Late clinical and electrophysiologic outcome of radiofrequency ablation therapy by the inferior approach in atrioventricular node reentry tachycardia

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.

Acute and Long-Term Results of Slow Pathway Ablation in Patients with Atrioventricular Nodal Reentrant Tachycardia-An Analysis of the Predictive Factors for Arrhythmia Recurrence

BACKGROUND

Predictors of atrioventricular nodal reentrant tachycardia (AVNRT) recurrence after radiofrequency ablation including the importance of residual slow pathway conduction are not known. The aim of this study was to report the acute and long-term results of slow pathway ablation in a large series of consecutive patients with AVNRT and to analyze the potential predictors of arrhythmia recurrence with a particular emphasis on the residual slow pathway conduction after ablation.

METHODS

The study included 506 consecutive patients with AVNRT (mean age 52.6 +/- 16 years, 315 women) who underwent slow pathway ablation using a combined electrophysiological and anatomical approach. The end point of ablation procedure was noninducibility of the arrhythmia. The primary end point of the study was the recurrence of AVNRT.

RESULTS

Acute success was achieved in 500 patients (98.8%). After ablation, 471 patients (93%) were followed up for a mean of 903 +/- 692 days. Of the 465 patients with successful ablation, 24 patients (5.2%) developed AVNRT recurrences during the follow-up. No significant differences in the cumulative rates of AVNRT recurrence were observed in groups with or without electrophysiological evidence of residual slow pathway conduction (P = 0.25, log-rank test). Multivariate analysis identified only age as an independent predictor of AVNRT recurrence (hazard ratio 0.96, 95% confidence interval 0.94-0.99, P = 0.004) with younger patients being at an increased risk for arrhythmia recurrence.

CONCLUSIONS

Our study demonstrated that only younger age, but not other clinical or electrophysiological parameters including residual slow pathway conduction predicted an increased risk for AVNRT recurrence after slow pathway radiofrequency ablation.

Atrioventricular nodal reentry tachycardia: slow pathway ablation using the transseptal approach

Four hundred twenty consecutive patients with symptomatic slow/fast atrioventricular nodal reentry tachycardia had attempted slow pathway radiofrequency ablation. All patients had successful slow pathway ablation and no inducible tachycardia after ablation using the standard right-sided approach except for three patients. The three unsuccessful patients had inducible slow/fast atrioventricular nodal tachycardia after attempted right-sided posterior and inferoposterior anatomic ablative techniques and with slow pathway potential electrogram guidance. Lesions were also delivered linearly in the triangle of Koch and within the coronary sinus ostium. A transseptal puncture was performed and slow pathway ablation was obtained in each of these patients. Ablation was performed from the septal mitral valve annulus, anterior to the os of the coronary sinus and inferior to the His-bundle catheter with elimination of slow pathway conduction. Prior to the ablation, two of the three patients exhibited initiation of tachycardia with a double fast/slow antegrade response, and all three patients had long AH intervals (mean 378 ms) during slow pathway conduction. These electrophysiological findings may be consistent with a large area of slow pathway conduction that may include the left atrial septum not approachable by conventional right-sided ablative techniques. Slow pathway ablation to eliminate atrioventricular nodal reentry tachycardia at times may require a left atrial/transseptal approach when conventional right-sided techniques are ineffective.

Junctional rhythm during slow pathway radiofrequency ablation in patients with atrioventricular nodal reentrant tachycardia: beat-to-beat analysis and its prognostic value in relation to electrophysiologic and anatomic parameters

INTRODUCTION

Junctional rhythm usually is considered a sensitive but nonspecific marker of successful ablation of the slow pathway in AV nodal reentrant tachycardia. Nevertheless, this junctional rhythm has been little studied, and its relations to recognized predictors of successful radiofrequency (RF) application were never established in any study.

METHODS AND RESULTS

Thirty-nine patients underwent RF ablation of the slow pathway for AV nodal reentrant tachycardia. Ninety RF applications were delivered, and each ablation site was determined using three different fluoroscopic projections. Six anatomic zones were defined from low posterior septum to the site of distal His-bundle recording (P1, P2, M1, M2, A1, and A2). Characteristics of junctional rhythm during RF applications were analyzed. Atrial electrogram characteristics at the ablation sites also were studied. All patients had successful slow pathway ablation, without any complication. The ablation sites were located as follows: 41 at P1, 26 at P2, 20 at M1, and 3 in M2. Forty RF applications were successful: 14 of 41 attempts at P1, 7 of 26 at P2, 16 of 20 at M1, and 3 of 3 at M2. Mid-septal ablation site (M1 and M2) was associated with higher occurrence of junctional rhythm (P < 0.0001), earlier first junctional beat (P = 0.008), and earlier occurrence of the longest junctional burst (P = 0.03) compared with posterior ablation site (P1 and P2). The combination of a mid-septal ablation site and a first junctional beat occurring < or = 3 seconds after onset of RF application identified successful RF application with 100% accuracy. Using multivariate analysis, the ablation site, duration of atrial electrogram (including slow pathway potential when present), and occurrence of junctional rhythm were independent predictors of success.

