Ambulatory blood pressure monitoring in children

INTRODUCTION — Ambulatory blood pressure monitoring (ABPM) is a valuable tool in evaluating blood pressure (BP) in children. It is recommended in a variety of clinical situations, including confirming the diagnosis of hypertension based on clinic BP readings, assessing for possible "white coat" hypertension, and evaluating for secondary forms of hypertension such as that caused by chronic kidney disease.

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 on 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 who are old enough to cooperate with the procedure and with height ≥120 cm [1]. It also has been successfully used to evaluate blood pressure (BP) in infants, toddlers, and older children in research settings. ABPM needs to be performed in a standardized, reliable fashion to provide accurate recordings, especially in small children and infants.

Device — ABPM uses a portable automated device that records BP over a specific time period (usually 24 hours). ABPM monitors most commonly used in children are small oscillometric devices, which are worn in a pouch on a belt. Oscillometric ABPM devices directly measure the mean arterial pressure and back-calculate the systolic and diastolic BP using an algorithm 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 [2]. Devices validated in children are listed at Stride BP. (See 'Technical limitations' below.)

Development of normative data for pediatric ABPM has been difficult because of the variation of each algorithm [1,3]. Devices utilizing the auscultatory technique are also available but are less frequently used in children because they are more cumbersome to wear [1,4]. In addition, there are no published normative pediatric ABPM data for auscultatory devices [1].

ABPM procedures — In our center, we follow the approach outlined in the 2022 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]:

●Training – 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.

●Cuff size – As with clinic BP measurement, an appropriately sized cuff must be used (figure 1). (See "Definition and diagnosis of hypertension in children and adolescents", section on 'Cuff size and placement'.)

●Placement – The ABPM cuff is placed on the nondominant arm. Exceptions include:

•Presence of a permanent dialysis access, kidney failure (chronic kidney disease 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 (with normal arch vessel anatomy), place the cuff on the right arm.

•If there is a significant interarm BP difference, the device should be placed on the arm with the higher BP.

●Calibration – 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.

●Guidance for patients and caregivers – Advice to the patient and their caregivers when placing the ABPM monitor should include [1,5]:

•The cuff will inflate to measure BP every 20 to 30 minutes while awake and every 30 to 60 minutes while asleep. This should result in enough readings for interpretation during both sleep and wake periods.

•Keep the arm with the cuff still while inflating to prevent exertion-induced error in BP measurement.

•The cuff should be snug but not loose. If it is uncomfortably tight, or so loose that it slides down the child's arm, undo the Velcro and readjust.

•Avoid competitive sports or other intense physical activity during ABPM. However, it is desirable to perform ABPM on a school day to capture the child's or adolescent's typical activity level.

•Keep a diary of sleep-wake times for use in interpreting the study results, and return it with the device.

•Do not let the ABPM device get wet.

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.

Variables reported — The following variables are calculated for the wake and sleep periods and for the entire 24 hours:

●Mean BP – Mathematical averages for systolic and diastolic BP readings captured in each monitoring period. These values are the basis for the definitions of ambulatory hypertension. (See 'Classification of blood pressure' below.)

●BP load – Percentage of readings above the 95^th percentile of systolic or diastolic BP based on ambulatory normative data, which is dependent on age, sex, and wake/sleep status. (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.

The dipping status is based on the percent of dipping, which is calculated for both systolic and diastolic BP using the following formula:

Failure of the BP to fall at least 10 percent during sleep is called nondipping. In adults, nondipping has been associated with left ventricular (LV) hypertrophy, heart failure, and other cardiovascular complications. In children, nondipping is more common in secondary forms of hypertension [6] and in those with obesity [7]. However, there are no long-term data available regarding the effects of nondipping on cardiovascular risk in children and adolescents. (See 'Nocturnal nondipping' below and "Out-of-office blood pressure measurement: Ambulatory and self-measured blood pressure monitoring".)

●Other – Data for ABPM recordings should be inspected visually for any gross inconsistencies in heart rate as well as sleep and awake BP measurements based on the child's age, which may lead to inaccurate interpretation of the results [1].

Normative data — The best available normative data for ABPM are shown in the tables, based on age (table 1A-B) or height (table 2A-B) [1,8,9]. These are based on data from a single study of ABPM in approximately 1000 Central European children and adolescents [8]. Limitations of these data are:

●Results only included information from White children from mid-European countries. It is uncertain whether they apply to children from other populations.

●Data were obtained by oscillometric monitors that rely on a proprietary algorithm to derive systolic and diastolic BP values. There was a lack of variability in diastolic BP, which was similar for both sexes and all heights, a finding that is in direct contrast with normative data for clinic BP measurements [1,3,10]. 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 age of the patient.

Note that normative data based on clinic-based measurements cannot be used as a standard for ABPM recordings. This is because BP increases with physical activity, as shown in two comparative studies [4,11]. Accordingly, the threshold ABPM values used to diagnose hypertension are typically higher than those used for clinic BP readings, which are usually obtained at rest [8,12].

