Study selection
Studies were considered if they provided specific information on younger vs. Older patients within the main article or subgroup and if they reported primary endpoints of interest in patients undergoing catheter ablation of AF. Catheter ablation is a type of endocardial ablation procedure (including radiofrequency or cryoablation). The following criteria were used to determine which studies would be included: 1. studies required to offer accurate information on at least one of the main endpoints; and (2) endpoints were to be reported as numerical occurrences rather than just hazard ratios, relative risks, or odds rates. We made an effort to get in touch with the associated authors to request further information if pertinent data were not given in the published studies. Retrieval results were examined by three writers to confirm that studies met the predetermined inclusion criteria.