Junctional tachycardias

doi:10.1136/bmj.324.7338.662

From trainee to consultant, BMJ Group offers doctors around the world tailored information, special events, learning resources and recruitment services at every step along their career path.

... by doctors, for doctors, for patients
We are open for entries!

Online learning

BMJ Learning

High-quality CME / CPD for doctors and other healthcare professionals. BMJ Learning features hundreds of accredited, peer-reviewed learning modules in text, video, and audio formats. Find out more

Courses and Qualifications

BMJ Masterclasses

BMJ Masterclasses, led by experts, help clinicians to use the latest evidence and recent guidelines in practice and meet their CPD/CME requirements. Find out more

Exam Preparation

The leading provider of online exam preparation, helping over 167,000 healthcare professionals to pass their exams. Find out more

onExamination

Search all BMJ education articles:

From

Limit by

The BMJ iPad app brings you the best of print and online, including live links to the latest news, blogs, video, and podcasts. Get the BMJ iPad app.
You can use bmj.com to help you with your continuing medical education. Find out about CME/CPD credits for BMJ articles
Keep up to date with cardiology: Access the latest cardiovascular medicine resources from across BMJ Group.
Countdown to London 2012: BMJ Group's Olympics portal highlights latest Olympics and sports medicine-themed research, comment and learning

Access to the full text of this article requires a subscription or payment. Please log in or subscribe below.

Demas Esberger,
Sallyann Jones,
Francis Morris

Any tachyarrhythmia arising from the atria or the atrioventricular junction is a supraventricular tachycardia. In clinical practice, however, the term supraventricular tachycardia is reserved for atrial tachycardias and arrhythmias arising from the region of the atrioventricular junction as a result of a re-entry mechanism (junctional tachycardias). The most common junctional tachycardias are atrioventricular nodal re-entrant tachycardia and atrioventricular re-entrant tachycardia.

Mechanism of atrioventricular nodal re-entrant tachycardia showing the slow and fast conduction routes and the final common pathway through the lower part of the atrioventricular node and bundle of His

Atrioventricular nodal re-entrant tachycardia

Atrioventricular nodal re-…

This is the most common cause of paroxysmal regular narrow complex tachycardia. Affected individuals are usually young and healthy with no organic heart disease.

Mechanism

In atrioventricular nodal re-entrant tachycardia there are two functionally and anatomically different distinct pathways in the atrioventricular node, with different conduction velocities and different refractory periods. They share a final common pathway through the lower part of the atrioventricular node and bundle of His. One pathway is relatively fast and has a long refractory period; the other pathway is slow with a short refractory period. In sinus rhythm the atrial impulse is conducted through the fast pathway and depolarises the ventricles. The impulse also travels down the slow pathway but terminates because the final common pathway is refractory.

A premature atrial impulse finds the fast pathway refractory, allowing conduction only down the slow pathway (left). By the time the impulse reaches the His bundle, the fast pathway may have recovered, allowing retrograde conduction back up to the atria—the resultant “circus movement” gives rise to slow-fast atrioventricular nodal re-entrant tachycardia (right)

The slow pathway has a short refractory period and recovers first. An atrioventricular nodal re-entrant tachycardia is initiated, for example, if a premature atrial beat occurs at the critical moment when the fast pathway is still …