Statistical analysis
Quantitative variables were expressed as means with standard deviation if they followed a normal distribution and medians (interquartile range) if they did not, and qualitative variables were expressed as percentages. Qualitative variables were compared with the χ2 test or Fisher’s exact test and quantitative variables with the Student’s t-test or Mann-Whitney test. P <0.05 was considered significant. The SPSS® statistical program (version 21.0, Chicago, USA) was used for data analyses.
In successful cases, baseline and paced QRS duration and pacing parameters were compared between implantation and 3 months post-implantation. We also compared paced QRS complex duration values as a function of the baseline duration and between procedures in patients with BBB at baseline. The degree of variation in the QRS complex under different circumstances was analyzed by using the QRS narrowing index (QCI): ([paced QRS duration minus baseline QRS duration]) divided by baseline QRS duration) x 100.14