Patterns of ambulatory blood pressure: clinical relevance and application

Abstract

Ambulatory blood pressure measurement (ABPM) is now recommended in all patients suspected of having hypertension. However, in practice, the mean daytime pressures are often used to make diagnostic and therapeutic decisions, and the information from abnormal patterns of blood pressure behavior is often overlooked. This paper presents daytime patterns (eg, white coat hypertension and siesta dipping), nocturnal patterns (eg, dipping, non‐dipping, reverse dipping, and the morning surge), and discusses ambulatory hypotension, and abnormal patterns and indices of related hemodynamic parameters (eg, heart rate, pulse pressure, and blood pressure variability).

1. INTRODUCTION

There is now general agreement that ambulatory blood pressure measurement (ABPM) should be used to diagnose sustained hypertension before the commencement of treatment. However, the valuable information to be obtained by identifying patterns of 24‐hour blood pressure (BP) is often neglected in clinical practice. Abnormal patterns of BP behavior may indicate specific forms of hypertension (eg, nocturnal hypertension) or may be associated with concomitant illnesses (eg, sleep apnea) and recognition of these abnormal patterns of BP behavior during the daytime and the nighttime periods can be helpful in the diagnosis and management of hypertension. ABPM recordings can also provide information on abnormal patterns and indices of related hemodynamic parameters, such as heart rate, pulse pressure, ambulatory arterial stiffness index and BP variability.1, 2, 3 These patterns of 24‐hour BP behavior may be summarized as follows and are listed in the Table 1.

Table 1.

Patterns of ambulatory blood pressure

Daytime hypertension

White coat hypertension

White coat effect

Systolic and diastolic hypertension

Isolated systolic hypertension

Isolated diastolic hypertension

Siesta dipping/post‐prandial hypotension

Nocturnal hypertension

Dipping: Nocturnal BP fall >10% of daytime values or night/day BP ratio <0.9 and >0.8—normal diurnal BP pattern

Reduced dipping: Nocturnal BP fall from 1% to 10% of daytime values or night/day BP ratio <1 and >0.9—reduced diurnal BP pattern

Non‐dipping: No reduction or increase in nocturnal BP or night/day ratio >1—associated with poor cardiovascular risk

Nocturnal risers: Nocturnal BP greater than daytime BP

Extreme dipping: Marked nocturnal BP fall >20% of daytime values or night/day ratio <0.8—debatable cardiovascular risk

Nocturnal hypertension: Increased absolute level of night time BP Associated with increased cardiovascular risk—may indicate OSA

Morning surge: Excessive BP elevation rising in morning Definitions, thresholds, and prognostic impact debatable

Ambulatory hypotension   Spontaneous, postural, post‐prandial and drug‐induced hypotensive patterns

2. DAYTIME BLOOD PRESSURE

The daytime window of ABPM is the period when the patient is away from the medical environment and engaged in usual activities.2 For almost all patients with hypertension, average BP during this window is lower than office or clinic BP. However, BPs during the day are subject to the effects of work and environmental stress, activity, body, and arm movement, and the effect of exercise and other activities, such as driving, whereas these effects are largely absent in BP measured during the night.1

White coat hypertension may be suspected from ABPM, when BP elevation during the first hour of measurement is often seen and, and in the absence of an office BP, provides an alternative means of diagnosing the white coat phenomenon. Likewise, white coat effect—elevation of BP in the first hour of recording that is higher than an elevated daytime BP—may also be evident on ABPM.1 Systolic and diastolic hypertension is the commonest daytime pattern in patients aged less than 60 years.1, 4 Average daytime BP is superior to clinic BP in predicting outcome but inferior to nocturnal BP in some populations and conditions.5 For example, white‐coat hypertension tends to be more common in women, isolated systolic hypertension and nocturnal hypertension tend to occur more frequently in the elderly, and isolated diastolic hypertension is found more frequently in younger individuals.4

The classical siesta is common in many countries, but many patients, particularly the elderly, take a rest after lunch and this may be accompanied by sleep; the combination of a postprandial fall in BP together with lowering of BP with sleep may induce a significant reduction in BP, and failing to account for this may distort the night/day ratio of ABPM and may lead to over‐diagnosis of non‐dippers.1 The influence of postprandial and siesta dips on clinical practice, and its effect on prognosis remains to be investigated.6 Software programs for ABPM should be able to allow for the effect of an afternoon dip in the calculation and interpretation of awake and asleep average ABPM values and the assessment of the nocturnal dip.1

3. NOCTURNAL BLOOD PRESSURE

There has been a tendency in clinical practice to concentrate on ABPM daytime pressures. However, the association of nighttime hypertension with the cardiovascular consequences of hypertension, such as stroke, has focused the scientific literature on nocturnal hypertensive patterns, such as isolated nocturnal hypertension, and a non‐dipping pattern of BP3, 7, 8, 9, 10 (Table 1). Indeed, on‐going research may show that nighttime BP better represents baseline BP measurement, but, at present, it is important to be aware that there may be causes for nocturnal hypertension, such as obstructive sleep apnoea (OSA),11, 12 and the increased risk of stroke with elevated nocturnal BP, makes it important to assess the response to BP lowering medication during sleep.

