Baseline characteristics and demographics
Eighty (80) of 135 subjects (from sites who agreed to participate in the effectiveness phase) from 13 centers re-consented to participate in the 12-month effectiveness evaluation, of which 2 were excluded because they did not meet eligibility criteria. Thus, a total of 78 patients were included in the EP. Figure 1 displays the details of the patient disposition flow chart.
Table 1 summarizes the demographics and pre-existing baseline medical conditions for the original SMART SF trial and for the subset of patients in the EP. Overall, the EP was similar to the full patient population. In the EP, the majority of participants were white (96.2%) and male (52.6%), with a median age of 64.8 ± 9.7 years. The most common pre-existing medical conditions in the EP were hypertension (61.5%), atrial flutter (30.8%), and coronary artery disease (20.5%). All enrolled patients and patients in the EP experienced symptomatic AF for an average of 47.9 and 41.3 months prior to enrollment, respectively. The median duration from patients’ initial AF diagnosis to enrollment was 24.0 months (all enrolled) and 19.5 months (EP). The mean follow-up duration for the 78 patients was 373.5 ± 45.38 days from index procedure. Compared with those who elected not to be included in the study extension through 12 months of follow-up (non-EP), patients in the EP (n = 78) had a slightly higher proportion of female participants (47.4% vs. 32.5%), higher mean age (64.8 vs. 60.5 years), higher proportion of patients with coronary artery disease (20.5% vs. 15.6%), and more symptomatic AF at baseline.
The Kaplan-Meier estimate of freedom from atrial tachyarrhythmia recurrence 12 months was 74.9% (90% CI [65.0%, 84.7%]) with 12 subjects experiencing recurrence of atrial fibrillation. The lower bound of the 90% confidence interval was greater than the pre-determined performance goal of 50%; thus, the effectiveness endpoint was met (Fig. 2). Table 2 summarizes the reasons for the 19 patients who failed the 12-month effectiveness criteria.
Using a univariate model, gender, duration of AF history, previous class I AAD history, baseline LA dimension, average contact force, and post-AF cardiac medications were identified as predictors of failure in regard to 12-month failure (Table 3). Using a multivariate logistic regression model, class I AAD history was a significant predictor of failure at p ≤ 0.05 (OR 5.3, 95% CI [1.32, 21.55]). Females tended to have lower 12-month success rate compared with males with OR = 3 (95% CI 0.79, 11.27). An additional month in duration of AF history increased the odds of failure by 1%. Patients with larger baseline LA dimension, higher contact force, and post-AF cardiac medications were less likely to fail (OR and 95% CI 0.94 [0.84, 1.05], 0.88 [0.74, 1.05], 0.34 [0.08, 1.38], respectively).
From 30-day post-ablation procedure through the 12-month follow-up, there were a total of 15 serious AEs (SAEs) that occurred in 6 patients. All SAEs were considered unrelated to the study device by the investigators. One pericardial effusion, discovered at 92 days post procedure, was classified as serious and related to the procedure. A second pericardial effusion occurred at 180 days post procedure and was classified as possibly procedure related. There were no events of pulmonary vein stenosis and no deaths reported through the effectiveness follow-up period.