Junctional tachycardia

Junctional tachycardias are one of the main causes of sudden-onset palpitations in healthy hearts. They are linked to an electrical short-circuit at the junction between the atria and ventricles.

Typical seizures are unexpected, with abrupt onset and termination, at a heart rate of between 130 and 200 bpm, and of variable duration, often short but sometimes lasting several hours. Seizures may sometimes subside after vagal manoeuvres (drinking a glass of ice-cold water, sino-carotid massage, Valsalva manoeuvre, etc.).

The 2 main mechanisms in junctional tachycardias are “intranodal reentry” and “accessory pathway reentry”:

• Intranodal reentry” is the most common mechanism (also known as Bouveret's disease).

This is an unusual pathway in the atrioventricular node (located between the atria and ventricles) which allows the electrical impulse to travel at a higher heart rate and then “loop” through the heart, repeating the tachycardia. 

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• « Accessory pathway re-entry » is the other mechanism of junctional tachycardias. It is rarer and is linked to the presence, from birth, of an additional electrical pathway (which should not normally be present) connecting the atria to the ventricles and allowing the electrical impulse to pass outside the usual ciruits then loop around the heart, repeating the tachycardia.

 

These junctional tachycardias need to be proven by recording an electrocardiogram during the seizure, and their treatment depends on the frequency of the seizures, their duration, and the patient's wishes and history... it may be medicinal or involve radiofrequency ablation of the pathway involved.

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