Junctional Tachycardia After Atrial Septal Defect Closure
After atrial septal defect (ASD) closure, a regular narrow-complex tachycardia may reflect enhanced automaticity in the atrioventricular junction rather than the sinus node. It is uncommon, yet recognition matters because prolonged junctional tachycardia can reduce cardiac output and may be misclassified as an atrial arrhythmia or atrioventricular nodal reentrant tachycardia. Management depends on documenting the mechanism and assessing haemodynamic consequences rather than labelling every postoperative tachycardia as junctional.
Evidence for automatic junctional tachycardia after septal repair is largely confined to case reports and small series, so the incidence remains uncertain and no reliable pooled percentage can be quoted. The practical questions are when it occurs, which electrocardiographic features support it, and where catheter ablation should target if conservative treatment fails. This approach combines established electrophysiology principles with pathways relevant to Australian congenital heart services.
Incidence and clinical context
Atrial septal defect closure removes a chronic left-to-right shunt, but the immediate postoperative period still contains several physiological disturbances. Pain, hypovolaemia, anaemia, fever, hypoxia and catecholamine stimulation can accelerate sinus or ectopic rhythms. The atria may also be more sensitive to stretch after the abrupt change in ventricular filling, while transient inflammation or myocardial injury can increase automaticity.
Reported junctional tachycardia after ASD closure is rare, and most publications are single cases without a denominator. It often appears during the first postoperative week, particularly after surgical repair, although delayed presentation is possible. A new tachycardia many weeks or months later should also prompt assessment for atrial fibrillation, atrial flutter, focal atrial tachycardia, accessory-pathway tachycardia and device-related or ventricular arrhythmia.
Wider context on postoperative arrhythmia is available in Journal of Arrhythmia’s arrhythmia special issues, which bring together reviews, guidelines and themed studies useful for departmental teaching and multidisciplinary review.
Mechanisms after septal repair
Several mechanisms have been proposed, and none should be treated as proven in an individual patient. Direct injury to the compact atrioventricular node or His bundle is less likely during a routine secundum repair because these structures lie outside the usual defect margin. Pericardial inflammation, transient ischaemia and postoperative autonomic imbalance may nevertheless lower the threshold for ectopic automatic discharge.
Closing the shunt increases left ventricular preload while reducing right-sided volume loading. The resulting changes in atrial pressure, stretch and baroreflex activity may transiently favour automatic foci. A catheter-based closure avoids open surgical injury but still alters loading conditions and may generate inflammatory or autonomic signals.
Electrolyte disturbance, residual hypoxaemia, pain, agitation, recent catecholamine exposure and stimulant medication can coexist and should be corrected before attributing tachycardia to a primary junctional focus. Postoperative junctional tachycardia is best viewed as a diagnosis requiring a compatible rhythm, exclusion of atrial and re-entrant mechanisms, and often supportive electrophysiological data.
Recognising the tachycardia on ECG
The ECG usually shows a regular narrow QRS tachycardia, often around 110–180 beats per minute in adults, with absent or retrograde P waves. Atrioventricular dissociation is the strongest clue: the atrial rate is slower than the ventricular rate, and occasional capture or fusion beats may appear. Retrograde P waves can follow each QRS with a short RP interval, making the rhythm difficult to recognise from a single lead.
Review a 12-lead ECG and a longer rhythm strip, then compare P-wave timing with the prior rhythm. Determine whether every P wave precedes a QRS, whether the RP interval is fixed, and whether the QRS morphology matches conducted supraventricular beats. Any wide-complex tachycardia should be managed as ventricular tachycardia until proven otherwise.
Junctional tachycardia may also be mistaken for sinus tachycardia with buried P waves, low-amplitude atrial activity or artefact. The post-closure setting adds atrial flutter and ectopic atrial tachycardia to the differential, particularly when temporary pacing wires or atrial surgery have altered conduction. Serial tracings, telemetry and a focused electrophysiology study are more informative than one postoperative rhythm strip.
Differential diagnosis in postoperative care
Sinus tachycardia generally has a consistent P wave before each QRS and should trigger a search for pain, bleeding, sepsis, volume depletion or increased catecholamine drive. Atrial tachycardia or flutter shows atrial activity preceding the ventricular response, and its P-wave morphology or flutter waves may differ from the sinus rhythm. Both can be mistaken for a junctional focus when P waves are low amplitude.
Atrioventricular nodal reentrant tachycardia usually has a short RP interval and is abruptly terminated by adenosine in a monitored setting. Concealed accessory-pathway tachycardia has retrograde atrial activation and may mimic a junctional rhythm when P waves are subtle. Automatic junctional tachycardia generally does not terminate with adenosine; AV nodal block may only slow ventricular activation or reveal the underlying atrial rhythm.
