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766
'White Coat' Hypertension
No Harm for the Heart
Philippe Gosse, Helene Promax, Philippe Durandet, Jacques Clementy
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The superiority of ambulatory blood pressure monitoring over casual blood pressure measurement for the
prediction of target-organ damage is now well established, although the significance of "white coat"
hypertension is still controversial. Is an office blood pressure measurement that is higher than the mean
ambulatory value an added risk? Because left ventricular hypertrophy is a potent risk factor, the effect of
hypertension on left ventricular mass merits attention. Left ventricular mass indexed for height was
measured by M-mode echocardiography in 204 essential hypertensive patients (140 males, 64 females;
mean age [SD], SO [11] years). Blood pressure over 24 hours was monitored routinely with a noninvasive
auscultatory device. Office blood pressure after 10 minutes of the subject in the supine position was
measured by the same physician under the same conditions. The white coat effect was defined as the
difference between the office and average daytime values of systolic and diastolic blood pressures. Patients
were divided into four quartiles according to their office and daytime blood pressures. Two-way analysis
of variance was used to assess the influence of the white coat effect at a given level of daytime blood
pressure on left ventricular mass. Left ventricular mass increased significantly (P<.001) with daytime
systolic blood pressure but was independent of white coat effect for both the whole population and the 143
untreated patients. We conclude that the white coat effect has no influence on left ventricular mass,
favoring the view that white coat hypertension is a benign condition. (Hypertension. 1993;22:766-770.)
KEY WORDS • blood pressure monitoring, ambulatory • hypertension, "white coat" • hypertrophy,
left ventricular
T
he measurement of blood pressure by a physician
may trigger a pressor response. This so-called
white coat effect has a high interindividual variability1"3 and may explain, at least partially, the marked
differences between office and ambulatory or self-measured blood pressure measurements. There is disagreement on the significance and prognostic implications of
white coat hypertension. Some believe that the physicianinduced rise in blood pressure represents a marker of the
patient's response to the stresses of everyday life,
whereas others hold that the white coat effect is a benign
conditioned response. It has been demonstrated that
target-organ damage, especially left ventricular hypertrophy, is more closely correlated with ambulatory than
office blood pressure. 47 In this study we addressed the
following question: For a given level of ambulatory blood
pressure, does a higher office blood pressure level have
any influence on left ventricular mass?
Methods
Population
All hypertensive individuals referred consecutively to
our department by their general physicians over a
4-year period and fulfilling the following criteria were
included: (1) casual blood pressure above 140/90
mm Hg on at least two occasions, (2) untreated or
Received March 11, 1993; accepted in revised form June 23,
1993.
From the Hopital Cardiologique, Pessac, France.
Reprint requests to Dr Philippe Gosse, Hopital Cardiologique,
CHU Bordeaux, Avenue de Magellan, 33604 Pessac, France.
without treatment for more than 7 days, and (3) goodquality M-mode echocardiographic recordings of the
left ventricle and 24-hour ambulatory blood pressure
monitor records during their daily routine. Secondary
causes of hypertension and coronary or valvular heart
diseases were ruled out by clinical examination, electrocardiogram, and routine laboratory tests.
Office Blood Pressure Measurement
Office blood pressure was measured by the same
physician under the same conditions. In the morning,
after the subject had been supine for 10 minutes in the
presence of the physician, three consecutive measurements were taken with a mercury sphygmomanometer
(phase V for diastolic blood pressure). The mean of the
three readings was noted.
Ambulatory Blood Pressure Monitoring
All recordings were performed with a Spacelabs 5200
auscultatory device and, more recently, a validated
ECG-gated auscultatory device (DIASYS 200, Novacor).8 The monitor was placed on the left arm at the end
of the consultation, and the blood pressure recording
was checked by the physician on the right arm. Patients
with differences of more than 15 mm Hg between the
two arms were excluded. The monitor was programmed
to measure blood pressure every 15 minutes from 6 AM
to midnight and every 15 or 30 minutes at night.
Recordings were taken during the patients' daily routine. No patient worked during the night. Recordings of
pulse pressure below 15 mm Hg and diastolic blood
pressure above 150 mm Hg were rejected, and record-
Gosse el al
ings were only included if at least 80% of the expected
daytime measurements were available. Daytime was
fixed arbitrarily as between 6 AM and 10 PM, and
nighttime as between 10 PM and 6 AM. Average daytime
and nighttime systolic and diastolic blood pressures
were calculated.
TABLE 1 .
Echocardiography
All echocardiograms were recorded by the same
physician according to standard recommendations910
just before the office blood pressure determination.
