Hemodynamic and Mechanical Properties of the Proximal Aorta in Young and Middle-Aged Adults with Isolated Systolic Hypertension: The Dallas Heart Study

The aim of this study was to assess characteristic impedance (Z_c) of the proximal aorta in young and middle-aged individuals with isolated systolic hypertension (ISH). Z_c is an index of aortic stiffness relative to aortic size. In the Dallas Heart Study, 2001 untreated participants 18 to 64 years of age (mean age: 42.3 years; 44% black race) were divided into the following groups based on office blood pressure (BP) measurements: (1) optimal BP (systolic BP [SBP] <120 mm Hg and diastolic BP [DBP] <80 mm Hg; n=837); (2) prehypertension (SBP 120-139 mm Hg and DBP 80-89 mm Hg; n=821); (3) ISH (SBP ≥140 mm Hg and DBP <90 mm Hg; n=121); (4) isolated diastolic hypertension (SBP <140 mm Hg and DBP ≥90 mm Hg; n=44); and (5) systolic-diastolic hypertension (SBP ≥140 mm Hg and DBP ≥90 mm Hg; n=178). Z_c, aortic arch pulse wave velocity, and minimum ascending aortic size were quantified using cardiovascular magnetic resonance. In multivariable-adjusted linear models, Z_c was highest in the ISH group compared with the optimal BP, isolated diastolic hypertension, or systolic-diastolic hypertension groups (103.2±4.0 versus 68.3±2.1, 75.4±6.0, and 88.9±4.8 dyne∗seconds/cm⁵, respectively; all P<0.05). The Z_c-ISH association did not differ by race. Aortic pulse wave velocity was highest in the ISH group compared with the optimal BP, isolated diastolic hypertension, or systolic-diastolic hypertension groups (6.3±0.3 versus 4.3±0.1, 4.4±0.4 and 5.5±0.3 m/s, respectively; all P<0.05), whereas aortic size was similar across groups (all P>0.2). Results were similar in a subgroup of 1551 participants 18 to 49 years of age. In a multiracial population-based sample, we found evidence of a mismatch between proximal aortic stiffness and diameter in young and middle-aged adults with ISH.