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!
References:
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Neal,
M., J. Medical pharmacology at a glance, 8th edition (2016). ISBN
978-1-118-90240-0 (pbk.)
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Raffa,
R. B., Rawls, S. M., Portyansky Beyzarov, E. Netter's illustrated pharmacology
(2014). ISBN: 978-0-323-22091-0
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Rang,
H. P., Dale, M. M., Ritter, J. M., Flower, R. J. Rang and Dale's pharmacology,
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K. Lippincott illustrated reviews: pharmacology, 6th edition (2015). ISBN
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https://www.grepmed.com/images/7267/cardiology-atrialfibrillation-patientinfo-afib-compared
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https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/symptoms-causes/syc-20373410
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https://www.who.int/news-room/fact-sheets/detail/hypertension
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