In the news, there has been a rush in stories linking Strokes in young and healthy patients, patients who also have COIVD-19.
Strokes in the young and healthy: how is COVID causing clotting disorders?
In the news, there has been a rush in stories linking Strokes in young and healthy patients, patients who also have COIVD-19. This is certainly worrying news, and at first glance, it is difficult to explain. How does a respiratory virus, one that is very similar to the coronavirus responsible for the common cold, cause such serious issues in a completely unrelated organ system? In this two-part series we will first go over the basics of clotting and its function, how clotting can cause problems, and finally how COVID can lead to clotting disorders.
Before we progress, if you or a family member are having any of the following symptoms, contact your local emergency services immediately. Strokes can be devastating, and treatment needs to be given as soon as possible to save as much of the brain as we can. Early recognition can be the difference between manageable long term effects and crippling disability.
Remember, act F.A.S.T
- Facial Droop on one side
- Arm or hand on one side feels numb or weak with reduced power (same in one leg)
- Slurred speech making it difficult to understand
- Time to phone an ambulance
Other symptoms can include sudden loss in balance, sudden loss in vision in one eye, problems swallowing, and more.
PLUGGING A HOLE
We have an intricate network of vessels to transport oxygen, nutrients, and signals to cells and organs across our bodies. Damage to these blood vessels causes blood loss, reduction in oxygen and nutrient delivery to these cells, and organ damage if the issue isn’t rectified. Failure in multiple organ systems across the body will eventually lead to death. Our blood has cells and proteins that work together to form a clot at the site of injury. This acts as a plug to physically stop the leak, but also encourages repair of the blood vessel and surrounding tissue.
A clot can be triggered in three different ways: blood stasis (pooling up in one area), exposure of blood vessel lining, and pro-coagulant factors released into the blood. When triggered a coagulation cascade occurs to form the building blocks of a clot – it works so well that even a small trigger can create a response big enough to repair the damage. These form a mesh trapping platelets and other blood cells into a plug. Immune cells also arrive to destroy any organisms that might enter from the trauma site that caused the injury, and these immune cells also instruct nearby cells to begin the repair process.
As with everything in our body the whole process is very tightly regulated. The cascade has triggers and accelerators, but it also has brakes. These brakes stop a clot from growing too big, or from clots forming spontaneously when they are not needed. They also help dissolve a clot once the vessel is repaired and it isn’t needed.
WHEN IT GOES WRONG
Heart attacks and strokes. These devastating cardiovascular diseases are well recognized by the public as a leading cause of disability and death. Both can be caused by abnormal clotting. How does our finely tuned clotting cascade turn abnormal? Let's go back to the three triggers of blood clotting.
Vessel damage: Eating a high fat and cholesterol diet can cause fatty plaques to build up in our arteries. This is known as atherosclerosis, and it is extremely common. The plaques can narrow your arteries and reduce blood flow. If this happens in your coronary arteries supplying your heart muscles, your heart might not receive enough oxygen when you exercise or exert yourself. This can cause chest pain, known as angina.
If the plaques burst open it can expose the vessel lining, causing a large clot to form. This clot can become dislodged and be carried away by the blood. It will eventually get lodged in a narrow artery, blocking it and stopping blood from entering. The tissue and cells supplied by that artery will not receive oxygen and eventually die. If this happens in the coronary arteries it can cause a heart attack. In the arteries supplying the brain, it can cause a stroke, leading to neurological deficits.
THIS IS THE MOST IMPORTANT LEARNING POINT, and this is why a healthy diet low in fat and sugars is so important.
Stasis: Our heart pumps blood at high pressures through the arteries. But in the veins, there is very little pressure to drive the blood back to the heart. In our arms and head, gravity helps blood flow down to the heart. But from our legs? When we walk the muscles in our legs squeeze the veins and move the blood. Valves make sure this flow is only one way, back to the heart.
If we sit or lie down in one place and don’t move, the blood isn’t pumped back and pools up in our legs, causing a clot to form. This usually happens in our calves (known as a DEEP VEIN THROMBOSIS, or DVT). The calf becomes swollen, painful, red, and hot. If this clot is dislodged, it can end up in our lungs causing a PULMONARY EMBOLISM. A large PE can block blood from entering the lungs and can be fatal. This is why you should take regular walks on long haul flights, to prevent blood from pooling.
Pro-coagulant: Sometimes the factors in our blood responsible for triggering a clot can be triggered accidentally. Cigarette smoke contains many toxins and harmful chemicals that, when inhaled, end up in your blood. These chemicals can cause damage to vessel linings, and also cause the clotting cascade to be triggered more easily. Some medications, such as the Combined Oral Contraceptive Pill, also have a similar effect, though the risk of getting a clot is still very low.
The immune system can also trigger a clot. The protein mesh formed in the blood can also capture bacteria and viruses around an infection site, making it easier for immune cells to find and destroy these invading organisms. In cancer patients, this process is sometimes triggered by unregulated cancer cells.
WHAT HAVE WE LEARNT?
Our clotting system stops us from bleeding to death from a small wound. People who have bleeding disorders are clear examples and need to be extremely careful if they injure themselves. But unregulated, our body can end up harming itself. If there is one thing you should take away from this, it is that a high sugar/high-fat diet with little exercise can directly increase your risk of having a heart attack or stroke. This is why doctors emphasize so much the importance of a good diet and exercise.
In our next blog, we will look at how this clotting problem is implicated in COVID patients.
Dr Rajan Choudhary, UK, Chief Product Officer, Second Medic Inc
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