INTRODUCTION — Ambulatory blood pressure monitoring (ABPM) has become an invaluable tool in evaluating blood pressure (BP) in children. It is increasingly used to assess patients with variable BP readings in the office, wide discrepancies between the BP readings at home and in the clinician's office (ie, "white coat" hypertension), and secondary forms of hypertension such as chronic kidney disease (CKD).
The utility and limitations of pediatric ABPM, and information on performing and interpreting ABPM studies in children will be reviewed here. The definition, diagnosis, and treatment of hypertension in children based upon clinic BP measurement (clinic BP) are discussed separately. (See "Definition and diagnosis of hypertension in children and adolescents" and "Nonemergent treatment of hypertension in children and adolescents".)
CLINICAL PROCEDURE — ABPM is feasible for clinical use in children old enough to cooperate with the procedure. ABPM needs to be performed in a standardized, reliable fashion to provide accurate recordings, especially in small children and infants [1]. It also has been successfully used in the evaluation of BP infants, toddlers, and older children in research settings [1-6].
Device — ABPM uses a portable automated device that records blood pressure (BP) over a specific time period (usually 24 hours). ABPM monitors most commonly used in children are small oscillometric devices, which are worn on a belt in a pouch. Oscillometric ABPM devices directly measure the mean arterial pressure and back-calculate the systolic and diastolic BP using an algorithm that is unique to each device manufacturer. Pulse wave amplitude and the elastic properties of the arterial wall, which are important factors in algorithm development, are different in children and adults. Thus, both the monitors and algorithms used in ABPM need to be validated using a standard protocol in children [7]. (See 'Technical limitations' below.)
Development of normative data for pediatric ABPM has been difficult because of the variation of each algorithm [4]. Devices utilizing the auscultatory technique are also available, but are less frequently used in children because they are more cumbersome to wear [1,8]. In addition, there are no published normative pediatric ABPM data for auscultatory devices [1].
Procedural approach — In our center, we follow the approach that is outlined in the 2014 Scientific Statement from the American Heart Association (AHA) on ABPM in children and adolescents, which includes the following key points for obtaining accurate, reliable, and reproducible results in children [1]:
●Trained personnel should maintain the functionality of the equipment, apply the device, and educate the patient and family/caregiver about the device, including accurate recording of medication, sleep, and activity during the recording period. Patients should be instructed not to get the ABPM device wet.
●As with office BP measurement, an appropriately sized cuff must be used. (See "Definition and diagnosis of hypertension in children and adolescents", section on 'Cuff size and placement'.)
●The ABPM cuff is placed on the nondominant arm. Exceptions include:
•Presence of a permanent dialysis access, kidney failure (CKD stage 5; formerly referred to as end-stage kidney disease) or arterial-to-pulmonary shunt in some children with cyanotic heart disease, in which case the dominant arm is used.
•In children with repaired aortic coarctation, the right arm should be used.
•If there is a significant interarm BP difference, the device should be placed on the arm with the higher BP.
●After applying the ABPM device, ambulatory BP should be measured and compared with resting BP obtained in the office (clinic BP), using the same technique as the ABPM device. If the average of three values is >5 mmHg higher or lower, cuff placement should be adjusted or the device checked for calibration.
●Patients are advised to keep the arm with the cuff still while inflating to prevent exertion-induced error in BP measurement [1,9]. It is desirable to perform ABPM on a school day in order to capture the child or adolescent's typical activity level. However, participation in competitive sports or other intense physical activity is typically discouraged during ABPM.
●Readings are usually taken every 20 minutes while awake and every 30 minutes while asleep. This should result in a sufficient number of recordings for interpretation during both sleep and wake periods. Patients or their parents/caregivers should be instructed to keep a diary of sleep-wake times for use in interpreting the study results.
Interpretation of data — Information from each measurement by the ABPM device is downloaded to a computer and then analyzed, usually with manufacturer-specific software. Using the diary supplied by the patient, the monitoring period is divided into wake and sleep periods.
