12.01.1 Epidemiology and Pathophysiology

Hypertension is high blood pressure, and is defined as anything ³ 140 systolic/90 diastolic mm Hg. It is very common disorder; 3.7 million Australians have hypertension or are being treated for hypertension, which about one-third of the population. Indeed hypertension is the most common cardiovascular disease. The incidence increases with age, such that at birth and in the young, there is a low incidence of hypertension. During middle age, there is an increasing incidence of hypertension, and by old age, there is a very high incidence. Hypertension is considered to be “the silent killer” as, unless the blood pressure is extremely high, there are no symptoms. Nevertheless the hypertension is doing harm. Hypertension is the leading risk factor for mortality (death). High blood pressure alone does not kill you, it is the things it does that hurt or kill you. Hypertension is the principle cause of stroke. Hypertension leads to coronary artery disease with myocardial infarction and sudden cardiac death. Hypertension is the major contributor to retinal haemorrhage (bleeding in eye), heart failure, renal insufficiency, and dissecting aneurysm of aorta (splitting of aorta).

The majority of people with hypertension have essential hypertension. In essential hypertension, the cardiac output is normal, but the total peripheral resistance is increased. The exact cause of essential hypertension is unknown. It is the combination of genetic disease with many loci involved, and environmental factors. The environmental factors include several aspects of a Western lifestyle; stress, smoking, salt, and obesity.

Essential hypertension is associated with pathological changes in heart and blood vessels. These pathological changes are compensatory changes to maintain cardiac output in the face of increasing total peripheral resistance. The heart has a thickening of the left ventricular wall, and this is known as hypertrophy (cardiac hypertrophy). The arteries also have hypertrophy of the smooth muscle, and injury to the endothelial cells lining the blood vessels.

The non-pharmacological treatments of hypertension that are effective an decreasing blood pressure include a body weight reduction, restricting the amount of Na⁺ in the diet, and initiating or increasing exercise. Blood pressure is also lowered when people avoid excessive alcohol or manage to decrease the stress in their lives.

In essential hypertension, the underlying cause is not singular, and this means we do not have a single target for a drug to attack. The treatment of essential hypertension is to lower blood pressure by any mechanism, preferable with as few side effects as possible. As subjects with hypertension lack symptoms, they are intolerant of adverse effect with drugs for hypertension. Other the years, drugs for hypertension have been developed that have few side effects, and, as a consequence, subjects are often prepared to take these on a regular basis. Often diuretics, drugs that increase water loss from the body, are often the initial drugs used to treat essential hypertension.