Journal of the American Society of Nephrology 2279 Ambulatory Blood Pressure Monitoring: Coming of Age in Nephrology1 Raymond R. Townsend2 and Virginia Ford R.R. Townsend, V. Ford, Department of Medicine, Renal-Electrolyte and Hypertension Division, University of Pennsylvania, Philadelphia, PA (J. Am. Soc. Nephrol. 1996; 7:2279-2287) ABSTRACT The number of patients undergoing ambulatory blood pressure monitoring (ABPM) and the number of publications using this technique to evaluate the risks and effects of high blood pressure on target organs has been increasing, and dramatically so, in the last 5 years. Much of this growth has centered on the role ofthe blood pressure load (the percentage of systolic or diastolic readings above a preset value during a specific time period) and the changes in blood pres- sures levels that occur with sleep. Although many studies are focused on the interaction between blood pressure (as assessed by ABPM) and the heart, interest is growing in the application of ABPM to the practice of nephrology. This paper discusses some of the technical aspects of ABPM, followed by a review of five areas of clinical research using ABPM, and which are relevant to renal medicine: microalbuminuria, renal function, renovascular hypertension, dialysis (hemodialysis and continuous ambulatory peritoneal dialysis), and transplantation. Despite a general lack of reimbursement for performance of the ABPM pro- cedure, the growth in its usage and the willingness of clinicians to withhold or alter therapy on the basis of ABPM readings is testimony to its clinical value in the management of hypertension. Key Words: Blood pressure monitoring, hypertension, circa- dian rhythm, transplantation, review A mbulatory blood pressure monitoring (ABPM) be- gan as an endeavor to improve the understand- ing of the relationship between blood pressure bevels and the development of target organ damage from high blood pressure ( 1). It has bong been known that blood pressure fluctuates greatly within an individual, and that casual office blood pressure readings were not always typical of the hemodynamic proffle of any 1 Received February 2, 1996. Accepted June 25, 1996. 2 correspondence to Dr. P.R. Townsend, University of Pennsylvania Medical center, Renal-Electrolyte and Hypertension DivIsion, 210 WhIte BuIldIng. 3400 Spruce Street, Philadelphia, PA 19104. 104&6673/071 1-2279$03.00/0 Journal of the American society of Nephrology copyright © 1996 by the AmerIcan society of Nephrology particular patient. Thus, it was logical to obtain more frequent blood pressure readings so that the hemody- namic proffie of an individual could be characterized more completely. Several prospective studies have confirmed that ambulatory recordings, compared with office values, improve the predictability of blood pres- sure as a risk factor for target organ damage (2,3). As blood pressure monitors were developed and subse- quently automated, it became possible to obtain read- ings even when a patient was asleep. This additional dimension expanded the pursuit of the relationship between hypertension and its effects on target organs to include an evaluation of the behavior of blood pressure during sleep, in addition to the daytime. Investigation of the nocturnal blood pressure pattern has yielded further information on the relationship between high blood pressure and target organ damage such as left-ventricular hypertrophy and renal failure (4-6). Figure 1 shows the number of publications using ABPM. As more reports appeared, and as the monitor- ing units became smaller and lighter in weight, inter- est in the clinical and research uses of ABPM has increased. The reasons why physicians in practice request ABPM was assessed by questionnaire in a recent study by Grin et a!. (7). The responses by community-based practitioners and subspecialists (including a few nephrobogists) were similar. ABPM was requested for the evaluation of borderline hyper- tension (27%), the adequacy of antihypertensive then- apy (25%), the evaluation of the “white-coat” phenom- enon (22% ; wherein “white coat” is understood to be average in-office diastolic readings > 90 mm Hg with average out-of-office daytime values below 86 mm Hg), investigation of resistance to drug therapy ( 16%), or for miscellaneous reasons, such as assessment of blood pressure levels during symptoms such as bight- headedness (10%). Many reviews center on the role of using ofABPM to evaluate patients for left-ventricular hypentrophy, overall cardiovascular risk, white-coat effect, etc. (8- 1 i). In this review, some of the technical aspects of ABPM, including the diurnal proffle and five areas of ABPM usage that are relevant to nephrobogy, will be covered. The brief coverage of the technical aspects of ABPM seems appropriate, because in the study quoted previously (7), although most community- based practitioners (61%) felt reasonably knowledge- able about ABPM, only 28% of subspecialists consid- ered themselves “well informed” about the technique. TECHNICAL ASPECTS ABPM requires the purchase ofan ambulatory blood pressure monitor, a computer system or monitor in-