The following variables are calculated for the wake and sleep periods, and for the entire 24 hours:
●Mean BP – Mathematical average of the systolic and diastolic BP readings captured in each monitoring period.
●BP load – Percentage of readings above the 95th percentile of systolic or diastolic BP based on ambulatory normative data, which is dependent on age, sex, and wake/sleep status. In adults, a high BP load is associated with cardiovascular (CV) risk. (See 'Normative data' below.)
●Nocturnal dipping – Normally, the average nocturnal BP is approximately 15 percent lower than daytime values, which is referred to as nocturnal dipping. Failure of the BP to fall at least 10 percent during sleep is called non-dipping. In adults, non-dipping has been associated with left ventricular hypertrophy, heart failure, and other CV complications. In children, non-dipping is more common in secondary forms of hypertension [10] and in the obese [11]. However, there are no long-term data available regarding increased CV risk for children with non-dipping nocturnal BP. (See 'Sustained hypertension and nocturnal nondipping' below and "Out-of-office blood pressure measurement: Ambulatory and self-measured blood pressure monitoring".)
The dipping status is based on the percent of dipping, which is calculated for both systolic and diastolic BP using the following formula:
Percent dip = [(mean awake BP – mean sleep BP) ÷ mean awake BP] x 100
Data for ABPM recordings should be inspected visually for any gross inconsistencies in heart rate, and sleep and awake BP measurements based on the child's age, which may lead to inaccurate interpretation of the results [1].
Normative data — Ideally, assessment using valid normative ambulatory pediatric BP values should be used to determine whether or not an individual patient has normal or elevated BP [1]. Unfortunately, such data are limited in children, especially in those with a non-European ethnic background [4]. Until such data are available, we use the normative data from a single study of approximately 1000 Central European children and adolescents, while recognizing their limitations (table 1 and table 2 and table 3 and table 4) [1,4,12]:
●Results only included information from White children from mid-European countries. It is uncertain whether they apply to other ethnic populations.
●Data were obtained by oscillometric monitors that rely upon a proprietary algorithm to derive systolic and diastolic BP values. There was a lack of variability in diastolic BP, which remained fixed for both sexes and height, a finding that is in direct contrast to normative data for clinic BP measurements [6,13]. This lack of diastolic variability regardless of height or age raises questions about the reliability of the algorithm used to calculate diastolic BP levels. In contrast, systolic BP appropriately varied with height and the age of the patient.
Since BP is increased by physical activity, normative data based upon resting BP values cannot reliably be used for ambulatory BP recordings [8]. This was illustrated by the following studies:
●In a study of 1120 British schoolchildren using ausculatory devices, both systolic and diastolic ambulatory BP were greater than normal resting levels [8].
●In a small study of Brazilian children using oscillometric devices, both mean systolic and diastolic BP from ABPM were greater than measurements obtained in the office setting or home [14].
Results from these studies demonstrate further efforts are needed to establish normative ABPM values for all pediatric populations and to correlate them with validated values that are office based. Until such data are available, we use the normative data from the Central European study, while recognizing their limitations.
Classification of BP — ABPM can provide additional information to clinic BP measurements in determining whether or not a child has hypertension (table 1 and table 2 and table 3 and table 4). In the United States, normative data for resting BP are based on BP data from the National Health and Nutrition Examination Survey (NHANES) and other population-based studies, which are categorized on sex, age, and height (table 5 and table 6) [6]. The BP percentiles are used to determine whether or not a child's clinic BP obtained is indicative of normal, elevated BP, or hypertensive values (table 7). (See "Definition and diagnosis of hypertension in children and adolescents", section on 'Definition'.)
The AHA scientific statement on pediatric ABPM has defined pediatric BP categories using information from both clinic and ambulatory BP data [1]. In our center, we use these definitions in determining the BP status of individual patients.
●Normal BP – Both clinic (<90th percentile) and ambulatory BP (mean systolic or diastolic BP <95th percentile, and systolic or diastolic BP load <25 percent) are normal.
