Department of Medicine, Sultan Qaboos University Hospital, Muscat, Oman
*Corresponding Author email: mansoursallam@yahoo.com

SQU Med J, December 2010, Vol. 10, Iss. 3, pp. 370-376, Epub. 14th Nov 10
Submitted 29th March 10
Revision ReQ. 21st June 10, Revision recd. 14th July 10
Accepted 24th August 10

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

 104
12009 2007
4         32
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   %4.46 73124 82134
%29.8%22.1 
P 0.043
 





aBstract: Objectives: Blood pressure (BP) measurements taken in a physician’s clinic do not represent readings 
throughout the day. Ambulatory blood pressure monitoring (ABPM) overcomes this problem by providing multiple 
readings with minimal interference with the patient’s daily activities. The purpose of our study was to evaluate the 
value of ABPM in risk assessment and management of hypertension compared to office measurements. Methods: A 
total of 104 consecutive hypertensive patients were retrospectively studied from January 2007 to December 2009. 
The following data were gathered: 1) clinic BP measurements; 2) routine blood test results; 3) electrocardiography, 
echocardiography, and 4) 24-hour ABPM. Results: The mean age of patients was 41.1 ± 8.6 years and 51.9% of them 
male. Indications for ABPM were: suspected “white coat” hypertension (10.6%), de novo hypertension (18.2%), 
resistant hypertension (27.9%) and others (43.3%). Mean daytime and nighttime BP were 134/82 and 124/73 
mmHg respectively. A non-dipping pattern was reported in 64.4%. Echocardiographic evidence of left ventricular 
hypertrophy (LVH) and diastolic dysfunction (LVDD) was encountered in 22.1% and 29.8% respectively. ABPM 
parameters were significantly correlated with LVDD (P = 0.043). Patients with proved “white coat” hypertension 
did not receive antihypertensive therapy. Conclusion: Twenty-four hour ABPM is an important yet underused 
tool for proper risk stratification of treated hypertensive patients. The non-dipping profile is associated with a 
higher incidence of diastolic dysfunction. Our collective results revealed the superiority of ABPM over office BP 
measurement.

Keywords: Hypertension; Blood pressure monitoring, ambulatory; Hypertrophy; Left Ventricular; Ventricular 
Dysfunction, Left.

Comparative Study of Ambulatory Blood 
Pressure Monitoring and Clinic Blood Pressure 

Measurement in the Risk Assessment  and 
Management of Hypertension

Hatem Farhan, Mona Al-Hasani, Mohamed Misbah and *Mansour Sallam

CLINICAL & BASIC RESEARCH



Hatem Farhan, Mona Al-Hasani, Mohamed Misbah and Mansour Sallam

Clinical and Basic Research | 371

Over the past three decades, the accuracy of using the conventional sphygmomanometer to measure blood 
pressure (BP) has been questioned, and efforts 
have been made to improve measurements with  
automated devices.1 Ambulatory blood pressure 
monitoring (ABPM) is being increasingly 
recommended for routine clinical practice. It may 
be particularly useful in evaluating the patient with 
variable BP readings in the office, or the patient 
with wide discrepancies between BP readings 
at home and in the physician’s office (i.e. “white 
coat” hypertension). ABPM and, in particular, 
nocturnal BP readings, may also provide prognostic 
data.2,3 This has focused attention on methods of 
measurement that provide profiles of BP rather 
than rely on isolated measurements made under 

