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Editorial
White Coat Hypertension: Time for Action
Thomas G. Pickering, MD, DPhil
A
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lthough increased blood pressure is one of the
most powerful predictors of cardiovascular morbidity, the prediction for the individual patient is
relatively weak. One reason for this is the inherent
variability of blood pressure and the distortions associated
with clinic measurement. It is widely accepted that blood
pressure measured in the clinic commonly overestimates
pressure measured in nonmedical settings and that the
discrepancy between the 2 varies greatly from 1 individual
to another. On the grounds that it is the average level of
blood pressure to which the circulation is exposed over
prolonged periods of time that causes the adverse effects of
hypertension, rather than the pressure at any 1 moment,
such as during a clinic visit, it is logical to suppose that
ambulatory blood pressure will give a better prediction of
risk than clinic pressure. A subgroup of patients with mild
hypertension whose blood pressure is high only in medical
settings has been identified as having white coat hypertension; this group typically comprises '20% of the hypertensive population.1 This is a potentially useful concept
because it may help to define a group of patients who are
at relatively low risk of cardiovascular morbidity and
hence do not merit antihypertensive drug treatment. However, the definition of white coat hypertension is arbitrary
and depends both on the cutoff point chosen to define a
hypertensive clinic pressure and a normal ambulatory
pressure.
study was the length of follow-up, which approached 10
years. There are 2 ways of analyzing the data obtained with
ABPM in prognostic studies. One is to estimate the
predictive value of ambulatory pressure after controlling
for clinic pressure for the entire cohort; the other is to
compare the event rates in patients with sustained hypertension and those with white coat hypertension. Khattar et
al chose the latter approach in their analysis of the
Northwick Park study. Theirs is actually the fifth published
report of the prospective significance of ambulatory blood
pressure; others are on the way. The first in the series,
published by Perloff et al,3,4 used noninvasive monitoring
performed during the day only and reported that those
whose ambulatory pressure was low in relation to their
clinic pressure were at lower risk of morbidity. The
second, by Verdecchia et al,5 monitored a group of 1187
normotensive and hypertensive individuals for 3 years.
The authors identified a subgroup of patients with white
coat hypertension but used somewhat different criteria
than Khattar et al. Verdecchia et al used a daytime blood
pressure of 131/86 mm Hg in women and 136/87 mm Hg
in men for defining the upper limit of normal ambulatory
pressure, whereas Khattar et al used a 24-hour average of
140/90 mm Hg, which would be equivalent to a daytime
pressure $145/95 mm Hg. Both groups used the same
cutoff point for defining clinic hypertension (140/
90 mm Hg). In the study by Verdecchia et al, the morbidity
differences between white coat and sustained hypertensives were more pronounced than in the Northwick Park
study: Verdecchia et al reported an event rate of 0.49 per
100 patient-years in white coat hypertensives (similar to
the rate of 0.47 in the normotensives); a rate of 1.79 in
hypertensive dippers, who constituted the majority of the
study population; and a rate of 4.99 in nondippers. The
Northwick Park event rate in white coat hypertensives was
higher at 1.32 per 100 patient-years, which may be
attributed to the higher cutoff point for defining white coat
hypertension. This would tend to include a larger number
of high-risk individuals.
The third published prospective study of ABPM comprises the pilot results of a population study in Ohasama,
Japan,6 which reported that ambulatory pressure was a
better predictor of morbidity than screening pressure. No
attempt was made to classify individuals as having white
coat hypertension. The fourth7 is a study of patients with
refractory hypertension, defined as a diastolic pressure
.100 mm Hg while taking $3 antihypertensive medications. Patients were classified in 3 groups according to
their daytime ambulatory pressure; those in the lowest
tertile (,88 mm Hg) had a significantly lower rate of
See p 1892
In this issue of Circulation, a study reported by Khattar
et al2 on the follow-up of a cohort of hypertensive patients
established by Dr Jim Raftery at Northwick Park Hospital
in London throws new light on the role of 24-hour
ambulatory blood pressure monitoring (ABPM) in predicting cardiovascular morbidity. The principal finding was
that patients with white coat hypertension were at substantially reduced risk of morbidity compared with patients
whose hypertension was sustained throughout 24 hours.
The patients underwent ABPM by the intra-arterial technique, which is still considered the gold standard of blood
pressure measurement but which is rarely used in epidemiological studies. A second important feature of this
The opinions expressed in this editorial are not necessarily those of the
editors or the American Heart Association.
