STATISTICAL ANALYSIS
This trial was powered for the primary safety and efficacy end points and for the change in mean24-hour ambulatory systolic blood pressure at 6 months (secondary efficacy end point). On the basis of the 9.8% safety performance criterion, 316 patients were required in the renal-denerva- tion group to provide 80% power, with the use of a one-sided significance level of 0.05. Owing to the 2:1 randomization ratio, 158 patients were required for the control group. After accounting for expected patient attrition, we calculated that we would need to enroll a total of 530 patients. In agreement with the Food and Drug Admin- istration, the superiority of denervation over the sham procedure was established by a margin of 5 mm Hg for the primary efficacy end point and by a margin of 2 mm Hg for the secondary effi- cacy end point. The superiority margin of 5 mm Hg for the primary efficacy end point was consid- ered a clinically meaningful blood-pressure reduc- tion on the basis of the observed decreases in cardiovascular morbidity with small reductions in systolic blood pressure (2 to 5 mm Hg) with pharmacologic therapy.15 The detailed power and sample-size calculations have been published previously.13 The analyses were performed on the basis of the intention-to-treat principle. Means and stan- dard deviations of continuous variables are pre- sented according to treatment group. Between- group differences and differences from baseline to the 6-month follow-up assessment were tested with the use of unpaired and paired t-tests, re- spectively. For categorical variables, counts and percentages are presented according to treatment group; values were tested with the use of the exact test for binary variables and the chi-square test for multilevel categorical variables. All re- ported subgroup analyses were prespecified.