Junctional tachycardia is an abnormally fast heart rhythm that originates from the middle of the heart, in or near the atrioventricular (AV) node, rather than from the heart’s natural pacemaker at the top. The heart rate exceeds 100 beats per minute, and the condition can be harmless and temporary or, in rare cases, serious enough to cause heart failure. It occurs in both children and adults, but the causes and severity differ significantly between these groups.
Where the Abnormal Rhythm Comes From
Your heart’s electrical system normally starts each beat in the sinus node, a cluster of cells at the top of the right atrium. That signal travels down to the AV node, a relay station between the upper and lower chambers, before continuing into the ventricles. In junctional tachycardia, cells in or near the AV node start firing on their own, faster than the sinus node, and take over the heartbeat.
The most widely accepted explanation is enhanced automaticity: the AV junction cells become overexcitable and generate electrical impulses at an abnormally fast rate. This is fundamentally different from other common fast heart rhythms like AV nodal reentrant tachycardia (AVNRT), where the electrical signal gets caught in a loop and circles back on itself. Junctional tachycardia is a focal rhythm, meaning it fires from a single point rather than spinning in a circuit. That distinction matters because it changes how doctors diagnose and treat it.
What It Feels Like
Many people with junctional tachycardia have no symptoms at all, especially if episodes are brief. When symptoms do occur, the most common ones include palpitations (a racing heart or the sensation of skipped beats), dizziness, fatigue, and occasionally fainting. These symptoms overlap with many other types of fast heart rhythms, which is why an ECG or heart monitor is needed to pin down the diagnosis.
The bigger concern is what happens if the rhythm persists for weeks or months without treatment. A heart that beats too fast for too long can weaken over time, a condition called tachycardia-induced cardiomyopathy. The congenital form, present from birth, carries the highest risk. Up to 9% of congenital cases are fatal without treatment, and the condition can progress to heart failure or dangerous rhythm disturbances like complete heart block.
Types and Causes
Junctional tachycardia falls into a few distinct categories depending on who gets it and why.
Postoperative (After Heart Surgery)
This is the most common form in children. It develops within 72 hours of surgery to repair congenital heart defects, caused by direct trauma, swelling, or reduced blood flow to the AV node area during the procedure. About 6% of infants undergoing cardiac surgery develop it, though rates vary widely between hospitals, ranging from 0% to nearly 18%. It typically resolves on its own within days as the surgical site heals, but it needs active management in the meantime because the fast rate can compromise the heart’s ability to pump effectively right after a major operation.
Congenital
Some infants are born with junctional tachycardia that has no surgical trigger. This form is rarer and harder to treat. Genetic factors play a role: deletions in specific genes related to heart muscle signaling have been linked to an increased susceptibility. In some cases, viral inflammation of the heart muscle (myocarditis) may be involved. Congenital junctional tachycardia tends to be persistent and requires long-term management.
Adult (Focal) Junctional Tachycardia
In adults, the condition can appear without an obvious cause (idiopathic) or as a result of specific triggers. One of the best-known triggers is digoxin toxicity. Digoxin is a medication used for heart failure, and taking too much of it can push the AV junction into an accelerated rhythm. Other triggers include heart attacks, electrolyte imbalances, and inflammation. The adult form often comes and goes (paroxysmal) and may respond to removing the underlying cause.
How It Shows Up on an ECG
On an electrocardiogram, junctional tachycardia has a few characteristic features. The QRS complex (the main spike representing each heartbeat) is typically narrow and regular, looking similar to a normal heartbeat in shape. What’s different is what happens to the P wave, the small bump that normally appears before the QRS and represents the upper chambers contracting.
Because the signal is starting in the middle of the heart instead of the top, the P wave often disappears entirely, hidden inside the QRS complex. When it is visible, it tends to show up just before or just after the QRS, and it’s inverted (flipped upside down) in certain leads, particularly the inferior leads (II, III, and aVF). That inversion tells doctors the electrical signal is traveling backward through the atria, confirming it didn’t start in the sinus node. These features, combined with a heart rate over 100 bpm, point toward a junctional origin.
Distinguishing junctional tachycardia from AVNRT on a surface ECG alone can be difficult because both produce narrow, regular rhythms with absent or abnormal P waves. During an electrophysiology study, doctors can deliver precisely timed electrical impulses to the heart to tell them apart. If a carefully timed impulse can disrupt the rhythm, that points to a reentrant circuit (AVNRT). If the rhythm keeps going unfazed, that supports junctional tachycardia.
Treatment Approaches
How junctional tachycardia is treated depends entirely on its type and severity.
For the postoperative form in children, the first priority is reducing the heart rate to allow effective pumping. Cooling the body to a core temperature of 32°C to 34°C (about 90°F to 93°F) for 24 to 36 hours is an established technique that suppresses the overactive cells. This requires sedation and mechanical ventilation, so it’s done in an intensive care setting. Medications are often used alongside cooling. Amiodarone has been the conventional drug choice, though newer options like ivabradine have shown comparable effectiveness with fewer side effects, particularly less blood pressure drop. Rewarming begins once the child has been stable for at least 24 hours.
In adults, treating the underlying cause is often enough. If digoxin toxicity is the trigger, stopping or adjusting the medication resolves the rhythm. For idiopathic cases that cause significant symptoms or risk weakening the heart, medications to slow the heart rate are tried first.
Catheter ablation, a procedure where a thin wire is threaded into the heart to destroy the tissue generating the abnormal rhythm, is reserved for cases that don’t respond to medication. A multicenter study of adults who underwent ablation found that while the initial procedure was successful in all 15 patients, the arrhythmia came back in 53% of them, requiring a second procedure. More concerning, 20% developed a serious complication: permanent damage to the heart’s normal electrical pathway that required a pacemaker. This high recurrence and complication rate reflects the fact that the abnormal tissue sits dangerously close to the AV node itself. Ablation for junctional tachycardia is considerably riskier than ablation for other common fast rhythms, and that tradeoff is something patients and their doctors weigh carefully.
Long-Term Outlook
The postoperative form has the best prognosis. It usually resolves within days as surgical inflammation subsides, and most children have no lasting rhythm problems. The congenital form is more challenging, often requiring ongoing medication through childhood, but many children can be managed effectively with close monitoring. In adults, idiopathic junctional tachycardia tends to be a chronic but manageable condition. The key is catching persistent cases early enough to prevent the heart muscle from weakening, since tachycardia-induced cardiomyopathy is often reversible once the heart rate is brought under control.