Accessory pathway ablation in Ebstein anomaly: challenges and results

Ebstein anomaly combines apical displacement of the tricuspid valve, atrialisation of part of the right ventricle and tricuspid regurgitation. Accessory atrioventricular pathways are common, so palpitations, Wolff-Parkinson-White pre-excitation and syncope may appear early in life or persist into adulthood. The altered right-heart anatomy can turn a familiar ablation case into a demanding electrophysiological procedure.

Modern electroanatomical mapping, intracardiac echocardiography and improved catheter technologies have improved identification and treatment of these pathways. Nevertheless, safety depends on understanding the displaced valve, the true annulus and the possibility of multiple connections. Surgical treatment and catheter ablation are complementary rather than competing strategies when symptoms are severe or anatomy is unsuitable.

For clinicians in Australia, access to high-volume congenital electrophysiology services matters because expertise and follow-up influence recurrence. Medicare, public hospital waiting lists, private insurance and interstate travel shape how families access care. A realistic plan must also address pregnancy, sport, exercise tolerance and the long-term effects of tricuspid regurgitation.

Why Ebstein anatomy changes the problem

Ebstein anomaly is more than a valve lesion. The septal and posterior tricuspid leaflets are displaced toward the apex, and the usual fluoroscopic landmarks for the tricuspid annulus become unreliable. Much of the right ventricle above the displaced valve becomes atrialised, altering chamber geometry, catheter contact and the relationship between the valve, annulus and coronary sinus.

Accessory pathways in this anatomy are usually right-sided and may be posteroseptal, posterior or lateral. Some are located near a markedly displaced annulus, while others occupy abnormal myocardial sleeves around the atrialised ventricle. Multiple pathways are sufficiently frequent that one apparent ablation target cannot be assumed to explain every tachycardia.

The baseline ECG may show a short PR interval, delta waves, a right bundle branch block pattern and right atrial enlargement, but interpretation can be difficult when several conduction abnormalities coexist. Pre-procedure review should integrate the 12-lead ECG, ambulatory recordings, echocardiography and any prior catheter or surgical findings rather than relying on a single surface pattern.

Defining the pathway before ablation

Electrophysiological study remains the reference method for distinguishing supraventricular tachycardia from ventricular arrhythmia and for identifying the mechanism of pre-excitation. During atrioventricular reentrant tachycardia, the operator should establish the pathway participation, determine its earliest ventricular activation and identify whether more than one accessory connection is present.

Careful differentiation is essential. A bystander pathway may be present without participating in the tachycardia, while unusual atrioventricular nodal or atriofascicular conduction can resemble a standard accessory pathway. Septal and para-His observations help avoid mistaking septal activation for a safe posterior target or delivering an unnecessarily aggressive lesion.

Electroanatomical mapping provides a three-dimensional representation of the displaced anatomy, while intracardiac echocardiography helps define valve leaflets, chamber boundaries and catheter contact. CT or cardiac MRI can supplement this information when the anatomy is unclear. Coronary assessment may also be useful before radiofrequency energy near the right coronary artery or an anomalous vessel.

Contemporary ablation strategies

Once the pathway has been identified, the usual target is its ventricular insertion. Radiofrequency catheter ablation remains the standard technique when stable catheter position and firm tissue contact can be achieved. Contact-force information, lesion tagging and careful monitoring of the PR interval help balance effective energy delivery against injury to nearby conduction tissue.

Cryoablation may be useful in children or when the target is close to a critical structure, although its fixed lesion size and greater risk of early reconnection can require additional applications. Pulsed-field electrocatheter ablation is promising for many conventional accessory pathways, but Ebstein-specific evidence remains limited. The proximity of coronary branches and the potential for collateral tissue injury mean that its use should be based on operator experience, imaging and individual anatomy.

Major risks include perforation and tamponade in the thin atrialised right ventricle, coronary artery injury, complete atrioventricular block, worsening tricuspid regurgitation and vascular access complications. Experienced teams use imaging, energy titration and anatomical rehearsal to reduce these risks. Anticoagulation should follow contemporary atrial ablation guidance, with particular attention to marked right atrial enlargement.

Results and predictors of success

The evidence base for accessory pathway ablation in Ebstein anomaly is encouraging but should be interpreted carefully. Contemporary series generally report immediate procedural success in the low-to-mid 90s, with long-term freedom from recurrent accessory-pathway tachycardia often falling between 85% and 95%. Recurrence rates are commonly around 5–10%, although definitions, follow-up duration and case mix differ substantially between studies.

