Chapter - 2: Definition and Classification of Hypertension

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The classification of high blood pressure is useful as clinicians must make treatment decisions based on the measured BP and the patients’ associated co-morbidities. Different guidelines published recently have proposed almost similar classification for treatment decision although different nomenclature was observed. The following classification has been adopted by the guideline committee. These criteria are for subjects who are adults (age 18 and older and not on any antihypertensive medication and not acutely ill (Table 1). In accordance with most major guidelines, it is recommended that hypertension be diagnosed when a person’s systolic blood pressure (SBP) in the office or clinic is ≥140 mm Hg and/or their diastolic blood pressure (DBP) is ≥90 mm Hg following repeated examination. Table 2 provides ambulatory and home BP values used to define hypertension; these definitions apply to all adults (>18-year-old) adopted from ISH 2020 Guideline9.

Table 1. Classification of office blood pressurea and definition of hypertension gradeb

Category

Systolic (mm Hg)

 

Diastolic (mm Hg)

Normal BP

<130

and

<85

High-normal BP

130–139

and/or

85–89

Grade 1 hypertension

140–159

and/or

90–99

Grade 2 hypertension

≥160

and/or

≥100

Isolated systolic hypertension

≥140

and

<90

BP= Blood Pressure; SBP= Systolic blood pressure.
aBP Category is defined according to seated clinic BP and by the highest level of BP, whether systolic or diastolic
bIsolated systolic hypertension is graded 1 or 2 according to systolic BP value in the ranges indicated.
The same classification is used for all ages from 16 years.

 

Table 2. Criteria for Hypertension Based on Office-, Ambulatory (ABPM)-, and Home Blood Pressure (HBPM) Measurement

Category

Systolic/Diastolic BP (mm Hg)

Office BP

≥140 and/or ≥90

ABPM

 

24-h average

≥130 and/or ≥80

Day time (or awake average)

≥135 and/or ≥85

Night time (or asleep average)

≥120 and/or ≥70

HBPM

≥135 and/or ≥85

How low is too low for blood pressure?

While there is no specific number at which day-to-day blood pressure is considered too low, a reading of less than 90/60 mm Hg is considered hypotension. Hypotension is the term for blood pressure that is too low. The condition is benign as long as none of the symptoms showing lack of oxygen are present.

Symptoms of low blood pressure

Most health care professionals will only consider chronically low blood pressure as dangerous if it causes noticeable signs and symptoms, such as:

  • Confusion
  • Dizziness or lightheadedness
  • Nausea
  • Fainting (syncope)
  • Fatigue
  • Neck or back pain
  • Headache
  • Blurred vision
  • Palpitations