [9,10].

Before lead implantation, subtle but meaningful differences were already evident between the two groups. Patients in the apical group demonstrated significantly greater right atrial (RA) enlargement and elevated pulmonary artery pressures (PAP), suggesting a latent predisposition toward elevated right-sided filling pressures or volume overload, even in the absence of overt differences in right ventricular (RV) systolic function as assessed by RVFAC and TAPSE. These baseline differences may reflect the complex interplay of conduction delay, pre-existing diastolic stiffness, or subclinical tricuspid valvular dysfunction that predispose the apical group to hemodynamic deterioration once pacing is initiated [11,12].

The post-implantation findings further magnified these disparities. Apical pacing was associated with significant increases in RV and RA chamber dimensions and a sustained elevation in PAP, reinforcing the notion that this lead position imposes greater mechanical and hemodynamic stress on the right heart. Notably, tissue Doppler imaging revealed a statistically significant reduction in early diastolic velocity (E’) in the apical group, a surrogate for impaired myocardial relaxation and elevated filling pressures [13]. The constellation of these findings, chamber dilation, increased afterload, and diastolic dysfunction, is characteristic of maladaptive right heart remodeling and is consistent with prior electrophysiological and imaging studies demonstrating that apical pacing can induce interventricular dyssynchrony and disrupt normal myocardial strain patterns, particularly in pacing-dependent patients [14].

While not all between-group differences reached conventional statistical significance (e.g., post-implantation RV size, P = 0.052), several trends observed in the data are likely to carry clinical relevance. In small-sample studies such as ours, modest differences in chamber dimensions or pressure parameters may fail to achieve strict P<0.05 thresholds despite reflecting physiologically meaningful changes. For instance, the larger average RV diameter in the apical group, alongside elevated pulmonary pressures and reduced diastolic velocities, forms a coherent pattern suggestive of early maladaptive remodeling. These near-significant findings should therefore be interpreted within the broader clinical and mechanistic context, rather than dismissed on statistical grounds alone. Further studies with larger sample sizes are needed to determine whether these trends represent early markers of right heart deterioration.

In contrast, septal lead positioning appeared to mitigate these deleterious effects. Patients in the septal group exhibited preserved right ventricular size, more favorable diastolic indices, and significantly lower pulmonary pressures. These findings suggest that septal pacing may maintain a more synchronous activation sequence, thereby reducing regional wall stress and preserving atrioventricular coupling. The preservation of E’ velocity in the septal group underscores its potential protective effect on right ventricular compliance and diastolic function, parameters that are increasingly recognized as critical prognostic determinants in device therapy recipients [15].

An important secondary endpoint of this study was the assessment of tricuspid regurgitation (TR) severity, both before and after implantation. Although mild TR was significantly more common in the apical group at baseline, no statistically significant differences were observed between groups in post-implantation TR severity. However, a trend toward increased moderate and severe TR was noted in the apical cohort, suggesting that longer-term follow-up may have revealed a more definitive trajectory of valve dysfunction. These observations align with mechanistic models and imaging studies, which indicate that apical lead placement can interfere with tricuspid leaflet coaptation, cause valvular tethering, or directly impinge on subvalvular structures. By contrast, septal leads follow a more central and orthogonal course, reducing the probability of direct mechanical interference and thereby limiting pacing-induced TR [16,17].

Importantly, the clinical profiles of the two groups were balanced concerning key comorbidities, including hypertension, diabetes mellitus, ischemic heart disease, and smoking status. This comparability reinforces the attribution of the observed echocardiographic differences primarily to lead position rather than confounding systemic disease processes. While the relatively short follow-up precludes long-term conclusions, the early post-implantation hemodynamic changes observed here provide a physiological basis for anticipating downstream adverse events in the apical group if lead-induced stress continues unmitigated over time [18-21].

Beyond the dichotomy of apical versus septal right ventricular pacing, recent advancements in conduction system pacing, particularly His-bundle pacing (HBP) and left bundle branch area pacing (LBBAP), have introduced a paradigm shift toward preserving physiological ventricular activation. Both techniques aim to mitigate the deleterious effects of dyssynchronous myocardial contraction inherent to traditional RV pacing, which underlies the very remodeling patterns observed in our apical pacing cohort [22]. Emerging data from multicenter observational studies and early randomized trials suggest that HBP and LBBAP are associated with superior left ventricular function, reduced pacing-induced cardiomyopathy, and improved tricuspid valve competence compared to conventional pacing approaches [23]. Although these techniques were not evaluated in the present study, our findings reinforce the broader narrative that pacing location and electrical activation sequence critically shape long-term cardiac remodeling. Future comparative studies should incorporate these novel modalities to define optimal pacing strategies across diverse patient populations, particularly in those with high pacing dependency or preexisting right-sided structural vulnerability [24].

