Background
Epidemiology of acute stroke in developing countries
differs from that in the developed world, for
example, the age at
stroke, risk factors, subtypes
of stroke and prognosis.
Hypertension remains a
dominant risk factor and prognostic indicator in
patients with stroke in all communities. The risk of
stroke is directly related to elevations of
blood
pressure. A number of clinical studies have shown
that the control of hypertension leads to a
reduction in the incidence of stroke in a community.
However there is still considerable controversy
surrounds the changes in blood pressure in various
subtypes of strokes and problem of management of
elevated BP after
stroke. We studied the circadian
rhythm of blood pressure in patients following
acute
stroke.
Methods
To study the circadian rhythm of blood pressure,
fifty consecutive patients with an acute stroke who
were admitted to medical emergency within 120 hours
of onset were included in the study. After a
detailed history and clinical examination, a
continuous blood pressure monitor (Spacelab 90207)
was attached on the side ipsilateral to intracranial
lesion (unaffected arm). The blood pressure was
recorded for 24 hours at 15 minutes interval during
daytime (6.00 am–6.00 pm) and 20 minutes interval
overnight (6 pm to 6 am).
Results
Risk factors for stroke in 50 patients included
hypertension in 31(62%),
diabetes mellitus in 4
(8%), smoking in 13 (26%) and previous history of
transient ischemic attack in 7 (14%) patients. Mean
systolic pressure and diastolic pressure at
admission were higher in patients with hemorrhagic
stroke -29 patients (177 ± 24 mmHg and 105 ± 19 mmHg
respectively) compared to patients with ischemic
strokes-21 patients (150 ± 36 mm Hg and 89 ± 18 mm
Hg respectively, p value <0.01 in both comparisons).
The normal diurnal variation in blood pressure
(night time dipping of more than 10%) was abolished
in 44 (88%) of patients. Out of 44 nondippers, 29
patients showed reverse dipping i.e. rise of BP
during night time compared to day time levels. None
of the risk factors, clinical or laboratory
variables, type of stroke or blood pressure changes
differed significantly between these two groups.
Conclusions
Therefore, we showed a pathologically reduced or
abolished circadian BP variation after stroke.
Absence of normal dipping results in a higher 24
hour blood pressure load and may have more target
organ damage than those with normal diurnal
variation of blood pressure.
Background
Epidemiology of acute stroke is different in
developing countries from that in developed world.
The age at stroke, risk factors, subtypes of stroke
and prognosis are different in developing countries.
In India, ischemic strokes constitute 70–75% while
hemorrhagic strokes account for 20–25% of total
cases [1]. However,
hypertension
remains a dominant risk factor and prognostic
indicator in patients with stroke in all
communities. The risk of stroke is directly related
to elevations of blood pressure. A number of
clinical studies have shown that
control of
hypertension leads to a reduction in the incidence
of stroke in a community[2].
Control of hypertension is important for
stroke
prevention in all age groups. An increased reported
incidence of intracerebral hemorrhage in India may
be due to undetected and uncontrolled hypertension
and a referral bias in a tertiary care center due to
the surgical management of many of these patients.
Many studies have focused on the nature and extent
of alterations of circadian blood pressure patterns
after acute ischemic stroke while only a few studies
have studied circadian rhythm of blood pressure in
the patients with acute intracerebral hemorrhage[3,4].
The accurate measurement of blood pressure after an
acute stroke is important because antihypertensive
therapy may be considered in some patients. However,
blood pressure may be falsely elevated or depressed
immediately after a
stroke depending on the level of
consciousness, severity of neurological deficit and
physical activity. Conventional recordings in the
wards may therefore be unreliable or misleading,
leading to inappropriate prescribing or withholding
of the antihypertensive therapy.
To overcome this problem ambulatory blood pressure
monitoring (ABPM) has been proposed as a method of
obtaining an accurate clinical assessment. ABPM
devices are increasingly being used in the
assessment of hypertension but their value in
patients after stroke has not been studied
systematically. Various studies have shown different
changes of circadian blood pressure patterns after
stroke depending on the pathogenesis and location of
stroke providing some prognostic and therapeutic
implications[3,4].
Still, considerable controversy surrounds the
changes in blood pressure in various subtypes of
strokes and problem of management of elevated BP
after stroke. Therefore, we studied the circadian
rhythm of blood pressure in patients following
acute
stroke.
Methods
50 consecutive patients (age 75 years or younger)
who were admitted after an acute stroke within 120
hours of its onset were included in the study.
