Blood pressure variability (BPV) is associated with adverse cardiovascular outcomes. Factors determining BPV are unclear. Arterial stiffness manifested by pulse pressure (PP) may be related to BPV, and is reflected in the pulse wave velocity (PWV), as well as the regression of diastolic on systolic pressure determined by the Ambulatory Arterial Stiffness Index (AASI). We hypothesized that arterial stiffness was associated with PP variability (PPVAR) and determined arterial stiffness using AASI and PWV.
Ambulatory blood pressure (BP) data from untreated subjects (n=56, 28 men) with SBP >130 to <160 mmHg with a mean age 49 ±11 yrs were obtained in our Research Center. We calculated AASI as 1-regression slope of diastolic on systolic BP and PWV by carotid-femoral tonometry (Sphygmocor). We calculated PPVAR by the Standard Deviation (SD) and the Average Real Variability (ARV) of PP over 24h, day, and night periods (by patient diary).
AASI correlated positively with day PPVAR (r=0.57, p <0.000) and night PPVAR (r=0.34, P = 0.01) by SD. AASI correlated positively with day PPVAR (r=0.53, P <0.000 Fig1A) and night PPVAR (r=0.43 and p<0.001 Fig1B) by ARV. AASI was not significantly correlated with 24h PPVAR by SD or ARV. PWV was not correlated with any PPVAR estimate.
The relationship between AASI and PPVAR was only evident when the blood pressure periods were broken down into day and night. The 24 hour regression relationship of diastolic on systolic blood pressure with PPVAR appears different between day or night compared with the 24 hour aggregate, suggesting circadian differences in factors which modify PPVAR. Poor PWV correlation with PPVAR is likely due to relatively young age of our subjects.