Ambulatory bp monitoring should it be routine?

AMBULATORY BP MONITORING-SHOULD IT BE ROUTINE?

TOPIC OVERVIEW

INTRODUCTION

MEASUREMENT OF ABP

INTERPRETATION OF ABPM

PROGNOSTIC VALUE OF ABPM

WHITE COAT HYPERTENSION

INDICATIONS FOR ABPM

INFLUENCE ON THERAPY OF HYPERTENSION

SUMMARY AND RECOMMENDATIONS


INTRODUCTION Ever since arterial blood pressure was first measured

by Stephen Hales’ more than 250 years ago, it has been understood that such pressure is not static, but a constantly varying entity.

At the same time, physicians have always been advised that the gold standard for blood pressure determination is a small number of clinical measurements made at relatively infrequent intervals


One of the first studies questioning the validity of clinic measurement of blood pressure was published in 1940 by Ayman and Goldshine.

They instructed 34 of their hypertensive patients to take their own blood pressures or to have family members take them at home.

The patients were followed for an average of 22 months, during which time they averaged 21 visits each to the authors’ clinic.

At the end of the study more than 2,800 clinic blood pressure measurements and more than 40,000 home measurements had been made and recorded.


The authors reported that in every one of the 34 cases the blood pressure readings taken at home were lower than those taken in the clinic by the doctor.

The average home readings were roughly 50 mmHg systolic and 25 mmHg diastolic less than the average clinic readings.


The development of ABPM originates with the work of Maurice Sokolow, an internist in San Francisco, who was impressed by the fact that many hypertensive patients with very high blood pressures experienced a normal life expectancy.

In 1962 he and his colleagues Hinman et al developed the initial semiautomatic ABPM device.

It consisted of a blood pressure cuff that was manually inflated by the subject, and a tape recorder on which the Korotkoff sounds were recorded.


MAURICE SOKOLOW


Sokolow et al. subsequently published a series of classic papers establishing the clinical value of ABPM.

These demonstrated the variability of blood pressure during the day and its relatively poor correlation with casual pressures taken in the office.


Sokolow et al. were the first to show that ambulatory pressures correlate more closely than clinical pressures with damage to heart and arteries caused by hypertension.


MEASUREMENT OF ABPM ABPM is determined using a device worn by the

patient that takes blood pressure(BP) measurements over a 24 to 48 hour period, usually every 15 to 20 minutes during the daytime and every 30 to 60 minutes during sleep.

These blood pressures are recorded on the device, and the average day (diurnal) or night (nocturnal) blood pressures are determined from the data by a computer.



INTERPRETATION OF ABPM Unique data provided by ABPM include:

24-hour average blood pressure (BP)daytime (awake) BP

Night time (asleep) BP

Systolic blood pressure load

Diastolic blood pressure load

Nocturnal dipping of the BP


Definition of hypertension 24-hour average BP - Normotension is defined as a BP

less than 130/80 mmHg, and hypertension is defined as a BP greater than or equal to 135/85 mmHg.

Daytime (awake) BP - Normotension is defined as a BP less than 135/85 mmHg, and hypertension is defined as a BP greater than or equal to 140/90mmHg.

Night time (asleep) BP - Normotension is defined as a BP less than 120/70 mmHg, and hypertension is defined as a BP greater than or equal to 125/75 mmHg


Blood pressure load The BP load is defined as the percentage of

ambulatory systolic and diastolic pressures exceeding 140 mmHg and 90 mmHg during the daytime, and 120 mmHg and 80 mmHg during sleep.

The overall BP load may also be a determinant of cardiovascular risk.


The systolic BP load in normotensive subjects increases from approximately 9 percent of readings in young adults to as high as 80 percent in the elderly.

The diastolic BP load does not appear to vary significantly with age.

Studies in untreated hypertensive subjects suggest that the likelihood of developing cardiac abnormalities is markedly increased when the daily BP load is 40 percent or more.


PROGNOSTIC VALUE OF ABPM


Prediction of cardiovascular risk



Progression of kidney disease A cohort study of 217 patients suggested that elevated

blood pressure by ABPM correlated more strongly with progression to end-stage renal disease (ESRD) than clinic systolic blood pressure.

In addition, night ambulatory blood pressure was a strong predictor of the composite outcome of death and ESRD


Masked hypertension As many as 10 to 40 percent of patients who are

normotensive by conventional clinic measurement are hypertensive by ABPM.

