How to Interpret the ABPM Profile

Ambulatory blood pressure monitoring-related medical terms and phenomena may be difficult to understand. This article is intended to highlight the most important factors in the ABPM profile and to provide support for learning more about ABPM measurements.

ABPM (ambulatory blood pressure monitor) is a programmable PC-based, small, lightweight and probably quiet device has been designed to monitor blood pressure over a 24-hour period. Only such ABPM monitors should be used which have been validated to international standards. Standards are provided by the British Hypertension Society (BHS) or by the American Association for the Advancement of Medical Instrumentation (AAMI).

What is included into the ABPM profile?

For correct interpretation, the ABPM profile should carefully be assessed in relation to the patient diary information and the medical therapy. The ABPM profile usually contains the blood pressure chart, histograms and detailed statistics about day-time, nigh-time and mean blood pressure, on the basis of which different blood pressure indexes, such as hypertensive time index, hypotensive time index, hyperbaric impact, diurnal index and morning surge are counted. To asses these indexes, defining normal ABPM values are necessary.

Normal ABPM values in adults

Defining normal ABPM blood pressure values is difficult, and normal values are different in adults, children and pregnant women. However, according to the most widely accepted criteria, normal day-time values are below 135/85 mmHg, while normal night-time values are less than 120/75 mmHg and values are below 130/80 mmHg for the whole 24-hour period in adults. The first number reflects systolic, the second reflects diastolic values. Systolic represents the maximum while diastolic represents the minimum pressure exerted on the arteries.

An ABPM blood pressure monitor provides information over and above traditional office blood pressure meters. Not only systolic, diastolic blood pressure and pulse are represented, but also other important index values which can be used as indicators of severe health problems.

Hypertensive Time Index
Hypertensice time index, or percent time elevation (PTE) is the proportion of time during which blood pressure values are higher than considered to be normal. The hypertension time index compares the period with elevated blood pressure to total time.

Hypotensive Time Index
Hypotensive Time Index or Percent Time Depression (PTD) reflects the proportion of time during which the blood pressure values are lower than hypotensive limits.

Hyperbaric Impact
Hyperbaric impact or hypertension load provides information on how long blood pressure is higher than normal and how much it is higher than the upper limit of normal ambualtory blood pressure during ABPM monitoring.

Diurnal Index
Diurnal or day / night index is the difference betwwen day-time and night-time blood pressure averages divided by the daytime average and multiplies by 100. If the day / night index is less than 10 percent, it may indicate target organ damage, diabetes or non-efficient antihypertensive drug treatment as well.

Morning surge
Morning surge is basically a normal rise from a lower night blood pressure level to a somewhat higher day blood pressure level. A high morning surge is an independent risk factor for cardiovascular event and fit is associatied with stroke.