As the name suggests, 24-hour ambulatory blood pressure monitoring (ABPM) measures blood pressure regularly in the course of the day and provides not only information about blood pressure levels during day- and nighttime but also on blood pressure rhythmicity over 24 hours.
A small, portable oscillometric blood pressure device with an appropriately sized cuff (for cuff selection criteria please see also ‘How do we appropriately measure blood pressure in children and adolescents’ by Prof. Stella Stabouli) is attached to the non-dominant arm of the child. After reliability of the ABPM measurement has been verified by comparison with simultaneous office BP reading, the device is programmed to measure blood pressure every 15 to 20 min during daytime and every 20 to 30 min during nighttime. Information on mean 24-hour, daytime and nighttime systolic, diastolic and mean arterial blood pressure, as well as heart rate are recorded by this technique. Hypertension by ABPM is diagnosed, if mean blood pressure values are above ABPM reference values for healthy children and adolescents.
The advantage of ABPM is that 60 to 80 measurements within 24 hours, allow for a more representative observation of blood pressure and measurements are done in a non-medical environment. Thus, the reliability of the measured blood pressure level outclasses single office measurements and there is substantial evidence that ABPM is superior to office blood pressure measurements in predicting cardiovascular risk in adults. Although clinical endpoint assessment in patients with childhood onset hypertension is still lacking, there is emerging evidence for a superior association between ambulatory blood pressure and preclinical target organ damage in youth.
Furthermore, ABPM is an essential tool to detect specific blood pressure patters: If a patient has elevated blood pressure levels by office measurements but has normal ABPM this is called ‘White coat’ or ‘office’ hypertension. The opposite condition, i.e., normal blood pressure in the doctor’s office but elevated blood pressure during the out-of-office ABPM readings, is called ‘Masked hypertension’.
ABPM is the only tool to evaluate nocturnal blood pressure level and ABPM read out of blood pressure measurements provides information about the difference between day- and nighttime blood pressure level (nocturnal blood pressure dipping). Physiologically, blood pressure is lower during sleep than during wake hours and changes in this blood pressure pattern may occur early in subjects at elevated risk for hypertension and cardiovascular disease. Vice versa, nocturnal non-dipping may be associated with an increased risk for cardiovascular morbidity and mortality regardless of the blood pressure level itself.
Current pediatric hypertension guidelines recommend ABPM in all children in whom hypertension is suspected by office BP measurements to confirm the diagnosis of hypertension and to rule out white-coat hypertension. It is also recommended regularly in all children and adolescents with increased risk for hypertension and cardiovascular disease. This is especially true for children with kidney or cardiac disease, after solid organ transplantation, and with diabetes, who are at significantly increased risk for masked and/or nocturnal hypertension.
After the diagnosis of hypertension and while on antihypertensive therapy, ABPM continues to be a valuable tool for monitoring blood pressure control. Six- to 12-monthly intervals are recommended for the evaluation of blood pressure level by ABPM.
Prof. Dr. Elke Wühl, Center for Pediatrics and Adolescent Medicine, University Hospital Heidelberg, Germany
