Atrioventricular node (AVN) ablation is an effective treatment for symptomatic patients with atrial arrhythmias who are refractory to rhythm and rate control strategies where optimal ventricular rate control is desired. There are limited data on the predictors of failure of AVN ablation. Our objective was to identify the predictors of failure of AVN ablation. This is an observational single-center study of consecutive patients who underwent AVN ablation in a large academic center. Baseline characteristics, procedural variables, and outcomes of AVN ablation were collected. AVN “ablation failure” was defined as resumption of AVN conduction resulting in recurrence of either rapid ventricular response or suboptimal biventricular pacing. A total of 247 patients drug refractory AF who underwent AVN ablation at our center with a mean age of 71 ± 12 years with 46% being males were included. Ablation failure was seen in 11 (4.5%) patients. There were no statistical differences between patients with “ablation failure” versus “ablation success” in any of the baseline clinical variables. Patients with moderate-to-severe tricuspid regurgitation (TR) were much more likely to have ablation failure than those with ablation success (8 [73%] vs 65 [27%]; p = 0.003). All 11 patients with ablation failure had a successful redo procedure, 9 with right and 2 with the left sided approach. On multivariate analysis, presence of moderate-to-severe TR was found to be the only predictor of failure of AVN ablation (odds ratio 9.1, confidence interval 1.99 to 42.22, p = 0.004). In conclusion, moderate-to-severe TR is a strong and independent predictor of failure of AVN ablation.
Ablation of atrioventricular node (AVN) and permanent pacing can produce adequate ventricular rate control, reduce symptoms, increase the exercise capacity, and overall have a positive impact on the quality of life in patients with severely symptomatic atrial fibrillation (AF). Several studies have demonstrated the positive impact of AVN ablation and permanent pacing on the quality of life. Historically, the success rate of AVN ablation using the conventional approach has ranged from 84% to 100%. However, there are very limited data on predictors of failure of AVN ablation. With the significantly increasing prevalence of AF, there may be an increase in number of patients needing AVN ablation. With improved technology and experience of the operators in RF ablation, the overall failure rates of AVN ablation are low. However, this procedure has further room for better success rates. Appropriate identification of predictors of failure will enable the operator to adopt strategies to decrease the rate of failure of and increase the success of AVN ablation further. Here, we sought to determine the incidence, clinical, and procedural predictors of failure of AVN ablation in patients with AF with drug-refractory suboptimal rate control.
Methods
We performed a single-center retrospective study including all consecutive patients who underwent AVN ablation at our center from 2007 to 2013. Demographic, clinical, and procedural data were collected using the hospital electronic health records. All patients underwent AVN ablation for a guideline recommended indication which was either for symptomatic AF with rapid ventricular rates or suboptimal biventricular pacing in patients with cardiac resynchronization therapy (CRT) due to AF, despite being on maximal tolerated rate-controlling medications. All patients were followed for 12 months after the procedure. We evaluated the incidence, clinical, and procedural predictors of failure of AVN ablation. Echocardiograms were read by the board-certified experienced cardiologist and assessed for the presence of severe tricuspid regurgitation (TR). We also reviewed all device interrogations performed in the first year after the procedure. Study protocol was approved by Human Subject Committee and Ethics Board at University of Kansas Medical Center. Informed consent was waived given the retrospective nature of the study.
Patients without existing cardiac devices had a temporary transvenous pacemaker inserted before the AVN ablation in the electrophysiology laboratory, and eventually, a permanent pacemaker was inserted post ablation. Patients with preexisting devices underwent AVN ablation directly without a temporary pacemaker. Standard techniques were used for radiofrequency ablation of the AVN. Femoral vein was accessed for conventional right-sided approach. Once the mapping catheter was in place, the His signal was sought for, and the catheter was then withdrawn into the atrium until the atrial signal was the same size as the ventricular signal. Ablation energy was delivered after catheter stability was confirmed. Choice of ablation catheter and use of sheath were at discretion of physician performing the procedure. After 30 minutes of wait time, AV conduction was reassessed to check for persistence of AVN block. Routinely, pacing was performed in the VVI-R or DDD-R mode with a lower rate of 80 beats/min during initial postablation period.
“AVN ablation failure” was defined as resumption of AVN conduction resulting in recurrence of either rapid ventricular response or suboptimal biventricular pacing not related to ventricular arrhythmias. Both acute procedure failure and delayed resumption of AVN conduction were considered as ablation failure.
Continuous variables are expressed as mean ± SD. Categorical variables were presented as proportions. Categorical variables were analyzed using the chi-square test with Fischer’s exact whenever needed. Continuous variables were analyzed using independent sample t test. Two tailed paired t test was performed for the continuous paired variables. Univariate and multivariate analysis was performed to assess for the predictors of success. All statistics were performed using IBM SPSS Statistics for Windows, version 22.0. (IBM Corp, Armonk, New York). A p value of <0.05 was considered statistically significant.
