Results
Of 114 patients study patients, 46 patients (40%) were found to develop incident AF during the follow-up period. Baseline characteristics, including age, BMI, and HATCH score were similar amongst patients who developed AF and those that did not develop AF (Table 1). There was a non-significant trend towards increased incidence of AF in patients with HATCH score ≥ 2 (48% vs 30%, respectively, p= 0.05). There was no significant difference in left ventricular dimension, left ventricular function, or frequency of significant valvular disease between study groups (Table 2). There was a trend towards increased left atrial diameter in patients that developed incident AF (4.4±0.6 vs 4.1±0.8, p=0.06), while LAVI was significantly greater in patients with incident AF when compared to those that did not (37 ± 12 cm/m2vs. 30 ±13 cm/m2, p= 0.004). CTI block was achieved in all patients. There were no significant differences in electrophysiology study data between those that developed AF and those that did not (Table 3).
Study patients were followed for 600 + 405 days after AFL ablation. Intra-procedure cardioversion of atrial fibrillation was required in a total of five patients and this did not significantly differ between patents that developed AF and those that did not (9% vs 2%, respectively, p-0.09). There were no post-procedural complications, which included development of hematoma, arteriovenous fistula/pseudoaneurysm, stroke, transient ischemic attack, or cardiac tamponade. One patient developed recurrent CTI dependent atrial flutter at 3 years follow-up. Routine post AFL ablation ambulatory arrhythmia monitoring was completed in 48 patients (42%). Frequency of routine monitoring did not significantly differ between groups that developed AF and those that did not (39% vs.44%, respectively, p= 0.7). Symptom driven ambulatory arrhythmia monitoring was performed in 17 patients (15%), and was performed with similar frequency in patients that developed AF and those that did not (19% vs. 12%, respectively, p= 0.3). Cardiac implantable electronic devices (implantable loop recorder, permanent pacemaker, or implantable cardioverter defibrillator) providing longitudinal arrhythmia monitoring were present in 16 patients (14%), and was present in similar frequency in patients that developed AF and those that did not (15% vs. 13%, respectively, p= 0.8).
Figure 1 shows the receiver operator curve (ROC) curve for predicting AF after AFL ablation based on LAVI. The area under the curve for LAVI as a predictor of AF was 0.7. A cutoff point of LAVI ≥ 30 ml/m2 derived from ROC curve analysis yielded a sensitivity 71%, specificity 60% for the ability to predict incident AF post-ablation. Univariate cox regression analysis identified LAVI and HATCH as independent predictors of incidence of AF after CTI AFL ablation (Table 4), Multivariate analysis including LAVI ≥ 30 ml/m2 and HATCH ≥ 2 as predictors of AF showed that LAVI ≥ 30 ml/m2 remained the only significant predictor of incidence of AF after CTI AFL ablation (adjusted HR=2.25 [1.14-4.45]. Patients were further stratified according to LAVI < 30 ml/m2 vs. LAVI ≥ 30 ml/m2 and clinical and echocardiographic data were reported for each group (Table 5-6). Figure 2 demonstrates the Kaplan-Meier estimates of AF-free survival stratified by LAVI ≥ 30 ml/m2, which shows that at a follow up of 3 years, the incidence of AF after CTI AFL ablation is significantly greater in those with LAVI > 30 ml/m2 than those with LAVI <30 ml/m2 (66% vs. 27%, p=0.004). A sensitivity analysis of Kaplan-Meier estimates of long term incidence of AF comparing patients with severely increased LAVI ≥ 40 ml/m2 to those with LAVI 30-40 ml/m2demonstrated no significant difference (67% vs 63%, p= 0.97).