5.STUDY LIMITATION
There are several limitations of this meta-analysis. First, the number of included patients was limited and most of the studies were cohort studies with inherent limitations that reduced the internal validity compared to randomized controlled trials. Second, there are limited data on the effect size of LBBAP on outcomes as the studies included were observational and did not all have comparative arms. Next, some data, including pacing pulse width and follow-up time, were variable and inconsistent, which may influence the study uniformity. In addition, there was no uniformity at this time in measuring QRS durations with selective and nonselective LBBAP. Finally, the indications for pacemaker placement defined by the studies we included were not uniform and were broad in scope. On the one hand, this demonstrates the great potential and promise of LBBAP for apply in patients with all types of pacemaker indications, and on the other hand, it creates an inevitable heterogeneity in the statistical analysis we perform.