●Prehypertension – Clinic BP >90th percentile but <95th percentile, mean ambulatory BP is normal (mean systolic or diastolic BP <95th percentile), but BP load is elevated (systolic or diastolic BP load ≥25 percent).
●Ambulatory hypertension (also referred to as sustained hypertension) – Both clinic BP (>95th percentile) and ambulatory BP are elevated (mean systolic or diastolic BP >95th percentile, and systolic or diastolic BP load between 25 and 50 percent).
●Severe ambulatory hypertension (at risk for end-organ damage) – Clinic BP (>95th percentile) is elevated and ambulatory BP is elevated with a markedly elevated BP load (mean systolic or diastolic BP >95th percentile, and systolic or diastolic BP load >50 percent).
●White coat hypertension – Clinic BP is elevated (≥95th percentile), but BP is normal (mean systolic or diastolic BP <95th percentile, and systolic or diastolic BP load <25 percent) outside the office setting.
●Masked hypertension – Clinic BP is normal (<90th percentile), but ambulatory BP is elevated (mean systolic or diastolic BP >95th percentile, and systolic or diastolic BP load between 25 and 50 percent).
WHO SHOULD BE EVALUATED BY ABPM
Indications — Indications for ABPM include the following [1,3,6,9,15-19]:
●Confirmation of the diagnosis of hypertension for children with elevated office BP for more than one year or with BP values at the stage 1 hypertension level after 3 visits (table 7).
●Differentiation between ambulatory (sustained hypertension) and white coat hypertension.
●Detection of masked hypertension (children with abnormal ambulatory BP despite normal clinic BP measurement).
●Evaluation of blood pressure (BP) in patients with chronic diseases associated with hypertension, such as chronic kidney disease (CKD), solid organ transplant, diabetes mellitus, autonomic dysfunction, obesity, sleep apnea, and genetic syndromes (eg, neurofibromatosis type 1, Turner syndrome, or Williams syndrome).
●Detection of recurrent hypertension in patients with repaired aortic coarctation. (See "Management of coarctation of the aorta", section on 'Recoarctation'.)
●Determination of the effectiveness of antihypertensive treatment.
ABPM has been shown to be particularly useful and cost-effective in patients with white coat and masked hypertension [20]. Limited data suggest ABPM may be useful in differentiating between primary and secondary hypertension, and predicting which children are at risk for early adult cardiovascular disease (CVD) and noncardiac end-organ damage [1].
White coat hypertension — ABPM may be cost-effective in identifying children with white coat hypertension who do not require further testing or treatment. A significant number of children have white coat or isolated office hypertension with normal values outside the office setting. Several observational studies report that between 13 and 46 percent of children referred for high BP evaluation at a tertiary center will have white coat hypertension [20-24]. The cost-saving utility of ABPM was illustrated in a retrospective review of 267 children referred to a pediatric hypertension tertiary clinic over an 18-month period of time from 2005 to 2006 [20]. In this cohort of 126 children, 58 patients (46 percent) had white coat hypertension, 62 (49 percent) had stage 1 hypertension, and 6 (5 percent) had stage 2 hypertension (severe hypertension). For a child with white coat hypertension, the estimated savings of initial detection by ABPM prior to performing the routine evaluation of hypertension at this center (ie, blood tests, kidney ultrasonography, and echocardiography) was USD $2155 per patient.
However, several studies suggest that pediatric white coat hypertension may not be a benign condition.
●Increased left ventricular (LV) mass ‒ Data suggest that the LV mass index of children with white coat hypertension falls between that of children with normal BP and those with ambulatory (sustained) hypertension matched by body mass index (BMI), sex, and age [21-23,25].
●Progression to sustained hypertension ‒ Adults with white coat hypertension are at risk for progression to ambulatory (sustained) hypertension (see "White coat and masked hypertension", section on 'Prognosis of white coat hypertension and white coat effect'). While similar data in children are limited [26], at least one small study has shown that ABPM profiles in children and adolescents may not be stable over time, suggesting that some children with WCH may indeed progress to ambulatory hypertension [27].