Further efforts are needed to establish normative ABPM values for all pediatric populations and to correlate them with validated clinic-based values. Until such data are available, we use the normative data from the Central European study, while recognizing their limitations.

Definition of elevated ambulatory blood pressure

●Age <13 years – Mean ambulatory BP ≥95^th percentile (for 24-hour or wake or sleep BP) or ≥adolescent cutpoints

●Age ≥13 years – Mean ambulatory BP ≥125/75 mmHg (24 hours) or ≥130/80 mmHg (wake) or ≥110/65 mmHg (sleep)

Classification of blood pressure — The 2022 AHA scientific statement on pediatric ABPM defines the following pediatric BP categories using information from both clinic and ABPM data [1]:

●Normal BP – Both clinic BP and ambulatory BP normal

●White coat hypertension – Clinic BP in the hypertensive range, ambulatory BP normal

●Masked hypertension – Clinic BP normal, ambulatory BP elevated

●Ambulatory hypertension – Both clinic BP and ambulatory BP elevated

The 2022 statement clarified that only clinic BP and mean ambulatory BP are needed for diagnosis of ambulatory hypertension, given data showing that BP load did not help identify children with increased risk of target-organ effects of high BP [1,13].

WHO SHOULD BE EVALUATED BY ABPM — Indications for ABPM in children include [1,5,10,14-18]:

●Persistently elevated clinic blood pressure (BP) – For children with elevated clinic BP for more than one year or with stage 1 hypertension level after three visits (table 3 and table 4), ABPM helps to distinguish between ambulatory hypertension (ie, both clinic and ambulatory BP elevated) and white coat hypertension (ie, clinic BP elevated but ambulatory BP normal).

●Normal or elevated clinic BP but clinical suspicion of hypertension – To detect masked hypertension (abnormal ambulatory BP despite normal clinic BP measurement). As an example, masked hypertension is more common in children with congenital solitary kidney [19].

●High-risk conditions – This includes children with chronic diseases frequently associated with hypertension, such as chronic kidney disease, solid organ transplant, type 1 or type 2 diabetes mellitus, autonomic dysfunction, obesity, sleep apnea, and certain genetic syndromes (eg, neurofibromatosis type 1, Turner syndrome, or Williams syndrome).

●Antihypertensive treatment – To assess BP control and guide changes in therapy for selected patients.

●Repaired aortic coarctation – To monitor for recurrent hypertension. (See "Management of coarctation of the aorta", section on 'Recoarctation'.)

ABPM is particularly useful and cost-effective in patients with white coat and masked hypertension [20]. Limited data suggest that ABPM may be useful in differentiating between primary and secondary hypertension and in predicting which children are at risk for early adult cardiovascular disease and noncardiac end-organ damage [1]. (See 'Clinical implications of ABPM results' below.)

CLINICAL IMPLICATIONS OF ABPM RESULTS

White coat hypertension — ABPM appears to be cost effective in identifying children with white coat hypertension because identifying these children can avoid unnecessary testing and treatment. Several observational studies report that between 13 and 46 percent of children referred for high blood pressure (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 children with white coat hypertension merit further follow-up because it 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, 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], two studies have shown that ABPM profiles in children and adolescents may not be stable over time, suggesting that some children with white coat hypertension may indeed progress to ambulatory hypertension [27,28].

Given these findings, our practice is to repeat ABPM at one- to two-year intervals in children with white coat hypertension because they appear to be at increased risk for developing ambulatory (sustained) hypertension [26].

Masked hypertension — Masked hypertension is associated with obesity and an increased LV mass, which are risk factors for early adult cardiovascular disease [29,30]. In a meta-analysis (136 studies, 28,612 participants), the prevalence of masked hypertension in the general pediatric population was 10 percent, with higher proportions in those with obesity, chronic kidney disease, sickle cell disease, or history of solid organ or stem cell transplant [30]. Children with masked hypertension were more likely to have LV hypertrophy (odds ratio 2.44, 95% CI 1.5-4.0).

In adults, masked hypertension 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".)

Nocturnal nondipping — Normally, the average BP during sleep at night, as measured by ABPM, is approximately 15 percent lower than daytime values; this circadian pattern is referred to as nocturnal dipping [8,15,31,32]. Failure of the BP to fall at least 10 percent during sleep is called nondipping. (See 'Variables reported' above.)

The presence of nocturnal nondipping may be helpful for distinguishing primary from secondary hypertension because children with untreated secondary hypertension are more likely to have nocturnal nondipping compared with those with untreated primary hypertension [6,33]. 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".)

Prediction of long-term risks

●Cardiovascular disease – Data regarding the association between elevated ABPM values and risk of early cardiovascular disease in children are limited [1]. The evidence is indirect and based on results from studies in children and adolescents that show an association between ambulatory BP parameters and LV mass index and obesity [34-38]. In a systematic review and meta-analysis, primary ambulatory hypertension was associated with an increased risk of LV hypertrophy (odds ratio 4.69, 95% CI 2.69-8.19), elevated carotid intima-media thickness, and other markers of cardiovascular disease [39]. Some of these associations persisted after adjusting for body mass index as a potential confounder. In adults, masked hypertension and, to a lesser degree, white coat hypertension have been associated with an increased risk of sustained hypertension [40] and cardiovascular morbidity. (See "White coat and masked hypertension", section on 'Prognosis'.)

