547 Supernormal conduction of an accessory pathway: the case of a young sportsman

Aims Ventricular pre-excitation is defined by the presence of all of the following electrocardiographic criteria: PQ interval duration ≤120 ms, QRS duration ≥120 ms, and presence of δ wave (defined as initial ‘slurring’ of the QRS complex). Ventricular pre-excitation together with the presence of symptoms (orthodromic and/or antidromic atrioventricular reentry tachycardia, atrial fibrillation) defines Wolff–Parkinson–White (WPW) syndrome. The anatomical substrate of ventricular pre-excitation consists of an extranodal accessory atrio-ventricular connection: the so-called Kent bundle. Such pathways can have antegrade, retrograde, or mixed conductive properties. Accessory pathways endowed with anterograde conductive capability may be responsible for manifest, intermittent, or non-manifest ventricular pre-excitation depending on whether it is respectively always visible on the ECG, not always visible on the ECG and not visible on the ECG even though the pathway has the ability to antegrade conduction. The rare phenomenon of supernormal conduction of anomalous pathways is part of the manifest pre-excitation, which represents the topic of the case reported below. Methods and results We report the clinical case of a young not agonist sportsman undergoing an electrophysiological study (SEF) because of he is suffering from ventricular pre-excitation. The SEF did not showed the inducibility of arrhythmias and, at the same time, apparently it showed low risk characteristics of the pathway even during adrenergic stimulus. However, a careful study, performed with atrial stimulation with couplings up to refractoriness of the atrioventricular node revealed supernormal conduction properties of the Kent bundle which proved to have high risk characteristics according to current guidelines and, therefore, was effectively treated with catheter ablation. Conclusions This case invites us to careful studying of accessory pathways properties, especially since, although rare, they may possess supernormal conduction characteristics capable of determining high ventricular rates in the case of sustained atrial tachyarrhythmias, especially in conditions of adrenergic hyperactivity.

Differentiating Atrioventricular Reentry Tachycardia and Atrioventricular Node Reentry Tachycardia Using Premature His Bundle Complexes

Background: Current maneuvers for differentiation of atrioventricular node reentry tachycardia (AVNRT) and atrioventricular reentry tachycardia (AVRT) lack sensitivity and specificity for AVRT circuits located away from the site of pacing. We hypothesized that a premature His complex (PHC) will always perturb AVRT because the His bundle is obligatory to the circuit. Further, AVNRT could not be perturbed by a late PHC (≤20 ms ahead of the His) due to the retrograde His conduction time. Earlier PHCs can advance the AVNRT circuit but only by a quantity less than the prematurity of the PHC. Methods: High-output pacing at the distal His location delivered PHCs. AVRT was predicted when late PHCs perturbed tachycardia or when earlier PHCs led to atrial advancement by an amount equal or greater than the degree of PHC prematurity. Results: Among the 73 supraventricular tachycardias, the test accurately predicted AVRT (n=29) and AVNRT (n=44) in all cases. Late PHC advanced the circuit in all 29 AVRTs and none of the AVNRTs (sensitivity and specificity, 100%). With earlier PHCs, the degree of atrial advancement was equal or greater than the PHC prematurity in 26/29 AVRTs and none of the AVNRTs (90% sensitivity and 100% specificity). The mean prematurity of the PHC required to perturb AVNRT was 48 ms (range, 28–70 ms) and the advancement less than the prematurity of the PHC (mean, 32 ms; range, 18–54 ms). Conclusions: The responses to PHCs distinguished AVRT and AVNRT with 100% specificity and sensitivity.

Permanent junctional reciprocating tachycardia

The term permanent junctional reciprocating tachycardia (PJRT) describes an orthodromic atrioventricular reentry tachycardia using a usually concealed slowly conducting accessory pathway with decremental properties as the retrograde limb. The accessory pathway is most commonly located in the posteroseptal region; however, other locations have been described. PJRT is a rare form of supraventricular tachycardia and can be found in all age groups but the majority of affected patients are children and young adults. The 12-lead electrocardiogram during PJRT shows negative P waves in the inferior lead II, III, and aVF, with a long RP interval. Atypical atrioventricular nodal reentry tachycardia and focal atrial tachycardia are important differential diagnoses. Due to the often incessant nature of PJRT, patients may be at risk for tachycardia-induced cardiomyopathy. Whereas pharmacological treatment is often only moderately effective, catheter ablation of the accessory pathway is highly effective with a low complication rate.

The role of echocardiography in fetal tachyarrhythmia diagnosis. A burden for the pediatric cardiologist and a review of the literature.

Supraventricular tachyarrhythmia represents the most frequent fetal dysrhythmia. In the lack of diagnosis and treatment these fetuses may develop hydrops and even death. For the therapeutic approach it is important to establish the diagnosis of the type of supraventricular tachycardia. In this paper we report 29 cases with different types of supraventricular tachycardia in which the diagnosis was established using our own protocol, which allowed us to make the difference between the types of tachycardia (atrioventricular reentry tachycardia due to the accessory pathway, atrial ectopic tachycardia and permanent junctional reciprocal tachycardia). We acquired the data by a series of recordings in M mode and pulsed Doppler by simultaneous recording of an artery and a vein flow. First of all, we diagnosed the supraventricular tachycardia type, with short or long ventriculoarterial interval, and afterwards, we made the difference between atrial ectopic tachycardia and permanent junctional reciprocal tachycardia using methods to decrease the atrioventricular conduction.