What is the clinical evidence from this study?

Study design: Observational. Population: Atrioventricular Nodal Reentrant Tachycardia (AVNRT) (n=71). Intervention: Dislocated antegrade fast pathway (A-FP) vs. Nondislocated A-FP. Primary outcome: St-H interval at the apex of the triangle of Koch (A-TOK) in ms (p=0.02).

January 1, 2007Open Access

Incidence and Mechanism of Dislocated Fast Pathway in Various Forms of Atrioventricular Nodal Reentrant Tachycardia

YTYasuaki TanakaYokosuka Kyosai Hospital HYHiroshige YamabeKoga Hospital KMKenji MorihisaElectrophysiology

Key Result

A dislocated antegrade fast pathway was identified in 56% of patients with atrioventricular nodal reentrant tachycardia and was associated with a significantly longer St-H interval at the apex of the triangle of Koch.

Study Design

Type

Observational (n=71)

Multicenter

Structured PICO

Population

71 patients with atrioventricular nodal reentrant tachycardia (AVNRT) referred for curative ablation (slow-fast form n=49, fast-slow form n=7, slow-intermediate form n=15), mean age 51 years, 34 males and 37 females.

Intervention

Atrial pace mapping to localize the antegrade fast pathway (A-FP) followed by slow and/or intermediate pathway ablation

Outcome

Location of the antegrade fast pathway (A-FP) defined as the site with the shortest interval between the stimulus and His potential (shortest St-H)surrogate

Dislocated antegrade fast pathways are common (56%) in AVNRT and are likely caused by inferior displacement of the entire AV node-His bundle apparatus, highlighting the risk of inadvertent AV block during anatomically guided slow-pathway ablation.

Main Result

Absolute Event Rate: 112.9% vs 91.6%

p-value: p=0.02

Limitations

Significant variation exists in the dimension of the triangle of Koch, meaning adjacent pacing sites might share a border.
Respiration or contraction of the heart might have influenced the location of the mapping catheter.
Lack of difference between the AH interval and the shortest St-H interval may have been caused by direct capture of the upper part of the compact AVN.

Abstract

BACKGROUND: The incidence and mechanism of the dislocated antegrade fast pathway (A-FP) were examined in various forms of atrioventricular nodal reentrant tachycardia (AVNRT). METHODS AND RESULTS: To localize the A-FP, 5 atrial sites comprising the inferior coronary sinus ostium (CSOS), apex of the triangle of Koch (A-TOK), and 3 equidistant sites on the atrioventricular junction extending from A-TOK to CSOS (site S, M, and I) were pace mapped at 100 beats/min in 71 patients with slow-fast (n=49), fast-slow (n=7) and slow-intermediate (n=15) forms of AVNRT. The site with the shortest interval between the stimulus and His potential recorded at the A-TOK (shortest St-H) was defined as the A-FP site. The A-FP was located at A-TOK in 31 patients (nondislocated group), and inferior to A-TOK in 40 patients (site S in 26, M in 13, and I in one patient; dislocated group). There was no significant difference in the location of the A-FP among the 3 forms of AVNRT. Although the shortest St-H did not differ between groups, the St-H at A-TOK in the dislocated group was significantly longer than that in the nondislocated group. Additionally, the His potential preceding that of the A-TOK was observed more frequently inferior to the A-TOK in the dislocated group than in the nondislocated group, suggesting that the A-FP dislocation was accompanied by displacement of the His bundle. CONCLUSIONS: Dislocated A-FP was frequently and uniformly observed among various forms of AVNRT, and is probably caused by inferior displacement of the entire atrioventricular node - His bundle apparatus.

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