Permanent junctional reciprocating tachycardia (PJRT)

ECG 9A: Tachycardia of 150 bpm with narrow QRS; there is a 1:1 ratio between atria and ventricles; atrial activity is positive in aVR and negative in the inferior leads which allows eliminating a sinus tachycardia and suggests a retrograde activation; the RP’ interval is longer than the P’R interval; the various possible hypotheses are: reentry due to accessory pathway, an atypical intranodal reentry (fast-slow type) or an atrial tachycardia/flutter with 1:1 conduction;

ECG 9B:

ECG 9B: This tracing was recorded after the previous tracing; the same initial tachycardia can be seen with a spontaneous termination (blocked on a QRS, no atrial activation); resumption of a sinus activity over 2 complexes (the ECG pattern appears normal on these 2 complexes); resumption of the same tachycardia without evidence of a triggering factor

Comments: These tracings in this young patient suggest the presence of a permanent junctional reciprocating tachycardia (PJRT), a type of reentrant tachycardia due to a relatively rare accessory pathway initially described by Professor Coumel (also known as Coumel tachycardia). The tachycardias usually begin in infants or children, are usually well tolerated and are often discovered by systematic examination in young asymptomatic patients. They can nonetheless be associated by signs of heart failure with development of a tachycardiomyopathy. These reciprocating tachycardias are often chronic, intermittant or permanent. During the tachycardia, the impulse descends to the ventricles through the nodo-Hisian pathways and ascends to the atrium through an accessory pathway predominantly located in the posteroseptal area of ​​the atrioventricular junction (located near the orifice of the coronary sinus). This accessory pathway exhibits very special characteristics since retrograde conduction to the atrium is slow and decremental. A long anterograde refractory period of the accessory pathway explains the frequent initiation of this type of tachycardia owing to modest accelerations of the sinus rhythm (acceleration of the heart rate, blocking of the activation of the anterograde accessory pathway because in refractory period, transmission by the atrioventricular node, retrograde conduction by the accessory pathway outside of its refractory period and onset of the reentry circuit). This type of accessory pathway has, similarly to nodal structures, decremental conduction properties (possibility of retrograde Wenckebach phenomenon) and is therefore sometimes considered as corresponding to an accessory atrioventricular node.

The different anatomical and electrophysiological characteristics explain the peculiarities of the electrocardiogram observed in these patients:

• The electrocardiogram shows a permanent tachycardia or bursts of tachycardia interspersed with a brief return to sinus rhythm. The tachycardia rate is generally found between 120 and 200 bpm with possible variations depending on catecholaminergic activation or drug intake. One of the elements evocative of this type of tachycardia resides in the mode of initiation and absence of initiating extrasystoles or of modification of the PR interval. A slight change in heart rate is sufficient to trigger the arrhythmia, which explains its subintrant or quasi-permanent nature.
• On the sinus complexes, when present, the QRS complex is narrow without pre-excitation pattern due to the poor anterograde conduction of this type of accessory pathway.
• During the tachycardia, the QRS complexes are generally narrow, the 1:1 relationship between atria and ventricles is essential for diagnosis and always preserved. The P’R interval is short, the RP’ interval is long in conjunction with the slow conduction in the pathway.
• Atrial depolarization is easy to identify and to analyze because it is remotely located from the T wave (no superposition with another electrical signal) due to the prolonged RP’ time. The P’ waves are retrograde, their morphology depending on their atrial insertion (most often posteroseptal, in proximity to the nodal structures and to the ostium of the coronary sinus). The P’ wave is therefore negative in the inferior leads (II, III and aVF); it is also often negative in leads V4-V6.

The evolution of this type of arrhythmias is rarely spontaneously resolutive, is not always benign in the long course and the diagnosis, although rare, must not be ignored. The effectiveness of antiarrhythmic drugs is far from ideal in this context, since substances with a depressant action on nodal conduction decrease the rate of the tachycardia without interrupting it. These disappointing results led to proposing a radiofrequency ablation procedure which is effective and curative in a majority of cases with a limited rate of complications and recurrence. Despite significant developments in recent years, access to this type of therapy in low-weight children remains limited. Ablation therapy usually allows improving cardiac function with a gradual return to normal in patients with rhythmic cardiomyopathy.

Take-home message: Permanent junctional reciprocating tachycardias are often chronic, intermittent or permanent; retrograde conduction to the atrium via the accessory pathway is slow and decremental; during the tachycardia, the QRS complexes are generally narrow, the P’R interval short and the RP’ interval long; on the sinus complexes, the QRS is narrow without pre-excitation pattern;