Tissue Plasminogen Activator (TPA)

A small piece of plaque (Fig. 5) can be trapped in a brain vessel. This is known as an embolus* (Fig. 6) and this is what causes the stroke.

Figure 5. Plaque in the blood vessel [8].

*The embolus is made of a “net” of blood cells and fibrin which holds it together.

Figure 6. Representation of the embolus [8].

TPA is a protein that enters the bloodstream through an IV and travels to the embolus to break it down (Fig. 7). It needs to be given within 4.5 hours from the time the stroke began in order to be effective [8].

Figure 7. TPA traveling to the blockage [8].

How does TPA break down the embolus?

1. TPA binds to a blood protein on the embolus called plasminogen (Fig. 8).

Figure 8. TPA binding to the plasminogen [8]. 

2. Plasminogen becomes an enzyme called plasmin (Fig. 9). Plasmin breaks apart the fibrin which composed the net holding together the embolus.

Figure 9. Plasminogen becomes plasmin [8]. 

3. The embolus breaks down (Fig. 10).

Figure 10. Embolus breaking down [8].

4. And blood flow is restored (Fig. 11)[8].

Figure 11. Blood flow is seen to be restored [8].

Mechanical Thrombectomy

If the embolus occurs in a blood vessel that is large (i.e. a few diameters), mechanical thrombectomy can be performed to get rid of the embolus, where physicians physically remove the embolus. This is done by making a small incision in the groin and placing catheters (a thin flexible tube) (Fig. 12) or stent retrievers (tiny mesh tubes) (Fig. 13) from the blood vessels of the groin all the way up to the brain where the embolus is. Either a device at the tip of the catheter is used to grab and remove the embolus or the stent retriever (which is inserted into the catheter) expands the artery where the embolus is, causing the embolus to flow into the mesh stent retriever [9].

Figure 12. Intravenous catheter demonstration [10].

Figure 13. Stent retriever demonstration [11].

Carotid Endarterectomy (CEA)

The carotid arteries are blood vessels running along the sides of the neck that supply blood to the brain. When plaque builds (Fig. 14) up in the artery, it can increase the patient’s risk of ischemic stroke since it can restrict blood flow to the brain.

Figure 14. Plaque buildup [12].

A carotid endarterectomy (CEA) (Fig. 15) is a surgery where the removal of any plaque that might be blocking a carotid artery is carried out to reduce the risk of ischemic stroke. This is done by making a small incision in the affected artery and physically removing the plaque from the artery [13, 14].

This is similar to TPA, but instead of using an enzyme to break apart the plaque, a healthcare provider will surgically remove the plaque from the artery [14].

Figure 15. Endarterectomy demonstration [15].

Current Treatment Limitations

Tissue Plasminogen activator:

– Currently, tPA (Fig. 16) is the only drug approved by the FDA to be used clinically. Though, only 10% of patients meet the standard for tPA use as a therapeutic drug.

– tPA must be used within 4.5 hours to have a therapeutic effect [16].

Figure 16. Tissue Plasminogen Activator visualized [17].

Mechanical Thrombectomy:

Limited access to trained providers, Trauma to vessels, Vessel dissection, Vasospasm (Fig. 17) [18].

 

Figure 17. Normal vessel vs. Vasospasm [19].

Carotid Endarterectomy

Restenosis, Myocardial infarction (Fig. 18), Risk of long-term stroke and/or death [20].

Figure 18. Myocardial infarction (heart attack) demonstration [21].