From the Hypertension Center, New York Hospital, New York, NY.
Correspondence to Thomas G. Pickering, MD, DPhil, Hypertension
Center, 525 East 68th St, New York, NY 10021.
(Circulation. 1998;97:1834-1836.)
© 1998 American Heart Association, Inc
1834
Pickering
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morbidity over the next 4 years despite similar clinic
pressures. Thus, although these 5 prognostic studies differed widely in design, ranging from a population study to
a study of refractory hypertensives, the results all point in
the same direction, namely, that ambulatory pressure gives
a better prediction of prognosis after controlling for clinic
pressure. The corollary is that patients with white coat
hypertension have a more benign prognosis than those with
sustained hypertension.
It has been suggested that white coat hypertension may
simply be a precursor of sustained hypertension.8 Although
there will undoubtedly be some true hypertensives who are
misclassified as having white coat hypertension on initial
assessment, the literature on this is inconsistent at present. In
the Northwick Park study, no attempt was made to repeat
ABPM during follow-up, but a substantial proportion of
patients had a comprehensive assessment of target organ
damage after an interval of 9 years. The assessment showed
that only 11% of white coat hypertensives had left ventricular
hypertrophy compared with 38% of sustained hypertensives,
and there were similar differences in carotid artery thickening. The lesser degree of target organ damage in white coat
hypertensives is not altogether surprising, since these patients
had lower clinic pressures than did sustained hypertensives
upon entry into the study (156/96 mm Hg compared with
164/101 mm Hg), although final clinic pressures were the
same in the 2 groups. In addition, white coat hypertensives
were receiving less antihypertensive medication than sustained hypertensives. All of these points are consistent with
the idea that white coat hypertension is, in most individuals,
a benign condition.
An argument sometimes raised against the concept of
white coat hypertension is that if patients are seen a sufficient
number of times in the clinic, blood pressure will return to
normal. Again, this may be true in a minority of patients, but
there are many in whom clinic pressure will remain high
indefinitely. Thus, in the Northwick Park study, the majority
of white coat hypertensives must have been considered by
their physicians to be truly hypertensive during the course of
the study, because 82% were taking antihypertensive medication at the end of the follow-up period.
How should these findings be put into practice? One of
the trends in management of mild hypertension in recent
years has been the attempt to select patients according to
their overall level of risk rather than treating everyone with
a clinic pressure above a certain value. Thus, the widely
quoted New Zealand recommendations9 are to treat people
whose risk of cardiovascular morbidity over 10 years is
.20%, unless blood pressure is .170/100 mm Hg, in
which case they should be treated anyway. The rationale
for the recommendations is that the benefits of treating
blood pressure below this level are very small. In the
Northwick Park study, the 10-year risk was 7.9% in white
coat hypertensives and 22% in sustained hypertensives.
Under the New Zealand guidelines, white coat hypertensives would not be prescribed antihypertensive medication,
whereas those with sustained hypertension would. Although there is still no consensus, most experts accept the
idea that patients with white coat hypertension do not
November 3, 1998
1835
require antihypertensive drug treatment. Furthermore,
there is evidence that even if treated, the drugs lower clinic
pressure but have little effect on ambulatory pressure.10
One implication of this is that the cost of performing
ABPM in clinical practice can be offset by the savings
resulting from avoiding unnecessary drug treatment in
patients identified as having white coat hypertension. It
has been estimated in a survey of a general medical
practice in Michigan that on the basis of the prevailing
costs of antihypertensive drug treatment and the prevalence of white coat hypertension, the break-even cost for
performing ABPM in newly diagnosed hypertensives
would be $188.11 The actual cost of a single recording has
been estimated to be much lower than this—$65.12
The number of studies demonstrating the clinical value
of ABPM continues to grow. Thus, there is evidence that
ABPM is not only superior in selecting patients for
treatment but also in assessing the effects of treatment. In
a study of 206 patients treated with lisinopril, it was found
that changes in ambulatory pressure correlate more closely
with regression of left ventricular hypertrophy than clinic
pressure.13 The only reliable method of diagnosing white
coat hypertension is ABPM. It is unfortunate that this
procedure is still not recognized for reimbursement by
Medicare and most other payers despite the fact that its
clinical utility has been recognized in the last 2 reports of
the Joint National Committee of the National High Blood
Pressure Education Program14,15 and by bodies such as the
American Society of Hypertension16 and the American
College of Cardiology.17 In many other countries, ABPM is
a recognized and reimbursed procedure. If its use is
properly regulated and the reimbursement rate kept low,
there is no reason why ABPM should not be recognized as
a clinically useful test in the United States.