Definition of stroke was based on World Health Organisation criteria; rapidly developing clinical
signs of focal and at times global loss of cerebral
function with symptoms lasting more than 24 hours or
leading to death with no apparent cause other than
that of vascular origin. Patients with transient
ischemic attacks, subarachnoid hemorrhage, cortical
vein thrombosis or atrial fibrillation were excluded
from the study. All patients had a detailed clinical
examination, laboratory studies and a CT scan study
of the brain on admission. As per our study
protocol, patients who were receiving
antihypertensive therapy at the time of admission to
the hospital were maintained on the same medication
for the duration of the study. No new
antihypertensive medication was given during the
study period. The Spacelab 90207 ambulatory
oscillometric blood pressure monitor (ABPM) was
attached at the time of admission. ABPM device was
attached on the side ipsilateral to intracranial
lesion after relevant difference between the two
limbs was ruled out by conventional checks of blood
pressure. The first reading obtained with the ABPM
device was compared with immediately preceding and
following manual measurements. The blood pressure
was automatically recorded for 24 hours after
application of the blood pressure monitor at 15
minutes interval during day time (6.00 a.m. – 6.00
p.m.) and 20 minutes interval overnight (6.00 p.m. –
6.00 a.m.). The mean daytime and nighttime BP were
calculated and the values were analyzed to determine
diurnal variation and any evidence of nocturnal fall
of blood pressure. Patients were considered to have
dipping if the mean arterial pressure (MAP) at night
was less than 90% of MAP during daytime. The blood
pressure changes were calculated and a relationship
with risk factors and nature of stroke was studied.
Patients were bedridden at the time of admission and
were subjected to ambulatory blood pressure
monitoring in that state only
Statistical comparisons between BP and heart rate
measurements were made with unpaired 't' test and
chi square test. A value of p < 0.05 was considered
statistically significant.
Results
50 patients (26 males, 24 females; age 57.5 ± + 11.5
years with range 22–74 years) admitted with acute
stroke (within 120 hours of onset) to the emergency
department of PGIMER, Chandigarh were studied (Table
1). The stroke patients were subclassified into
hemorrhagic stroke (29 patients, 58%) and ischemic
stroke (21 patients, 42%) based on CT scan findings.
Hypertension was the commonest risk factor (31
patients, 62%). Other risk factors included
diabetes
mellitus in 4 (8%), smoking in 13 (26%) and previous
history of transient ischemic attack in 7 (14%)
patients. The incidence of risk factors namely
hypertension, diabetes mellitus, smoking, history of
transient ischemic attacks and
coronary artery
disease did not differ significantly between
patients with hemorrhagic and ischemic strokes. 81%
(25 patients) of the patients with a history of
hypertension were on antihypertensive medication
prior to the development of stroke. In all the
patients, who were treated too, also had an
uncontrolled blood pressure as could be assessed
from the previous medical records. This was
attributed to a poor compliance.
Mean systolic blood pressure at admission in this
study was 166 ± 32 mm Hg and it was higher in
patients with hemorrhagic stroke (177 ± 24 mm Hg)
compared to that with ischemic stroke (150 ± 36 mm
Hg, p < 0.01) (Table
2). Similarly, mean diastolic blood pressure at
admission was also higher in hemorrhagic group
compared to ischemic subgroup (105 ± 19 mmHg vs 89 ±
18 mm Hg, p < 0.01). All parameters of blood
pressure changes monitored under this study (mean,
SBP, mean DBP, mean MAP) were significantly higher
in patients with hemorrhagic stroke compared to
those in ischemic stroke during day time, night time
and total 24 hours. Admission SBP and DBP were
higher in patients with history of prior
hypertension (174 ± 32 mm Hg and 103 ± 21 mmHg
respectively) than in patients without history of
previous hypertension (152 ± 30 mm Hg and 91 ± 18 mm
Hg respectively, p value < 0.05 in both
comparisons). Admission SBP was positively
correlated with age of the patient (p < 0.005) and
negatively correlated with time after onset of
stroke. The admission SBP or DBP was not influenced
by previous history of
coronary artery disease,
smoking, diabetes mellitus, and transient ischemic
attack at the time of admission.
The normal diurnal variation in blood pressure i.e.
night time dipping was abolished in 44 (88%) of
patients. This nondipping was seen equally in both
hemorrhagic and ischemic subgroups without any
statistically significant difference.