This phenomenon is called masked hypertension or isolated ambulatory hypertension.

It has only been identified by screening clinical studies, since patients who are normotensive by office readings do not typically undergo ambulatory monitoring.


Masked hypertension has been associated with an increased long-term risk of sustained hypertension and cardiovascular morbidity .

Because of the risk associated with masked hypertension, ambulatory blood pressure monitoring should be considered in patients referred for possible hypertension.


Nocturnal blood pressure and nondippers

A cohort study of 7458 patients in six countries from Europe, Asia, and South America found that both daytime and night time BP predicted all cardiovascular events.

Night time blood pressure, adjusted for daytime BP, predicted total, cardiovascular, and non cardiovascular mortality.

In contrast, daytime blood pressure, adjusted for blood pressure measured during sleep, only predicted noncardiovascular mortalityAMBULATORY BP MONITORING-SHOULD IT

BE ROUTINE?



The average nocturnal BP is approximately 15 percent lower than daytime values in both normals and hypertensive patients.

Failure of the BP to fall by at least 10 percent during sleep is called nondipping.

The underlying mechanisms of nondipping are unknown, but intrinsic renal defects may contribute.

There is also some evidence suggesting that melatonin plays a role.


Independent of the degree of hypertension, nondipping is a risk factor for the development of left ventricular hypertrophy (LVH), heart failure and other cardiovascular complications .

Extreme "dipping" (eg, >20 percent nocturnal decline in BP) and a large morning increase in BP are also potentially deleterious .


Nondipping has also been associated with microalbuminuria and faster progression of nephropathy in patients with diabetes mellitus.

Nondipping may be a risk factor for decline in glomerular filtration rate, and ESRD and death among patients with chronic kidney disease.

The presence of sleep apnea should also be considered in nondippers.


WHITE COAT HYPERTENSION ANXIETY- MAIN CAUSE

The diagnosis of white coat hypertension (also called isolated clinic or office 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.

Having the BP in the office taken by a nurse or technician, rather than the clinician, may minimize the white coat effect.



In patients diagnosed as being hypertensive on a first visit to a new clinician, there is a mean 15 and 7 mmHg fall in the systolic and diastolic BP, respectively, by the third visit , with some patients not reaching a stable value until the sixth visit .

It is recommended that a patient with mild to moderate elevation in BP should not be diagnosed with hypertension unless the BP remains elevated after three to six visits, unless there is evidence of ongoing end-organ damage


In cross-sectional studies, the prevalence of white coat hypertension ranges from 10 to more than 20 percent, and appears to be higher in children and the elderly .

White coat hypertension can also be seen in patients with apparently resistant hypertension.

The likelihood of normal ambulatory pressures is low (less than 5 percent) in patients with office diastolic pressures ≥105 mmHg.


In one study of nearly 500 treated hypertensive patients (over 60 percent on three or more antihypertensive agents), 37 percent had normal BP on ABPM.


PROGNOSIS OF WHITE COAT HYPERTENSION

The cardiovascular risk associated with white coat hypertension may be slightly higher compared with persistent normotension but well below the risks associated with either masked or sustained hypertension.


In a study of 6000 subjects followed for a median of 5.4 years after having ABPM, stroke rates were significantly higher in patients with sustained hypertension compared with those who had persistent normotension (0.65 versus 0.35 percent per year).

Stroke rates were also higher in those who had white coat hypertension (0.59 versus 0.35 percent per year), but this was not statistically significant.


In a population-based cohort of 2051 adults who underwent office, home, and ambulatory blood pressure measurements, those with white coat hypertension had a significantly higher rate of all-cause mortality during 16 years of follow-up as compared with persistent normotension (19.7 versus 6.4 percent).


Patients with white coat hypertension are also at high risk for developing sustained hypertension.

In a study of 81 patients with office hypertension (mean BP 154/97 mmHg) and normal 12 hour ambulatory BP (mean BP 125/77 mmHg), 60 had a mean ambulatory BP above 140/90 mmHg after five to six years of follow-up (74 percent).


Optimal approach to patients with white coat hypertension is uncertain.

Careful monitoring is indicated for the possible development of worsening hypertension or of end-organ damage, while the patient is encouraged to modify unhealthy lifestyle habit.


