Conduction system pacing in young patients with atrioventricular block

Permanent pacing can be life-saving in a young person with advanced atrioventricular (AV) block, yet the first implant may remain in place for many decades. That long horizon changes the clinical priorities. Avoiding unnecessary ventricular dyssynchrony, preserving venous access, limiting lead complications and maintaining options for future upgrades all matter alongside the immediate need to prevent bradycardia and syncope.

Conduction system pacing (CSP), including His-bundle pacing and left bundle branch area pacing (LBBAP), offers a physiological alternative to conventional right ventricular apical or septal pacing. By recruiting the native His–Purkinje network, it aims to preserve ventricular activation and reduce the risk of pacing-induced cardiomyopathy. In children, adolescents and young adults, this approach is attractive, but feasibility depends on anatomy, operator experience, underlying disease and the expected pacing burden.

The evidence is developing rather than definitive. Much of the published experience comes from adults, while paediatric and congenital heart populations are smaller and more heterogeneous. A careful decision therefore requires more than a successful implant: clinicians must consider growth, lead extraction, future cardiac procedures, exercise, pregnancy, access to specialist follow-up and the practical realities of lifelong device care.

Why pacing strategy matters early in life

Patients with complete or high-grade AV block may require near-continuous ventricular stimulation. Traditional right ventricular pacing can create an abnormal electrical activation pattern, particularly when the lead is placed at the apex. Over years, this may contribute to ventricular dysfunction, functional mitral or tricuspid regurgitation, atrial arrhythmia and heart failure. The risk is not identical for every patient, but a young person has more time in which cumulative pacing effects can become clinically important.

CSP attempts to maintain a narrower QRS complex and more coordinated contraction. His-bundle pacing is the closest approach to native conduction, although capture thresholds may be higher and lead performance can be less predictable. LBBAP generally offers a larger target and stable electrical parameters, but it involves deep septal lead deployment and has a shorter long-term evidence base, especially in children.

The underlying diagnosis should guide the conversation. Congenital complete AV block, postoperative block, progressive conduction disease, inflammatory injury and genetic cardiomyopathy do not carry the same risks. A patient with unexplained syncope or ventricular arrhythmia also needs a broader assessment; resources such as this review of the idiopathic ventricular fibrillation workup illustrate why apparently isolated electrical disease may require extended follow-up.

Selecting suitable young patients

CSP is most compelling when a patient is expected to have a high ventricular pacing percentage and has preserved or recoverable ventricular function. It may also be considered when conventional pacing is likely to produce dyssynchrony, or when an existing pacemaker patient develops a decline in left ventricular ejection fraction. A narrow native QRS does not exclude the possibility of CSP, but it can make the benefits and technical trade-offs less obvious.

Age alone should not determine the choice. A small child may have a narrow septum, limited venous calibre and a higher likelihood of future lead revision. A teenager may have more favourable anatomy but decades of exposure to lead-related problems. In patients with congenital heart disease, unusual cardiac orientation, surgical patches, prosthetic valves or intracardiac shunts can make both mapping and lead positioning more complex.

Assessment should include echocardiography, a detailed ECG review and, when indicated, cardiac magnetic resonance imaging or genetic testing. The clinician should establish whether AV block is stable, progressive or intermittent, and whether there is ventricular scar or a cardiomyopathic process. Arrhythmogenic right ventricular cardiomyopathy is a useful example of why pacing decisions should sit within a wider risk assessment; discussion of arrhythmogenic cardiomyopathy risk can help frame the distinction between treating bradycardia and addressing sudden death risk.

Technical feasibility and procedural planning

His-bundle pacing can be difficult when the conduction system is diseased or displaced. The implanting team must identify a site that provides reliable His capture at an acceptable output, then confirm selective or non-selective capture with surface ECG criteria, threshold testing and paced QRS analysis. In young patients, a small change in lead position over time or progression of conduction disease may affect capture, so a safety margin and a clear contingency plan are essential.

LBBAP has become increasingly attractive because the lead target is more readily accessible in many patients and capture thresholds are often favourable. Confirmation should include evidence of conduction system recruitment rather than relying solely on a deep septal position. Septal perforation, lead dislodgement, rising thresholds and the uncertain implications of a deeply embedded lead at later extraction remain relevant concerns.

