Pressure that keeps us alive

Being under constant pressure can have serious impact on our everyday life. But, being without one spells certain death. We are, of course, talking about the blood pressure. While many people know the problems it can cause, a far lesser amount knows how it works!

Blood pressure is a combination of factors that indicate how strongly the blood pushes the walls of our arteries. It is dependent on the strength of our heart's squeeze, its frequency, the volume it can eject, and the thickness of the blood (not taking into account blood loss from injuries or similar).  

The strength of the heart is called the stroke strength and depends on the thickness of the heart muscle (the myocard) and its condition. If the heart is undamaged and not lacking nutrients, the stroke volume will be easily regulated.

Heart frequency is the number of times the heart can eject blood in a minute. This depends on the availability of several hormones, such as adrenaline and serotonin, and the overall state of the human body. The heart frequency drastically increases while exercising, as well as while performing more pleasurable activities, such as kissing. The shape of the body indirectly plays a role in heart frequency regulation by having a more or less developed musculature. This is due to the blood's main function – oxygen and nutrient distribution. The body with more developed musculature (in better shape) is more efficient with its energy and oxygen consumption than its underdeveloped counterpart, and therefore needs lesser amounts of circulating blood to satisfy its needs in times of muscle contractions, which is always, to some degree. Therefore, the body in „better shape“ will usually have a lower heart frequency.

The heart frequency is defined as coordinated contraction of heart ventricles, also known as the sinus rhythm, which is a cascading jolt of electrical impulses carefully generated and propagated throughout the heart muscle. Ions like sodium, potassium and calcium are responsible for the onset of such contractions and for keeping our heart beating throughout our lives. Too much of those ions can cause more frequent contractions and therefore a higher blood pressure.

The ejected volume of blood from our heart is called the mean stroke volume. It is proportional to the size of the heart, but also on its stroke strength. A larger person will usually have a greater stroke volume than a smaller person.

Blood thickness, or viscosity, is a measure of blood fluidity, or how well it can flow. Thick blood can be a sign of factors such as dehydration, thrombosis, blood infection, diabetes, erythrocyte malfunction, and similar. Parameters which add liquids (usually water) to the blood make it thinner, while parameters which add particles (obstacles to its flow), make it thicker. The thicker the blood is, the more liquid it attracts, and the higher the blood pressure gets.



Picture 1: view of the heart rhythm and its components. As the ventricular pressure rises (blue line), it pumps out the blood from the ventricle, lowering the ventricular volume (purple line), but raise the aortic pressure (aorta is the main artery leading from the heart, red line). The cascading sinus rhythm creates the well-known electrocadiogram (green).

Problems with high blood pressure

High blood pressure, or hypertension, is a common condition in which the force of blood against artery walls is high enough to cause health problems over a prolonged period of time. A person can have high blood pressure for years without exhibiting any symptoms, but it doesn't mean they aren't at risk. The higher the blood pressure, and the longer it persists, the more damage it can cause! Heart attack and stroke are common complications of untreated high blood pressure. It causes hardening and thickening of arteries, also known as atherosclerosis, which, in turn, causes heart attacks and strokes. Aneurysm is another life-threatening condition caused by high blood pressure. A blood vessel wall, especially in the brain can weaken and bulge under constant pressure, and be fatal if it ruptures. Other complications include heart failure from the heart being overworked by the constant pressure, kidney failure from filtering at higher pressure, loss of vision due to glaucoma, troubles with memory and cognition, dementia, and more.

 

What causes unnatural blood pressure?

As previously stated, blood pressure is a result of intricate interplay between various factors, and, as with every other intricate system, it can go awry in many ways. Usually they all balance each other out, but if one of them sticks out too much, blood pressure can rise or fall to a level of concern. Here are several of them explained.

 

Skipping a beat: arrhythmias

Arrhythmias are a series of conditions that have the heart rhythm disorder in common. They can be divided by the place of origin or by frequency distrortion, and they are diagnosed with electrocardiogram.

All of the types of arrhythmia cause palpitations and dizziness, and in more severe cases loss of consciousness. Atrial fibrillation is a common case of arrhythmia where the heart's atrium fires electrical impulses with irregularity, causing the ventricules to not be able to eject the blood in normal volumes.

Picture 2: schematic view of atrial fibrillation

Other types of common arrhythmias include supraventricular tachychardia with its fast and regular heart beats, and ectopic heart beats, which many have experienced, and feel like it's the last beat your heart will ever make.

 

Fibrosis

Fibrosis is the forming of excess connective tissue at the expense of functioning, healthy tissue. If it happens in the heart or the blood vessel walls, it leads to decreased electric impulse propagation, decreased blood availability. It is caused by old wounds, tumors, certain conditions and some aggressive drugs.

 

Ischemia

Ischemia is the lack of oxygen in a certain tissue, or the whole body. The most common cause is aterosclerosis or a blood vessel clot. If ischemia happens in the heart (ischemia of the myocard), it can lead to angina pectoris, which is the characteristic pain spreading through the chest and the neck after physical exertion or excitement. If the angina pectoris persists and isn't treated, it can lead to myocard infraction, also known as a heart attack. This is the complete blockage of the coronary artery, which is often fatal.

Other causes of aberrant blood pressure include obstructive sleep apnea, kidney disease or failure, certain tumors, thyroid problems, congenital defects, cocaine, some medications, and unbalanced diet as the most common cause.

 

All of the causes mentioned influence one of the mechanisms keeping the blood pressure balanced, lowering or elevating it to the extreme. The other parts of it can stabilize high (or low) blood pressure to an extent, but they also falter after a prolonged period of time. The silent killer, as it is commonly called is affecting more than 1.3 billion adults worldwide, with almost half of them being unaware, and with only 1 in every 5 affected having it under control with medication or dietary changes!

The WHO aims to reduce the prevalence of hypertension by 33% by 2030. It's easy to measure, and medications can work wonders for your everyday life!

 

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9.       https://www.who.int/news-room/fact-sheets/detail/hypertension