A global crisis
The heart is a vital muscle whose main function is to pump blood around the body, beating about 70 times per minute on average.
As humans age, so does the heart, thereby making it less able to pump blood around the body. This usually occurs because the heart has become too weak or stiff. Nowadays, however, more and more younger people are experiencing problems with their hearts. This makes heart-related conditions the leading cause of death worldwide, with the most common being a myocardial infarction, a medical emergency commonly known as a ‘heart attack’. In fact, it is estimated that there are over 100,000 hospital admissions each year in the UK due to a heart attack; that’s one in every five minutes!
Like all other muscles, the heart requires oxygen to function. If it does not receive enough oxygen, its performance deteriorates and the heart muscle begins to die, resulting in a heart attack. What’s more, if the damage is extensive and the patient does not receive treatment promptly, they could die.
Figure 1: Heart attack. This image was created using BioRender.
What causes a heart attack?
Fats and cholesterol are molecules that are essential for humans; they are transported around the body by our blood. However, having too much of both can cause problems.
In particular, the excess fats and cholesterol will begin to accumulate along the walls of our arteries and form what is known as an atheromatous plaque. This plaque essentially reduces the diameter of blood vessels, meaning that less blood can flow through them and thereby resulting in atherosclerosis. When this happens in our coronary arteries (which are the vessels that supply blood to the heart), it is referred to as coronary heart disease.
Eventually, the plaques become so large that they could partially block the blood flow to the heart. And in more severe cases, the plaque could break apart and completely block the artery. They are a number of factors that increase our chance of developing coronary heart disease, such as diet, exercise, smoking, drinking, genetic predisposition, diabetes, and age, which also increase the risk of a heart attack.
Figure 2: The development of coronary heart disease. This image was created using BioRender.
How to identify a heart attack
Knowing the signs of a heart attack and reacting promptly could save your or someone else’s life. Although the symptoms can vary from person to person, most patients feel a sharp pain in the chest.
The pain can begin to feel like it is spreading across your body, back, jaw, and left arm. Meanwhile, other signs include breathlessness, nausea, sweating, as well as feeling weak and light-headed.
In some cases, the person might not have any symptoms at all, and this is known as a silent heart attack. They are more common amongst men or people with diabetes.
Treating a heart attack
If someone is suffering from a heart attack, it is important to re-establish the blood flow to the affected area as quickly as possible and prevent further blockages. To achieve this, doctors have a range of medications and surgical procedures at their disposal.
Medication
Medications are used to break down blockages and prevent the arteries from getting blocked again. For instance, one of the first medications patients receive in an event of a heart attack is aspirin, which helps to prevent blockages from occurring. In some cases, however, treatment with medication is not enough and surgical procedures may be necessary.
Coronary angioplasty
When treatment with medications is deemed to be insufficient, doctors may carry out a surgical procedure known as an angioplasty. This procedure is basically used to widen narrowed arteries.
The process begins with a needle being inserted into the patient’s radial artery (which is located in their wrist) or femoral artery (in the leg). Once that’s done, a long wire is passed through the artery all the way to the site of the blockage in the heart. At the end of the wire is a small balloon covered by a metal mesh called a stent. When the balloon is in place, at the site of the narrowing, it is inflated causing the artery to widen. After that, the balloon is removed and the stent is left there to make sure the artery remains open.
Figure 3: A simple illustration of coronary angioplasty. This image was created using BioRender.
Coronary artery bypass graft
In some cases, an alternative procedure called a coronary artery bypass graft may be required. Here, a vein or artery from another part of the body, usually the arm or leg, is removed and used to circumvent the blockage.
Figure 4: A brief illustration of the coronary artery bypass graft procedure. This image was created using BioRender.
Post-heart attack treatment
Even after successful treatment, in many cases, a heart attack can leave people with permeant damage to their hearts. Over time the heart becomes weaker and less able to pump blood around the body. This is called heart failure and leads to further complications, which must also be treated.
Heart transplant
If the heart is unable to pump blood effectively after the initial heart attack, it may need to be replaced via a procedure called a heart transplant. The replacement heart is donated by an ‘organ donor’, a person who, before passing away, has agreed for their organs (heart, liver, kidney, etc.) to be given to someone else.
The problem is – there are very few hearts available; and in some cases, patients have to wait for years just to receive a new heart.
Scientists have been trying to solve this problem for a while. One idea involves using animal hearts. This has been largely unsuccessful until recently when surgeons in the U.S. successfully performed the first-ever pig-to-human heart transplant using a genetically-modified pig. Although the procedure could save millions of lives, many might disagree with the use of animals for this purpose.
If you think having an animal heart placed inside you is weird, then what about a completely artificial heart? That’s right, scientists are currently attempting to create mechanical devices that will be able to replace damaged hearts. This, in turn, could also help us overcome the ethical issues associated with the use of animals in such a context.
Regenerative medicine
Zebrafish possess the remarkable ability to repair their hearts efficiently, whilst human hearts are, unfortunately, unable to accomplish the same feat.
But, what if we can make them do so?
Over the past 25 years, scientists have been investigating a new approach to treatment, called ‘regenerative medicine’. This branch of medicine aims to develop protocols that utilize stem cells to regrow, repair, or even replace damaged organs and tissues in our bodies.
Unlike other cells in the body, stem cells do not have a specific function. However, they do possess two important qualities that other cells do not. They are able to (1) self-replicate indefinitely, and (2) they can turn into any type of cell in the body.
One approach to regenerative medicine involves growing patches of heart cells (cardiomyocytes) in a Petri dish using stem cells, which are then transplanted onto the damaged area of the heart. Alternatively, the stem cells could be injected directly into the heart. The stem cells that are used can either be taken from certain parts of the body, such as our bones, or they can be produced by turning other cells, such as skin cells, into them. To find out more about this, go and check out the Primer article ‘3D bioprinting of Tissues and Organs’ by Lucy Chen.
Another technique attempts to stimulate the heart to repair itself using medication. As it turns out the heart does contain a small number of stem cells, giving it very limited regenerative capacity. This has sparked interest amongst chemists who are now attempting to design medicines that can enhance these regenerative properties.
As exciting as these techniques might sound, they are still years away from being used routinely in hospitals. But, who knows, you could be the scientist that makes them a reality!
Figure 5: A quick summary of the different regenerative medicine strategies available for cardiologists. This image was created using BioRender.
How to prevent a heart attack
Some of the factors that increase the risk of heart attack are, unfortunately, out of our control (e.g., genetic predisposition and age).
There are however plenty of things we can do. By not smoking, drinking less, exercising more, and eating a healthy and balanced diet, we can considerably reduce the risk of developing coronary heart disease and, as a consequence, the risk of a heart attack.
Final thoughts
A heart attack is an extremely serious medical condition. If you think that you or someone around you might be experiencing a heart attack, call 999 immediately.
For more information on what to do during a heart attack, follow the link: https://www.sja.org.uk/get-advice/first-aid-advice/heart-conditions/heart-attack/. Ultimately, the best cure for a heart attack is prevention. So, take care of your heart, and it will take care of you.
Acknowledgments
I am extremely grateful to Dr. Zhivko Zhelev from the University of Exeter Medical School for his assistance during the writing of this article. I would also like to thank Professor Paolo Madeddu, Professor Gianni Angelini, and Professor Saadeh Suleiman from the University of Bristol Medical School for their expert advice on this topic.
Author
Bozhidar Zhelev
MScR Biochemistry
University of Bristol