2.3 Statistical analysis
The baseline characteristics of patients with internal and external
BiVAD were compared using the χ2 test for categorical
variables and analysis of variance for continuous variables. The Poisson
regression model was used to assess the change in estimated quarterly
volumes of internal, external, and all BiVADs. Finally, we sought to
explain the national trends using exploratory subgroup analyses. The
total population was divided into patients who survived the index
hospitalization and those who died during the hospitalization. We
performed regression analyses using comorbidities and complications as
covariates. STATA was used to perform all analyses. Statistical
significance was considered to be p < 0.05.