Deep Vein Thrombosis: Definition & Causes

Instructor: Heather Mangino
In this lesson, you will learn what deep vein thrombosis (DVT) is. This includes learning about how a blood clot develops. You will also discover what types of health conditions cause DVT to form.

What Is Deep Vein Thrombosis?

Believe it or not, plumbing and the cardiac system have many things in common. Just like pipes need to be clear of blockages for running water, the heart's plumbing system needs to flow and pump easily to bring oxygenated blood to the body. The blood that circulates through the body is a system of pipes. Veins are the pipes that bring blood back to the heart so that the blood can receive oxygen. Blood is brought back to the heart with the help of muscles and special flaps of tissue known as valves.

But just like a water pipe can experience blockages, the circulatory system's flow can be interrupted by an obstruction known as deep vein thrombosis (DVT).

Deep Vein Thrombosis Blocking A Vein
Blood Clot

DVT is a blood clot that develops in one of the large deep veins in the circulatory system. The most common areas for blood clots are the legs and pelvis. Occasionally, a blood clot can occur in an arm, if there has been significant trauma to a deep vein. The thrombus, or blood clot, consists of red blood cells and two special enzymes called fibrin and thrombin. Fibrin and thrombin are helpers in the clotting process.


When a pipe gets clogged, a plumber needs to fix it so that water doesn't back up and cause the pipe to burst. The same thing is true for DVT, which can cause blood to back up in the venous system. The increased pressure causes swelling and pain. There is also a risk that too much pressure will cause the clot to be pushed through the bloodstream and block oxygenated blood from reaching the lungs. This is a serious complication that could lead to death if not treated.

When fixing a clogged pipe, plumbers need to figure out what the blockage is and how it got there. Similarly, doctors also need to figure out what caused a blood clot to form. Blood clots can develop if venous flow is slowed down, or the blood is too thick. Some people have health conditions that make blood thicker, such as cancer or heart failure. There are also hereditary blood conditions that can cause thickened blood, such as sickle cell anemia.

Poor circulation can also damage a vein's valves so the blood pools in the vein instead of flowing back to the heart. The pooling is known as venous stasis. Clots can also form if there has been tissue damage, such as when a patient has experienced a trauma like a car accident or surgery. This is because it's a natural process to form clots when part of the body is damaged, but in the case of DVT, the system malfunctions.

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