Briefly, M-mode recordings of the left ventricle guided
by two-dimensional imaging were traced on a strip-chart
recorder running at 100 mm/s. All recordings were
coded and read blind by two observers according to the
Penn convention. Left ventricular mass was calculated
from Devereux's formula and was indexed for height.
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Statistical Analysis
Statistical analysis was carried out using PCSM software (Deltasoft, France). The white coat effect was
defined as the difference between office and ambulatory
daytime blood pressures and was calculated for both
systolic and diastolic values. The Kolmogorov-Smirnov
test was used to check that the parameters were distributed normally. Linear correlations were then calculated
between (1) the white coat effect and age, weight, and
office and ambulatory heart rates and (2) left ventricular mass and office and ambulatory blood pressures and
white coat effect. We also carried out a linear stepwise
multiple regression analysis. To assess the influence of
the white coat effect for a given level of ambulatory
daytime blood pressure, we divided patients into four
quartiles according to their values of daytime blood
pressure and four quartiles according to their values of
white coat effect. The influence of white coat effect and
daytime blood pressure on left ventricular mass was
evaluated by two-way analysis of variance. Left ventricular mass, ambulatory blood pressure, and white coat
effect were affected by age, which was therefore introduced as a covariate. Means were compared with the
Newman-Keuls test when the analysis of variance
showed significant differences or interaction. Systolic
and diastolic blood pressures were analyzed separately.
The results are presented as means with their corresponding standard deviations.
Results
Population Studied
Two hundred and four patients were included in the
analysis (140 males, 64 females; mean age, 50 [11] years;
range, 16 to 74 years). Most of them (143) were untreated, and the others had been without treatment for
an average of 3 months (7 days to 12 months). All
patients were reported to have a blood pressure above
140/90 mm Hg on at least two occasions. The average
office blood pressure at the time of the visit was 166
(18)/102 (10) mm Hg. Table 1 lists the main parameters
for the population. The distributions of office and
daytime blood pressures and of the white coat effect
(shown in the Figure) were not significantly different
from normal.
White Coat Hypertension
767
Population Studied
Mean
SD
Range
50
11
16-74
Office SBP, mm Hg
166
18
130-230
Office DBP, mm Hg
102
10
70-128
Daytime SBP, mm Hg
143
16
106-200
Daytime DBP, mm Hg
95
10
71-134
Systolic WCE, mm Hg
23
16
-11-75
9
-17-37
Parameter
Age, y
Diastolic WCE, mm Hg
LVMI, g/m
6.5
140
38
57-284
SBP indicates systolic blood pressure; DBP, diastolic blood
pressure; WCE, white coat effect; and LVMI, left ventricular mass
index.
Relations With White Coat Effect
Age (r=.36, P<.01) and office heart rate (r=.17,
F<.05) were positively correlated with the extent of the
systolic white coat effect. Weight was negatively correlated with systolic white coat effect (r= — .24, P< .01). In
the multivariate analysis, these three variables remained
significantly correlated with systolic white coat effect but
together accounted for only 18% of its variance. No
significant relation was observed with diastolic white
coat effect. There was a significant, albeit weak, correlation between systolic and diastolic white coat effects
(r=.56, P<.Q\).
Relations With Left Ventricular Mass
Left ventricular mass index was more closely correlated with the daytime (r=.30, /><.001) than with the
office (/'=.18, F<.01) systolic blood pressure. Coefficients of correlation with diastolic blood pressures were
.18 (P<m) for daytime and .20 (/><.01) for office
values. No significant correlation was observed with
white coat effect. In the multivariate analysis, only the
systolic daytime blood pressure was significantly and
independently correlated with left ventricular mass. In
the untreated population, the coefficient of correlation
between left ventricular mass index and average daytime systolic blood pressure was .32 (P<.001).
Relation of White Coat Effect With Left Ventricular
Mass at a Given Level of Ambulatory Daytime
Blood Pressure
The whole population was divided in four quartiles
according to their values of ambulatory daytime blood
pressure and white coat effect. A white coat effect
exceeding 22 mm Hg for systolic and 8 mm Hg for
diastolic blood pressure was found in 50% of the
population studied.
Relation of White Coat Effect With Left Ventricular
Mass at a Given Level of Systolic Blood Pressure
The two-way analysis of variance identified a significant increase in left ventricular mass from the first to
the fourth quartiles of daytime systolic blood pressure
(P<.01) but no significant influence of white coat effect.
As shown in Table 2, there was no constant elevation of
left ventricular mass with white coat effect in each
quartile of the daytime blood pressure. Introduction of
age as a covariate did not affect the results of the
768
Hypertension
Vol 22, No 5 November 1993
SYSTOLIC WHITE COAT EFFECT
M (SD)=23 mm Hg (16)
Bar graphs show distribution of white coat effect
defined as the difference between office and
average daytime blood pressures. M, mean.
