What is the definition of normal and hypertension based on ambulatory blood pressure monitoring (ABPM)?
Definition of normal:
One of the unresolved issues in ambulatory monitoring is the definition of what constitutes normal and elevated BP. A meta-analysis of normotensive subjects found mean 24-hour and daytime values to be 118/72 and 123/76 mmHg, respectively; the former is lower since the BP normally falls with sleep.
Most experts agree that 24 hour blood pressure <130/80 mmHg is probably normal, and 135/85 mmHg is probably abnormal.
Definition of hypertension:
The diagnosis of hypertension using on ABPM depends on the time span over which it is interpreted:
- 24-hour average above 135/85 mmHg
- Daytime (awake) average above 140/90 mmHg
- Nighttime (asleep) average above 125/75 mmHg
A daytime ambulatory average BP below 135/85 is infrequently associated with left ventricular hypertrophy (LVH) and almost always represents normotension. An echocardiogram can be used to ascertain the possible presence of significant hemodynamic stress or LVH if the daytime average is between 135/85 and 140/90.