Relation Between the AH Interval and the Ablation Site in Patients with Atrioventricular Nodal Reentrant Tachycardia

AH jump duration is associated with elimination of slow pathway during ablation of atrioventricular nodal reentrant tachycardia

Introduction

Ablating the slow pathway (SP) is the superior treatment for atrioventricular nodal reentrant tachycardia (AVNRT) with a low complication rate. However, the ablation of the SP could result in either complete elimination or modification of the SP. We aimed to investigate whether the duration of AH jump pre-ablation associated with the outcome of elimination of SP.

Methods

We included 56 patients with typical AVNRT (slow-fast), 20 males and 36 females, aged 44.2 ± 15.1 years. Slow pathway ablation was performed using classical approach. Univariate and multivariate analysis was performed for potential predictors of SP elimination.

Results

Typical AVNRT was inducible in all patients. Post-ablation, non-inducibility of AVNRT was obtained in all 56 (100%) patients, with SP elimination in 33 (61%) patients and SP modification in 23 (39%) patients. Patients with SP elimination had significantly longer AH jump than patients with SP modification. Cox regression analysis showed that AH jump duration was the independent predictor of SP elimination, in which every 20 ms increase in AH jump duration was associated with 1.30 higher rate of SP elimination. Furthermore, ROC curve analysis indicated that the AH jump duration of ≥100 ms had 6.14 times higher probability for complete elimination of the SP with a sensitivity of 79%, specificity of 70%, PPV of 79% and NPV of 70%.

Conclusions

AH jump duration pre-ablation is associated with complete elimination of slow pathway during AVNRT ablation.

Utility of low-dose adenosine triphosphate sensitivity in slow-fast atrioventricular nodal reentrant tachycardia

PURPOSE

Low-dose adenosine triphosphate (LD-ATP) is useful for diagnosing ATP-sensitive atrial tachycardia. However, the clinical implications of the sensitivity of LD-ATP in atrioventricular nodal reentrant tachycardia (AVNRT) still remain unknown. This study aimed to evaluate the mechanism of LD-ATP sensitivity in slow-fast AVNRT.

METHODS

We estimated the sensitivity of LD-ATP in slow-fast AVNRT by a 2-4-mg ATP intravenous injection during the tachycardia. We evaluated the atrial-His (A-H) interval, tachycardia termination mode, prevalence of a lower common pathway (LCP), and successful ablation site in slow-fast AVNRT with LD-ATP sensitivity. LCPs were defined as His-atrial interval differences of at least 5 ms between that during ventricular pacing at the tachycardia cycle length and that during the tachycardia.

RESULTS

Twenty-eight patients (mean age = 58 ± 11 years old, 18 females) with slow-fast AVNRT, who underwent catheter ablation of the antegrade slow pathway, were enrolled. Seventeen of 28 (61%) patients had LD-ATP sensitivity defined as termination of the tachycardia and/or a prolongation of the A-H interval of over 30 ms after an LD-ATP injection. The patients with LD-ATP sensitivity had a significantly higher prevalence of an LCP than those without (15/17 vs0/11, P < 0.0001). The successful ablation site in the LD-ATP sensitive group was significantly closer to the His bundle area than that in the LD-ATP nonsensitive group (13.3 ± 3.8 vs 20.5 ± 5.4 mm; distance to His bundle area in the left anterior oblique fluoroscopic view, P < 0.0001).

CONCLUSIONS

LD-ATP sensitivity in slow-fast AVNRT may suggest the existence of an LCP. The successful ablation site in patients with LD-ATP sensitivity could be closer to the His bundle region.

Electroanatomically estimated length of slow pathway in atrioventricular nodal reentrant tachycardia

