The change in 24-hour ambulatory systolic blood pressure was -6.7515.11 mm Hg in the denervation group and -4.7917.25 mm Hg in the sham-procedure group , for a difference of -1.96 mm Hg ( 95 % CI , -4.97 to 1.06 ; P = 0.98 for superiority with a margin of 2 mm Hg ) .