Thrombolysis is an effective treatment method to dissolve dangerous blood clots within the vessels. It is generally applied in cases of acute ischemic stroke and myocardial infarction because rapid intervention is required in these situations. During thrombolysis, drugs such as tissue plasminogen activator or streptokinase are used to break down the protein called fibrin. It is especially important to perform the procedure within the first 3–4.5 hours after symptom onset in stroke patients. However, the treatment must be administered carefully because side effects such as bleeding or allergic reactions may occur. Therefore, patient selection is of great importance and must be done meticulously.
| Treatment Method | Thrombolysis |
| Definition | A treatment method, usually administered intravenously, used to dissolve a blood clot formed in a blood vessel and restore blood flow. |
| Applications | Used in occlusive conditions caused by clots such as acute ischemic stroke, pulmonary embolism, deep vein thrombosis (DVT), and myocardial infarction (heart attack). |
| Advantages | Early treatment can open the occlusion, salvage the affected tissue, and prevent loss of function; yields effective results especially in stroke and heart attack. |
| Procedure | Typically involves intravenous administration of thrombolytic drugs (like tPA) that dissolve the clot and reopen the vessel; in some cases, a catheter is used to deliver the drug directly to the occluded area. |
| Side Effects | Risk of bleeding (especially in the brain and gastrointestinal system), allergic reactions, hypotension, and rarely embolism formation. |
| Success Rate | High success rate when applied early in acute stroke and myocardial infarction; varies depending on clot size and time to treatment. |
| Follow‑Up | Monitoring for signs of bleeding and vital signs after treatment is crucial; clot resolution can be assessed with MRI, CT, or angiography as needed. |
| Alternative Methods | Thrombectomy (surgical clot removal), anticoagulant therapy (blood thinners to prevent clots), endovascular treatments. |
| Related Conditions | Acute ischemic stroke, pulmonary embolism, deep vein thrombosis, myocardial infarction. |
| Precautions | Use of anticoagulants, bleeding disorders, and active bleeding are contraindications for thrombolysis; assessing the patient’s bleeding risk before the procedure is important. |
Prof. Dr. Özgür KILIÇKESMEZ
Interventional Radiology / Interventional Neuroradiology
What Is Thrombolysis and How Does It Work?
Thrombolysis uses specialized drugs to dissolve blood clots in cerebral vessels and restore blood flow. The most commonly used thrombolytic agents are alteplase and tenecteplase. Alteplase activates plasminogen to plasmin, which breaks down fibrin, and must be administered within 4.5 hours of symptom onset.
Tenecteplase is a genetically modified form with the same effect but greater fibrin specificity, allowing for a single bolus dose. It also has a longer half‑life than alteplase. These drugs offer significant advantages in ischemic stroke treatment because:
- They reduce brain damage and accelerate recovery.
- Tenecteplase allows for easier administration.
- They demonstrate good efficacy and safety profiles.
- Consequently, tenecteplase is increasingly used in thrombolysis therapy.
In Which Cases Is Thrombolysis Applied to Stroke Patients?
Thrombolysis is administered to acute ischemic stroke patients who meet specific criteria to dissolve clots. The standard treatment window is within 4.5 hours of symptom onset. When performed within this timeframe, it yields the most effective results. However, certain key criteria must be met for thrombolysis:
- Ischemic stroke diagnosis must be confirmed through clinical evaluation.
- No major contraindications such as recent surgery, active bleeding, or uncontrolled hypertension.
- Non‑contrast brain CT must show no significant hypodensity.
In some cases, advanced imaging can extend the treatment window beyond 4.5 hours. Therapy may continue up to 9 hours or even 24 hours in select patients by using techniques such as CT perfusion or diffusion‑weighted MRI to identify salvageable brain tissue. These methods enable treatment without strict time constraints.
- Perfusion imaging assesses the ratio between ischemic core and penumbra.
- Clinical trials like EXTEND‑DAWN and DEFUSE‑3 have shown that advanced imaging can extend thrombolysis eligibility up to 24 hours.
*We recommend filling out all fields so we can respond in the best possible way.
What Are the Risks and Complications of Thrombolysis?
Although thrombolysis is used to treat acute ischemic stroke, it carries significant risks and complications. Major complications include hemorrhagic transformation (HT), intracerebral hemorrhage (ICH), and systemic bleeding. Hemorrhagic transformation, a serious complication where brain tissue bleeds, occurs in about 6% of patients after thrombolysis. Risk factors include advanced age, large infarct size, high NIHSS score, hypertension, hyperglycemia, and atrial fibrillation. HT increases both mortality and disability, worsening treatment outcomes.
