What are the Indications for and Contraindications to Thrombolytics?
Mr. XXX is a 66-year-old male who is postoperative day number one after hip replacement surgery and complains of acute onset of chest pain and shortness of breath. An electrocardiogram (ECG) is performed that shows new ST-segment elevation in leads II, III, and aVF. You are alone in Community General Hospital, which does not have a percutaneous coronary intervention (PCI) team. As you begin treatment, you recall that Good Heart University Hospital has a PCI team and that door-to-catheterization-table time from your hospital to theirs is 90 minutes. You administer oxygen, nitroglycerin, morphine, aspirin, metoprolol, and heparin and contemplate your next step.
ST-elevation myocardial infarction (STEMI) is a myocardial infarction usually associated with acute plaque rupture and occlusion of a coronary artery. In addition to the therapies described earlier, patients with STEMI require immediate reperfusion therapy. This can be achieved with either thrombolytic therapy or percutaneous coronary intervention. Upon identification of STEMI, the practitioner should consider the following.
- Generally, thrombolytics are more effective if given earlier. If presentation is within 3 hours from symptom onset, there is no preference between thrombolytic or percutaneous coronary intervention therapy. After 3 hours PCI (when available) is preferred over thrombolytics.
- Generally, when the risk of mortality is high, PCI is preferred over thrombolytics.
- The higher the patient’s risk of bleeding with thrombolytic therapy, the more strongly the decision should favor PCI.
- When the differences in time for door to balloon and door to needle is less than 1 hour, PCI is preferred.
Indications for Thrombolytic Therapy (All Required)
- Symptoms of myocardial ischemia
- ST elevation greater than 0.1 mV in at least two contiguous leads or new left bundle branch block on presenting ECG
- Onset of symptoms within 12 hours
- Presentation in a facility without capability of percutaneous coronary intervention within 90 minutes or prolonged transport (>1 hour) to such a facility
- Any prior intracranial hemorrhage
- Known cerebral vascular lesion
- Known malignant intracranial neoplasm
- Ischemic stroke within 3 months
- Suspected aortic dissection
- Active bleeding or bleeding diathesis (except menses)
- Significant closed head or facial injury within 3 months
Relative Contraindications to Thrombolytics
- History of chronic, severe, or poorly controlled hypertension
- Severe uncontrolled hypertension on presentation (systolic blood pressure >180 mm Hg or diastolic blood pressure >110 mm Hg)
- History of prior ischemic stroke greater than 3 months, dementia, or known intracranial pathology not covered in contraindications
- Recent traumatic or prolonged cardiopulmonary resuscitation or major surgery (<3 weeks)
- Recent (2 to 4 weeks) internal bleeding
- Noncompressible vascular punctures
- For streptokinase or anistreplase: prior exposure (>5 days ago) or prior allergic reaction
- Active peptic ulcer
- Current use of anticoagulants: the higher the international normalized ratio (INR), the higher the risk of bleeding
Choice of Agents
Thrombolytic agents are all plasminogen activators. They function enzymatically to produce the active compound plasmin from plasminogen. Plasmin functions in the breakdown of thrombus. Three agents are approved for treatment of STEMI. Both reteplase and tenecteplase have the advantage of being bolus administered.
- Altepase: 100 mg over 90 minutes
- Reteplase: 10 units Ã— 2, each over 2 minutes
- Tenecteplase: 30 to 50 mg (depending on weight) bolus
After administration of thrombolytic therapy, the pattern of ST elevation should be monitored over the next 60 to 90 minutes. If signs and symptoms of reperfusion do not occur (relief of symptoms, maintenance or restoration of hemodynamic stability, electrical stability, reduction in initial ST-segment elevation), rescue PCI should be considered.
Before hospital discharge, patients who have had a STEMI and thrombolytic therapy require further risk stratification. This includes structural evaluation echocardiography (ECG) and functional evaluation (stress testing) to determine the need for catheterization and revascularization.