A drug that dissolves blood clots. Alteplase is used to treat heart attack, stroke, or pulmonary embolism (clot in the artery of the lungs.) Alteplase, which is also known as t-PA, or tissue-type plasminogen activator, is one of several promising drugs to dissolve blockages rather than create detours around them, such as in artery bypass surgery. Alteplase can be used to open clogged arteries during and after an acute heart attack, unlike bypass surgery. which can only prevent one Alteplase may be effective for strokes, but only if it is given within 3 hours of he first symptoms.