A pulmonary embolism , a stroke or a heart attack can trigger thrombi due to clogged blood vessels . These blood clots impede the regular flow of blood in the body. One consequence of the thrombus is a deficient supply of blood and oxygen to the cardiovascular system . Cell death and tissue damage release activators that lead to fibrin formation via complex reactions .

This can result in vascular occlusions as well as traumatic lesions that trigger bleeding . Thrombolysis is a physiological mechanism that removes obstacles to interference in the affected organs by dissolving the blood clot. Thrombolysis is carried out using tissue-specific plasminogen activators . In order to prevent serious and life-threatening damage to the affected organs and the general state of health, these thrombi must be dissolved as quickly as possible.

For this purpose, the physicians administer drugs to the affected patients as part of drug therapy, which is known as thrombolysis. Physicians introduce various medications into the patient’s body systemically through an infusion via the bloodstream or locally at the thrombus. These drugs contain enzymes that cause specific reactions in the patient’s body cells and release agents to activate specific enzymes in the body.

Function, effect & goals

Stroke, pulmonary embolism and heart attack are the result of clogged blood vessels. These are caused by the blood clumping together. This process is triggered by the protein fibrin. The precursor to fibrin is fibrinogen, which is constantly in the bloodstream. This endogenous substance in itself is harmless until it is activated, for example by damage to a vascular wall, and is converted into fibrin.The fibrin now forms a fine and dense network that catches blood cells and converts them into a plug that eventually clogs the blood vessels of the affected organs and triggers a thrombus. In cardiology, thrombolysis is now the “gold standard”. This drug therapy is also known under the abbreviation “lysis”. To treat a heart attack caused by a thrombus, cardiologists use three active substances: 1) the protein streptokinase produced by the bacterium streptococci , 2) the body’s own protein urokinase, which is found in urine and tissue, 3) the genetically manufactured substance tissue plasminogen activator ( tPA), which resembles an endogenous anti-coagulant.

The tPA substance is used in particular in the thrombolysis of stroke patients. Tissue Plasminogen Activator is genetically engineered. This is why the abbreviation rtPA is often used, with the first letter standing for recombinant (genetically engineered). The human body regularly produces tPA in very small amounts, which acts as the body’s own police force in the fight against the effects of pollutants. As soon as there is a risk of blood clotting or blood clotting, the tPA ensures that these undesirable blood phenomena are dissolved in healthy people.

If, in the event of a heart attack or a stroke, a larger blood clot forms with the risk of blood clotting, the rtPA injected by means of thrombolysis activates the endogenous substance plasminogen. This attacks the fibrogen network and the resulting thrombus and dissolves it. The lysis is carried out in two ways. In local therapy, the rtPA is delivered as close as possible to the clot in the bloodstream.

Through an infusion, the rtPA is distributed systemically throughout the body. Which of the two methods the physicians use depends on the extent to which the thrombus is accessible. Lysis is also the first acute measure in the case of strokes, since the patients recover more quickly from the consequences within a time window of three to four hours than patients who have not undergone this drug therapy. The time window for thrombolysis is four hours to rule out life-threatening consequential damage. This shows that the principle “time equals brain” is once again justified.

Every quarter of an hour counts to successfully carry out thrombolysis. Every fifteen minutes lost increases the probability that patients can be discharged home safely by three percent. The sooner the thrombolysis is carried out successfully, the less the patients suffer from the consequences of cerebral hemorrhage , cardiac thrombus or pulmonary embolism. The death rate falls by four percent (American NINDS study on thrombolysis, US medical journal JAMA (2013; 309: 2480-2488).

Risks, side effects & dangers

Thrombolysis is exclusively an instrument for acute emergency situations. It is not suitable for regular use because the corresponding drugs are associated with a high risk of bleeding. Despite these treatment risks, thrombolysis has become established as an emergency measure in recent years after large-scale studies have shown that the benefits of this therapy far outweigh the disadvantages associated with the risks.

There are some contraindications to lysis. It must not be used if you are allergic to the medication used. If the symptoms are more than three hours old or if they cannot be clearly assigned, the lysis must never be used. Other contraindications are a stroke within the last three months and a heart attack within the last three weeks. There is a great risk of bleeding, for example, when heart patients take blood-clotting medication. Other contraindications are too high or too low a blood sugar level and high blood pressure .

Before thrombolysis is used, if a stroke is suspected, a computed tomography must be carried out to determine whether this is due to an ischemic insult, i.e. reduced blood flow. Lysis therapy must be initiated within the first three hours after onset of symptoms. Within this time, the patient is taken to the clinic’s stroke unit, where the option of a cranial emergency CT (image of the skull) is always available.

This therapy is carried out exclusively under the supervision of an experienced physician in neurological intensive care medicine. The performing radiologist must be qualified in the evaluation of cranial computed tomography in the early phase of the ischemic insult. In addition, interdisciplinary cooperation with a nearby neurosurgical center must be guaranteed.