circumstances that may influence BP.4 Early clinical 
uses of ABPM were limited in identifying patients 
with white-coat hypertension; however, ABPM 
has evolved into a useful modality for stratifying 
cardiovascular risk and guiding therapeutic 
decisions. Left ventricular hypertrophy (LVH) is an 
important predictor of cardiovascular morbidity 
and mortality.5 The prevalent circadian pattern in 
both normotensive and hypertensive individuals is 
characterised by a marked decrease of systolic and 
diastolic BP during the night (dippers), but there 
is a noticeable fraction of subjects who exhibit a 
diminished nocturnal decline in BP (non-dippers).6 
Many clinical studies with non-invasive ABPM have 
shown that some cardiovascular complications 
of hypertension, namely LVH, tend to be more 
frequent in patients in whom BP does not fall, or 
falls only minimally at night and who consequently, 
suffer a prolonged exposure to high BP levels over 24 
hours.7,8  The purpose of our study was to evaluate 
the value of 24-hour ABPM in the risk assessment 
and management of hypertension compared to the 
traditional office measurements. 

Methods
This retrospective study included 104 existing or 
newly diagnosed essential hypertensive patients 
attending the out-patient Cardiology Clinic at 
Sultan Qaboos University Hospital, Oman, from 
January 2007 to December 2009. Only records 
of patients with at least three readings showing 
diastolic BP ≥ 90 mmHg and/or systolic BP ≥ 
140 mmHg, or established hypertensive patients 
who were currently on treatment were included. 
All patients had to have undergone the following 
procedures: 1) detailed history taking, general 
and cardiovascular examination including 
repeated clinic BP measurements; 2) blood 
sampling for routine chemistry examinations; 
3) 12-leads electrocardiography, transthoracic 
echocardiography, and 4) 24-hour ABPM. Patients 
with congestive heart failure, previous myocardial 
infarction, significant cardiac valve diseases, or 
poor echocardiography window were excluded.

BP was measured from both of the patient’s arms 
in the hospital’s out-patient clinic by a dedicated 
nurse using a well calibrated automated BP machine 
(Datascope: Trio, China, 2005), and after the patient 
had rested for 5 minutes in the sitting position. The 
higher reading was recorded.

Twenty-four-hour ABPM was carried out on 
the arm with the higher reading using a (24/48 hour 
BP recorder, (BR-102 plus, Schiller, Switzerland, 
2006). The device was set to obtain BP readings 
at 30 minutes interval during the daytime and at 
60 minutes interval during night-time according 
to the patient’s lifestyle. Daytime and nighttime 
were individually predetermined depending upon 
the individual patient’s awake and sleep times; for 
example, if a patient normally woke  at 6 am and 
went to sleep at 10 pm, his or her daytime recordings 
were taken from 6 am to 10 pm and nighttime ones 
from 10 pm to 6 am. The patients were instructed 
to continue with their usual daily activities, but to 

Advances in Knowledge 
1. The present study sheds light on the important role of 24-hour ambulatory blood pressure monitoring (ABPM) in the management and 

risk stratification of hypertensive patients.
2. It draws attention to the advantages of this procedure and compares our results with studies in the available literature.

Application to the patient care
1. In patients with treated hypertension, a higher ambulatory systolic or diastolic BP predicts adverse cardiovascular events.
2. ABPM provides useful information for determining which patients have isolated office hypertension and in guiding drug regimen 

modification.



Comparative Study between Ambulatory Blood Pressure Monitoring and Clinic Blood Pressure Measurement  
in the Risk Assessment  and Management of Hypertension

372 | SQU Medical Journal, December 2010, Volume 10, Issue 3

remain still at measurement times. The recording 
was then analysed to obtain 24-hour daytime and 
night-time average systolic blood pressure (SBP), 
diastolic blood pressure (DBP) and heart rates. 
Only SBP was used to assess dipping.

Two-dimensional, M-mode, and Doppler 
echocardiographic examinations were performed 
using the commercially available instruments 
(Acuson Sequoia 265, USA, 2003 and Geving MED 
system V, Norway, 2000). End-diastolic and end-
systolic left ventricular internal diameter (LVIDd 
and LVIDs); interventricular septum thickness 
(IVST); posterior wall thickness (PWT); ejection 
fraction (EF) and fractional shortening (FS) were 
calculated from two-dimensionally guided M-mode 
tracing. Left ventricular filling to evaluate diastolic 
function was assessed by recording mitral flow and 
the ratio of the early to late flow velocity peaks (E/A 
ratio) was assessed.

