Laboratory Testing Before Alteplase Administration in Acute Myocardial Infarction
You do not need to send CBC, PT, or INR before giving alteplase for acute myocardial infarction unless there is clinical suspicion of bleeding abnormality, thrombocytopenia, or known anticoagulant use.
Essential Pre-Treatment Laboratory Testing
Only blood glucose measurement is mandatory before initiating alteplase - this is the single test that must be obtained in all patients before treatment 1, 2. All other laboratory tests should be sent but should not delay treatment unless specific clinical concerns exist 1.
When Coagulation Studies Are Required
You should wait for CBC, PT/INR, and aPTT results before administering alteplase only in these specific circumstances 1:
- Clinical suspicion of bleeding abnormality or thrombocytopenia - if the patient has signs of active bleeding, petechiae, or known hematologic disorder 1
- Known warfarin use - PT/INR must be ≤1.7 and PT <15 seconds by local laboratory standards 1, 3
- Known heparin use - aPTT must be normal 1
- Uncertain anticoagulation history - if you cannot determine whether the patient has been taking anticoagulants 1
Contraindications Based on Laboratory Values
Alteplase should not be administered if coagulation studies reveal 1, 3:
Recommended Laboratory Panel
While these tests should be sent, they should not delay treatment 1, 4:
- Complete blood count with platelets - to detect anemia, thrombocytopenia, or polycythemia 4
- Serum electrolytes and renal function - creatinine and eGFR for medication dosing 4
- Cardiac biomarkers - troponin to confirm myocardial infarction 1, 4
- Coagulation studies - PT/INR and aPTT (unless clinical suspicion warrants waiting) 1, 4
Critical Timing Considerations
Time is muscle in myocardial infarction - every minute of delay increases mortality 1. The benefit of alteplase is greatest when administered early, with efficacy proven up to 12 hours after symptom onset but diminishing effectiveness after this window 5, 6.
For patients without clinical suspicion of coagulopathy or anticoagulant use, treatment can be initiated before laboratory results are available, but should be discontinued if abnormal values return 1.
Common Pitfalls to Avoid
- Never delay treatment for routine laboratory testing in patients without bleeding concerns or known anticoagulant use 1, 2
- Do not confuse stroke and MI protocols - while this guidance applies to MI, stroke guidelines have similar principles but different specific contraindications 1
- Remember that DOAC use within 48 hours is a contraindication unless specific factor Xa or thrombin assays are normal and renal function is normal 1, 3