DIASTOLIC WHITE COAT EFFECT
M (SD)=6.5 mm Hg (9)
-17.«/-H.1
-7.B/-2.1
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analysis, and the same results were observed in an
analysis restricted to the 143 untreated patients. Because the mean daytime blood pressure is affected by a
variety of factors, such as the level of physical activity,
the same analysis was carried out on the difference
between office and nighttime systolic blood pressures
used as a measure of the white coat effect. Seven
patients for whom less than 80% of the required measurements were available were excluded from the analysis. The results of this additional analysis were similar to
those of the initial analysis (Table 3). The two methods
of estimating systolic white coat effect produced closely
correlated results (r=.8O, P<.001).
Relation of White Coat Effect With Left Ventricular
Mass at a Given Level of Diastolic Blood Pressure
The two-way analysis of variance of left ventricular
mass index according to the quartiles of daytime diastolic blood pressure and diastolic white coat effect
identified a significant interaction between the two
factors (F<.001). Only one patient, who had a high left
ventricular mass index, belonged to both the higher
white coat effect quartile and the higher daytime blood
pressure quartile. However, there was no consistent
difference in left ventricular mass among the quartiles
of the white coat effect in the Newman-Keuls test (see
Table 4).
Discussion
Measurement of blood pressure by a physician generally produces higher values than those recorded by
patients themselves at home. This consistent overestimate of blood pressure by the physician is not merely a
reflection of the normal variations in blood pressure. In
a study of continuous intra-arterial blood pressure
recordings in the hospital, Mancia et al2 found that
approach of a physician and recording of blood pressure
from an arm cuff was accompanied by an abrupt rise in
arterial pressure. Although this procedure gives a relatively rigorous estimate of the white coat effect, even
with the use of noninvasive methods, it tends to be
confined to a clinical research setting. Increasing use is
TABLE 2. Left Ventricular Mass Index According to Daytime Systolic Blood Pressure and Systolic White Coat Effect
Defined From Daytime Blood Pressure
Daytime SBP Quartiles
Systolic White Coat
Effect Quartiles
1
2
(106-133 mmHg)
(133.1-142 mmHg)
3
(142.1-152 mmHg)
(152.1-200 mmHg)
Mean
Total
1 (-11-11 mmHg)
136(35)
149 (26)
136(41)
161 (38)
152(36)
(n=5)
(n=12)
(n=9)
(n=27)
(n=53)
2 (11.1-22 mm Hg)
118(36)
123(32)
133(24)
159(34)
133 (32)
(n=9)
(n=9)
(n=23)
(n=8)
(n=49)
3 (22.1-33 mm Hg)
116(29)
140(38)
146(33)
150(42)
137(36)
(n=12)
(n = 18)
(n = 14)
(n=6)
(n=50)
4 (33.1-75 mmHg)
125 (30)
146(42)
186(36)
133 (59)
139 (44)
(n=23)
(n = 13)
(n=6)
(n=10)
(n=52)
123(31)
141 (36)
144 (35)
154(43)
(n=49)
(n=52)
(n=52)
(n = 51)
Mean total
SBP indicates systolic blood pressure. Values are mean (SD) in grams per meter.
4
n=204
Gosse el al White Coat Hypertension
769
TABLE 3. Left Ventricular Mass Index According to Daytime Systolic Blood Pressure and Systolic White Coat Effect
Defined From Nighttime Blood Pressure
Daytime SBP Quartlles
Systolic White Coat
Effect Quartlles
1
(106-133 mmHg)
2
(133.1-142 mmHg)
3
(142.1-152 mmHg)
4
(152.1-200 mmHg)
Mean
Total
1 (-11-29 mm Hg)
130(40)
141 (38)
130(41)
174(35)
149 (41)
(n = 5)
(n=14)
(n=10)
(n=15)
(n=44)
114(36)
146(28)
141 (31)
145 (38)
136(35)
(n = 13)
(n=11)
(n=15)
(n=14)
(n=53)
123(20)
132 (33)
137(26)
145 (38)
135(31)
(n=8)
(n=16)
(n=12)
(n=13)
(n=49)
125(32)
146(45)
159(31)
148(62)
141 (53)
(n = 20)
(n = 11)
(n=12)
(n=8)
(n=51)
122(31)
141 (36)
142 (33)
154(43)
(n=46)
(n=52)
(n=49)
(n=50)
2 (29.1-41 mmHg)
3 (41.1-50 mmHg)
4 (50.1-112 mmHg)
Mean total
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n=197
SBP indicates systolic blood pressure. Values are mean (SD) in grams per meter.