A ‘non-dipping BP profile’ is defined as a 
nocturnal systolic BP fall of less than 10% compared 
to daytime values.6,9 Left ventricular hypertrophy 
is defined as increased left ventricular mass as 
assessed by 2D guided M-mode echocardiographic 
examination of interventricular septum and 
posterior wall thickness in diastole equal to more 
than 1.2 cm.10 Left ventricular diastolic dysfunction 
is defined as abnormality in the left ventricle’s 
filling during diastole as assessed by the utility of 
mitral annulus Doppler flow velocity with reversed 
E/A ratio.11 There is no consensus definition of 
borderline hypertension; however,  some studies 
in the literature have defined borderline HTN as 

“prehypertension” described as systolic BP 135-
139 mmHg and/or diastolic BP 85-89 mmHg.12 
The term “white coat” hypertension is applied to 
patients with office readings that average more than 
140/90 mmHg and reliable out of office readings 
that average less than 140/90 mmHg.4 Resistant 
hypertension is defined in the 2008 American Heart 
Association scientific statement as BP that remains 
above goal in spite of concurrent use of three 
antihypertensive agents of different classes. Thus, 
patients whose BP is controlled with four or more 
medications should be considered to have resistant 
hypertension.13 Orthostatic hypotension is defined 
as at least a 20 mmHg fall in systolic pressure and 
or 10 mmHg fall in diastolic pressure after quiet 
standing for 2 minutes.14 Episodic (paroxysmal) 
HTN with symptoms is defined as an abrupt 
elevation of BP that is documented by a clinician 
or home BP monitor associated with abrupt onset 
of distressful physical symptoms, such as headache 
or palpitation.15

Statistical analyses were carried out using the 
Statistical Package for the Social Sciences (SPSS), 
Version 15, (SPSS Inc., Chicago, IL). Continuous 
data were expressed as mean value ± standard 
deviation (SD) and categorical data as percentages. 
Continuous variables were compared using  
the Student’s paired t-test. Categorical data were 
compared using chi-square (X2) analysis. Data were 
first identified in a univariate fashion with linear 
regression analysis for continuous variables and X2 
test for dichotomous variables. A P value of 0.05 or 
less was considered statistically significant. 

Results
The demographic and clinical characteristics of 
the study population are reported in Table 1. The 

