hypertension

Hypertension is a high resting arterial blood pressure. The problem with defining hypertension as a disease state rises from the fact that, in the population, blood pressure varies from person to person with the distribution approaching that of a Bell curve.

There is evidence that having a higher blood pressure predisposes you to having a higher risk of stroke, myocardial infarction (heart attacks) and renal (kidney) damage but the problem is determining the cutoff level.

The currently accepted values for saying someone is hypertensive is a blood pressure that is either above 140 mmHg systolic or above 90 diastolic or both.

Current medical guidelines suggest that anyone with a blood pressure exceeding these values should be treated.

Hypertension = High arterial blood pressure. It is measured in milimeters of mercury (mmHg) using a sphygmomanometer.

Symptoms of Hypertension

It occasionally causes headache, but hypertension per se is asymptomatic. The causes (listed below) may have other symptoms.

Causes of Hypertension

95% of clinical hypertension is "primary" or "essential", meaning idiopathic. The causes of secondary hypertension are three quarters renal, e.g. polycystic kidney disease, acute glormerulonephritis, pyelonephritis, systemic sclerosis, or renovascular ie atheromatous plaques in the renal arteries.

Endocrine causes of secondary hypertension include Conns disease, Cushings disease, phaeochromocytoma and hyperparathyroidism.

Drugs that increase blood pressure include the Combined Oral Contraceptive Pill, Monoamine Oxidase Inhibitors and Steroids.

Other causes of hypertension include pregnancy and coarctation of the aorta.

Why Treat?

The incidence of coronary artery disease and stroke is closely related to average blood pressure.¹ Anti-hypertensive therapy reduces the incidence of stroke and, to a lesser extent, coronary artery disease.

When to Treat

Any cut off point to define hypertension is arbitrary as the higher the blood pressure, the higher the risks. Even a person with an average blood pressure would reduce their risk by anti-hypertensive treatment. In an attempt to balance the risks and costs of treatment with the benefits, A cut off point for treatment of > 140 mmHg systolic or > 90 mmHg diastolic (see measuring blood pressure) is used in practice. Although hypertension seems to increase naturally with age, treating a given blood pressure has more benefit in an elderly person.

Other risk Factors for cardiovascular disease, when present, make it more important to treat hypertension in any particular individual. For example, males, blacks, smokers, diabetics, those with poor diet, a relevent family history, high cholesterol or pre-existing vascular disease benefit more from treatment to lower their blood pressure.

Treatments of Hypertension - Modification of risk factors

lifestyle modifications can reduce blood pressure. For example, reducing the sodium content in the diet, reducing alcohol use, increasing vegetables in the diet, increasing exercise and reducing obesity all help. Stress should also be addressed, particularly in those with personality type 'A'.

Pharmacological Treatment of Hypertension

• Thiazide diuretics eg. bendrofluazide
• beta blockers eg. atenolol
• ACE inhibitors eg. enalapril
• Calcium channel blockers eg nifedipine
• Angiotensin II blockers eg. losartan
• alpha blockers eg. doxazosin

After these, options such as clonidine, and methyldopa can be considerd. Diabetic patients should be started immediately on ACE i. Target blood pressures for diabetic patients are also lower.

1. Chobanian AV, Bakris GL, Black HR, et al. Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Hypertension 2003;42(6):1206-52