ABSTRACT
INTRODUCTION Blood pressure (BP) is characterized by a highly dynamic behavior presenting marked short-term fluctuations not only within 24 hours (i.e., beat-to-beat, minute-to-minute, hour-to-hour, and day-to-night changes) but also over more prolonged periods (i.e., between days, weeks, months, seasons, and even years). The physiological relevance of BP variability (BPV) has been demonstrated by experimental and clinical studies, which showed it to be the result of complex interactions between extrinsic environmental and behavioral factors on one side and intrinsic cardiovascular regulatory mechanisms (humoral and neural central or reflex influences) on the other side, rather than a randomly occurring phenomenon. Depending on the method used for BP monitoring (i.e., continuous recordings, office, ambulatory, or home measurements) and on the time interval considered for its assessment (i.e., beatto-beat, within 24 hours, day-to-day, or between visits), the clinical significance and prognostic implications of a given measure of BPV may substantially differ. Evidence on the prognostic relevance of BPV has been provided by observational studies, and meta-analyses of clinical trials in hypertension showing that the adverse cardiovascular risk associated with hypertension may depend not only on mean BP values but also on an increased BPV. Indeed, it has been shown that an increased BPV either in the short or in the long term is associated with development, progression, and severity of cardiac, vascular, and renal organ damage and with an increased incidence of cardiovascular events and mortality, independently adding to cardiovascular risk, over and above the contribution of elevated mean BP levels. In particular, post hoc analyses of intervention trials in hypertension have shown that an increased intraindividual visit-to-visit BPV is a strong predictor for cardiovascular morbidity and in some instances found to be superior to mean BP values (1). Based on this evidence, it has been suggested that the benefits of antihypertensive treatment in terms of cardiovascular protection could be potentiated if it were targeted not only to achieve control of mean BP values but also to stabilize BPV. However, a better understanding and definition of the BPV phenomenon as well as of its different components is still needed
before recommending its routine assessment in clinical practice as an additional target of antihypertensive treatment. This chapter will review the different types of BPV, their mechanisms, as well as the methods currently used for their assessment in clinical practice. Emphasis is placed on the clinical interpretation and prognostic relevance of different components of BPV, addressing the question of whether BPV should become a target of antihypertensive treatment to improve cardiovascular protection.