Table 1: Baseline clinical characteristics of the study 
population

Parameter Result 

Age in years ± standard deviation 41.1 ± 8.6

Male gender % 51.9

Dyslipidemia % 21.2

Diabetes mellitus % 13.4

Renal impairment % 6.7

Obstructive sleep apnea %? 1.9

Cerebrovascular accident % 3.8

Hypertension Duration/years 4.7 ± 6.03

Office systolic blood pressure mmHg 146.9 ± 22.7

Office diastolic blood pressure mmHg 86.6 ± 13.7

Mean office heart rate beats per minute  63.0 ± 24.1

Table 2: Indications of ambulatory blood pressure 
monitoring

Indication %

Suspected “white coat” HTN 10.6

Recent onset HTN 18.2

Resistant HTN 27.9

Borderline HTN 16.3

Orthostatic hypotension 7.7

Episodic HTN with symptoms 19.3

Legend: HTN = hypertension



Hatem Farhan, Mona Al-Hasani, Mohamed Misbah and Mansour Sallam

Clinical and Basic Research | 373

mean age of the patients was 41.1 ± 8.6 years, with 
slightly more males than females (51.9%). Mean 
office SBP and DBP were 146.9 ± 22.7 and 86.6 ± 
13.7 mmHg respectively. Hypertension duration 
was reported as 4.7 ± 6.03 years; however, we 
declare that in our database we could not find the 
exact duration of hypertension for all patients. 
Table 2 illustrates our indications of ABPM. Table 
3 illustrates ABPM parameters. From this latter 
table, it is clear that, only 35.6% of patients showed 
a fall in SBP/DBP > 10% during nighttime compared 
to daytime measurements and were categorised 
as dippers, while the remaining 64.4% showed a 
fall ≤ 10% and were categorised as non-dippers. 
There were significant differences between systolic 
and diastolic BP measured at the office and the 
mean 24-hour systolic and diastolic BP measured 
by ABPM with P = 0.0001. Table 4 depicts the 
electrocardiogram (ECG) and echocardiographic 
findings. LVH was reported in 6.7% of analysed 
ECG readings; however, it was remarkably higher, 
22.1% of the study population, when measured 
by echocardiography. Left ventricular diastolic 
dysfunction was noted in 29.8% of our patients.

As to circadian BP variation and cardiac 
structure and function, when the echocardiographic 
data were analysed in a categorical way as a 
presence or absence of LVH, the prevalence of LVH 
was similar in dippers and non-dippers (P = 0.09). 
A significant correlation was found between left 
ventricular diastolic dysfunction and mean systolic 
and diastolic daytime BP (P < 0.043).  

Discussion
The purpose of our present study was to observe 
whether or not 24-hour ABPM improved the risk 
assessment and management of hypertensive 
patients. By its unique 24-hour BP evaluation 
outside the medical field, ABPM was considered 
to be an effective tool to assess the average BP 
over the day in addition to circadian variation. 
Many prospective studies have reported that 
such measurements give a better prediction of 
clinical outcomes compared to conventional 
clinic measurements. Currently, it is the only tool 
available to exclude the well known phenomenon of 
“white coat” hypertension and has a role in assessing 
apparent drug-resistant hypertension, hypertension 
in pregnancy, during symptomatic episodes of 
hypotension or hypertension, and in monitoring 
adequacy of BP control in patients at high risk of 
cardiovascular disease.2-4 

According to circadian variation in BP, ABPM 
allows stratification into “dipper” or “non-dipper” 
status. In our study, we found 64.4% of patients were 
non-dippers. As many studies have related target 
organ damage to the non-dipping phenomenon,6 
we intended to optimise the BP of those patients, 
especially diabetics. The interesting finding was 
that 16.6% of the non-dippers were found to have 
a normal ambulatory blood pressure (ABP) profile. 
There is as yet no consensus about the proper 
management strategy for non-dippers with a 

Table 3: Ambulatory blood pressure monitoring 
(ABPM) parameters

Parameter mmHg

Mean 24 hour SBP 131.2±14.8

Mean 24 hour DBP 79.5 ±9.3

Mean daytime SBP 133.9 ± 15.3

Mean daytime DBP 81.7 ± 9.7

Mean nighttime SBP 123.6 ± 14.7

Mean night-time DBP 73.4 ± 9.4

Mean dipping % 8.2 ± 4.8

Dipper % 35.6

Note: Many ABPM parameters have been proposed. This table
illustrates some of those commonly used. From this table,
it is clear that, only 35.6% of patients could be considered as dippers. 
Legend: SBP = systolic blood pressure; DBP = diastolic blood pressure

Table 4: Baseline electrocardiogram and 
echocardiography findings

Parameter Result

ECG-LVH % 6.7

Echo-LVH % 22.1

LVEDD/mm 48.3 ± 5.3

LVESD/mm 29.6 ± 4.8

IVST/mm 10.9 ± 1.7

PWT/mm 10.3 ± 1.6

EF % 68.1 ± 6.7

FS % 38.3 ± 5.8

LV diastolic dysfunction % 29.8

Legend: ECG = electrocardiography; LVH = left ventricular 
hypertrophy; Echo = echocardiography; LVEDD/mm = left ventricular 
end diastolic diameter; LVESD = left ventricular end systolic diameter; 
IVST = interventricular septal thickness; PWT = posterior wall 
thickness; EF = ejection fraction; FS = fractional shortening ; LV= left 
ventricular.



