Fibrinolytic therapy, or thrombolysis, involves administering powerful medications to dissolve dangerous blood clots that cause conditions such as heart attacks (ST-elevation myocardial infarction, STEMI), strokes (acute ischemic stroke), and pulmonary embolisms. However, because these agents act systemically, they carry a significant risk of severe bleeding, particularly intracranial hemorrhage. For this reason, a comprehensive evaluation is always necessary to determine if a patient has any contraindications that would make the therapy unsafe. These contraindications are categorized as either absolute, meaning the therapy is generally prohibited, or relative, where the risks must be carefully weighed against the potential benefits.
Absolute Contraindications: Restrictions to Fibrinolytic Therapy
Absolute contraindications are conditions where the risk of administering a fibrinolytic agent is considered unacceptably high, outweighing any potential benefit. In these cases, the therapy is not given under almost any circumstance.
Prior Intracranial Hemorrhage
A history of any intracranial hemorrhage (ICH), such as a hemorrhagic stroke, is a primary absolute contraindication. The risk of a fatal bleed is exceptionally high when fibrinolytic agents are used in patients with pre-existing cerebral bleeding. Any suspicion of a current ICH, often requiring a CT scan for confirmation, also precludes therapy.
Known Structural Cerebral Vascular Lesion
Patients with known vascular malformations in the brain, such as an arteriovenous malformation (AVM) or an intracranial aneurysm, are at a very high risk of catastrophic bleeding if fibrinolytic drugs are administered. These structural weaknesses can be exacerbated by the clot-busting medication, leading to severe or fatal hemorrhage.
Recent Ischemic Stroke
An ischemic stroke within the last three months is typically considered an absolute contraindication. However, a notable exception exists for acute ischemic stroke treated within the first few hours (often 3 to 4.5 hours), where alteplase therapy is a standard treatment option for eligible patients. The recent infarct increases the risk of hemorrhagic transformation, a complication where the ischemic area starts bleeding.
Significant Head Trauma or Intracranial Surgery
Patients who have experienced significant closed head or facial trauma within three months, or recent intracranial or intraspinal surgery, are not candidates for fibrinolytic therapy. These events can create areas of vulnerability or microhemorrhages that the fibrinolytic agent could cause to bleed catastrophically.
Suspected Aortic Dissection
An aortic dissection, a tear in the inner layer of the aorta, is a critical contraindication because fibrinolytic therapy could worsen the tear and lead to a life-threatening hemorrhage. The medication would act on the already compromised blood vessel, which is a major, life-threatening emergency.
Active Bleeding or Bleeding Diathesis
Active internal bleeding, such as a major gastrointestinal bleed, or a pre-existing bleeding disorder (diathesis) like hemophilia, is an absolute contraindication. Fibrinolytics can exacerbate any active bleeding, leading to uncontrolled hemorrhage.
Relative Contraindications: Balancing Risks and Benefits
Relative contraindications are conditions that increase the risk of bleeding but do not automatically prohibit fibrinolytic therapy. The decision to treat is based on a careful assessment of the individual patient's condition, the severity of the presenting illness (e.g., STEMI or stroke), and the potential for a positive outcome.
Uncontrolled Hypertension
Severe, uncontrolled hypertension (often defined as systolic pressure >180 mmHg or diastolic >110 mmHg) at the time of presentation is a relative contraindication. High blood pressure can increase the risk of an intracranial bleed during therapy. However, if the blood pressure can be safely controlled with medication, the patient may still be eligible.
Recent Major Surgery or Traumatic CPR
Traumatic cardiopulmonary resuscitation (CPR) lasting more than 10 minutes or major surgery within the last three weeks are often considered relative contraindications. These events can cause internal injuries that might bleed if therapy is administered. Similarly, noncompressible vascular punctures performed recently present a risk.
Pregnancy
Pregnancy is a relative contraindication because of the increased risk of bleeding and potential harm to the fetus. The decision to treat is complex and must weigh the risks and benefits for both mother and baby, especially in life-threatening situations like a massive pulmonary embolism.
Concurrent Anticoagulant Use
Patients already on oral anticoagulants, such as warfarin, require careful consideration. If the International Normalized Ratio (INR) is significantly elevated, the risk of hemorrhage is increased. However, depending on the specific drug and circumstances, anticoagulation status might be managed to allow for therapy.
Comparing Absolute vs. Relative Contraindications for Fibrinolytic Therapy
| Feature | Absolute Contraindications | Relative Contraindications |
|---|---|---|
| Neurological History | Prior intracranial hemorrhage, known AVM or neoplasm, recent ischemic stroke (< 3 mos) | Prior ischemic stroke (> 3 mos), dementia |
| Recent Trauma/Surgery | Significant closed-head/facial trauma (< 3 mos), recent intracranial/intraspinal surgery | Major surgery (< 3 wks), traumatic CPR (> 10 min) |
| Active Bleeding | Active internal bleeding, bleeding diathesis | Recent internal bleeding (2-4 wks), active peptic ulcer |
| Cardiovascular Conditions | Suspected aortic dissection | Severe uncontrolled hypertension (at presentation or chronic), pericarditis |
| Other Factors | None specified for all agents | Pregnancy, noncompressible punctures, concurrent anticoagulant use |
| Decision-Making | Therapy is prohibited | Risk-benefit analysis is performed |
Conclusion: The Critical Role of Screening
Fibrinolytic therapy can be a life-saving intervention for patients with acute thrombotic events, but its use is critically dependent on careful patient selection to avoid severe, and potentially fatal, bleeding complications. As demonstrated by the extensive list of restrictions, determining what is a contraindication for fibrinolytic therapy is a complex process that requires a thorough review of the patient's medical history, current clinical status, and the type of vascular event. For instance, a prior intracranial hemorrhage represents an absolute barrier due to its high-risk nature, while uncontrolled hypertension is a relative barrier that may be managed to proceed with treatment. The distinction between absolute and relative contraindications guides clinicians in making informed decisions that prioritize patient safety while maximizing the potential for recovery. The complexity of these assessments highlights why this powerful therapeutic tool must be administered under strict medical supervision. Further insight can be found in a detailed review of thrombolytic therapy provided by the National Institutes of Health(https://www.ncbi.nlm.nih.gov/books/NBK557411/).
