Stroke is a medical condition in which poor blood flow to the brain results in cell death. The number of deaths caused by stroke in Chinese residents had reached nearly 1.5 million in 2018. There are two main types of stroke: hemorrhagic stroke and ischemic stroke.
The primary therapeutic goal for patients with AIS is the timely restoration of blood flow to salvageable ischemic brain tissue that is not already infarcted. To achieve this objective, intravenous thrombolysis is used as a standard treatment for all eligible patients. Mechanical thrombectomy (MT), as a frontline endovascular therapy, can be operated jointly with intravenous thrombolysis or independently when intravenous thrombolysis is not applicable in specific patients cases.
MT devices encompass a wide array of endovascular tools for removing thrombi from the neurovasculature in AIS patients. Currently, MT devices mainly consist of applying aspiration device and stent retriever, each approved by the FDA in 2008 and 2012, respectively.
Stent retriever is the latest-generation stroke treatment device. It is a self-expanding stent that is deployed in the occluded vessel to push aside thrombus and entangle it within the stent struts. The stent and thrombus are then withdrawn back into the catheter.
Mechanical Thrombectomy (MT)
Mechanical Thrombectomy (MT) is a type of minimally-invasive therapy in which blood clot is removed from arteries using imaging techniques guiding medical devices through patients’ arteries to the blood clot. During a mechanical thrombectomy procedure, the physician inserts an introducer sheath into the groin area and then passes a micro-catheter into the blocked vessel in the brain. A stent retriever is then navigated within the micro-catheter using X-ray guidance and positioned through the blood clot. After the stent retriever is deployed, the blood clot is embedded within the stent retriever that self-expands and can be safely removed from the body.
Acute Ischemic Stroke (AIS)
Acute Ischemic Stroke (AIS), caused by thrombotic or embolic occlusion of a cerebral artery, is characterized by the sudden loss of blood circulation to an area in the brain, resulting in a corresponding loss of neurologic function. AIS is responsible for almost 90% of all strokes. AIS can be caused by conditions such as old age, gender, race, high blood pressure, unhealthy diet, atrial fibrillation, carotid or other artery disease, physical inactivity and obesity and diabetes.
According to the Chinese Guideline for Endovascular Treatment of Acute Ischemic Stroke 2018, the treatment of acute ischemic stroke has been critical on clearing the obstructed blood vessels as early as possible to save the ischemic penumbra. To achieve this objective, intravenous thrombolysis is used as a standard treatment for all eligible patients. Mechanical thrombectomy (MT), as a frontline endovascular therapy, can be operated jointly with intravenous thrombolysis or independently when intravenous thrombolysis is not applicable in specific patients cases.
As there is strict time window on intravenous thrombolysis, less than 3% of patients can benefit from the above. At the same time, there is huge room for optimization on the treatment results. Since the end of 2014, a series of related studies had been published with more consistent research results. In the screening of patients with anterior ischemic stroke in main vessels, endovascular treatment primarily oriented with mechanical thrombectomy can deliver express benefits. Compared to the 2015 version of China AIS Endovascular Therapy Guide, which recommended using a combination of thrombolytic drugs and MT devices in anterior circulation within six hours based on the onset of AIS, the 2018 version of this guide extended that time window to 24 hours based on imaging-aid diagnosis. The extended time window for MT will largely expand its eligible patient group and potentially cause MT to become a more conventional procedure to treat AIS.
Ischemic Cerebrovascular Disease
Ischemic cerebrovascular disease occurs when blood vessels become blocked, usually from a clot formed from fat and cholesterol, causing blood to not reach the brain and neurons to suffer from a lack of nutrients and oxygen. In general, ischemic cerebrovascular diseases can be categorized into five subtypes based on clinical manifestations: transient ischemic attack, AIS, steal syndrome, intracranial atherosclerotic disease, and other chronic cerebral ischemia.
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Treatments for Cerebral Aneurysm Overview
Endovascular coiling can treat all patients with cerebral aneurysm except for those with severe arteriosclerosis or vasospasm or who are dying and cannot receive embolic treatment, etc. Recommended treatments for subsequent aneurysm subarachnoid hemorrhage also include endovascular coiling. The goal of endovascular coiling is to isolate an aneurysm from normal blood circulation without blocking off any small arteries nearby or narrowing the main vessel.
Endovascular coiling is a minimally invasive technique that is a relatively new method for cerebral aneurysm treatment. It is suited for large aneurysms that are difficult to remove or difficult to access by surgery, patients who are elderly or cannot tolerate surgery due to other diseases, patients who have had unsuccessful surgical clipping, fusiform wide-necked aneurysms, no-necked aneurysms or saccular aneurysms. Devices used in endovascular coiling mainly include embolization coils, intracranial aneurysm stent, vessel reconstruction devices and supporting devices.
Embolization coils are mainly made of tungsten and platinum alloys that come in different sizes and shapes. The coil is released into the cavity of the intracranial aneurysm, causing the blood clot in the cavity to embolize the aneurysm. Common coil release methods include hydrolytic release, electrolytic release, mechanical release, and heat-fusion release.
Cerebral Aneurysm Overview
Cerebral aneurysm, also known as intracranial aneurysm, is characterized by a pathological wall structure with internal elastic lamina and media disruption that leads to focal weakened pouches of the arterial wall. Hemodynamic stress initiates early-stage aneurysm formation. Aneurysm formation progresses when degenerative changes exceed vessel repair due to vascular remodeling. Cerebral aneurysm can put pressure on the nerves or brain tissue, thus causing fatigue, peripheral visual impairment, thinking problems, verbal complications, loss of balance and coordination, etc. The most serious condition of cerebral aneurysms is aneurysm rupture and subsequent aneurysm subarachnoid hemorrhage. According to statistics, the mortality rate of patients with ruptured aneurysms is as high as 66.7%, and for the remaining one-third of patients who can survive, many of them become disabled.
According to the Chinese Expert Consensus on Intravascular Interventional Therapy for Intracranial Aneurysms (2013), the prevalence of intracranial aneurysms was about 2%-7% of the population. It can occur at any age, common in 40-60 years old. Several studies have shown that the occurrence of intracranial aneurysms is related to smoking, alcoholism, hypertension, and gender. The incidence of cerebral aneurysms in China increased from 47.7 million cases in 2014 to 50.5 million cases in 2018 at a CAGR of 1.5%, and is estimated to further increase to 54.9 million cases in 2025 at a CAGR of 1.2% from 2018 to 2025.
Cerebral aneurysm endovascular coiling procedure is an interventional procedure for cerebral aneurysm treatment, which is performed to block blood flow into an aneurysm to isolate an aneurysm from the normal circulation without blocking off any small arteries nearby or narrowing the main vessel.
A hemorrhagic stroke occurs when a blood vessel ruptures within the brain (intracerebral hemorrhage) or into the space surrounding the brain (subarachnoid hemorrhage). Hemorrhagic stroke accounts for about 20% of all strokes. Among patients older than 60 years old, intracerebral hemorrhage is more common than subarachnoid hemorrhage. The number of deaths associated with hemorrhagic stroke in China has decreased steadily year by year, from 868.1 thousand in 2014 to 772.6 thousand in 2018, due to the establishment of more stroke centers, the development of medical therapies treating hemorrhagic stroke, increasing popularity of early screening and detection, and increased awareness of disease prevention.