[Discussion]
Satisfactory long-term management of atrial fibrillation is seldom achievable ,fortunately, AVNA combined with permanent pacing therapy is practically confirmed to significantly reduce cardiac symptoms while improving quality of life [6] , owing to the well-established safety and efficacy of this proficient technique[7] , AVNA and permanent pacing is regards as IIa class of recommendation (evidence level: B) to control heart rate when pharmacological therapy is inadequate and rhythm control is not achievable [8] , they are suggested to be a valuable option in patients with refractory atrial arrhythmia resistant to other treatment modalities [9] .
Among HCM patients, AF is primarily caused by left atrial dilatation and remodeling as a common sustained arrhythmia, conversely, AF can contribute to progressive decline of cardiac function, worsen heart failure and increase risk of systemic thromboembolism [10] . Recent years, LBBP provides significant advantage in patients with conduction disease at the distal His bundle , LBBP emerges for its better sensing ,a lower and more stable capture threshold[1,2,3] , however, implantation indications of this novel technique require further clinical investigation, the role of AVJA combined with LBBP remains unknown in refractory AF and HCM cohorts, whereas safety and feasibility of AVNA combined with HBP have been proven in patients with AF and difficulty in rate control by studies of Vijayaraman P. et al.[4] .
In this case, the rapid ventricular response to AF did not respond promptly to pharmacological therapies and contributed to ongoing symptoms, furthermore, this patient had a history of recurrence of AF after radiofrequency ablation, therefore, ablation and pacing were accepted by her to achieve better rate control. Implantation of ICD was reasonable for high risk of sudden death induced by atrial tachyarrhythmia or HCM, besides her conclusive history of ventricular fibrillation [11] . By 1.5-year follow-up of this case, AVJN and LBBP strategy is confirmedly associated with improvement in symptoms, quality of life, and exercise capacity. Feasibility and safety of AVJA combined with LBBP for refractory AF patients with HCM, was concluded by this case firstly. The situation of refractory AF patients may become worse if they suffer from HCM meanwhile, because both diseases can worsen the symptomatic condition of each other, lead to the increasement of possibility of sudden death and response poorly to drug treatments, obviously, the combination strategy is a better option, a more reasonable and efficient treatment than AVNA combined with HBP for these patients.
In addition, our success may wider the application in HCM patients for whom pacing therapy is reasonable. The hypertrophy interventricular septum may make the manoeuvr of pacemaker implantation more challenging, our report may provide a valuable reference for similar patients. During the operation of implantation of pacemaker, the lead was moved approximately 1cm distally towards the RV apex, followed by deeply screwing the lead helix into the hypertrophy interventricular septum, this experience of LBBP for HCM patient is also in line with that from Huang W .et al.[5] .Conventionally, ablation of the atrioventricular node may produce a slightly faster, more stable escape rhythm derived from the His bundle with a narrow QRS complex, whereas ablation lower at the His bundle is likely to produce a slower, broad QRS complex which may be less reliable. However, the total time of performance is longed given that the pacemaker and ICD have to be implanted besides the ablation, after achievement of pacemaker implantation which serves as a safeguard of ablation, the proximity of His bundle was chosen as the target of ablation instead of atrioventricular node in order to reduce total performance time.
Undoubtedly, long-term follow-up and more such cases are needed for further investigation to evaluate the benefits and safety of AVJA combined with LBBP strategy.