being made of ambulatory measurements and patient
self-measurement to estimate the white coat effect,
although the concordance between these results and the
more rigorous procedure used by Mancia et al has yet to
be established. In the present study, the white coat
effect was evaluated from the difference between office
blood pressure and the mean ambulatory value. We
found an average value of 23 mm Hg for the systolic and
6 mm Hg for the diastolic white coat effect, with extremes of 75 and 37 mm Hg, respectively. These values
are close to those reported by Mancia et al.2 Other
studies have also noted the frequent overestimation of
blood pressure when measured by a physician with
respect to average daytime values.3 Ambulatory values
are assumed to include the normal response to the
stresses of everyday life provided that the recordings are
made, as in the present study, during the patient's daily
routine. However, the daytime ambulatory value is
affected by a variety of factors (such as physical activity,
emotions, duration of sleep), which may in turn affect
the estimation of the white coat effect. Nevertheless,
there appears to be a good reproducibility for the values
of mean ambulatory blood pressure in different reported studies." We examined whether the difference
between office and mean nighttime values would give a
different estimate of the white coat effect. In fact, we
found a high correlation between the two estimates
(office-nighttime versus office-daytime). White coat hypertension is based on rather arbitrary criteria; therefore, in the absence of a clear definition of normal
ambulatory blood pressure, it seems best to use daytime
ambulatory values as a reference rather than nighttime
or self-measured values, which are not affected by the
stresses of everyday life. There is considerable individual variability in white coat effect, and it does not
appear to bear any relation to clinical findings. We
TABLE 4. Left Ventricular Mass Index According to Daytime Diastolic Blood Pressure and Diastollc White Coat Effect
Defined From Daytime Blood Pressure
Daytime DBP Quartlles
1
(71-89 mm Hg)
2
(89.1-95 mm Hg)
3
(95.1-102 mmHg)
4
(102.1-134 mmHg)
Mean
Total
1 (-17-0 mmHg)
132 (24)
145(25)
140(27)
148(36)
144(31)
(n=6)
(n = 11)
(n = 13)
(n=23)
(n=53)
2 (0.1-8 mmHg)
138(13)
137 (42)
133(41)
134(36)
134(37)
(n=4)
(n = 11)
(n = 20)
(n = 18)
(n = 53)
118(29)
147 (37)
125(24)
163(29)
143 (36)
(n=51)
Diastollc White Coat
Effect Quartiles
3 (8.1-12 mmHg)
4 (12.1-37 mmHg)
Mean total
(n = 10)
(n=22)
(n=6)
(n=13)
128 (31)
153(64)
153(21)
246
141 (47)
(n=27)
(n=15)
(n=4)
(n=1)
(n=47)
127(29)
146(44)
136(33)
149(38)
(n=47)
(n=59)
(n=43)
(n=55)
DBP indicates diastolic blood pressure. Values are mean (SD) in grams per meter.
n=204
770
Hypertension
Vol 22, No 5 November 1993
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noted only a weak correlation for the systolic value with
age, office heart rate, and weight. Other studies have
tended to produce conflicting results with low
correlations.1213
Opinion is divided on the significance of the white
coat effect.13 For some, it is an alarm response, and its
extent is taken to be a marker of the patient's response
to the stresses of everyday life. For others, the white
coat effect is a conditioned response stemming from a
defense reflex independent of true fluctuations in blood
pressure and is an essentially benign phenomenon.
Target-organ damage from hypertension appears to be
better correlated with the ambulatory than the office
value of blood pressure, although the prognostic significance of the ambulatory value remains to be established, the study of Perloff et al14 having to be confirmed
on a prospective design. The risk from the white coat
effect clearly needs to be assessed. In a survey of 737
young subjects in Tecumseh, Mich, with office and home
self-monitored blood pressure values, Julius et al15
found a similar risk profile in "sustained" borderline
hypertensive and white coat borderline hypertensive
individuals as estimated from heart rate, systemic vascular resistance, minimal forearm vascular resistance,
plasma triglycerides, and high-density lipoproteins.
Nevertheless, the group with white coat hypertension
still had a significantly higher home blood pressure than
the normotensive group. The white coat effect therefore
should be evaluated at strictly comparable levels of
ambulatory or home blood pressure. Our results indicate that for a given level of ambulatory blood pressure,
the white coat effect has no influence on left ventricular
mass. In view of the high prognostic significance of an
elevated left ventricular mass, our observations are in
favor of a benign nature for the white coat effect.
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'White coat' hypertension. No harm for the heart.
P Gosse, H Promax, P Durandet and J Clementy
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Hypertension. 1993;22:766-770
doi: 10.1161/01.HYP.22.5.766
Hypertension is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231
Copyright © 1993 American Heart Association, Inc. All rights reserved.
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