Masked hypertension: a phenomenon of measurement.

Abstract

Conventional measurement of blood pressure (BP) in individual patient care has several limitations that include causing spurious elevation of BP (white-coat hypertension) or giving normal readings when, in fact, the patient is hypertensive (masked hypertension).1 Out-of-office BP measurements using home BP monitoring (HBPM) or ambulatory BP monitoring (ABPM) provide insight into the true behavior of BP in individual patients during various daily activities at home and at work and during sleep (with ABPM). Although it is acknowledged at the outset that masked phenomena are a consequence of the methodology of BP measurement, the condition, nevertheless, has serious consequences for the diagnosis and management of patients with hypertension. Recent advances in our understanding of masked hypertension will be examined in this review. Conventional BP in the office or clinic is considered to be normal if it is <140/90 mm Hg. In contrast, out-of office BP values must take into consideration the period of the day simply because BP levels are different during the day and night, and BP may be elevated during either of these periods or throughout the 24-hour period. Indeed the 24-hour period can be further subdivided into the white-coat window (generally the first hour and possibly also the last hour) when the patient is subject to the influence of the medical environment, and the preawakening period when the subject may exhibit a morning surge in BP.1,2 Current consensus guidelines define out-of office hypertension as daytime BP ≥135/85 mm Hg, nighttime BP ≥120/70 mm Hg, and 24-hour average BP ≥130/80 mm Hg (Table 1).1 View this table: Table 1. Ambulatory and Home Blood Pressure Values (mm Hg) The daytime cutoff BP values for hypertension pertain to both ABPM and HBPM. Thus, for daytime measurements, the definition of masked hypertension in untreated individuals is an in-office BP of <140/90 …