Harvard Heart Letter

Blood clots: The good, the bad, and the deadly

Those arising from atherosclerosis and atrial fibrillation can be very dangerous.

When you poke yourself on a thorn while gardening or get a paper cut at the office, your body marshals the forces needed to stop the flow of blood and repair the damage. If it weren't for the blood's ability to clot (form a thrombus, in medicalese), even these minor scrapes of daily living could cause us to bleed uncontrollably. These healing clots also form inside the body at sites of blood vessel injuries. Normally, when the clot's job is done, it dissolves away.

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