2.5 Statistical analysis
Continuous variables were expressed as median (interquartile range), and
categorical variables were presented as numbers and percentages. Student
paired t test or Wilcoxon signed rank test were used to compare
pre- and post- procedure variables within patients, as appropriate.
Comparisons between patients with or without significant increase in
LVOT gradient were performed using the student’s t test, Wilcoxon
rank sum test, or chi-square test, as appropriate.
LVOT areas and dimensions among 3
levels: valve stent distal edge, middle portion, and aortic annulus,
were compared using one-way analysis of variance with post hocTukey-Kramer testing. The linear regression between continuous variables
was made using Pearson’s correlation coefficient. For linear
correlation, ΔPG was log-transformed after adding a constant number
(2.0) to the variables to make them positive and non-zero.
To
identify the independent association with LVOT area at the valve stent
distal edge, multivariate linear regression was used among variables
including those LV end-systolic volume (LVESV), LV ejection fraction
(LVEF), and AM angle which were significantly associated with LVOT area
at the valve stent distal edge in univariate analysis. A P value of
<0.05 was considered significant. All statistical analyses
were performed with JMP 10.0 (SAS Institute Inc., Cary, North Carolina).