Ablation outcomes in patients with HCM
Atrial fibrillation with a rapid ventricular response causes an increase in the heart rate, shorter diastolic filling time, and loss of an effective atrial contraction, which contributes to a reduction in the cardiac output, especially in patients with an impaired diastolic function such as HCM patients. Pozzoli et al.28reported that the onset of AF was associated with a significant worsening of the NYHA class, cardiac index, and increased mitral regurgitation. Therefore, rhythm control for AF in patients with HCM is of great importance. A previous systematic review showed that the overall rate of the freedom from an AF/AT recurrence with a single CA procedure was 38.7% and that with multiple CA procedures was 51.8% in HCM patients, while those were 49.8% and 71.2% respectively in non-HCM patients29. In the present study, the overall rate of the freedom from AF/AT recurrences with a single CA procedure in HCM patients was 38%, which was comparable with that reported in the systematic review. However, the arrhythmia free rate after multiple CA procedures was 80%, which was better than the previous studies29,30. The reason for better outcome may be due to the difference in the number of CA procedures, CA strategy, and usage of antiarrhythmic therapy after the ablation. The mean number of ablation procedure in the present study was 1.7 ± 0.8, which was more frequent than that in the previous reports29. Regarding the ablation strategy, a posterior wall isolation was performed in 80% of the subjects and additional mitral isthmus ablation was performed in one-third of the subjects. Previously, Santangeli et al.31 reported that non-PV triggers were observed in the majority of the HCM patients with a late recurrence of AF after ablation, and elimination of non-PV triggers were associated with an improvement in the ablation outcome. As non-PV triggers are commonly observed on the posterior wall and in the coronary sinus32, those additional ablation lesions might have improved the success rate33. In the present study, antiarrhythmic therapy, mostly amiodarone, was continued in 58% of the HCM patients after the last ablation. Amiodarone contains a risk of life-threatening side effects including interstitial pneumonia, thyroid dysfunction, and liver dysfunction, and therefore its discontinuation is desirable. However, the use of long-term antiarrhythmics was often required according to the meta-analysis of AF ablation in patients with HCM29. As atrial remodeling is ongoing due to the pathologically progressive nature of HCM, an aggressive therapeutic approach by catheter ablation and anti-arrhythmic agents may be needed for the maintenance of sinus rhythm in the HCM patients.