Adenosine should be used cautiously and only with continuous monitoring in a regular, narrow-complex tachycardia. It is inappropriate as an empiric test in irregular tachycardia or wide-complex tachycardia. Suspected atrial flutter with rapid conduction requires a rhythm strategy rather than reliance on AV nodal blockade. Failure of adenosine to terminate a tachycardia is informative but does not establish a junctional mechanism.
Electrophysiological mapping principles
Electrophysiological study can separate competing mechanisms when the ECG is uncertain or tachycardia persists. His bundle recordings establish atrial, His and ventricular activation timing, while atrial activation sequences test whether an atrial tachycardia is driving the rhythm. Ventricular-atrial dissociation during tachycardia and absence of consistent retrograde atrial activation support a junctional source.
For a focal junctional focus, the mapping target is the region showing the earliest appropriate local activation relative to the His and ventricular electrograms. The compact atrioventricular node, His region and immediately perinodal tissue are the usual search area. Isoproterenol or another suitable catecholamine may accentuate automatic tachycardia, while overdrive pacing may suppress or reset it, although these manoeuvres support rather than define the diagnosis.
Programmed stimulation and atrial or ventricular pacing help exclude atrioventricular nodal reentry and accessory-pathway-mediated tachycardia. If conduction is accessory-pathway dependent, ablation should be directed to that pathway. If atrial activation precedes the tachycardia, the defect margin, atrial scar or another atrial focus should be mapped instead. This distinction is essential before radiofrequency energy is applied close to the normal atrioventricular conduction system.
Ablation targets and procedural outcomes
When the diagnosis is secure, ablation can target the compact atrioventricular node, His bundle or adjacent perinodal myocardium displaying the earliest focal activation. The exact site is chosen from electrophysiological data rather than anatomy alone. Operators often use cautious energy delivery near the His bundle and confirm preserved antegrade and retrograde conduction before accepting the result.
Ablating the His region carries a recognised risk of complete atrioventricular block, particularly in patients with congenital conduction disease or prior surgery. Temporary pacing capability and immediate recognition of conduction deterioration are mandatory. If the tachycardia proves to be an atrial focus near the repaired septum, focal ablation at that site is safer and more logical than targeting the junction.
Current evidence consists mainly of successful individual procedures, with variable follow-up and no dependable pooled success or complication rate. Catheter ablation can be highly effective in selected patients, but it should be discussed as a centre-dependent option with a recognised risk profile. Persistent automatic tachycardia may also be treated with carefully selected medication or pacing suppression before an ablation decision.
Management and follow-up in Australia
In the unstable or low-output setting, initial care centres on reversible drivers: oxygenation, haemoglobin, volume status, potassium, magnesium, fever, pain, agitation and catecholamine exposure. Once these are addressed, a clinician may consider rate control or rhythm-directed antiarrhythmic therapy, taking account of ventricular function and congenital conduction disease. Pharmacological choices require individual assessment rather than a fixed postoperative protocol.
Atrial or ventricular overdrive pacing can temporarily suppress an automatic junctional focus. Electrical cardioversion is generally unreliable for automatic tachycardia because the circuit is not re-entrant, although cardioversion remains appropriate when another arrhythmia with a re-entrant mechanism is demonstrated. Persistent postoperative tachycardia warrants early involvement of an experienced electrophysiologist, and recurrent symptoms justify rhythm monitoring rather than repeated assumption-based treatment.
Australian congenital cardiac services are concentrated in major public and private tertiary centres in Melbourne, Sydney, Brisbane, Adelaide and Perth. Many patients travel considerable distances for device checks, so coordinated adult congenital heart disease follow-up, local general-practice support and telehealth can reduce unnecessary travel. Medicare and the Medicare Benefits Schedule affect access to ambulatory monitoring, electrophysiology studies and ablation, while public-hospital procurement and Australian TGA requirements influence device availability.
For unexplained falls when an arrhythmia is suspected, an implantable loop recorder analysis can help determine when long-term ECG monitoring is cost-effective in the Australian setting. The technology is particularly relevant to postoperative palpitations, syncope or falls that are intermittent and poorly captured by ward telemetry or short-term Holter monitoring. A symptom–arrhythmia correlation then directs the next electrophysiology or device-management decision.
Departmental protocols should specify when a postoperative narrow-complex tachycardia is referred, how a 12-lead ECG and rhythm strip are captured, and which reversible causes must be excluded. Readers can use the Journal of Arrhythmia’s current and past articles alongside local adult congenital heart disease guidance to prepare electrophysiology, anaesthesia and cardiology teams for a coordinated pathway.
When junctional tachycardia follows ASD closure, record the rhythm, document the atrioventricular relationship, correct reversible perioperative factors and obtain early review at an adult congenital heart disease and electrophysiology service. Establish the mechanism before labelling the arrhythmia or targeting the atrioventricular node, because a different origin changes both the ablation site and the risk.