Defining normal ambulatory blood pressure in relation to target organ damage and prognosis.

It is premature to state that ambulatory blood pressure (ABP) values below a given level should be considered normal, and those above it abnormal, in terms of prognostic implications on cardiovascular (CV) morbidity. We do not know whether CV morbidity in hypertensive subjects with apparently normal ABP (white coat hypertension) is less than that in patients with higher ABP levels and similar to that of healthy normotensive subjects, or whether the effects of antihypertensive drug treatment on CV morbidity are superior to placebo in white coat hypertension. It is important to achieve agreement on a temporary working definition of normal ABP to be used to test two main hypotheses: 1) in subjects with white coat hypertension, CV morbidity is less than that in patients with higher ABP levels; and 2) drug treatment is not superior to placebo in reducing CV morbidity in white coat hypertension. Normal ABP values can be derived empirically from population based samples, in selected groups of healthy subjects, or from meta-analyses. However, the significance of the definition of a normal ABP range is the identification of clinically hypertensive patients at low risk of future CV morbid events. Using echocardiographic left ventricular (LV) mass as a surrogate outcome measure, we found that the coexistence of mean daytime ABP levels < 134 mm Hg systolic and < 90 mm Hg diastolic, regardless of gender (< 136/87 mm Hg in men and 131/86 mm Hg in women) identifies a subgroup of clinically hypertensive subjects with echocardiographic LV mass, and associated prevalence of left ventricular hypertrophy (LVH) similar to those found in healthy normotensive control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)