Hypertension

Hypertension is one of the most common diseases worldwide, and causes many deaths due to the damage it causes to some of the bodies organs.

Systolic pressure is the pressure when the heart contracts and pumps blood into the arteries. Diastolic pressure is the pressure when the heart relaxes.

Measurement is routinely done on the upper arm, which measures the pressure in the brachial artery. The measurement is in millimeters of mercury (mmHg)

If the blood pressure is elevated, it is termed high blood pressure (hypertension). A patient with a blood pressure that is persistently above 140/90 is generally regarded as having hypertension.

Consequences of Chronic Hypertension
If chronic hypertension is not treated then it is very damaging to the body. However, there are generally no symptoms of hypertension in the early years. This is why it is sometimes called the “silent killer”, as the symptoms usually only become apparent once the damage is severe. 

Untreated chronic hypertension can cause:

• Damage to the kidney – high pressures damage the delicate blood vessels in the kidneys, resulting in chronic kidney disease.
• Damage to the eyes – high pressures damage the delicate blood vessels in the retinas, resulting in impaired vision or even blindness.
• Damage to blood vessels – high pressures in the arteries damages the inner surface of the artery walls, causing or worsening atherosclerosis. Atherosclerosis can cause myocardial infarction or ischemic stroke.
• Damage to the cerebral arteries – high pressures can cause a cerebral artery to rupture, causing a hemorrhagic stoke.
• Damage to the heart – high pressures can cause the left ventricle to increase in size (left ventricular hypertrophy). This can lead to heart failure or cardiac arrhythmias.
• Damage to the aorta – high pressures can weaken the wall of the aorta, causing aortic aneurysm or aortic dissection.

Classification of Hypertension
Hypertension is classified into two types, depending on the cause. Primary hypertension is hypertension that is not caused by a particular medical condition, but instead is caused by a variety of abnormalities. Secondary hypertension is hypertension that is caused by a specific underlying medical disease.

Primary Hypertension
Primary hypertension makes up 90-95% of hypertension cases.

The cause of primary hypertension is complex and due to a combination of factors, for example, natural chemicals in the blood, blood vessel elasticity, diameter of the vessels, volume of circulating blood, and stimulation from the sympathetic nervous system.

The risk factors for developing primary hypertension include smoking cigareaes, excessive alcohol consumption, obesity, having a sedimentary lifestyle, and excess dietary salt intake. These risk factors are modifiable. Unmodifiable risk factors include advanced age and genetic predisposition.

Primary hypertension is treated by taking regular antihypertensive medications. Examples of medications that might be prescribed are:

•  Angiotensin converting enzyme (ACE) inhibitors (such as lisinopril, enalapril)
• Beta-blockers (such as atenolol, propranolol)
• Calcium channel blockers (such as nifedipine, amlodipine)
• Thiazide diuretics (such as hydrochlorothiazide)

Lifestyle modifications may also be required, including consuming a healthy diet that is low in salt and low in cholesterol, as well as regular exercise. Smoking cessation and alcohol reduction is advised for those whom partake in such activities. 

Secondary Hypertension
Secondary hypertension makes up only 5-10% of hypertension cases. Secondary hypertension is  caused by a specific underlying medical disease, such as:

• Kidney disease - which causes hypertension through various mechanisms, such as activating the renin-angiotensin system
• Renal artery stenosis - narrowing of the renal arteries reduces the blood supply to the kidneys. This causes activation of the renin-angiotensin system, which results in the blood pressure being increased
• Certain disorders of the endocrine system, such as excessive production of the thyroid hormone by the thyroid gland (a condition called hyperthyroidism)

Hypertensive Emergency
A hypertensive emergency is when the blood pressure is extremely high. This is generally accepted to be a systolic pressure exceeding 180, or a diastolic pressure exceeding 110. Blood pressures this high acutely damage the organs in the body, and can cause hemorrhagic stroke. Furthermore, extremely high blood pressures can cause cerebral edema. Cerebral edema causes headache, altered vision (such as flashing lights), vomiting, and if severe may cause seizure, confusion and coma.

If there is evidence of organ dysfunction then the blood pressure needs to be reduced aggressively, but not so aggressively to cause cerebral or cardiac hypoperfusion. Intravenous hydralazine may be required, although should be given in small doses with the blood pressure closely monitored.

Pregnancy Induced Hypertension
Please note that pre-eclampsia and eclampsia have not been discussed here. Those conditions and their treatment are discussed elsewhere.