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

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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.