Statistical Methods:
Retrospective data of the use of dobutamine in our EP lab since March 2015 was used for the sample size calculation, which showed that the mean and standard deviation for the difference between the change as a percent from baseline in the SCL and the change from baseline in the AVNBCL is 7.7% ± 16.0% at 20 mcg/kg/min of dobutamine. We enrolled 40 patients based on the finding that a study of 37 patients yields 80% power with respect to the primary endpoint with an alpha of 0.05 using a paired 2-tail t-test.
The change per dose of dobutamine from baseline to each dosing level of dobutamine received by the patients, comparing AVNBCL, VABCL and SCL, was tested using mixed-effect regression.
Dobutamine dose level was tested for association with relative changes from baseline of each electrophysiologic parameter (SCL, AVNBCL, VABCL, AVNERP, AH and QT intervals) using mixed-effects regression. The Holm-Bonferroni method was used to adjust for multiple testing. Estimates of the change from baseline in each electrophysiologic parameter at each dose of dobutamine were provided along with 99% confidence intervals and plots.