ambulatory blood pressure monitoring [abpm]
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AMBULATORY BLOOD PRESSURE MONITORING
[ABPM]BY
DR.VASUDEVA CHETTY.PSENIOR RESIDENT
DEPT. OF CARDIOLOGY
SVIMS,TIRUPATI.
CAPSULE ON INVESTIGATION
INTRODUCTION
ABPM , 50 YRS BACK MODERN
BP VARIABILITY
MEASURES OF BP VARIABILITY,INSTABILITY,REACTIVITY
High BP is a trait as opposed to a specific disease and represents
a quantitative rather than a qualitative deviation from the norm.
Any definition of hypertension is therefore arbitrary.
Thus a practical definition of hypertension is ‘the level of BP at
which the benefits of treatment outweigh the costs and hazards’.
DAVIDSON’S PRINCIPLES AND PRACTICE OF MEDICINE 21ST ED
True BP vs Surrogate
Any clinical measurement of blood pressure may be regarded as
a surrogate measure for the “TRUE” blood pressure of the
patient, which may be defined as the mean level over prolonged
periods.
Two techniques have been developed to improve the estimate of
true blood pressure — ambulatory monitoring and home
monitoring (or self-monitoring).
ABPM
Ambulatory blood pressure (ABP)
monitoring involves measuring
blood pressure (BP) at regular
intervals (usually every 20–30
minutes) over a 24 hour period
while patients undergo normal
daily activities, including sleep.
The portable monitor is worn on a belt
connected to a standard cuff on the
upper arm .
When complete, the device is connected
to a computer that prepares a report of
the 24 hour, day time, night time, and
sleep and awake (if recorded) average
systolic and diastolic BP and heart rate.
ABPM – measuring Method Ambulatory BP monitors use cuff oscillometry.
The cuff is inflated until the pressure occludes flow within the brachial
artery. As the pressure is released, blood begins to flow causing
fluctuations (oscillations) in the arterial wall that are detected by the
monitor. These oscillations increase in intensity then diminish and cease
when blood is flowing normally.
The monitor defines the maximal oscillations as mean arterial BP and
then uses an algorithm to calculate systolic and diastolic BP.
ANALYSIS OF ABPM
Reference ‘normal’ ABP values for nonpregnant adults are:
24 hour average <115/75 mmHg (hypertension threshold
130/80 mmHg)
Day time (awake) <120/80 mmHg (hypertension threshold
135/85 mmHg)
Night time (asleep) <105/65 mmHg (hypertension threshold
120/75 mmHg).
ABPM – Diagnostic ThresholdsCategory 24hr
systolic/diastolic(mm Hg)
Daytime(mm Hg)
Nighttime(mm Hg)
NORMAL <115/75 <120/80 <105/65
HTN >130/80 >135/85 >120/75
Ambulatory BP values above ‘normal’ and below thresholds for
hypertension are considered ‘high normal’.
Night time (sleeping) average systolic and diastolic BP should
both be at least 10% lower than day time (awake) average.
Blood pressure load (percentage of time that BP readings exceed
hypertension threshold during 24 hours) should be <20%.
Indications for ABPM Suspected white-coat hypertension (including in pregnancy)
Suspected masked hypertension (untreated subject with
normal clinic BP and elevated ABP)
Suspected nocturnal hypertension or no night time reduction
in BP (dipping)
Hypertension despite appropriate treatment
Patients with a high risk of future cardiovascular events (even if
clinic BP is normal)
Suspected episodic hypertension.
Ambulatory BP monitoring may also be useful for:
Titrating antihypertensive therapy
Borderline hypertension
Hypertension detected early in pregnancy
Suspected or confirmed sleep apnoea
Syncope or other symptoms suggesting orthostatic Hypotension,
where this cannot be demonstrated in the clinic.
CLASSIFICATION BASED ON ABPM
WHITE COAT HYPERTENSION
White-coat hypertension is defined as a clinic blood pressure of
140/90 mm Hg or higher on at least three occasions, with at least
two sets of measurements of less than 140/90 mm Hg in non-clinic
settings, plus the absence of target-organ damage.
MASKED HYPERTENSION
Defined as a normal clinic blood pressure and a high ambulatory
blood pressure.
This condition is the reverse of white-coat hypertension.
The clinic blood pressure of patients with masked hypertension
may underestimate the risk of cardiovascular events.
ABPM --PREDICTING CLINICAL OUTCOMES
Global Leading Risks for Death
Systolic blood pressure > 115 mmHg
Global Burden of Disease Study 2010 , Lancet 2012; 380: 2224–60
India- Soon Heading Towards Being Hypertension Capital
60.4
107.3
57.8
106.2
0
20
40
60
80
100
120
2000 2025No
. of
pe
op
le w
ith
hy
pe
rte
ns
ion
in
Ind
ia (
mill
ion
s)
Men Women
Lancet 2005;365:217-23; JHH 2004;18:73-8J Assoc Physicians India 2007;55:323-4
At least 1 out of every 5 adult Indians has hypertension
Age > 20 yrs
Hypertension is responsible for 57% of all stroke deaths and 24% of all CHD deaths in India
ABPM --ENDORSEMENT
NICE GUIDELINES 2011
CONCLUSION Ambulatory monitoring can be regarded as the gold standard for
the prediction of risk related to blood pressure, since prognostic
studies have shown that it predicts clinical outcome better than
conventional blood-pressure measurements.
Therefore, a good case can be made for using this technique in
all patients in whom hypertension has been newly diagnosed by
means of clinic blood-pressure measurements.