●Kidney damage – Limited evidence has shown an association between elevated ABPM values in children and adolescents and an increased risk of kidney damage, including reduction in creatinine clearance [41,42], renal scarring [43,44], progressive kidney disease in patients with diabetes mellitus [45-47], increased urinary protein excretion [42], and poorer allograft function in children who have undergone kidney transplantation [48,49].

These data suggest that repeated ABPM would be useful to optimize antihypertensive therapy, which may lead to a decreased risk of progressive kidney damage. (See "Chronic kidney disease in children: Complications", section on 'Hypertension'.)

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.

Challenges in defining ambulatory hypertension — In children, defining hypertension either using clinic or ambulatory values is difficult because of the limited normative population data and long-term outcome measures. As a result, pediatric hypertension is defined statistically for both clinic and ambulatory measurements [1]. (See 'Normative data' above.)

Another challenge is determining when and how to transition to adult definitions for ambulatory hypertension. The American Heart Association (AHA)'s thresholds for defining ambulatory hypertension in adolescents ≥13 years of age now mirror those for adults in the most recent American College of Cardiology/AHA guideline [1,50]. European guidelines take a somewhat different approach, using percentile values or adult definitions (whichever is lower) until 16 years of age [9].

The advantage of using adult thresholds is that they are based on large datasets that correlate BP values with outcome measures, such as cardiovascular disease 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 clinic readings or clinically relevant outcome measures and validate the current consensus ABPM definition of hypertension. Additionally, further work is needed to determine the ideal age to adopt adult ABPM thresholds.

Technical limitations — Pulse wave amplitude and the elastic properties of the arterial wall are different in children compared with 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 had only fair performance 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 an appropriate cuff size [54]. Thus, it is important to note if the patient did not tolerate the ABPM well (especially overnight) when interpreting results. 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 & Medicaid Service 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, especially with new evidence demonstrating the cost-effectiveness of identifying white coat hypertension, which avoids unnecessary testing and treatment of hypertension. (See 'White coat hypertension' above.)

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 5^th to 6^th 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 10^th to 12^th 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.)

●Basics topic (see "Patient education: High blood pressure in children (The Basics)")

●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)")

SUMMARY AND RECOMMENDATIONS

●Procedure – Ambulatory blood pressure monitoring (ABPM) uses a portable automated blood pressure (BP) device that records BP over a specific time period (usually 24 hours). Accurate ABPM requires use of an appropriately sized cuff and trained personnel to maintain and apply the device and educate the patient and family/caregiver; analysis is based on normative data in children by age (table 1A-B) and height (table 2A-B). (See 'Device' above and 'ABPM procedures' above and 'Normative data' above.)

●Variables reported – Key results are the average systolic and diastolic BPs for the 24-hour period, daytime, and sleep, which are used to define elevated ambulatory BP. Other variables include BP load and nocturnal dipping. (See 'Variables reported' above and 'Definition of elevated ambulatory blood pressure' above.)

●Classification of BP – Using both ambulatory and clinic BP measurements, the BP status of an individual child can be classified into the following categories (see 'Classification of blood pressure' above):

•Normal BP – Both clinic BP and ambulatory BP normal

•White coat hypertension – Clinic BP in the hypertensive range; ambulatory BP normal

•Masked hypertension – Clinic BP normal; ambulatory BP elevated

•Ambulatory hypertension – Both clinic BP and ambulatory BP elevated

●Indications and clinical implications of findings – ABPM is a valuable component of the clinical evaluation for children with (see 'Who should be evaluated by ABPM' above and 'Clinical implications of ABPM results' above):

•Persistently elevated clinic BP (especially with normal BP readings at home) – ABPM helps to distinguish between ambulatory hypertension and white coat hypertension. Identifying white coat hypertension can avoid unnecessary testing and treatment but also requires clinical follow-up. (See 'White coat hypertension' above.)

•Normal or borderline clinic BP but clinical suspicion of hypertension – To detect masked hypertension. Masked hypertension is associated with risk factors for adult cardiovascular disease. (See 'Masked hypertension' above.)

•High-risk conditions – To evaluate children with chronic conditions associated with hypertension, including obesity, chronic kidney disease, diabetes, solid organ transplant, and others.

•Antihypertensive treatment – To assess BP control and guide changes in therapy.

•Repaired aortic coarctation – To monitor for recurrent hypertension.

●Limitations – The major limitations of using ABPM in children are limited normative BP data, with associated challenges in defining ambulatory hypertension, technical limitations, and costs. (See 'Normative data' above and 'Limitations' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Tej Mattoo, MD, DCH, FRCP, who contributed to earlier versions of this topic review.