An early invasive strategy refers to proceeding to coronary angiography with possible percutaneous coronary intervention (PCI or coronary stenting) within 4 to 24 hours of hospital admission. An initial conservative management consists of medical therapy only without plans to proceed to coronary angiography and PCI.

Factors that would warrant an early invasive strategy include:

1. Increased cardiac biomarkers (troponin, CK-MB)
2. New ST segment depression
3. Signs or symptoms of congestive heart failure (rales on examination, hypoxia with pulmonary edema on chest x-ray)
4. Hemodynamic instability
5. Sustained ventricular tachycardia or ventricular fibrillation
6. Recent coronary intervention within 6 months
7. Prior coronary artery bypass grafting
8. High TIMI risk score
9. Reduced left ventricular systolic function (EF < 40%)
10. Recurrent angina at rest or with low level activity
11. High risk findings from non-invasive testing

The ICTUS trial showed no difference in the above approaches in 3 years. The RITA-3 trial showed no difference at 1 year, but there was a reduction of death or myocardial infarction at 5 years in the early invasive arm, mainly in high risk patients which justifies the above approach (only performing angiography/PCI on high risk patients).