The length of the slow pathway (SP-L) in atrioventricular (AV) nodal reentrant tachycardia (NRT) has never been measured clinically. We studied the relationship among (a) SP-L, i.e., the distance between the most proximal His bundle (H) recording and the most posterior site of radiofrequency (RF) delivery associated with a junctional rhythm, (b) the length of Koch’s triangle (Koch-L), (c) the conduction time over the slow pathway (SP-T), measured by the AH interval during AVNRT at baseline, and (d) the distance between H and the site of successful ablation (SucABL-L) in 26 women and 20 men (mean age 64.6 ± 11.6 years), using a stepwise approach and an electroanatomic mapping system (EAMS). SP-L (15.0 ± 5.8 mm) was correlated with Koch-L (18.6 ± 5.6 mm; R 2 = 0.1665, P < 0.005), SP-T (415 ± 100 ms; R 2 = 0.3425, P = 0.036), and SucABL-L (11.6 ± 4.7 mm; R 2 = 0.5243, P < 0.0001). The site of successful ablation was located within 10 mm of the posterior end of the SP in 38 patients (82.6 %). EAMS-guided RF ablation, using a stepwise approach, revealed individual variations in SP-L related to the size of Koch’s triangle and AH interval during AVNRT. Since the site of successful ablation was also correlated with SP-L and was usually located near the posterior end of the SP, ablating anteriorly, away from the posterior end, is not a prerequisite for the success of ablation procedures.

Characterization of the nodal slow pathway in patients with nodal reentrant tachycardia: clinical implications for guiding ablation

INTRODUCTION AND OBJECTIVES

Nodal slow pathway ablation is the treatment of choice for nodal reentrant tachycardia. No demographic, anatomic, or electrophysiologic variables have been reported to predict an exact location of the slow pathway in the atrioventricular node or its proximity to the fast pathway. The purpose of this study was to analyze these variables.

METHODS

The study prospectively included 54 patients (17 men; mean age, 55 [16] years) who had undergone successful slow pathway ablation. The refractory periods of both pathways and their differential conduction time were measured, and calculations were performed to obtain the distance from the His-bundle region (location of the fast pathway) to the coronary sinus ostium (to estimate the anteroposterior length of the triangle of Koch) and to the slow pathway area.

RESULTS

The differential conduction time (139 [98] ms) did not correlate with the His-coronary sinus distance (19 [6] mm; P=.6) or the His-slow pathway distance (14 [4] mm; P=.4). When the His-coronary sinus distance was larger, the His-slow pathway distance was also larger (r=0.652; P<.01) and the anatomic correlation between the triangle dimensions and the separation between the two pathways was confirmed. In patients older than 70 years, smaller triangle sizes and a shorter distance between both pathways were observed (P<.001).

CONCLUSIONS

A greater anteroposterior dimension of the triangle of Koch is associated with a slow-pathway location farther from the fast pathway. In elderly patients the two pathways are closer together (higher risk of atrioventricular block).

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

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.

Sustained Slow Pathway Conduction: Superior to Dual Atrioventricular Node Physiology in Young Patients with Atrioventricular Nodal Reentry Tachycardia?

BACKGROUND

Young patients with atrioventricular nodal reentry tachycardia (AVNRT) frequently do not display discrete dual AV node physiology (DAVNP) as classically defined. The purpose of the study was to investigate the prevalence of sustained slow pathway conduction (SSPC; PR > RR during atrial pacing) in young patients with AVNRT and compare it to dual atrioventricular node physiology.

METHODS

The presence of SSPC and DAVNP was prospectively assessed before and after radiofrequency catheter ablation in 61 young patients (age 4-23 years) with typical AVNRT.

RESULTS

Prior to ablation, 32 (52%) displayed DAVNP, while 46 (75%) displayed SSPC; 7 patients (11%) had neither marker. Patients with DAVNP were older than those without (15 +/- 3 vs 13 +/- 4, P = 0.027) and the prevalence increased with age (38% <13 years, 50% 13-15, 70% >15, P = 0.041), while SSPC showed no age predilection. Patients under 13 years displayed SSPC more commonly than DAVNP (81% vs 38%, P = 0.004). DAVNP persisted after ablation in 10/32 (31%) patients, compared to 6/46 (13%) with persistent SSPC after ablation. The ability to use loss of the marker (present before, absent after ablation) as a surrogate for successful ablation was greater for SSPC than for DAVNP (66% vs 36%, P = 0.001).

CONCLUSION

SSPC is more common than DAVNP in young patients with AVNRT. SSPC is eliminated more frequently than DAVNP after acutely successful ablation, and appears to be a better indicator of the substrate for AVNRT. Elimination of SSPC may serve as a useful surrogate endpoint for slow pathway ablation.