CONCLUSION

Successful slow pathway ablation depends on many factors. Junctional rhythm characteristics are related to the site of RF delivery and can be helpful in assessing successful slow pathway ablation.

Reduction of atrial fibrillation inducibility by radiofrequency ablation: an experimental study

A study is made of the antifibrillatory effects of radiofrequency (RF)-induced atrial lesions using nine Langendorff-perfused rabbit hearts in which the atrial electrophysiological properties and atrial fibrillation (AF) inducibility were modified by atrial stretching. Using a multiple electrode consisting of 121 unipolar electrodes, determinations were made of the atrial refractory periods, conduction velocity, wavelength of the atrial activation process, and the inducibility of sustained AF episodes (duration over 30 s) by atrial burst pacing in four situations: (a) control; (b) following dilatation of the right atrium; (c) after adding an RF linear lesion at the cava-tricuspid annulus isthmus; and (d) after adding two RF linear lesions rounding the base of the right atrial appendage and extending from the inferior zone of the sulcus terminalis to the anterior wall of the appendage. Under control conditions, AF was not induced in any of the experiments. The wavelengths were 10.5 +/- 1.2 cm for basic cycles of 250 ms and 6.6 +/- 0.5 cm for cycles of 100 ms. Following dilatation, a significant decrease was recorded in the atrial refractory periods, conduction velocity, and wavelength, which reached values of 6.1 +/- 0.7 cm (250-ms cycle, P < 0.01), and 3.9 +/- 0.3 cm (100-ms cycle, P < 0.01); AF was induced in five cases (P < 0.05). After producing the lesion at the cava-tricuspid isthmus, the electrophysiological modifications induced by atrial dilatation persisted (wavelength = 6.2 +/- 0.6 cm (250-ms cycle) and 4.3 +/- 0.3 cm (100-ms cycle); P < 0.01 vs the control) and AF was triggered in eight cases (P < 0.0001). In turn, on adding the two lesions at the right atrial free wall and appendage, AF was induced only in one experiment (P = NS vs control), and the dilatation-induced decrease in refractoriness and wavelength was attenuated. Nevertheless, differences remained significant with respect to the controls, with the exception of the functional refractory periods determined at cycles of 100 ms. In this phase, the wavelength was 6.6 +/- 0.7 cm (250-ms cycle, P < 0.01 vs control) and 4.9 +/- 0.5 cm (100-ms cycle; P < 0.05). Atrial conduction between the zones separated by the lesions was blocked at any frequency, or selectively at rapid atrial activation frequencies.

IN CONCLUSION

(a) the production of three linear lesions in the right atrium (cava-tricuspid isthmus, atrial appendage, and inferior free wall) reduces AF inducibility in the experimental model used; (b) conduction block (either absolute or frequency dependent) through the lesions, reduction in tissue mass caused by lesion creation, and possibly the attenuation of the shortening of atrial refractoriness and wavelength in the zones not separated by the lesions are implicated in the reduction of AF inducibility; and (c) the single lesion in the cava-tricuspid isthmus does not impede AF inducibility.

[Long-term follow up of patients with nodal reentry tachycardia who had undergone radiofrequency ablation]

INTRODUCTION

The aim of this study was to assess the long term results (minimum of 3 years) of radiofrequency catheter ablation in patients with common (slow-fast) atrioventricular nodal reentrant tachycardia.

PATIENTS AND METHODS

Sixty consecutive patients (mean age 56 +/- 16 years, range 14 to 83, 16 men and 44 women) underwent slow pathway (n = 51, Group A) or fast pathway (n = 9, Group B) radiofrequency catheter ablation between January 1992 and March 1994. All patients were followed at 1, 3, 6 and 12 months after ablation with serial examinations and electrocardiograms and the last follow-up was made on April 1997.

RESULTS

During a mean follow-up period of 48 +/- 7 months (range 38 to 63) all evaluated patients remained asymptomatic. Eight recurrences were observed at a mean of 1 +/- 2 months (range, 0.5 to 7) after a successful ablation procedure. A second procedure was effective in eliminating the dual atrioventricular nodal pathway in each of them. In Group A patients, the pre-ablation PR interval, at 12 months after ablation and at last follow-up were 122 +/- 11, 124 +/- 13 and 124 +/- 15 ms, respectively. In Group B patients, the pre-ablation PR interval, at 12 months after ablation and at last follow-up were 130 +/- 24, 200 +/- 12, 200 +/- 24 ms, respectively. No significant atrioventricular conduction disturbances in any patient were observed. One patient developed a new onset left bundle branch block and 4 patients died of noncardiac causes.