References
1. Pickering TG, James GD, Boddie C, Harshfield GA, Blank S, Laragh JH.
How common is white coat hypertension? JAMA. l988;259:225–228.
2. Khattar RS, Senior R, Lahiri A. Cardiovascular outcome in white-coat
versus sustained mild hypertension: a 10-year follow-up study. Circulation. 1998;98:1892–1897.
3. Perloff D, Sokolow M, Cowan R. The prognostic value of ambulatory
blood pressure. JAMA. l983;249:2793–2798.
4. Perloff D, Sokolow M, Cowan RM, Juster RP. Prognostic value of
ambulatory blood pressure measurements: further analyses. J Hypertens.
1989;7(suppl 3):S3–S10.
5. Verdecchia P, Porcellati C, Schillaci G, Borgioni C, Ciucci A, Battistelli
M, Guerrieri M, Gatteschi C, Zampi I, Santucci A, Santucci C, Reboldi G.
Ambulatory blood pressure: an independent predictor of prognosis in
essential hypertension. Hypertension. 1994;24:793– 801.
6. Ohkubo T, Imai Y, Tsuji I, Nagai K, Watanabe N, Minami N, Itoh O,
Bando T, Sakuma M, Fukao A, Satoh H, Hisamachi S, Abe K. Prediction
of mortality by ambulatory blood pressure monitoring versus screening
blood pressure measurements: a pilot study in Ohasama. J Hypertens.
1997;15:357–364.
7. Redon J, Campos C, Narciso ML, Rodicio JL, Pascual JM, Ruilope LM.
Prognostic value of ambulatory blood pressure monitoring in refractory
hypertension: a prospective study. Hypertension. 1998;31:712–718.
8. Bidlingmeyer I, Burnier M, Bidlingmeyer M, Waeber B, Brunner HR.
Isolated office hypertension: a prehypertensive state? J Hypertens. 1996;
14:327–332.
9. Jackson R, Barham P, Bills J, Birch T, McLennan L, MacMahon S,
Maling T. Management of raised blood pressure in New Zealand: a
discussion document. BMJ. 1993;307:107–110.
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White Coat Hypertension
10. Pickering TG. White coat hypertension. Curr Opin Nephrol Hypertens.
1996;5:192–198.
11. Yarows SA, Khoury S, Sowers JR. Cost effectiveness of 24-hour ambulatory blood pressure monitoring in evaluation and treatment of essential
hypertension. Am J Hypertens. 1994;7:464 – 468.
12. Pickering TG, Harshfield GA, Alpert BS, O’Brien E, De Swiet M,
Shennan AH. Ambulatory Blood Pressure. SpaceLabs Medical;
1994:149. Biophysical Measurement Series.
13. Mancia G, Zanchetti A, Agebeti-Rosie E, Benemio G, de Cesaris R,
Fogari R, Pessina A, Porcellati C, Salvetti A, Trimarco B. Ambulatory
blood pressure is superior to clinic blood pressure in predicting treatmentinduced regression of left ventricular hypertrophy. Circulation. 1997;95:
1464 –1470.
14. Fifth Report of the Joint National Committee on Detection, Evaluation,
and Treatment of High Blood Pressure. Bethesda, Md: National Institutes
of Health; 1993. Publication 93–1088.
15. Sixth Report of the Joint National Committee on Detection, Evaluation,
and Treatment of High Blood Pressure. Bethesda, Md: National Institutes
of Health; 1997. Publication 98 – 4080.
16. Pickering TG, Kaplan NM, Krakoff L, Prisant LM, Sheps S, Weber MA,
White WB, American Society of Hypertension Expert Panel. Conclusions
and recommendations on the clinical use of home (self) and ambulatory
blood pressure monitoring. Am J Hypertens. 1996;9:1–11.
17. Sheps SG, Clement DL, Pickering TG, Krakoff LR, White WB, Messerli
FH, Weber MA, Perloff D. ACC position statement: ambulatory blood
pressure monitoring. J Am Coll Cardiol. 1994;23:1511–1513.
KEY WORDS:
pressure
Editorials
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hypertension
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follow-up
study
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blood
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White Coat Hypertension: Time for Action
Thomas G. Pickering
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Circulation. 1998;98:1834-1836
doi: 10.1161/01.CIR.98.18.1834
Circulation is published by the American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231
Copyright © 1998 American Heart Association, Inc. All rights reserved.
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