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Blood pressure
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Blood pressure should be measured in all adults from 18 years of age at least every 2 years (A).
The risk of CVD is continuous across a range of blood pressures beginning at 115/75 and doubles with each increment of 20/10. Thus, the benefit of lowering blood pressure should be considered in all patients, especially those with other risk factors (A)
The U.S. Preventive Services Task Force (USPSTF) strongly recommends that clinicians screen adults aged 18 and older for high blood pressure. (A)
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Clinical Considerations
- Hypertensive diseases constituted 9.8% of all the admitted cases of CVD in DOHMS and were more frequent among females (17.0%). It is one of the ten leading causes of death among Emirates in 2005. Among the Emirate population, 72 (49.0%) were males and 51.0% were females. The frequency distribution of hypertension increased with increase in age, but hypertension was more prevalent among females in the age group 45-64 years and males in the age group 65 years and above (Health in Dubai Situational Analysis and Future Prospects', Department of Planning and Statistics DOHMS Dubai 2007)
- Office measurement of blood pressure is most commonly done with a sphygmomanometer. High blood pressure (hypertension) is usually defined in adults as a systolic blood pressure (SBP) of 140 mm Hg or higher, or a diastolic blood pressure (DBP) of 90 mm Hg or higher. Due to variability in individual blood pressure measurements (occurring as a result of instrument, observer, and patient factors), it is recommended that hypertension be diagnosed only after 2 or more elevated readings are obtained on at least 2 visits over a period of 1 to several weeks.
- There are some data to suggest that ambulatory blood pressure measurement (that provides a measure of the average blood pressure over 24 hours) may be a better predictor of clinical cardiovascular outcome than clinic-based approaches; however, ambulatory blood pressure measurement is subject to many of the same errors as office blood pressure measurement.
- The relationship between SBP and DBP and cardiovascular risk is continuous and graded. The actual level of blood pressure elevation should not be the sole factor in determining treatment.
- Clinicians should consider the patient’s overall cardiovascular risk profile, including smoking, diabetes, abnormal blood lipids, age, sex, sedentary lifestyle, and obesity, in making treatment decisions.
- Evidence is lacking to recommend an optimal interval for screening adults for high blood pressure. The Joint National Committee, 7th report (JNC 7) calls for routine blood pressure measurement at least once every 2 years for adults with a systolic blood pressure below 120 mm Hg and a diastolic blood pressure below 80 mm Hg, and every year for systolic blood pressure 120-139 and diastolic blood pressure 80-89 mm Hg.
Who is at higher risk of vascular disease or hypertension?
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Who is at higher risk?
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What should be done?
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How often?
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Average risk of vascular disease
and/or hypertension
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Adults 18-50 years of age (dependent on risk factors identified through absolute cardiovascular risk assessment)
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Measure BP
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Every 2 years from age 18 years if systolic BP <120 and diastolic BP <80
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Increased risk of vascular disease and/or hypertension
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Lifestyle risk factors:
- smoking
- physical inactivity
- overweight /obesity
- poor nutrition
- lower SES and psychological factors
- excessive alcohol Consumption
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Measure BP
Lifestyle risk factor counseling
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Every 12 months
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South Asians
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Measure BP
Assess absolute cardiovascular
Risk Lifestyle risk factor counseling
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Every 6 months
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Interventions and Technique
Measure BP with sphygmomanometer at initial visit, then two subsequent visits with two readings at each visit if above 120/80.
Absolute cardiovascular risk assessment – Assessment of the risk of a coronary event or stroke in the next 5-10 years. Required information is gender, age, total cholesterol, HDL, presence of diabetes, and smoking status. Computer and paper based tools are available using algorithms derived from Framingham and other study findings (see Appendix VIII).
Assessing cardiovascular risk and treatment benefits
The Framingham coronary prediction algorithm
The Framingham coronary prediction algorithm (see Appendix VIII) is used to assess cardiovascular risk and it provides patient’s absolute risk of total CHD risk (risk of developing one of the following; angina pectoris, myocardial infarction, or coronary disease death) over the course of 5-10 years.
- Separate score sheets are used for men and women
- The factors used to estimate risk include age, blood cholesterol, HDL cholesterol, blood pressure, cigarette smoking, and diabetes mellitus.
- Relative risk for CHD is estimated by comparison to low risk Framingham participants. The low risk was calculated using the following factors:
- Persons of the same age group
- Optimal blood pressure
- Total cholesterol 160-199 mg/dl
- HDL cholesterol 45 mg/dl for men or 55 mg/dl for women
- Non-smoker
- No diabetes
How to use the tables
- Identify the table relating to the person’s sex, diabetic status, smoking history and age.
- Within the table choose the cell nearest to the person’s age, blood pressure and TC: HDL ratio.
- For example, the lower left cell contains all non-smokers without diabetes who are less than 45 years and have a TC: HDL ratio less than 4.5 and a blood pressure less than 130/80 mm Hg.
Please note:
- When the systolic and diastolic values fall in different risk levels, the higher category applies.
- People who fall exactly on a threshold between cells are placed in the cell indicating higher risk.
Notes for users of this risk algorithm
After determining the cardiovascular risk using the Framingham table, the following groups should be moved up by one risk category (5%). This is because their cardiovascular risk may be underestimated in the Framingham risk equation.
- People with a family history of premature coronary heart disease or ischemic stroke in first-degree male relative before the age of 55 years or a first-degree female relative before the age of 65 years.
- People from Indian subcontinent.
- People with both diabetes and microalbuminuria.
- People who have had type 2 diabetes for more than 10 years or who have an HBA1c consistently greater than 8%.
- People with metabolic syndromes.
Please note:
- These adjustments should be made once only for people who have more than one criteria
- The maximum adjustment is 5%.
Extreme risk factor levels
- The risk factor levels are extreme and the person is classified at least at higher risk (>15%) and should receive specific lifestyle advice and medication to lower their risk, irrespective of their calculated cardiovascular risk, if:
- The blood pressure is consistently greater than 170/100 mm Hg or
- Total cholesterol greater than 312 mg/dl (8 mmol/L) or
- TC: HDL ratio grater than 8
- For age greater than 75 years the 5- year cardiovascular risk is greater than 15% in nearly all individuals.
Intervention benefits
Based on the conservative estimate, each intervention such as aspirin, blood pressure treatment (lowering systolic blood pressure by 10 mm Hg) or lipid modification (lowering LDL-C by 20%) reduces cardiovascular risk by about 25% over 5 years.
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Risk level:
5-year CV risk (fatal and non-fatal)
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Benefits: NNT for 5 years to prevent on event
(CVD events prevented per 100 people treated for 5 years)
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1 Intervention
(25% risk reduction)
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2 Interventions
(45% risk reduction)
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3 Interventions
(55% risk reduction)
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30%
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13
(7.5 per 100)
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7
(14 per 100)
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6
(16 per 100)
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20%
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20
(5 per 100)
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11
(9 per 100)
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9
(11 per 100)
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15%
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27
(4 per 100)
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15
(7 per 100)
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12
(8 per 100)
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10%
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40
(2.5 per 100)
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22
(4.5 per 100)
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18
(5.5 per 100)
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5%
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80
(1.25 per 100)
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44
(2.25 per 100)
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36
(3 per 100)
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