2 Methods
The study was designed as a randomized controlled single-center study.
2.1 Patients
Patients aged >18 years with symptomatic AF refractory to at least one class I or class III antiarrhythmic drug, and referred for a first catheter ablation procedure at Changhai Hospital between March 2019 and October 2019 were enrolled. All patients provided written informed consent. Consecutive 218 patients were randomized to either BigThumb Group (BT Group) or Traditional Follow-up Group (TF Group) by means of random number table. The baseline clinical features were noted for each patient and compared for different follow-up strategies. The study was conducted in accordance with the Declaration of Helsinki. The study was approved by the institutional review board of Shanghai Changhai Hospital, Second Military Medical University.
2.2 Ablation procedures
For all cases, standard femoral venous access was achieved using Seldinger technique with a 6-French and a 7-French sheath in the left femoral vein and two 8.5-French Swarz sheaths in the right femoral vein. Coronary sinus catheter and right ventricle catheter were advanced through left femoral vein. Transseptal access was achieved with fluoroscopic guidance. A Tacticath Quartz catheter (St Jude Medical, St. Paul, MN, USA) was used for radiofrequency catheter ablation in each procedure. The ablation strategy for each case was left to the discretion of the primary operator.
2.3 The BigThumb heart monitor
The technologies used to monitor AF are advancing at a rapid pace. Among them, the BigThumb (Shanghai Yueguang Medical Technologies Inc, Shanghai, China) heart monitor is a National Medical Products Administration (NMPA) approved smartphone handheld tool that permits easy and rapid collection of a “one-lead” ECG (bECG) with two thumbs of users on the device (Figure 1). In parallel, the bECG will also be sent to doctors automatically. Users can store and review bECGs on their cellphones. Artificial intelligence (AI) algorithm was applied in new version of BigThumb (Supplemental information 1). It may improve the accuracy of automatic diagnosis. The feasibility of the BigThumb applied in follow-up of patients after ablation was characterized.
2.4 Follow-Up Strategies
Patients in BT Group were provided with and trained to use a BigThumb ECG monitor, and were instructed to take at least three bECGs every day and additional bECGs if symptomatic. The patients should mark symptoms when bECGs were collected. AF was detected by both an automated AF detection algorithm and an AI algorithm. Two cardiologists will confirm the diagnosis separately. While AF recurrence of patients in TF Group were monitored with Holters 3, 6 and 12 months after ablation and ECGs if there are symptoms. Monitoring data and patient management strategies were collected and analyzed. A blanking period was defined as three months after ablation. Oral anticoagulation was recommended after the “blanking period” when the CHA2DS2-VASc score >1. Subsequent adherence on oral anticoagulation of patients were also recorded.
2.5 Statistical Analysis
Continuous variables are expressed as mean ± standard deviation, and categorical variables are expressed as a number and percentage. Continuous variables were compared using the two-tailed Student’s t-test, and categorical variables were compared using the χ2 test or Fischer’s exact test. In order to investigate the influence of follow-up strategies on AF recurrence detection, Kaplan-Meier survival curve and log rank analysis were performed. For Cox regression, univariable regression was performed first. Variables with a P-value of <0.2 were included in the multivariable model. A level of significance was set at <0.05 for all reported P-values, and confidence intervals were calculated at the 95% level. All statistics were calculated using SPSS (Version 24, IBM, Armonk, NY, USA).