2.3 Data extraction and quality assessment
A standardized data collection form was extracted by two investigators independently to obtain the following data from each study including name of the first author, year of publication, country of origin, study population, inclusion and exclusion criteria, demographic data of participants, ablation procedure details. Disagreements were arbitrated by a third person in re-review. The original author was contacted by mail for access if the full text could be obtained. For literature in which the same study populations were reported many times or repeatedly published, only one with the most complete data was included. The quality of these studies was evaluated by two investigators (Shuyu Jin and Yumei Xue) using NewCastle Ottawa scale (NOS) for observational studies and the Cochrane Collaboration tool for assessing risk of bias of randomized controlled studies (RCTs). The NOS system consisted of eight questions with nine possible points. Higher scores represent higher study quality11,12.