From a broader clinical perspective, these findings challenge the traditional paradigm that regards apical pacing as the default anatomical target for right ventricular lead implantation. Although technically convenient, apical pacing may not be benign, especially in patients with high anticipated pacing burden. The observed structural and functional differences in this study underscore the need to re-evaluate implantation strategies through the lens of myocardial mechanics and chamber interdependence. As the field moves toward physiologic pacing, including His-bundle, left bundle branch, and targeted septal approaches, our findings further justify a departure from apical pacing in favor of alternatives that preserve electromechanical integrity.

This study highlights that even modest changes in lead positioning can exert measurable effects on right heart geometry, function, and pressure load within a relatively short period following implantation. Septal lead placement was associated with reduced chamber enlargement, lower pulmonary pressures, and preserved diastolic function, supporting its role as a more adaptive and potentially protective pacing configuration. These findings carry important implications for device implantation practices and warrant further validation in larger, randomized trials with extended follow-up and integration of advanced imaging modalities.

Limitations

While the findings of this study offer valuable insights into the comparative impact of apical versus septal right ventricular pacing on cardiac function, several limitations must be acknowledged when interpreting the results.

First and foremost, the sample size was relatively small, comprising only twenty patients equally divided between the two pacing strategies. This limited cohort reduces the study’s statistical power. It may obscure subtle but clinically relevant differences, particularly in parameters such as tricuspid regurgitation severity, which exhibited trends but did not reach statistical significance post-implantation. Small sample size also restricts the ability to perform subgroup analyses, such as stratification based on sex, pacing mode (single vs. dual chamber), or baseline diastolic function.

Second, the study design was observational and non-randomized. Group allocation was based on the implanting physician’s intraoperative judgment rather than random assignment, introducing the potential for selection bias. Although baseline characteristics were largely comparable between the two groups, unmeasured confounding factors, such as operator experience, anatomical variations, or subtle differences in comorbidity burden, may have influenced both the lead positioning and the outcomes.

Third, the duration of follow-up was limited to one month post-implantation. While early echocardiographic changes provide important mechanistic insights, they may not capture the full extent of pacing-induced remodeling or the long-term progression of tricuspid regurgitation and right heart dysfunction. A longer follow-up period would be necessary to determine the durability of the observed hemodynamic differences and to evaluate potential downstream effects on clinical outcomes, such as heart failure hospitalizations, arrhythmia burden, or the need for lead revision.

Fourth, although a blinded and experienced cardiologist performed echocardiographic assessments, the study relied on a single observer and a single imaging modality. Interobserver variability was not assessed, and no advanced imaging techniques, such as 3D echocardiography or cardiac MRI, were employed further to quantify right ventricular strain or tricuspid apparatus displacement. Moreover, tissue Doppler-derived indices, although informative, can be influenced by load-dependent factors and may not fully reflect the intrinsic myocardial relaxation.

Lastly, the generalizability of the study may be limited due to its single-center nature and the specific population characteristics of the institution where it was conducted. Larger multicenter studies are needed to validate the findings across diverse patient populations and clinical settings.

Despite these limitations, the study provides meaningful preliminary evidence that septal pacing may confer structural and functional advantages over apical pacing, reinforcing the importance of considering lead positioning not only for technical feasibility but also for long-term cardiac performance.

Conclusion

This prospective echocardiographic study highlights the significant influence of right ventricular lead positioning on right heart structure and function following permanent pacemaker implantation. Patients receiving apical pacing exhibited early adverse remodeling, characterized by enlarged right heart chambers, elevated pulmonary artery pressures, and impaired diastolic function. In contrast, septal pacing was associated with preserved diastolic function, reduced pressure burden, and more favorable geometric remodeling.

These findings underscore the importance of pacing site selection as a modifiable factor that may impact long-term hemodynamic outcomes. While apical pacing remains technically straightforward, our results support a paradigm shift toward septal lead positioning as a more physiologically adaptive alternative, particularly in patients with high anticipated pacing burden. Given the short-term follow-up and limited sample size, further large-scale, randomized studies with extended follow-up and integration of advanced imaging modalities are warranted to validate these observations and inform future guidelines on optimal lead placement strategies.

Disclosure of conflict of interest

None.