Hypertension is also known as high blood pressure. It is the rise in the pressure of the blood beyond 140/90mmHg. So, what is blood pressure, how does it rise and why should you be bothered? Let us start from the very beginning:
The blood is part of the circulatory system which is critical for human life. The circulatory system also called the Cardiovascular system consists of the heart, the blood vessels, and the blood. The lymphatic system is also part of the circulatory system. The blood is the major transport medium in the body and it has several functions which include:
- Supply of Oxygen and nutrients and hormones around the body
- Removal of carbon dioxide and waste products from the cells
- Maintenance of body temperature and PH
The human blood moves in a closed system within the circulatory system. The blood vessels are; the arteries that carry oxygenated blood away from the heart to the rest of the body and the veins that carry deoxygenated blood to the heart. The exception to the rule is the pulmonary and umbilical arteries and veins which play reverse roles. The other vessels are the capillaries which are very tiny blood vessels found at the point of connection between arteries and veins where the exchange of nutrients occurs.
The normal heart is a muscular organ the size of a fist weighing about 250 to 350g consisting of 4 chambers. To supply blood, the heart contracts to pump blood out and then rests to fill up. This process produces a rhythm known as the sinus rhythm. Your pulse or heart rate is the number of times your heart beats every minute. At rest, the heart rate is between 60 to 100 times in a person 10 years and above. It is slightly higher in children because of their higher rate of body metabolism.
The force or pressure with which the heart pumps blood is a function of the Cardiac output; which is the amount of blood pumped through the circulatory system in one minute and the Systemic vascular resistance (SVR) also known as Total peripheral resistance. The SVR is the resistance by arteries to blood flow within them, It is the force of blood on the walls of the arteries required to maintain the flow of blood in the arteries.
Therefore, an increase in cardiac output or an increase in SVR can lead to increased blood pressure also known as hypertension. The blood pressure is also regulated by a hormonal system called The renin-angiotensin system (RAS), or renin-angiotensin-aldosterone system (RAAS). This system also regulates fluid and electrolyte balance, as well as systemic vascular resistance.
Blood pressure is measured using 2 figures, the first also known as systole is the maximum pressure when the heart contracts to pump out blood and the second is the minimum pressure when it rests for filling juts before another contraction.
According to the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC), the normal blood pressure is less than 120/80mmHg. Readings of 120-139 systolic or 80-89 diastolic are known as prehypertension, 140-159 or 90-99 is Stage 1 hypertension and greater than 160 systolic or 100 diastolic is stage 2 hypertension. Diagnosis of hypertension by blood pressure measurement of greater the 140/90mmHg measured on 2 different days.
Hypertension can be classified as Primary or essential hypertension or secondary hypertension. In Primary hypertension, also called idiopathic hypertension there is no specific identifiable cause. It is found to be caused by a combination of genetic, lifestyle, and environmental factors. Secondary hypertension on the other hand can be linked to an underlying disease.
Risk factor for hypertension include:
*Nonmodifiable risk factors: As the name implies, these factors cannot be altered or controlled
- Age: With age, the arteries become stiffer, this leads to increased vascular resistance and thus increased blood pressure
- Family history of hypertension: Several studies have shown that family history is a major risk factor for hypertension. In one study, 5000 Sri Lankans were surveyed and it was observed that there is a strong link between the development of hypertension and a family history of the disease
- Race: Hypertension is more common in blacks
- Genetics: The individual make up of a person can predispose them to hypertension
*Modifiable risk factors are factors that can be worked on to reduce your risk of becoming hypertensive:
- Obesity or being overweight: Obesity induces hypertension by several mechanisms. Increase in body weight increases the oxygen and nutrient requirement of your body, it can lead to activation of the Renin-angiotensin system
- Physical inactivity. Physical inactivity can lead to obesity which can in turn lead to hypertension. With Physical inactivity, there is a tendency for higher heart rate and increased Cardiac output
- High salt diet. A high sodium diet can lead to an increase in the volume of blood because salt generally attracts water. The kidney is not able to effectively get rid of the water and increased blood volume means increased cardiac output. Over time, this excess fluid can also damage the kidneys
- smoking: Active and passive smoking leads to arterial stiffness, inflammation and increased adhesion in the blood vessels which increases Vascular resistance and blood pressure
- Alcohol consumption: This increases the risk of hypertension by affecting the Renin-Angiotensin system.
- Stress: Stress leads to the production of cortisol which causes sodium retention and volume expansion
- Other underlying diseases that can cause secondary hypertension like diabetes Mellitus.
Hypertension is called the Silent killer because it generally has no symptoms. A patient with high blood pressure can continue with routine life activities without realizing how much at risk they are. Some patients however have reported cases of headaches, blurred vision, ringing in the ear, and irregular heartbeats.
A hypertensive urgency occurs when the blood pressure reaches 180/110 without any damage to the body organs which is easily managed with antihypertensive medicines while a hypertensive emergency occurs when the blood pressure is uncontrolled and becomes so high leading to complications and affecting the body organs like the brain, kidneys, the eyes and the heart itself amongst others. This can be seen as an aneurysm or ballooning of an artery which can when it bursts can cause a stroke which is bleeding in the brain, damage to the kidneys, heart failure, and heart attack, etc.
The goal of treatment is to prevent end-organ damage. It is well known that prevention is better than cure. The best way to prevent is to control the modifiable risk factors and to regularly check your blood pressure. Dietary Approach to stop Hypertension (DASH) and lifestyle modification are the first-line management for hypertension. Antihypertensive medication can also be added to keep blood pressure under control.