What is junctional tachycardia?
Junctional tachycardia is one of the main causes of palpitations that start and stop abruptly and affect healthy hearts (those that are not diseased). It is related to an electrical short circuit originating in the junction between the atria and the ventricles.
What are the symptoms?
Clinical presentation is characterized by palpitations related to the perception of very fast heartbeats (generally between 180 and 240 beats per minute) that are very regular (like a metronome). Typically, these episodes are completely unpredictable and unexpected. They begin suddenly (from one heartbeat to another) and stop just as suddenly. The length of the episodes varies from a few seconds to several hours. The frequency of junctional tachycardia episodes varies widely from one person to another. Sometimes, they’re quite rare (a few times per year), but can also be much more frequent and debilitating. Typically, the episodes are grouped together during a particular time of life (for example, during hormone disturbances, pregnancy, periods of sleeplessness) alternating with relatively long periods of calm. The age of initial onset various, but symptoms often begin in adolescence.
What are the causes?
There are two main mechanisms that cause junctional tachycardia: (1)”nodal reentry” and (2) “accessory pathway reentry.”
(1) Nodal reentry is the most frequent mechanism by far. This is sometimes referred to as Bouveret’s syndrome. The cause is a small electrical short circuit in a region called the atrioventricular (AV) node at the junction between the atria and ventricles. This tachycardia is significantly more common in women, as it’s estimated that 70 out of every 100 people affected are women. The exact reason this predominance among women has not been established with certainty. It has also been shown that seizures often tend to increase during pregnancy in women with junctional tachycardia.
(2) Accessory pathway reentry is the other junctional tachycardia mechanism. It is rarer and linked to a congenital anomaly (present since birth), characterized by the presence of an additional electrical cable (which should not normally be present) connecting the atria to the ventricles.
How is this condition diagnosed?
In order to diagnose junctional tachycardia, an electrocardiogram must be recorded during the palpitation episode. There has often a delay in diagnosis, sometimes several years, because it’s not always easy to do an electrocardiogram at the exact time of an episode, especially when it’s short. Things have changed though, because an electrocardiogram can now be used on smart devices like watches or smartphone apps. The most reliable devices are the KARDIA smartphone app (AliveCor), AppleWatch and Withings watch (moveECG). These tools have revolutionized junctional tachycardia diagnosis. They are particularly useful when episodes are infrequent and short because they facilitate a reliable and rapid diagnosis.
What should you do during an episode?
There are several ways to interrupt junctional tachycardia episodes called vagal maneuvers. The most effective is called the Valsalva maneuver, which consists a forced expiration against a closed glottis (holding your breath). TO make it more effective, it can be combined with an abrupt change of position (lying down and lifting your legs). Other maneuvers include massaging the carotid artery (on your neck) or drinking a big glass of ice water. If these measures are ineffective, the episode can be stopped by taking an oral medication (bradycardia or beta-blocker calcium channel blocker). If these different methods don’t stop the tachycardia, the last resort is to see a doctor to stop the episode with a medication injected via IV infusion (adenosine).
How can you avoid recurrences?
If episodes are rare and not very troublesome, therapeutic abstention is possible in most cases. Conversely, when episodes of junctional tachycardia are frequent and debilitating, the top treatment to prevent recurrences is called radiofrequency ablation. In this procedure, the area causing the tachycardia is cauterized. It lasts about an hour on average. Catheters inserted into vessels in the groin provide minimally invasive access to the heart cavities. The abnormal short circuit is identified and then cauterized. An overnight stay in hospital is usually necessary. The success rate of this type of procedure is high, estimated at 95%, with a relatively low risk of complications (<1%). Long-term medication to prevent recurrence is generally not recommended, as it is less effective and more risky than ablation (due to the risk of side effects). However, this is sometimes used as a temporary solution, pending completion of the ablation procedure.
The experts at Women’s Cardiovascular Healthcare Foundation recommend talking to your doctor if you have tachycardia symptoms to anticipate new episodes and take action with specific cardiology care.