Thrombolysis softens a thrombus with the help of drugs (fibrinolytics). However, this procedure is only possible for small and fresh thrombi. The synonym for thrombolysis is lysis therapy. The medical specialties for thrombolysis are internal medicine, neurosurgery, and cardiology.
What is thrombolysis?
Thrombolysis softens a thrombus using drugs (fibrinolytics). However, this procedure is only possible for small and fresh thrombi. A pulmonary embolism, stroke, or heart attack can cause thrombi due to clogged blood vessels. These blood clots obstruct 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. Both vascular occlusions and traumatic lesions can result, causing bleeding. Thrombolysis is a physiological mechanism that removes obstructions in the affected organs by dissolving the blood clot. Thrombolysis is performed using tissue-specific plasminogen activators. To prevent serious and life-threatening damage to the affected organs and general health, these thrombi must be dissolved as quickly as possible. To this end, physicians administer drugs to the affected patients as part of a drug therapy known as thrombolysis. The physicians introduce various drugs into the patient’s body systemically through an infusion via the bloodstream or locally at the thrombus. These drugs contain enzymes that cause certain reactions in the patient’s body cells and release agents to activate specific enzymes in the body.
Function, effect, and goals
Strokes, pulmonary embolisms, and heart attacks result from clogged blood vessels. These result from blood clumping together. This process is triggered by the protein fibrin. The precursor of fibrin is fibrinogen, which is constantly present in the bloodstream. This endogenous substance is harmless in itself until it is activated, for example by damage to a vessel wall, and converts into fibrin. The fibrin now forms a fine and dense network that traps blood cells and converts them into a plug that eventually clogs the blood vessels of the affected organs and causes a thrombus. In cardiology, thrombolysis is the “gold standard” today. This drug therapy is also known by the short term “lysis”. To treat a heart attack caused by a thrombus, cardiologists use three active substances: 1) the protein substance streptokinase produced by the bacterium streptococcus, 2) the body’s own protein substance urokinase, which is found in urine and tissue, 3) the genetically produced substance tissue plasminogen activator (tPA), which is similar to an endogenous anti-clotting substance. The tPA substance is particularly used in thrombolysis of stroke patients. Tissue Plasminogen Activator is produced by genetic engineering. This is why it is often abbreviated rtPA, where the first letter stands for recombinant (genetically engineered). In very small quantities, the human body regularly produces tPA, which acts, so to speak, as the body’s own police force in the fight against the effects of harmful substances. As soon as there is a risk of blood coagulation or blood clotting, tPA ensures that these undesirable blood phenomena dissolve in healthy people. If, in the case of a heart attack or stroke, a large blood clot forms with the risk of blood clotting, the rtPA injected by means of thrombolysis activates the body’s own substance plasminogen. This attacks the fibrogen network and the resulting thrombus and dissolves it. Lysis is performed in two ways. In local therapy, the rtPA is brought as close as possible to the clot located in the bloodstream. Infusion distributes the rtPA systemically throughout the body. Which of the two methods physicians use depends on the extent to which the thrombus is accessible. Lysis is also the first acute measure for strokes, as patients recover more quickly from the consequences within a time window of three to four hours if it is successfully applied than patients who have not undergone this drug therapy.The time window for thrombolysis is four hours to rule out life-threatening sequelae. This shows that the principle “time equals brain” is once again justified. To perform thrombolysis successfully, every quarter of an hour counts. Every fifteen minutes of time lost increases the probability that patients can be discharged home in good health by three percent. The earlier thrombolysis is successfully performed, the less patients suffer the consequences of cerebral hemorrhage, cardiac thrombus or pulmonary embolism. The mortality rate decreases by four percent (American NINDS Study of Thrombolysis, U.S. Medical Journal JAMA (2013; 309: 2480-2488).
Risks, side effects, and hazards
Thrombolysis is exclusively a tool for acute emergency situations. It is not suitable for regular use because the drugs involved are associated with a high risk of bleeding. Despite these treatment risks, thrombolysis has become widely accepted as an emergency treatment in recent years after large-scale studies demonstrated that the benefits of this therapy far outweigh the disadvantages associated with its risks. There are some contraindications to lysis. It must not be used in case of allergies to the drugs used. If the symptoms have been present for more than three hours or if they cannot be clearly attributed, lysis must not be used under any circumstances. Other contraindications are a stroke within the last three months and a heart attack within the last three weeks. A major risk of bleeding exists, for example, when cardiac patients are taking blood-clotting medications. Other contraindications are too high or too low blood sugar levels and elevated blood pressure. Before thrombolysis is used, it is essential to perform a computer tomography scan in the event of a suspected stroke to determine whether it is due to an ischemic insult, a reduced blood flow. Lysis therapy must be initiated within the first three hours after the onset of symptoms. Within this time, the patient is taken to the stroke unit of the hospital, where the possibility of a cranial emergency CT (imaging of the skull) is permanently available. This therapy is performed exclusively under the supervision of an experienced physician in neurological intensive care. The performing radiologist must be qualified in the evaluation of cranial computed tomography scans in the early phase of ischemic insult. In addition, interdisciplinary collaboration with a nearby neurosurgical center must be ensured.