Given these findings, we repeat ABPM at one- to two-year intervals in children with white coat hypertension, as we believe that they are at risk for the development of ambulatory (sustained) hypertension [26].
Masked hypertension — Masked hypertension is associated with an increased LV mass and obesity, which are risk factors for early adult CVD [21,28,29]. Although similar data are not available in children, masked hypertension in adults has been associated with an increased risk of sustained hypertension and cardiovascular morbidity (see "Out-of-office blood pressure measurement: Ambulatory and self-measured blood pressure monitoring"). Observational studies have shown that ABPM in children and adolescents at-risk for hypertension can identify pediatric masked hypertension, defined as hypertensive ambulatory measurements for a child with normal BP reading in the office setting [15,21,28].
●In a Spanish study, 34 of 592 children (6 to 18 years of age) had masked hypertension [28]. Children with masked hypertension were more likely to be obese, have a positive family history for hypertension, and have a higher LV mass index.
●In a Greek study, masked hypertension was identified in 8 of 85 children referred for evaluation for hypertension [21].
●In a study of 66 prepubertal children, 11 of 42 obese children had masked hypertension [29]. All 22 lean children in this study were normotensive with normal BP values measured in both the office setting and by ABPM.
Sustained hypertension and nocturnal nondipping — Some children with hypertension are less likely to have a normal decrease in BP during sleep (ie, nondipping pattern). Normally, BP follows a circadian pattern, being highest late in the day and falling 13 to 20 percent below daytime levels during sleep at night [12,15,30,31]. On ABPM studies, this circadian variation is referred to as "dipping." A nondipping pattern is defined as less than a 10 percent nighttime fall in systolic BP. Children with sustained hypertension are less likely to have nocturnal dipping compared with normotensive children, and children with white coat hypertension have a risk of a "nondipping" BP pattern in between the two groups.
Sustained nighttime elevation of BP and the absence of nocturnal dipping have been reported to be more common in untreated children with secondary hypertension compared with those with untreated primary hypertension [10,32]. These findings suggest that ABPM may be helpful in differentiating primary from secondary hypertension. Additional studies are necessary to confirm these findings. However, if ABPM can reliably identify patients with secondary hypertension, it may become a valuable tool in the evaluation of pediatric hypertension. (See "Out-of-office blood pressure measurement: Ambulatory and self-measured blood pressure monitoring" and "Definition and diagnosis of hypertension in children and adolescents".)
[33].
Risk for cardiovascular disease — Data regarding the association between elevated ABPM values and risk of early CVD in children are limited [1]. The evidence is indirect and is based on results from studies in children and adolescents that show an association between ambulatory BP parameters and LV mass index and obesity [17,34-37]. In adults, masked hypertension, and to a lesser degree white coat hypertension, has been associated with an increased risk of sustained hypertension [38] and CV morbidity. (See "Nonemergent treatment of hypertension in children and adolescents", section on 'Rationale for intervention' and "Out-of-office blood pressure measurement: Ambulatory and self-measured blood pressure monitoring" and "White coat and masked hypertension", section on 'Prognosis'.)
Kidney damage — Limited evidence has shown an association between elevated ABPM values and an increased risk of renal damage, including reduction in creatinine clearance [39,40], renal scarring [41,42], progressive kidney disease in patients with diabetes mellitus [43-45], increased urinary protein excretion [40], and poorer allograft function in children who have undergone kidney transplantation [46,47].
These data suggest that ongoing ABPM would be useful in determining whether or not interventions to reduce elevated BP are effective, which may lead to a decreased risk of progressive kidney damage. (See "Chronic kidney disease in children: Complications", section on 'Hypertension'.)