Intracerebral hemorrhage is another potentially fatal complication, with higher risk in patients with a history of hypertension. Thrombolysis is not recommended for patients with blood pressure over 180/105 mmHg due to increased bleeding risk. Recent major surgery or a history of hemorrhagic stroke also heighten this risk.
Systemic bleeding refers to hemorrhage in other parts of the body, such as the gastrointestinal tract or recent surgical sites, and represents a contraindication for thrombolysis in patients who have undergone recent surgery.
Exclusion Criteria:
- Recent Surgery: Major surgery within the last 14 days.
- Uncontrolled Hypertension: Blood pressure above 185/110 mmHg.
- Coagulopathy: Low platelet count or INR >1.7.
What Are the Latest Advances in Thrombolysis Research?
Recent studies continue to refine the clinical use of tenecteplase and alteplase in acute ischemic stroke treatment. Tenecteplase, a genetically modified form of alteplase, offers longer half‑life and higher fibrin specificity, resulting in faster clot dissolution and improved reperfusion. Trials such as TASTE‑A and EXTEND‑IA TNK have shown that tenecteplase yields better outcomes than alteplase in patients with large vessel occlusion, including improved neurological recovery and functional outcomes at 90 days in pre‑hospital mobile stroke unit settings.
No significant difference in safety profiles between tenecteplase and alteplase has been observed; rates of symptomatic intracranial hemorrhage and mortality are comparable. Meta‑analyses indicate similar 90‑day functional outcomes for both agents, although tenecteplase offers a slight early advantage.
Optimal dosing studies for tenecteplase generally favor 0.25 mg/kg:
- This dose is considered balanced for safety and efficacy.
- Higher doses are associated with increased bleeding risk.
Future research aims to develop more effective protocols by combining thrombolytic therapy with anticoagulants and other interventions.
Frequently Asked Questions
Thrombolysis is indicated for patients with acute ischemic stroke who present within 4.5 hours of symptom onset and have no evidence of intracranial hemorrhage on CT imaging. This treatment increases the chance of post‑stroke independence by approximately one‑third in early presenters. The efficacy of thrombolysis is highly time‑dependent; benefits decrease as treatment initiation is delayed. Rapid assessment and initiation of therapy are critical to maximizing patient outcomes.
Thrombolytic drugs such as alteplase, reteplase, and tenecteplase convert the protein plasminogen into plasmin. Plasmin breaks down fibrin, the main protein component of blood clots, dissolving the clot and restoring blood flow. These agents are critical in treating acute myocardial infarction, pulmonary embolism, and ischemic stroke. Due to bleeding risks, careful patient selection and monitoring are essential during treatment.
Thrombolytic therapy, particularly with alteplase, carries a risk of intracranial hemorrhage, with an excess of 58 bleeds per 1,000 treated cases (95% CI, 49–68) and 25 additional deaths per 1,000 cases within the first 7 days (95% CI, 11–39). In patients on direct oral anticoagulants (DOACs), the risk of symptomatic intracranial hemorrhage is higher. However, in elderly patients (≥80 years) with acute ischemic stroke, intravenous thrombolysis can improve short‑ and long‑term prognosis without significantly increasing intracranial hemorrhage or mortality. The benefit of IV thrombolysis before thrombectomy diminishes as time from symptom onset increases, becoming negligible after approximately 2 hours and 20 minutes. While beneficial, thrombolysis increases bleeding and early death risks, especially in certain patient groups and with delayed treatment.
Yes, vessel occlusion can recur after thrombolysis. Studies show that patients with ≥5% residual pulmonary vascular obstruction (RPVO) after anticoagulant therapy have twice the risk of recurrent venous thromboembolism (VTE) compared to those with <5% RPVO—11.7% vs. 5.8% at one year. Conditions like May‑Thurner syndrome also increase DVT risk after catheter‑directed thrombolysis. Although thrombolysis effectively dissolves existing clots, underlying conditions or residual obstructions maintain recurrence risk.
The duration of the thrombolysis procedure varies by condition and drug delivery method. Intravenous thrombolysis for acute ischemic stroke must be administered within 4.5 hours of symptom onset, with a door‑to‑needle time under 60 minutes. Administration typically involves an initial bolus followed by a 60‑minute infusion. Catheter‑directed thrombolysis for conditions like DVT can last from several hours up to 48 hours, depending on clot size, location, and clinical protocol.
Prof. Dr. Özgür Kılıçkesmez graduated from Cerrahpaşa Medical Faculty in 1997. He completed his specialization at Istanbul Education and Research Hospital. He received training in interventional radiology and oncology in London. He founded the interventional radiology department at Istanbul Çam and Sakura City Hospital and became a professor in 2020. He holds many international awards and certificates, has over 150 scientific publications, and has been cited more than 1500 times. He is currently working at Medicana Ataköy Hospital.
Vaka Örnekleri