Recurrence has been associated in some cohorts with younger age at ablation, multiple pathways, more severe structural disease and longer follow-up. It may reflect recovery at the tissue interface, identification of a previously unrecognised connection or progressive changes in the abnormal anatomy. A failed first procedure does not automatically preclude a later successful ablation, particularly when technical limitations rather than pathway biology were responsible.

Major complication rates are generally in the low single digits in experienced centres, while older series sometimes reported higher rates because they included earlier equipment and less refined imaging. The strongest evidence comes from multidisciplinary teams that combine congenital cardiology, electrophysiology and imaging expertise. Apparent numerical superiority between techniques should therefore be assessed alongside patient selection, operator volume and the completeness of follow-up.

Choosing surgery, catheter ablation, or both

Patients with severe tricuspid regurgitation, cyanosis, right ventricular dysfunction or a major atrial septal defect may require surgery irrespective of their arrhythmia. In this setting, surgical mapping and ablation of accessory pathways can be performed during valve repair or replacement, avoiding a separate percutaneous procedure and allowing several right-sided connections to be treated during one operation.

Concomitant surgical ablation is particularly attractive when multiple pathways are suspected, but it increases operative and cardiopulmonary-bypass time. Observational series generally show good arrhythmia control, yet comparisons with catheter ablation are limited by selection bias and differences in baseline structural disease. The decision should consider arrhythmia burden, valve function, shunt burden, prior procedures and the risk of leaving a symptomatic pathway untreated.

A staged approach remains appropriate when the valve does not yet require surgery and catheter anatomy appears favourable. Preoperative electrophysiological assessment can define pathway distribution and set expectations for percutaneous success. Conversely, a combined surgical procedure may offer greater procedural certainty when severe regurgitation, unusual anatomy and multiple tachycardias converge in the same patient.

Special considerations across the lifespan

In children, symptoms may be subtle and recurrent tachycardia can contribute to cardiomyopathy or sudden cardiac death. Small vessels, growth and the proximity of the conduction system increase the importance of careful mapping, lower-energy strategies and radiation reduction. Paediatric follow-up must also account for changing anatomy as the child grows.

Pregnancy adds a different balance of concerns. Cardioversion is generally preferred for unstable episodes, while ablation may be considered before conception for refractory, symptomatic supraventricular tachycardia. Counselling should address fetal radiation exposure, anaesthesia, haemodynamic changes and the possibility that structural disease will require treatment after delivery. Coordination among electrophysiology, obstetrics and congenital cardiology is essential.

For athletes, the journal’s athlete risk guidance offers a useful framework for individualised advice, although its atrial fibrillation recommendations should not be applied uncritically to Ebstein anomaly. Return-to-play decisions should consider recurrent symptoms, ventricular function, residual tricuspid regurgitation, medication effects and the risk associated with the underlying structural defect. The absence of pre-excitation after ablation is reassuring but does not remove the need for ongoing assessment.

Access and training in Australia

Specialist care is concentrated around major tertiary services in Melbourne, Sydney and Brisbane, with additional referral networks in Perth and Adelaide. These centres combine electrophysiology with adult congenital cardiology, paediatric cardiology, imaging and cardiac surgery. Patients in Hobart, Darwin, regional Queensland or northern NSW may face lengthy journeys, making interstate referral and coordinated local follow-up important parts of care.

Most patients enter treatment through Medicare-funded public hospitals or private electrophysiology services. Public care generally provides broad access without private-insurance membership, but waiting lists can be long. Private health insurance may shorten access to an elective procedure or preferred hospital, although it can also create out-of-pocket costs. Administrative planning should occur alongside clinical assessment so that referral and admission delays do not prolong symptomatic arrhythmia.

Remote ECG review and telehealth consultations can support patients in regional areas, while procedural care still requires an experienced on-site team. At the counselling table, Australian teams often keep the language practical: one clear plan, a fair go at definitive treatment and a no-drama backup if the first attempt does not work. For continuing education, the journal’s current collections bring together peer-reviewed research, reviews and themed material relevant to complex electrophysiology practice.

Current evidence supports experienced catheter ablation for most appropriately selected patients, with surgical or combined treatment retaining an important role in complex structural disease. Clinicians should use the journal’s open-access evidence to update departmental protocols, discuss unusual cases with congenital electrophysiology peers and contribute detailed outcome data. For Australian patients, the actionable next step is referral to a service experienced in Ebstein anomaly and right-sided accessory pathway ablation, followed by structured monitoring of symptoms, arrhythmia recurrence and structural heart disease.