When a blood clot blocks a blood vessel, it is a very dangerous situation, as it can mean that parts of the brain, the heart muscle or the lungs no longer receive an adequate blood supply. This can result in a stroke, a heart attack or a pulmonary embolism. There are medications that can dissolve a blood clot—also known as a thrombus. However, depending on the clot's size, getting them to where they are needed can be difficult.