OUR APPROACH — In our tertiary center hypertension program, the indications for ABPM are consistent with the 2014 American Heart Association (AHA) scientific statement and the 2017 AAP guidelines for high BP [1,6]. Specifically, we routinely use ABPM as follows (see 'Indications' above):
●To confirm the diagnosis of hypertension in a patient with elevated clinic/office BP measurements. ABPM may differentiate between sustained and white coat hypertension.
●To evaluate for the presence of masked hypertension when there is clinical suspicion of hypertension in the setting of normal clinic/office BP measurements.
●To assess BP patterns in patients who are at risk for hypertension including those with repaired aortic coarctation, chronic kidney disease, diabetes mellitus, solid organ transplants, and severe obesity.
●To evaluate the effectiveness of antihypertensive drug therapy.
The devices that we use have been validated for use in children (BP device validation status) and we ensure that an appropriate size cuff is used (figure 1 and figure 2) [6]. Our standard approach includes application of the device to the nondominant arm, comparing ambulatory readings with an office measurement for correlation, and instructions to the patient and parents/caregivers on daily recording of medication, activity, and sleep periods. In order to obtain a sufficient number of recordings for interpretation, we program the device to take readings every 20 minutes while awake and every 30 minutes while asleep. (See 'Device' above and 'Procedural approach' above and 'Technical limitations' below.)
We interpret ABPM levels based on the currently available ABPM pediatric normative data, although we recognize their limitations (table 1 and table 2 and table 3 and table 4). ABPM measurements include mean arterial pressure, BP load, and percent dipping. These values are then combined according to the AHA recommendations to determine a result for each study. A summary report is generated and placed in the patient's electronic medical record. We also individually review the ABPM study results with patients and families/caregivers at a follow-up office visit.
LIMITATIONS — In addition to the lack of normative ambulatory blood pressure (BP) data for all pediatric populations, as discussed previously (see 'Normative data' above), other limitations of ABPM in children include difficulty in defining ambulatory hypertension, technical issues specific to pediatric patients, tolerability of the procedure and costs.
Defining ambulatory hypertension — In children, defining hypertension either using clinic or ambulatory values is difficult because of the lack of substantial normative population data and long-term outcome measures. As a result, pediatric hypertension for both clinic and ambulatory measurements is defined statistically [1,24]. In addition, there may not be good agreement between the two definitions of ABPM hypertension used in children: mean BP >95th percentile or BP load >30 percent (percent of BP readings >95th percentile). In one study, agreement between these definitions was only moderate to good [48]. Other studies have also questioned whether BP load on ABPM is useful for prediction of intermediate cardiovascular outcomes such as left ventricular hypertrophy [49].
Based on the available literature, the threshold ABPM values used to diagnose hypertension are typically higher than those used for clinic/office thresholds [12,13]. 2016 guidelines from the European Society of Hypertension recommend using the adult definition for hypertension when pediatric ambulatory BP values exceed the accepted criteria for adults (24 hour mean value of 130/80 mmHg, mean daytime value of 135/85 mmHg and mean night-time value of 125/75 mmHg) [50]. In adults, the definition of hypertension is based on large datasets that correlate BP values with outcome measures, such as cardiovascular disease (CVD) and progression of kidney disease. In addition, ABPM normative data are available from sizeable adult cohorts, and long-term results on outcome from smaller studies. These data are presented separately. (See "Overview of hypertension in adults", section on 'Definitions' and "Overview of hypertension in adults", section on 'Complications of hypertension' and "Out-of-office blood pressure measurement: Ambulatory and self-measured blood pressure monitoring".)
In the pediatric age group, further research is needed to improve the correlation of measurements between ABPM and office readings or clinically relevant outcome measures and validate the current consensus ABPM definition of hypertension.
Technical limitations — Pulse wave amplitude and the elastic properties of the arterial wall are different in children and adults. These are important factors in the development of the algorithms used in ambulatory oscillometric monitors. Thus, both the monitors and algorithms used in ABPM need to be validated in children. Data from a few studies show that commercially available monitors developed for adults performed only fairly in the accurate and consistent recording of BP in children [51-53].