The definition of the so‐called “dipping status” of a patient is traditionally based on the behavior of BP going from wakefulness to sleep, depending on whether BP falls, rises, or remains constant. In physiologic conditions, there is a decline in BP when shifting from wakefulness to sleep. This BP fall is usually quantified by defining the daytime and the nighttime periods based on the patient's diary, or through use of fixed time intervals.1

In some patients, the nocturnal decline in BP may be absent (non‐dipping) so that BP does not reach what could be defined as “basal” levels during sleep.1, 13, 14 In some instances, BP may even rise during sleeping hours to reach levels that are higher than daytime levels (reverse dipping or rising), and these patients are at highest risk.15 Alternatively, there may be a marked fall in BP during the night window to give the phenomenon of extreme dipping.16 The magnitude of the rise in BP in the morning around the awakening time may also yield valuable prognostic information, and is commonly referred to as the “morning surge.”1, 16, 17 Given the limited reproducibility of daytime BP levels, due to interference by individual daytime activities, cardiovascular risk stratification might be more accurate if based on nighttime BP levels. An increase in nighttime BP may indicate the occurrence of pathologic conditions, such as OSA.12

Nocturnal BP has the best overall reproducibility with the majority of people having a dipping nocturnal pattern, and a diminished nocturnal fall in BP is associated with poor cardiovascular outcome both in population studies and in hypertensive patients.1 This association parallels the finding that for each 10‐mm Hg increase in mean nighttime systolic BP, the mortality risk increases by 21%.1, 18

There are, thus, many patterns of nocturnal BP behavior, and although these may be associated with an adverse prognosis, there has been relatively little study into the benefits of therapeutic modification of night‐time BP. However, there is overall agreement that nocturnal hypertension should be treated to achieve BP control over the entire 24‐hour period.

4. AMBULATORY HYPOTENSION

Treatment may cause excessive lowering of BP, especially in the elderly and frail, when falls and the resultant morbidity become especially important.19 Recent evidence suggests that some patients may be adversely affected by excessive lowering of nocturnal BP. In these patients, the vasculature to the heart, and/or brain, may be compromised by atherosclerotic disease that leaves the patient dependent on a critical level of BP to maintain adequate perfusion. It is important, therefore, to use ABPM to prevent excessive BP lowering with medication, especially at night. Quite apart from this vulnerable group excessive, medication can induce postural symptoms in healthy young patients when hypertension is treated excessively and ABPM is the most effective method for demonstrating treatment‐induced postural hypotension.1 The recently published US guidelines on hypertension advocate that treatment should be aimed at lowering BP to below 130/80 mm Hg.20 However, although international scientific opinion favors the recommendation for more effective control of hypertension, concerns have been raised about the elderly in whom excessive lowering of BP may have adverse effects.21 The use of ABPM in the elderly therefore becomes a mandatory investigation to avoid excessive lowering of BP by hypotensive medication, especially at night.

5. ASSOCIATED HEMODYNAMIC PATTERNS

Patterns of blood pressure variability

Blood pressure is a highly dynamic parameter characterized by continuous fluctuations.22 Short‐term BP variability assessed on ABPM may improve risk stratification in population and cohort studies. However, the evidence is not convincing, and it does not yet represent a parameter for routine use in clinical practice because of the current lack of generally accepted thresholds separating normal from pathologic BP variability levels.

Abnormal patterns of heart rate

The provision of 24‐hour heart rate measurement, in addition to BP, is often ignored in the assessment of ABPM recordings. Indeed, scrutiny of heart rate behavior during the day and night may reveal the presence of daytime, or nocturnal, bradycardia, or tachycardia, which can be indicators of heart block, the excessive effect of treatment (eg, beta‐adrenergic blocking drugs), or persistent tachycardia may indicate paroxysmal supraventricular tachycardia or atrial fibrillation. Masked tachycardia is associated with an adverse outcome,23 and recently, a non‐dipping nocturnal heart rate has been suggested as being of prognostic relevance.24 ABPM devices capable of detecting atrial fibrillation are presently being evaluated.25

CONFLICT OF INTEREST

EOB has conducted validation studies for various manufacturers and advised manufacturers on device development. KK has received research funding from A &D Co., Ltd.

O'Brien E, Kario K, Staessen JA, De La Sierra A, Ohkubo T. Patterns of ambulatory blood pressure: clinical relevance and application. J Clin Hypertens. 2018;20:1112–1115. 10.1111/jch.13277