Results
A total of 247 consecutive patients who underwent AVN ablation were included in the study. Mean age of the study population was 71 ± 12 years with 114 patients (46%) being males. Permanent AF was noted in 77 patients (35%), and the remaining patients had symptoms related to tachy–brady syndrome. Preexisting device was present in 136 (55%) of patients. Mean preprocedural left ventricular ejection fraction was 44 ± 18%. Moderate-to-severe right atrial enlargement was found in 99 patients (40%). A long sheath was used in 67 patients (30%) because of procedural difficulty ( Table 1 ).
| Characteristics | Total (N=247) | Ablation Failure (N=11) | Ablation Success (N=236) | p value |
|---|---|---|---|---|
| Age (years) | 71 ± 12 | 71± 9 | 71±12 | 0.96 |
| Male | 114 (46%) | 3 (27%) | 111 (47%) | 0.19 |
| BMI (kg/m 2 ) | 29±7 | 30±6 | 29±7 | 0.67 |
| Hypertension | 163 (66%) | 8 (73%) | 155 (66%) | 0.75 |
| Coronary Artery Disease | 114(46%) | 6 (55%) | 108 (46%) | 0.55 |
| Permanent Atrial Fibrillation | 77 (35%) | 4 (36%) | 73 (32%) | 1.00 |
| Previous cardiac surgery | 59(24%) | 1(9%) | 58(25%) | 0.30 |
| Diabetes | 63 (27%) | 4 (36%) | 59(27%) | 0.49 |
| Chronic obstructive pulmonary disease | 59 (24%) | 4(36%) | 55(23%) | 0.29 |
| Congestive heart failure | 124(50%) | 5(46%) | 119 (50%) | 0.76 |
| Cardiomyopathy | 112 (46%) | 6(50%) | 106 (47%) | 0.13 |
| Pre-existing device | 136 (55%) | 6 (55%) | 130 (55%) | 1.00 |
| QRS duration | 121 ± 40 | 112 ± 28 | 121 ± 40 | 0.49 |
| Left Ventricular Ejection Fraction | 44±18 | 46±16 | 44±18 | 0.73 |
| Procedure time (min) | 32±8 | 31±8 | 30±1 | 0.71 |
| Long sheath Use | 67 (30%) | 4 (44%) | 63 (28%) | 0.33 |
| Irrigated catheter use | 48 (22%) | 4 (44%) | 44 (21%) | 0.12 |
| Atrial Fibrillation during procedure | 144(59%) | 9(81%) | 135 (59%) | 0.12 |
| Sinus rhythm during the procedure | 31 (12%) | 2 (18%) | 29(12%) | 0.63 |
| LA size(cm) | 5.0 ± 3.3 | 4.6 ± 0.8 | 5.0 ± 3.4 | 0.65 |
| ≥Moderate Right Atrial enlargement | 80 (32%) | 5 (46%) | 75 (31%) | 0.34 |
| ≥Moderate Left Atrial enlargement | 143 (58%) | 5 (46%) | 138 (59%) | 0.53 |
| ≥Moderate Right Ventricular enlargement | 11 (5%) | 1 (9%) | 10 (4%) | 0.40 |
| ≥Moderate Pulmonary Hypertension | 15 (6%) | 2 (18%) | 13 (5%) | 0.14 |
| ≥Moderate Mitral Regurgitation | 69 (28%) | 4 (36%) | 65 (26%) | 0.50 |
| ≥Moderate Tricuspid Regurgitation | 73 (30%) | 8 (73%) | 65(27%) | 0.003 |
Of 247 patients who underwent AVN ablation, 11 patients (4.5%) had “ablation failure” and 236 patients (96%) had AVN ablation success. Of 11 patients who had an ablation failure, 2 patients (18%) had acute failure and the remaining 9 patients (81%) developed AVN conduction diagnosed over a period of 3 to 90 days. There were no significant differences in age, gender distribution, prevalence of hypertension, chronic kidney disease, heart failure (HF), permanent AF, right atrial size, left atrial size, left ventricular size, and left ventricular ejection fraction between ablation failure versus ablation success groups.
The rate of ablation failure was not significantly different whether the ablation was performed in sinus rhythm (2 [18%] vs 29 [12%], p = 0.63) or in AF (9 [81%] vs 135 [55%], p = 0.12) between ablation failure and ablation success groups. Use of irrigation catheter (4 [36%] vs 44 [21%], p = 0.09) or long sheath (4 [36%] vs 63 [30%], p = 0.736) was not significantly different between the 2 groups. The prevalence of moderate-to-severe TR was significantly higher in patients with “ablation failure” than in patients with “ablation success” (8 [73%] vs 65 [27%], p = 0.003). In patients who had moderate-to-severe TR, the use of long sheath did not differ significantly in patients who had the ablation failure versus ablation success, respectively (4 [50%] vs 17 [28%]. p = 0.24). In multivariate analysis, presence of moderate-to-severe TR was found to be the only independent predictor of failure of AVN ablation (odds ratio [OR] 9.1, confidence interval [CI] 1.99 to 42.22, p = 0.004). The predictors of failure on multivariate analysis are listed in Table 2 . There were no complications except for 1 patient who had inadvertent puncture of femoral artery with no significant consequence.
