Paradoxical effect of age on improvements in pulse pressure during blood pressure lowering

Abstract

Resistant hypertension (rHTN) is defined as blood pressure (BP) that remains above goal in spite of using 3 different classes of antihypertensive medications at optimal dosages with one being a diuretic. Pulse pressure (PP, systolic BP diastolic BP) has been associated with adverse cardiovascular (CV) events. Aging is associated with an increase in PP, but the effect of aging on changes in PP remains during BP lowering is unknown. Adults with rHTNbetween January 1, 2008 andMay 1, 2013were retrospectively analyzed. Demographics, office BP, comorbidities andmedication use were collected at baseline. The office BP was again measured at the last follow-up visit. The 2nd of 2 consecutive manual office BP readings was used. The change in PP was calculated as the baseline PP follow-up PP. BP measurements were done using standard techniques: allowing patients to sit for 5 minutes, using the appropriate sized cuff, back supported and feet on the floor and measured arm supported at chest level. A total 336 patients were included in the analysis. The mean and median days from baseline visit to the last follow-up was 273 and 56 days, respectively. After adjusting for days of follow-up (p 1⁄4 0.06), change in PP was associated with baseline PP, such that for every PP one unit higher at baseline, PP decreased by 0.6 mmHg at follow-up (p < 0.0001). After adjusting for systolic BP (Table 1), age was associated with change in PP (p 1⁄4 0.0122).There was a significant decrease in PP at the follow-up visit across all age groups. There was a greater change (decrease) in PP with decreasing age, with the greatest change among patients 41-50 years; however, the trend was absent in patients <40 years old. This observation was consistent even after adjusting for SBP. The decrease in PP among individuals with 51-60 years and 41-50 years (14.1 and 15 mm Hg, respectively) was significantly greater than those 71 years (4.7 mmHg). The blunted change in PP in older individuals ( 71 years) seems consistent with increased vascular stiffness. Fixed vascular stiffness in older individuals may render their vessels resistant to improvements in PP during BP lowering. The blunted PP among younger subjects (<40 years) is surprising and suggests that antihypertensive therapy is less effective in reducing a marker of vascular stiffness in young individuals with resistant hypertension.