Is 24 hour blood pressure monitoring necessary?

Is 24 hour blood pressure monitoring necessary,and what do I do with the information?

Patients with evidence of target organ damage, previous cardiovascular events, high outpatient blood pressure, and older age are at high risk of developing vascular complications of hypertension. They are therefore likely to require antihypertensive treatment, irrespective of the 24 hour blood pressure profile. Ambulatory monitoring is therefore generally reserved for the assessment of those patients with mild hypertension without evidence of cardiovascular damage (possible “white coat” hypertension),hypertension that appears to be drug-resistant and in the assessment of antihypertensive treatment,particularly with symptoms suggestive of hypotension.

What do I do with the information from a 24 hour ambulatory BP result?
One problem associated with the use of ambulatory blood pressure monitoring in clinical practice has been the lack of internationally accepted reference values. Population studies have been used to define normal ambulatory blood pressure ranges, according to age and sex, and it is now possible to plot 24 hour blood pressures for each patient and determine if they fall within these accepted bands. The disadvantage of this method has been that many of the earlier published data were not obtained from population-based samples. Nonetheless,there are more than 30 cross-sectional studies that have linked ambulatory blood pressure to target organ damage using the parameters of left ventricular hypertrophy, microalbuminuria, retinal hypertensive changes and cerebrovascular disease.These studies have revealed ambulatory blood pressure to be a more sensitive predictor of target organ damage than single casual measurements, and it has been assumed that these surrogate end points of target organ involvement can be extrapolated to the ultimate end points of cardiac or cerebrovascular death and morbidity.

“White coat” hypertensives
The clinical significance of white coat hypertension has yet to be established. Some echocardiographic studies of left ventricular size have reported that people with white coat hypertension have similar indices to normotensive people, and one follow up study has even suggested that they have a similar prognosis. In contrast, some studies have reported that left ventricular dimensions in white coat hypertension are somewhere between those of normotension and sustained hypertension.

Dippers and non-dippers
The significance of average night time blood pressure readings remains equally uncertain. Stroke, silent cerebrovascular disease, and left ventricular hypertrophy are more common in patients who do not demonstrate the normal nocturnal fall in blood pressure, and this has led to the assumption that non-dipper status is an independent predictor of cardiovascular morbidity and mortality. There are a number of potential problems that may complicate this interpretation. Vascular disease itself could impair nocturnal blood pressure fall through impairment of cardiovascular reflexes. It remains uncertain whether this nondipper status genuinely reflects a greater daily blood pressure load or whether it merely means that the patient did not sleep as soundly, having been disturbed by the inflation of the blood pressure cuff. The results of a number of large scale studies of ambulatory blood pressure and prognosis are awaited. These include the European study OVA, the study on ambulatory blood pressure and treatment of hypertension (APTH), the SAMPLE study and the ABP arm of the European Working Party on High BloodPressure Syst-Eur study.

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