White-coat effect (WCE) and morning blood pressure surge (MBPS) are two particular phenomena assessable with ambulatory blood pressure monitoring (ABPM), that could have common pathophysiological mechanisms represented by an hyper-activation of the sympathetic nervous system.Design and method:
We examined the relationship between WCE and MPBS in 252 ABPM (M/F 94/158) characterized by WCE, i.e. when the first recorded value was at least 10 mmHg greater than the mean diurnal systolic blood pressure (SBP). In these ABPM we also evaluated WCE duration and WCE magnitude (WCEd and WCEm, respectively represented as number of values at least 10 mmHg greater than mean diurnal SBP multiplied by the interval between recordings and the mean of SBP values both calculated during the first two hours of recording). MBPS was examined as mean of SBP values between 6:00 and 10:00 AM and their increase with respect to mean nocturnal SBP (mNSBP).Results:
As expected, we found a progressive decrease of systolic values during the first three hours of recording, expression of WCE (WCEm 148 mmHg, WCEd 65 minutes) and an increase of hourly SBP from 6:00 AM to 10:00 AM (respectively 125, 132, 137 and 140 mmHg) while mNSBP was 124 mmHg. We found a significant but week correlation between mean SBP values of the whole four hours period and in particular with 8:00 – 9:00 AM mean, and WCEm (r = 0.56, r = 0.53; p < 0.01 for both); correlations were even weaker when considering WCEm and hourly increment from mNSBP; whereas the correlation between WCEd and MBPS (hourly increment and mean) were not statistically significant.Conclusions:
Our data suggest that WCE and MSBP share only in part the same pathophysiological mechanisms.