Results
A total of 28 consecutive patients with obstructive HCM [mean age: 58.3±11.3 years, males: 21 (75%)] were enrolled in the study. Regarding AF type, 12 patients (42.9%) displayed paroxysmal AF (PAF) and 16 (57.1%) persistent and long-standing persistent AF (non-PAF). All patients were on amiodarone before ablation, and it was stopped 3 months after the index procedure. After this period, amiodarone was restarted in patients with arrhythmia recurrence. Beta‐blocker were used in all patients. After PS matching had been performed, 28 non-HCM patients were selected [(mean age: 53±14 years, males: 22 (78.5%)], and served as control group.
After the 3-month blanking period, 10 HCM patients (35.7%) displayed an atrial arrhythmia recurrence, while 18 patients (64.3%) remained in sinus rhythm. The baseline clinical, echocardiographic, electrophysiologic and procedural characteristics of HCM patients with and without arrhythmia recurrence are provided in Table 1 . Specifically, sinus rhythm was maintained in 75% of PAF and 56.3% of non-PAF patients. All subjects with arrhythmia relapse underwent a repeated procedure (3 patients for AF, 5 patients for LA micro- or macro-reentrant atrial tachycardia, and 2 patients for cavotricuspid right atrial flutter). After 1.35 catheter ablation procedures per patient, 8 HCM patients (28.5%) had an arrhythmia recurrence, while 20 HCM patients (71.5%) remained in sinus rhythm at the end of follow-up period (39.1±15.1 months). There were no procedural related complications. Univariate analysis revealed that the only predictor of AF recurrence was the extent of LA fibrosis. Specifically, patients with arrhythmia recurrence showed significantly greater low voltage areas defined as either bipolar voltage ≤0.25 mV (22.5±10% vs. 5.5±6.4%, p=0.001) or ≤0.4 mV (32±13.9% vs. 5.9±5.1%, p<0.001) compared to those who remained in sinus rhythm (Table 2 and Figure 2 ). ROC analysis demonstrated that the presence of low voltage areas ≤0.25 mV greater than 13.1% of the total surface area predicts AF recurrence with high sensitivity (100%) and specificity (88.9%), while the existence of low voltage areas ≤0.4 mV greater than 14.1% of the total LA area also predicts arrhythmia recurrence with great sensitivity (100%) and specificity (100%). The fibrotic areas of non-PAF patients were significantly wider compared to PAF patients by using the 0.4mV cut-off value (16.5±13.8% vs. 9.4±13.7%, p=0.03), but not for the 0.25mV cut-off value (11.5±6.0% vs. 8.4±12.8%, p=0.19). Detailed data regarding the location of fibrotic areas in relation to LA segments in subjects with HCM are provided in Table 2. After PS matching with non-HCM patients who underwent AF catheter ablation, patients with HCM exhibited wider low voltage areas based on the 0.25mV criterion compared to non-HCM patients (9.7±10.7% vs. 2.8±3.2%, p=0.016). No statistically significant differences were seen using the 0.4mV criterion (12.4±14.3% Vs. 5.9±5.3%, p=0.116). A comparison of low voltage areas with respect to specific LA segments in patients with and without HCM, before and after PS matching, is depicted in Table 3 .