CONCLUSIONS

In patients with atrioventricular nodal reentrant tachycardia, radiofrequency catheter ablation is a safe and effective therapy, with substantial good results that persist during long term follow-up, with a low recurrence rate and without complications during short and long term outcome.

Atrioventricular node reentrant tachycardia in patients with a prolonged AH interval during sinus rhythm: clinical features, electrophysiologic characteristics and results of radiofrequency ablation

Among a consecutive series of 600 patients who underwent radiofrequency catheter ablation for AV node reentrant tachycardia, 14 patients (age 29-76 years) had a prolonged AH interval during sinus rhythm (172 +/- 18 ms, range 140 to 200). Seven of them had unsuccessful ablation during the previous ablation sessions. Eight patients with anterograde dual AV node pathway physiology received anterograde slow pathway ablation, and the other 6 patients without dual-pathway physiology received retrograde fast pathway ablation. All patients had successful elimination of AV nodal reentrant tachycardia after a mean of 4 +/- 4 radiofrequency applications, power level 36 +/- 6 watts and a pulse duration of 42 +/- 4 seconds. The postablation AH interval remained unchanged. During a follow-up period of 25 +/- 13 months, one patient who received slow pathway ablation developed 2:1 AV block with syncope. As compared with the other 586 patients without a prolonged AH interval, these 14 patients had significantly poorer anterograde AV nodal function and lower incidence of anterograde dual AV node physiology (P < 0.01). We concluded that slow pathway ablation in patients with dual pathway physiology, and retrograde fast pathway ablation in patients without dual pathway physiology were effective and safe in patients with a prolonged AH interval. However, delayed onset of symptomatic AV block is possible and careful follow-up is necessary.

Catheter ablation for atrioventricular nodal reentrant tachycardia

The current status of catheter ablation techniques for the management of atrioventricular nodal reentry tachycardia is outlined in this article. Some pertinent aspects of the atrioventricular nodal anatomy and physiology are discussed, to the extent that they are essential for understanding of the mechanism of this arrhythmia and the technique of catheter ablation.

Future ablation concepts of tachyarrhythmias

Application of radiofrequency energy to arrhythmogenic substrates after careful cardiac mapping could ensure a high success rate in eliminating certain types of tachyarrhythmias. Future studies of catheter ablation will focus on how to improve ablation efficacy and achieve a better result in various types of tachyarrhythmias. More information about the arrhythmogenic mechanisms will be provided to improve the knowledge of diagnostic and interventional electrophysiology.

Slowing of the ventricular rate during atrial fibrillation by ablation of the slow pathway of AV nodal reentrant tachycardia

INTRODUCTION

The mechanisms whereby radiofrequency catheter modification of AV nodal conduction slows the ventricular response are not well defined. Whether a successful modification procedure can be achieved by ablating posterior inputs to the AV node or by partial ablation of the compact AV node is unclear. We hypothesized that ablation of the well-defined slow pathway in patients with AV nodal reentrant tachycardia would slow the ventricular response during atrial fibrillation.

METHODS AND RESULTS

In 34 patients with dual AV physiology and inducible AV nodal reentrant tachycardia, atrial fibrillation was induced at baseline and immediately after successful slow pathway ablation and at 1-week follow-up. The minimal, maximal, and mean RR intervals during atrial fibrillation increased from 353 +/- 76, 500 +/- 121, and 405 +/- 91 msec to 429 +/- 84 (P < 0.01), 673 +/- 161 (P < 0.01), and 535 +/- 98 msec (P < 0.01), respectively. These effects remained stable during follow-up at 1 week. The AV block cycle length increased from 343 +/- 68 msec to 375 +/- 60 msec (P < 0.05) immediately and to 400 +/- 56 msec (P < 0.01) at 1-week follow-up. The effective refractory period of the AV node prolonged from 282 +/- 83 msec to 312 +/- 89 msec and to 318 +/- 81 msec after 1 week (P < 0.05), respectively.

CONCLUSION

This study shows a decrease in ventricular response to pacing-induced atrial fibrillation after ablation of the slow pathway in patients with AV nodal reentrant tachycardia. Since the AV nodal conduction properties could be defined, this study supports the hypothesis that the main mechanism of AV nodal modification in chronic atrial fibrillation is caused by ablation of posterior inputs to the AV node.