Hypertension (high blood pressure)

• What is Hypertension (High Blood Pressure)?
• Statistics
• Risk Factors
• Progression
• Symptoms
• Clinical Examination
• How is it Diagnosed
• Prognosis
• Treatment
• References

What is Hypertension (High Blood Pressure)?

Hypertension is defined as elevated blood pressure and is the leading cause globally of death and disability. It is the major risk factor for heart attack and stroke, and is also a significant risk factor for for chronic kidney disease and chronic heart failure. Because individuals with hypertension usually don’t have any symptoms, it is a disease that is often under-diagnosed. Diagnosis relies upon routine blood pressure screening to monitor and detect affected individuals.

Statistics

 In 2000, it was estimated that nearly one billion individuals worldwide were hypertensive. This figure equates to approximately 26.4% of the total global adult population.
The Australian Diabetes, Obesity and Lifestyle Study (AusDiab) conducted in 1999–2000 reported that 30% of Australians (32% of males and 27% of females) over 25 years of age, or 3.7 million Australians, were hypertensive (blood pressure > 140/90 mmHg).
In general, males are more likely to have hypertension than females, except for between the ages of 45 and 64, when females are at equal risk to males.
The incidence of hypertension is three times higher in Indigenous Australians compared to non-indigenous Australians.
 

Risk Factors

Approximately 95% of hypertension cases are classified as essential or primary hypertension, in which the underlying cause is unknown. The remaining cases are classified as secondary hypertension, in which there is an identifiable cause (e.g. renal artery stenosis).
Major studies have identified the following factors as key predisposing factors for hypertension:

• Prehypertensive systolic state (115–139 mmHg);
• Age-dependent increase in diastolic state;
• Female gender;
• Increasing BMI beyond a value of 25;
• Smoking; and
• Parenteral hypertension.

Factors that have been identified in the Australian 2008 National Heart Foundation Hypertension Guidelines include:

• Sedentary lifestyle;
• Smoking;
• Waist measurement > 94 cm in men and 80 cm in women, or BMI > 25;
• High dietary salt intake; and
• Alcohol consumption.

Progression

If hypertension remains uncontrolled, it ultimately leads to end organ damage. Hence, uncontrolled hypertension is the major risk factor for coronary artery disease and stroke – two important endpoints in the disease process.
Similarly, chronic renal failure, diabetes, eye disease, erectile dysfunction and chronic heart failure are also significant diseases associated with the progression of uncontrolled or poorly controlled hypertension.

Symptoms

Most people with hypertension are unaware that they have a problem. This is because hypertension has few, if any symptoms. Therefore, primary hypertension is usually detected through routine screening when visiting a GP. Longterm uncontrolled hypertension is associated with an increased risk of heart attack and stroke, amongst other diseases.

Clinical Examination

Hypertension is assessed via the measurement of blood pressure. A diagnosis of hypertension can be made if, after several readings on separate occasions, an elevated value is consistently recorded.
As a guide, a blood pressure reading greater than 140/90 taken on three different occasions is sufficient to diagnose hypertension.  Ambulatory blood pressure monitoring can also be used to assess average blood pressure readings over a 24 hour period.
In addition to blood pressure measurement, a full cardiovascular exam should be performed, noting any signs of an enlarged heart or arterial disease. Additional examinations that should be included if hypertension is suspected include an eye exam, waist circumference and body mass index.
For more information, see blood pressure investigation.

How is it Diagnosed

Some investigations that may be ordered to assist with diagnosis include:

• Dipstick urinalysis for blood and protein;
• Urinalysis: Spot urine albumin/creatinine ratio
• Blood tests: Urea and electrolytes, lipid profile and fasting blood sugar.
• ECG: To assess for heart enlargement.

More specific investigations may also be required, including:

• Renal artery duplex ultrasoundto exlude renal disease if suspected;
• Renal CT angiography to look for renal artery stenosis;
• Echocardiogarphy to assess for an enlarged heart;
• Carotid Doppler; and
• Plasma aldosterone/renin ratio.

Prognosis

Hypertension at 50 years of age is associated with a 5 year reduction in life expectancy. If hypertension is properly controlled, the risk of stroke reduces by more than the risk of heart attack.

Treatment

The decision about how and when to intervene with hypertension is dependent upon the severity of the diagnosis, the absolute cardiovascular risk profile and the evidence of end organ damage.

Immediate medical intervention
Immediate treatment is required with any of the following:^3,15,16,19

• Severe hypertension;
• Evidence end organ damage (regardless of blood pressure);
• Diabetes where BP > 140/90 mmHg;
• High absolute cardiovascular risk measurement; and
• Indigeneity.

Lifestyle modification
In all circumstances, the first management step is lifestyle modification, focusing on:

• Regular physical activity (minimum 30 minutes a day moderate intensity);
• Smoking cessation;
• Dietary modification (salt intake < 4 g/day, plenty of fruit and vegetables, low fat);
• Weight and waist reduction (aim for BMI < 25, waist < 94 cm (men), 80 cm (women)); and
• Limit or avoid alcohol (one standard drink per day).

Medications
Four major classes of drug are routinely used:

• Diuretics (especially thiazide diuretics);
• Angiotensin converting enzyme inhibitors and the related angiotension II receptor blockers;
• Calcium channel blockers; and
• Beta-blockers.

All of the drug classes appear to have similar short and medium term protective effects, however, issues of tolerability may lead to beta-blockers being considered a second line medication.
Most drugs take 4–8 weeks for maximum effect. Thus, it is recommended that a minimum period of 6 weeks is trialled before changes to medications are made.Generally treatment starts with a single drug. Recent large studies have shown that cheaper, older drugs, are just as effective as newer drugs. If a single drug fails to achieve blood pressure goals, other agents can be added in.

More information

For more information on high blood pressure, including investigations and treatments, as well as some useful animations, videos and tools, see Hypertensions (High Blood Pressure).

References

1. Hypertension. Stedman’s Medical Dictionary [27^th edition]. Baltimore: Lippincott Williams and Wilkins; 2000. 855.
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3. National Blood Pressure and Vascular Disease Advisory Committee. Guide to management of hypertension 2008 [online]. National Heart Foundation of Australia. 1 August 2008 [cited 20 March 2009]. Available from URL http://www.heartfoundation.org.au/ SiteCollectionDocuments/ A%20Hypert%20Guidelines2008%20Guideline.pdf  
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17. Mulatero P, Stowasser M, Loh KC, Fardella CE, Gordon RD, Mosso L, et al. Increased diagnosis of primary aldosteronism, including surgically correctable forms, in centers from five continents. J Clin Endocrinol Metab. 2004; 89:1045-50.
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19. Turnbull F, Neal B, Algert C, Chalmers J, Chapman N, Cutler J, et al. Effects of different blood pressure-lowering regimens on major cardiovascular events in individuals with and without diabetes mellitus: Results of prospectively designed overviews of randomized trials.  Arch Intern Med. 2005; 165(12): 1410-9.
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24. Bangalore S, Parkar S, Grossman E, Messerli FH. A meta-analysis of 94,492 patients with hypertension treated with beta blockers to determine the risk of new-onset diabetes mellitus. Am J Cardiol. 2007; 100(8): 1254-62.
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