P3.04 AORTIC STIFFNESS IS INDEPENDENTLY ASSOCIATED WITH WHITE COAT EFFECT

Abstract

Introduction: The difference between systolic blood pressure (SBP) measured in clinic and during the daytime phase of ambulatory BP measurement (ABPM) (Δclinic-day ABPM SBP) has been used as a measure of white-coat effect. We hypothesised that this was mediated through increased aortic stiffness resulting in greater increase in SBP from increased sympathetic activity in response to a hospital visit. Methods: Patients enrolled in the Anglo-Cardiff Collaborative Trial between 2000–2009 underwent measurement of aortic stiffness by carotid-femoral pulse wave velocity (C-F PWV, Sphygmocor) and 24h ABPM (Spacelabs-90207). Δclinic-day ABPM SBP was calculated. C-F PWV was adjusted for mean BP, and it was log-transformed for analysis due to non-parametric distribution. Results: The total study population was 477 subjects, mean age 45±20 years, 44.9% male, 1.6% diabetic and 33.3% current or ex-smokers. Mean clinic BP was 146±18/88±12 and mean 24h day ABPM was 137±13/83±1.1 LogC-F PWV correlated with Δ clinic-day ABPM SBP (rho=0.13, P<0.01) and there was a significant trend for increased logC-F PWV with increased tertiles of increased Δclinic-day ABPM SBP (P<0.01). In stepwise multivariate analysis, independent determinants of Δclinic-day ABPM SBP were logC-F PWV, heart rate and age (total R2=0.11, P<0.001) while diabetes, gender, smoking and BMI were excluded. Conclusion: Aortic stiffness is independently associated with the degree of rise of SBP between home and clinic in a population with a broad age range and low co-morbidity. This may have important implications for using clinic values of BP to guide antihypertensive treatment in patients with high aortic stiffness.