“Time is brain”, after a cerebral infarction occurs, is thrombolysis or thrombectomy the preferred approach?

Author: Li Xiaogang, Chief Physician, Peking University Third Hospital

Deputy Director of Neurorehabilitation Group, Chinese Medical Association Neurology Branch

Reviewer: Li Jingjing, Chief Physician, Beijing Tiantan Hospital, Capital Medical University

Stroke, which is commonly called "stroke", is simply a problem with the brain blood vessels.

Stroke is divided into hemorrhagic stroke (cerebral hemorrhage) and ischemic stroke (cerebral infarction). The following mainly introduces the emergency treatment of ischemic stroke.

1. What is the difference between thrombolytic therapy and thrombectomy therapy for ischemic stroke?

Thrombolytic therapy generally refers to intravenous thrombolysis, in which the thrombolytic agent is injected into the vein by infusion.

After an ischemic stroke occurs, many blood clots will form in the blocked arteries. Thrombolytics are injected into the body through the veins. The thrombolytics combine with the fibrin in the blood clots, causing the blood clots to disintegrate, thus achieving the purpose of recanalizing the blood vessels.

If thrombolytic agents are not used, the blood clot can be removed directly from the artery through catheter intervention, which is called intravascular thrombectomy.

The methods of thrombolysis and thrombectomy are completely different, one is through the vein and the other is through the artery. Intravenous thrombolysis is very simple, just like infusion, it can be injected into the vein, while intravascular thrombectomy, the arterial catheter is usually inserted from the femoral artery, which is an invasive operation.

Figure 1 Original copyright image, no permission to reprint

2. How long does it take to be suitable for intravenous thrombolytic therapy after an ischemic stroke?

Thrombolytics cannot be used at any time. They are only effective when used within the effective time window. What is the time window? It is the time from the onset of the disease to the injection of thrombolytics into the patient's blood vessels.

At present, the time window for thrombolytic therapy of ischemic stroke is 4.5 hours, that is, from the onset of the disease to the final use of thrombolytics, the total time is only 4.5 hours. If this time window is exceeded, thrombolytics cannot be used easily, otherwise there may be a risk of bleeding.

What if the onset time exceeds 4.5 hours? Is thrombolysis impossible? According to research, if the onset time is between 4.5 hours and 9 hours, doctors need to use magnetic resonance imaging or multi-modal CT and magnetic resonance imaging to determine whether thrombolysis is possible. In hospitals that have the conditions to use magnetic resonance imaging for further evaluation, the time window can now be extended to 9 hours.

After a stroke, 1.9 million neurons die in the brain for every minute of delay, and 19 million neurons die for every 10-minute delay. Neuronal death is irreversible. If thrombolysis can be performed 10 minutes earlier, 19 million more neurons can be saved. Therefore, there is a saying that "time is brain".

Figure 2 Original copyright image, no permission to reprint

One of the commonly used thrombolytic agents for intravenous thrombolytic therapy is alteplase (rt-PA), which is usually completed in about an hour. After calculating the total dose of the thrombolytic agent based on kilograms of body weight, 10% of the drug is first pushed into the vein, and the remaining 90% of the drug is pumped into the vein using an infusion pump in about an hour.

The effective time window for intravenous thrombolysis is generally only 4.5 hours, and the time window for arterial thrombectomy is generally 6-8 hours. For some special patients, it can even be up to 24 hours through multimodal imaging assessment. If the aorta is blocked and it has been more than 4.5 hours when you come to the hospital, but within 6-8 hours, intravenous thrombolysis cannot be done, and direct arterial thrombectomy can be used, which is also a method.

For cerebral infarction caused by blockage of large arteries, there is another way to do bridging therapy. When the patient arrives at the hospital, he/she will first undergo intravenous thrombolysis within the effective time window of 4.5 hours. During the intravenous thrombolysis, the intra-arterial thrombectomy will be prepared immediately. This combination of treatment methods is called bridging therapy. After all, intravenous thrombolysis is administered intravenously, and the drug concentration reaching the arterial thrombus will be relatively low. It is not easy to dissolve large thrombi. If the thrombi are removed through the artery on the basis of intravenous thrombolysis, the blood vessels will be easily unblocked. Therefore, bridging therapy is often used for blockage of large arteries.

In general, if the ischemic stroke meets the conditions for intravenous thrombolysis, intravenous thrombolysis is preferred. On the basis of intravenous thrombolysis, if the conditions for intra-arterial stent thrombectomy are met, arterial thrombectomy can be performed later. Bridging treatment is done from vein to artery in one go, and the treatment effect will be better.

3. Which ischemic stroke patients cannot undergo thrombolytic therapy?

Thrombolytic agents are only effective within the effective time window, so the time window is very important, but any treatment has indications and contraindications.

For example, if you have had a cerebral hemorrhage before and now have a cerebral infarction, whether you can receive thrombolytic therapy this time should be evaluated based on the previous cerebral hemorrhage situation; thrombolysis cannot be performed if your coagulation function is not good or you have been taking anticoagulants; if you have had surgery recently, thrombolysis cannot be performed to prevent dangerous oozing and bleeding from the surgical wound; if your blood pressure is particularly high, exceeding 185/110 mmHg, you must control your blood pressure below 185/110 mmHg before thrombolysis, otherwise it is easy to bleed after thrombolysis.