INDICATIONS FOR ABPM In accordance with published practice guidelines and

expert panel recommendations, ambulatory monitoring should be considered in the following circumstances :

Suspected white coat hypertension

Suspected episodic hypertension (pheochromocytoma)

Hypertension resistant to increasing medications

Hypotensive symptoms while taking antihypertensive medications

Autonomic dysfunction


OTHER POTENTIAL INDICATIONS To establish nondipper status or nocturnal

hypertension

Large variations in self-measured blood pressure values

To evaluate whether antihypertensive therapy is moderating the early morning blood pressure surge

Elevated office blood pressure in pregnant women, with preeclampsia suspectedAMBULATORY BP MONITORING-SHOULD IT

BE ROUTINE?

If there is significant hypertension on ABPM, or resistance to antihypertensive therapy, an echocardiogram to screen for left ventricular hypertrophy (LVH) may be indicated, as LVH may be an early sign of end-organ damage which is otherwise undetectable.

Due to issues of cost and inconvenience, ABPM is not recommended for the evaluation of patients with uncomplicated hypertension or to screen for hypertension.




INFLUENCE ON THERAPY OF HYPERTENSION

Therapeutic decisions can be made according to the ambulatory blood pressure (BP) findings.

Ambulatory or self-recorded home readings may detect the early morning BP surge that may contribute to the increased incidence of sudden death, myocardial infarction, and stroke in the early morning hours.


Modulation of this early morning surge in BP may not occur with supposedly long-acting, "once-daily" agents which do not provide 24-hour coverage.

Such drugs, including atenolol or enalapril, may lose much of their effect during the early morning hours, and therefore may need to be taken twice daily.

Preferably, long-acting medications with effects that truly last for 24 hours should be substituted.


http://www.uptodate.com/contents/atenolol-drug-information?source=see_link

http://www.uptodate.com/contents/enalapril-drug-information?source=see_link

In those with nocturnal hypertension or nondipping, ABPM may helps determine the best timing of administration of antihypertensive agents.

In one study, valsartan taken before bedtime reestablished the nocturnal reduction in BP.


http://www.uptodate.com/contents/valsartan-drug-information?source=see_link


HOME BP MEASUREMENTS In view of the cost and limited availability of

ambulatory monitoring, increasing attention is being given to home monitoring with inexpensive semi-automatic devices.

Casual blood pressure (BP) measurements taken at home or work correlate more closely with the results of 24-hour or daytime ambulatory monitoring than with the BP taken in the clinician's office .

Home BP measurements are more predictive of adverse outcomes (eg, stroke, end-stage renal disease) than clinic blood pressures.



GUIDELINES FOR MEASURING HOME BP

While seated, the patient should take two measurements (separated by one to two minutes) in the morning and in the evening (ie, four measurements per day) for at least three, and preferably seven, consecutive days. These measurements should be recorded.

Measurements from the first day should be discarded; the home blood pressure is defined as the average of all remaining measurements.

In stable hypertensive patients with controlled BP, this same procedure of 12 to 14 measurements taken over one week should be repeated approximately every three months to determine whether the BP remains controlled .


SUMMARY AND RECOMMENDATIONS


The diagnosis of hypertension based upon ABPM depends upon the time span over which it is interpreted :

A 24-hour average above 135/85 mmHg

Daytime (awake) average above 140/90 mmHg

Nighttime (asleep) average above 125/75 mmHg

Cardiovascular complications correlate more closely with 24-hour or daytime ABPM than with the office BP.


White coat hypertension may be associated with an increased risk of stroke, possibly related to later development of sustained hypertension.

The risk of cardiovascular complications associated with masked hypertension is similar to that seen with persistent hypertension.

Failure of the BP to fall by at least 10 percent during sleep (nondipping), may also be associated with increased cardiovascular risk.


ABPM may facilitate achieving blood pressure control and reduce unnecessary treatment.

ABPM should be considered in the following situations :

Suspected white coat hypertension Suspected episodic hypertension Hypertension resistant to increasing medication Hypotensive symptoms while taking antihypertensive medications Autonomic dysfunction

Self-recorded home BP measurements are an excellent alternative if ABPM is not available or cost is a concern.

Home BP monitoring may also improve hypertension control.



THANK YOU


Ambulatory bp monitoring should it be routine?

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