OP.1C.10] WHITE-COAT EFFECT IS ASSOCIATED WITH A MARKED INCREASE OF BLOOD PRESSURE VARIABILITY ON AMBULATORY BLOOD PRESSURE MONITORING

Abstract

Objective: The increase of 24-hours blood pressure (BP) variability, assessed by ambulatory blood pressure monitoring (ABPM), is an independent risk factor for cardiovascular events. However white-coat effect (WCE) can influence at least the first part of ABPM leading to higher mean BP values and over-diagnosis of arterial hypertension. We aimed at examining to what extent WCE may affect BP variability. Design and method: We analysed 281 ABPM (M/F 101/180) in which the first systolic BP value was at least 10 mmHg higher than mean diurnal systolic blood pressure (mDSBP). WCE was evaluated during the first two hours of recording (WCE window, WCEw) as magnitude i.e. as mean SBP values (WCE magnitude, WCEm) and as duration (WCEd) i.e. the sum of the time intervals following a SBP value at least 10 mmHg higher than mDSBP. According to median values of WCEd we identified two subgroups: long-WCE (WCEd > 60 minutes) and short-WCE (WCEd =< 60 minutes) whereas for WCEm patients were subdivided in those with high-WCE (WCEm > 150 mmHg) and low-WCE (WCEm =< 150 mmHg). BP variability was assessed as mean diurnal systolic and diastolic BP standard deviation (SD). Results: Considering all ABPMs, SDs for mDSBP and for mean diurnal diastolic BP (mDDBP) were respectively 22.0 ± 0.3 and 17.8 ± 0.3 without differences between genders. After the exclusion of WCEw, these SDs fell respectively to 21.1 ± 0.3 (p < 0.05 for trend) and 17.1 ± 0.3. Considering WCEm, in the subgroup with high-WCE, SDs were higher for mDSBP and mDDBP than in the subgroup with low-WCE (respectively 23.6 ± 0.4 vs. 20.4 ± 0.4 and 19.0 ± 0.4 vs. 16.5 ± 0.4, p < 0.0001 for both), and these differences in SDs remained significant even when mDSBP and mDDBP were calculated with the exclusion of WCEw (table). In contrast no differences were observed in SDs in subgroups with long and short WCEd.Conclusions: WCE is associated with a very high systolic and diastolic BP variability on ABPM that is higher in patients with greater WCEm and persists beyond the two initial hours of recording used to classify patients as having WCE.