What is Hypertension ?

Hypertension means high blood pressure, that is pressure or tension in the arteries. Arteries are the vessels that carry blood from the pumping heart to all the tissues and organs of the body. Blood pressure measures the force that the blood applies to the walls of the arteries as it flows through them. It's normal for blood pressure to increase when you exert yourself, or when you feel stressed or anxious. But if the blood pressure is consistently higher than normal at rest, this is high blood pressure, also known as hypertension. The systolic blood pressure represents the maximum pressure in the arteries as the heart contracts and pumps blood into the arteries. The diastolic pressure represents the minimum pressure in the arteries as the heart relaxes after the contraction. The diastolic pressure, therefore, reflects the minimum pressure to which the arteries are exposed. Thus an elevation of systolic and/or the diastolic pressure (systolic pressure consistently over 140, and diastolic pressure consistently over 90) is referred to as hypertension. Whereas it was previously thought that diastolic blood pressure elevations were a more important risk factor than systolic elevations, it is now known that for individuals older than 50 years of age systolic hypertension represents a greater risk. Blood pressure depends on the combination of two factors:

  • How forcefully heart pumps blood around the body

  • How narrowed or relaxed the arteries are

Hypertension occurs when blood is forced through the arteries at an increased pressure. Standard blood pressure readings are always written as so many ‘millimeters of mercury’, abbreviated as ‘mmHg’. The systolic pressure is always listed first, then the diastolic pressure. A typical normal blood pressure reading is 120/80 mmHg.


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Types of Hypertension

There are two major types of hypertension:

Primary Hypertension: This type is also called essential hypertension, and it is by far the most common type of hypertension, and is diagnosed in about 95 % of cases. Essential hypertension has no obvious or yet identifiable cause. Although the precise origin of primary hypertension is unknown, both genetic (50%) and environmental (50%) factors play a role. Salt sensitivity, obesity, excessive alcohol consumption, a sedentary lifestyle and a diet low in potassium and other nutrients must be considered. Keep in mind that families not only share a ‘gene-pool’, but also many lifestyle habits. It is this common type of hypertension that is responsible for the term, “the silent killer”. Unfortunately, it rarely causes symptoms or signs that could warn individuals. As a consequence, complications may occur before the hypertension is diagnosed and treated. Therefore, all adults must be screened for hypertension every 2 to 5 years.

Secondary hypertension: It is often caused by reversible factors, and is sometimes curable. Secondary hypertension is high blood pressure caused by another disorder. This may include: Adrenal gland tumours, 2 Cushings syndrome, Kidney disorders such as glomerulonephritis (inflammation of kidneys), renal vascular obstruction or narrowing , renal failure, Use of medication, drugs, or other chemicals, Oral contraceptives, Hemolytic- Uremic syndrome, Chronic alcohol abuse, Hormonal disturbances, Sleep apnea, Stress, Hypo- or hyperthyroidism.

Signs & Symptoms
Most people with high blood pressure have no symptoms. The only way to know whether your blood pressure is high is to have a health professional measure it. In fact, high blood pressure is often called "the silent killer," because it may cause no symptoms for a long time. However there may be many coincidental symptoms that are widely believed to be associated with high blood pressure which include: tiredness, confusion, vision changes, angina-like chest pain (crushing chest pain), heart failure, blood in urine, nosebleed, irregular heartbeat, ear noise or buzzing.

ETIOLOGY

  • AGE: Over time the number of collagen fibres in the arteries and arteriole walls increases, making blood vessels stiffer, reducing elasticity, leading to smaller cross- sectional area of systole, raising arterial pressure

  • High salt intake

  • Sedentary lifestyle

  • Tobacco smoking

  • Alcoholism

  • High levels of saturated fats in the diet

  • Obesity

  • Stress

  • Low birth weight

  • Diabetes mellitus

  • Various genetic causes

  • Occupational, aircraft, and roadway pollution

What is Malignant Hypertension ?

 Malignant hypertension may be a third type of hypertension which is characterized by very high blood pressure usually accompanied by other organ damage. Malignant hypertension is a medical emergency. Multiple organs of the body such as brain, eyes, blood vessels, heart and kidneys may sustain damage. Malignant hypertension is distinct as a late phase in the condition. Systolic blood pressure consistently between 130 and 139 or diastolic blood pressure consistently between 80 and 89 is called pre-hypertension.


PATHOPHYSIOLOGY

  • Inability of the kidney to excrete sodium, resulting in the natriuretic factor being secreted to promote salt excretion

  • Overactive renin- angiotension system leads to vasoconstriction and retention of sodium and water, leading to an increase in blood volume and hypertension

  • Overactive sympathetic nervous system

Treatment of Hypertension

Doctors recommend weight loss and regular exercise as the first steps in treating mild to moderate hypertension. Discontinuing smoking does not directly reduce blood pressure but is important as it reduces the risk of many dangerous outcomes of hypertension such as stroke and heart attack. Mild hypertension is usually treated by diet, exercise and improved physical fitness. A diet rich in fruits and vegetables and fat- free dairy foods and reduction in salt intake lowers blood pressure. Reduction in environmental stressors such as high sound levels and over illumination can be an additional method of ameliorating hypertension.

There are many classes of medications for treating hypertension, together called antihypertensives, which act by lowering blood pressure. 


Commonly used drugs include:

  • Angiotensin converting enzyme(ACE) inhibitors: They stop the production of hormone angiotensin that make blood vessels narrow. As a result vessels expand improving blood flow. Tension in the circulation is also lowered by the kidneys filtering more fluid from blood vessels into urine. Eg-Lisinopril, Captopril.

  • Angiotensin receptor antagonists: They work in a similar way to ACE inhibitors. But instead of stopping the production of hormone angiotensin, they block its action. Eg-Losartan, Valsartan.

  • Beta blockers: They block the effect of the hormone adrenaline and the sympathetic nervous system on the body. This relaxes the heart so that it beats more slowly lowering blood pressure. Eg- metoprolol, atenolol.

  • Alpha blockers: They cause the blood vessels to relax and widen. Cobining them with beta blockers has a greater effect on the resistence in the circulation. Eg- terazosin, prazosin.

  • Calcium channel blockers: They reduce muscle tension in the arteries expanding them and creating more room for blood flow. In addition, they slightly relax the heart muscle so that it beats more slowly reducing blood pressure. Eg-Amlodipine, Verapamil.

  • Diuretics: They help the body get rid of excess salt and fluids via the kidneys. In certain cases they relax blood vessels, reducing the strain on circulation. Eg- chlortalidone, hydrochlorothiazide.

Complications in Hypertension
While elevated blood pressure alone is not an illness it requires proper treatment due to its short- and long-term effects on many organs. The risk associated with hypertension includes:

  • Hypertensive heart disease(CVAs or strokes)

  • Myocardial infarction (heart attack)

  • Hypertensive cardiomyopathy (heart failure due to chronically high blood pressure)

  • Hypertensive retinopathy (damage to the retina)

  • Hypertensive nephropathy (chronic renal failure due to chronically high blood pressure)

  • Hypertension of pregnancy( 10% of women develop high blood pressure during their childbearing age)

Measuring blood pressure is thus one way of assessing the risk of health problems, particularly the risk of having a heart attack or stroke. Some tests to see if hypertension is having an effect on the rest of your body may include: analysis of your urine (protein in your urine may be the first sign of a kidney problem), a blood test, to check the condition and working of your kidneys, a chest X-ray, to identify any enlargement of the heart muscle, an ECG (electrocardiogram), to look for any heart strain and eye checks.

 

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Article Contributed By: Shilpa V
 

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