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in the Risk Assessment  and Management of Hypertension

374 | SQU Medical Journal, December 2010, Volume 10, Issue 3

normal BP profile. We assume that the non-dipping 
group with a normal ABPM profile may be highly 
susceptible for future persistent hypertension 
requiring shorter-term follow-up by office and 
ABPM measurements [Figure 1a-d].

The association between diurnal BP profile 
and target organ damage remains controversial.7,16 
Our data are in agreement with several studies 
which failed to detect significant differences 
between dipper and non-dipper hypertensive 
patients and LVH assessed by either ECG or 
echocardiography.17,18 Despite this, there was a 
trend towards increased incidence of LVH in 
the non-dipper group (P = 0.09). The reduced 
nocturnal fall in BP was found in the majority 
of our study population (64.4%), and appeared 
particularly high in the group with resistant and 
refractory hypertension. Contradictory to the non-

significant correlation between LVH and ABPM, 
left ventricular diastolic function was found to be 
closely related to ambulatory, rather than clinic BP 
measurements, the mean nocturnal diastolic BP 
being a powerful marker of LV filling impairment (P 
= 0.043). This was in agreement with other studies 
which have addressed this issue.19,20  

“White coat” hypertension was suspected in 
10.6% of our study population (as they were not 
receiving any antihypertensive drug). One third 
of those patients had a normal ABP profile; many 
of them described attacks of dull aching internal 
discomfort just before attending the hospital and 
others described palpitation and flushing. Most of 
these patients had an elevated last BP reading before 
disconnecting the machine thus constituting the 
typical presentation of office hypertension. This is 
consistent with reports by many authors who found 

Figure 1a Figure 1b

Figure 1c Figure 1d

Figure 1:  Example graph from ambulatory blood pressure monitoring (ABPM) report of 62-year old male diabetic 
and hypertensive patient with normal average active, resting and total 24-hour blood pressure readings. It shows the 
association between non-dipper status [1a & 1b] and the echocardiographic evidence of left ventricular hypertrophy 
[1c] and diastolic dysfunction  [1d]. Despite his office blood pressure measures being persistently high, the ABPM 
noticeably showed a “white coat” effect.



Hatem Farhan, Mona Al-Hasani, Mohamed Misbah and Mansour Sallam

Clinical and Basic Research | 375

that the incidence of this condition ranges from 15-
48%.21 This phenomenon can only be detected by 
ABPM and reported by some patients who have the 
facility of self-monitoring. Actually, most of those 
patients had either emotional or physical stress or 
a family history of hypertension. A high proportion 
of patients with borderline hypertension may 
actually exhibit “white coat” hypertension which 
exaggerates BP measurement immediately before 
arriving at the clinic. Measurements obtained by 
means of ABPM can provide additional information 
for risk stratification in patients with borderline 
elevations in BP.

Resistant hypertension is defined as the inability 
to reach a target BP lower than 140/90 mmHg 
despite 3 or more drug regimens in correct dosages. 

A total of 29% of our patients fulfilled this criterion. 
Interestingly, ABPM identified that 42% of them 
had controlled BP.

There are many limitations of the current 
study. The sample size was relatively small for a 
retrospective study; however, many studies with 
larger samples have shown similar results.2 These 
data represent the acute outcome; however, our aim 
was to highlight the value of ABPM over traditional 
office BP measurements. Our study is still ongoing 
as we have subsequently added more patients and 
increased the range of indications and the follow-up 
duration.   

Conclusion
Ambulatory BP monitoring is an established 
and robust technology, but an underused tool in 
hypertension management and risk assessment 
either before or after drug treatments. Further 
prospective studies in selected group of patients are 
indicated. 

c o n f l i c t o f i n t e r e s t
The auhtors reported no conflict if interest. 

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