Will knowing the variability of ambulatory blood pressure improve clinical outcome? An additional consideration in the critical evaluation of this technology.

The range through which blood pressure varies from moment to moment and from wakefulness to sleep confounds the assessment of the patient with suspected hypertension. The clinical application of this information depends upon the needs and resources available to the physician. Awareness of the variance between average clinic and average ambulatory blood pressures, acquired by ambulatory monitoring, may influence diagnostic and therapeutic decisions to the benefit of the patient. However, the hypothesis that those 20-30% of patients referred for management of mild to moderate hypertension after initial screening who are normotensive when remote from the clinic environment do not require treatment has not been tested prospectively. Two studies using intra-arterial recordings and one large study using a non-invasive device have demonstrated a relationship between ambulatory blood pressure variability and cardiovascular consequences of hypertension that is independent of the level of arterial pressure. Loss of information and problems with accuracy during activity preclude similar calculations of blood pressure variability by currently available portable non-invasive recorders. The hypothesis that actions based upon knowledge of blood pressure variability can improve clinical outcome is attractive, but waits, for its confirmation, large and rigorous trials based on advances in technologic capabilities that will permit accurate, continuous, yet non-invasive monitoring of ambulatory blood pressure.