Harvard Heart Letter

When a clot interferes with blood flow

It can happen to anyone, but heart disease increases the risk.

Blood clots are widely known to cause heart attacks and strokes. But many people aren't aware they can also cause venous thromboembolism (or VTE). In VTE, a blood clot slows or stops the flow of blood through the veins, most often in the legs (called deep vein thrombosis, or DVT) or lungs (called pulmonary embolism, or PE).


DVT typically causes pain and swelling in the affected limb. The sensations are uncomfortable enough that most people are compelled to seek medical care. If the clot travels to the lungs, it can be fatal: 25% of people die before—or shortly after—they seek help. People with coronary artery and cardiopulmonary disease are at increased risk for death from PE, and a large clot puts an enormous strain on the heart.

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