The procedure should be undertaken by an electrophysiology team familiar with paediatric or congenital anatomy when appropriate. In Australia, this may mean referral from a regional service to a tertiary centre such as the Royal Children’s Hospital in Melbourne, Sydney Children’s Hospital or a major Brisbane electrophysiology unit. Public hospital pathways and private cardiology services operate differently, and device availability can depend on local procurement, operator training and whether a patient is treated through a metropolitan hub or transferred from the bush.

Lifelong follow-up and Australian realities

A young person needs a device strategy that remains workable through school, sport, employment and adult congenital care. Remote monitoring can reduce some travel, but it does not replace periodic in-person assessment of thresholds, battery longevity, lead integrity and ventricular function. Families living in regional Western Australia, the Northern Territory or far north Queensland may face long journeys for specialist review, making reliable remote connectivity and coordinated local support especially valuable.

Growth introduces additional considerations. Lead slack must accommodate development without creating excessive loops, while venous obstruction may compromise future access. Transvenous systems may be unsuitable in very small children or in patients with limited venous pathways, whereas epicardial leads avoid some intravascular issues but carry their own surgical and longevity disadvantages. The choice should be revisited as the patient moves from paediatric to adult services rather than treated as permanent at the first implant.

Australian clinicians also need to discuss the practical costs of lifelong care. Medicare-supported public treatment may involve different waiting times and follow-up arrangements from private care, and families may need help coordinating travel, accommodation and school or work commitments. Device clinics should provide clear advice about contact sports, electromagnetic interference, driving rules and pregnancy. These conversations are particularly important when a young patient is “feeling fine” after implantation but remains dependent on pacing.

Battery longevity and future extraction deserve explicit attention. High outputs, frequent pacing and additional diagnostic features can shorten generator life. Lead extraction in a young patient may be more complex after decades of fibrosis, while leaving abandoned leads can limit venous access and complicate MRI or future device upgrades. A strategy that performs well today should therefore be judged against likely procedures at ages 30, 50 and beyond.

Evidence gaps and shared decision-making

The strongest argument for CSP in young people is physiological plausibility supported by growing observational evidence. Studies in adults with AV block suggest that His-bundle pacing and LBBAP can preserve ventricular function and reduce electrical dyssynchrony compared with conventional right ventricular pacing. However, follow-up is often relatively short, patient selection is non-randomised and definitions of successful capture vary between studies.

Paediatric evidence remains limited. Small cohorts may report encouraging implant success and stable follow-up, but they cannot fully establish the incidence of late septal complications, extraction difficulty, venous obstruction or pacing-related cardiomyopathy across decades. Families should hear both the potential advantage and the uncertainty. “Physiological” does not mean risk-free, and a technically elegant implant still requires ongoing surveillance.

Shared decision-making should include the young person’s developmental stage and preferences. An adolescent may prioritise sport, body image, independence and minimal restrictions, while parents may focus on procedural safety and future interventions. In an adult with congenital AV block, reproductive plans, occupational requirements and access to specialist care may be central. The discussion should compare CSP with conventional dual-chamber pacing, epicardial pacing where relevant, and deferral only when clinical circumstances genuinely permit it.

The wider arrhythmia phenotype must also be considered. A patient with hypertrophic cardiomyopathy, for example, may require a different balance of pacing, obstruction management and sudden death prevention; a review of atrial fibrillation in hypertrophic cardiomyopathy highlights why rhythm care cannot be reduced to the ventricular lead location alone. Multidisciplinary review is particularly valuable when AV block coexists with cardiomyopathy, congenital heart disease or inherited arrhythmia syndromes.

For now, CSP is a feasible and increasingly persuasive option for selected young patients with AV block, especially when a high pacing burden is expected and long-term ventricular synchrony is a priority. Its use should be supported by careful anatomical assessment, robust implant verification, device-clinic continuity and honest discussion of what remains unknown.

Explore the evidence, compare local practice with international experience and contribute well-designed long-term data through the Journal of Arrhythmia. Clinicians and researchers working with young patients can help define which pacing strategies deliver durable benefit across the many decades that follow an initial AV block diagnosis.