Other technical issues include patient acceptance and tolerance of the device, especially in young children, and ensuring the use of the appropriate cuff size [54]. Thus it is important to note if the patient did not tolerate the ABPM well when interpreting results.
Accuracy of measurement is age dependent, as lower systolic BP values, which occur in infants and young children, are associated with poorer monitoring quality because the cardiac cycle is shorter, resulting in a shorter time to measure oscillation. Allergy to latex in some BP cuffs also may preclude ABPM.
Costs — In the United States, one of the major limitations of the use of ABPM is the lack of coverage by third party payers. However, our experience has been that reimbursement can be obtained for most ABPM studies if appropriate documentation, including justification for the study and a report of the study results, is provided to the patient's insurance carrier. In July 2019, the Centers for Medicare and Medicaid Service (CMS) issued a new coverage determination that expanded coverage of ABPM for Medicare and Medicaid beneficiaries to include evaluation of both suspected white coat and suspected masked hypertension [55]. It is hoped that other third-party payors will follow suit.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Hypertension in children".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Beyond the Basics topics (see "Patient education: High blood pressure in children (Beyond the Basics)" and "Patient education: High blood pressure treatment in children (Beyond the Basics)")
●Basic topics (see "Patient education: High blood pressure in children (The Basics)")
SUMMARY AND RECOMMENDATIONS
●Purpose – Ambulatory blood pressure monitoring (ABPM) is a useful tool in evaluating blood pressure (BP) in children (table 1 and table 2 and table 3 and table 4). It is increasingly used to assess variable BP readings, wide discrepancies between the BP readings at home and in the clinician's office (ie, "white coat" hypertension), the effect of antihypertensive therapy, and the BP patterns in patients with chronic diseases associated with hypertension. (See 'Introduction' above.)
●Procedure – ABPM uses a portable automated BP device that records BP over a specific time period (usually 24 hours). Accurate ABPM is dependent upon use of an appropriately sized cuff; trained personnel to maintain and apply the device and educate the patient and family/caregiver; and analysis based on sex, age, and height-specific ABPM normative data. (See 'Device' above and 'Procedural approach' above and 'Interpretation of data' above.)
●Classification of blood pressure – Using both ambulatory and clinic BP measurements, the BP status of an individual child can be classified into the following categories (see 'Classification of BP' above):
•Normal BP – Both clinic and ambulatory BP are normal.
•Prehypertension – Clinic BP >90th percentile but <95th percentile, and mean ambulatory BP is normal but BP load is elevated.
•Ambulatory hypertension (also referred to as sustained hypertension) – Both clinic BP (>95th percentile) and ambulatory BP are elevated.
•Severe ambulatory hypertension (at risk for end-organ damage) – Clinic BP (>95th percentile) is elevated and ambulatory BP is elevated with a marked elevated BP load.
•White coat hypertension – Clinic BP is elevated (>95th percentile), but ambulatory BP is normal.
•Masked hypertension – Office/casual BP is normal, but ambulatory BP is elevated.
●Indications - In children, ABPM is used in the following settings (see 'Who should be evaluated by ABPM' above):
•Confirm the diagnosis of sustained (ambulatory) hypertension by excluding white coat hypertension
•Identify patients with masked hypertension
•Determine the effectiveness of antihypertensive treatment
•Evaluate BP patterns in children with chronic diseases associated with hypertension (eg, chronic kidney disease [CKD])
•Confirmation for children with elevated office BP for more than one year or with stage 1 hypertension (table 8)
●Limitations – The major limitations of using ABPM in children are lack of normative BP data, the difficulty of defining ambulatory hypertension, technical limitations, and costs. (See 'Normative data' above and 'Limitations' above.)
ACKNOWLEDGMENT — The editorial staff at UpToDate acknowledge Tej Mattoo, MD, DCH, FRCP, who contributed to an earlier version of this topic review.
