Current status of endovascular stroke treatment

Abstract

The management of acute ischemic stroke is rapidly developing.Although acute ischemic stroke is a major cause of adult disability and death, the number of patients requiring emergency endovascular intervention remains unknown, but is a fraction of the overall stroke population. Public health initiatives endeavor to raise public awareness about acute stroke to improve triage for emergency treatment, and the medical community is working to develop stroke services at community and academic medical centers throughout the United States. There is an Accreditation Council for Graduate Medical Education–approved pathway for training in endovascular surgical neuroradiology, the specialty designed to train physicians specifically to treat cerebrovascular diseases. Primary and comprehensive stroke center designations have been defined, yet questions remain about the best delivery model. Telemedicine is available to help community medical centers cope with the complexity of stroke triage and treatment. Should comprehensive care be provided at every community center, or should patients with complex medical needs be triaged to major stroke centers with high-level surgical,intensive care, and endovascular capabilities? Although the answers to these and other questions about stroke care delivery remain unanswered owing to the paucity of empirical data, we are convinced that stroke care regionalization is crucial for delivery of high-quality comprehensive ischemic stroke treatment. A stroke team available 24 hours per day, 7 days per week requires specialty skills in stroke neurology, endovascular surgical neuroradiology, neurosurgery, neurointensive care, anesthesiology, nursing, and technical support for optimal success. Several physician groups with divergent training backgrounds (i.e., interventional neuroradiology, neurosurgery,neurology, peripheral interventional radiology, and cardiology) lay claim to the treatment of stroke patients,particularly the endovascular or interventional methods. Few would challenge neurologists over the responsibility for emergency evaluation and triage of stroke victims for intra intravenous fibrinolysis, even though emergency physicians are most commonly the first to evaluate these patients. There are many unanswered questions about the role of imaging in defining best treatment. Perfusion imaging with CT or MRI appears to have relevance even though its role remains undefined and is the subject of ongoing research. Meanwhile, investigators are exploring new, and perhaps more specific,imaging methods with cerebral metabolic rate of oxygen and cellular acid-base imbalance. There are currently 6 ongoing trials of stroke intervention, many with proprietary technologies and private funding, competing for the same patient population as multicenter trials funded by the NIH. At the same time, much of the interventional stroke treatment currently occurs outside of trials in the community and academic settings without the collection of much-needed data. Market forces will certainly shape future stroke therapy, but it is unclear whether the current combination of private and public funding for these endeavors is the best method of development.

Figure 1

Higher rates of recanalization, approaching 90% in the Penumbra Pivotal Trial, do not correspond with similar rates of clinical improvement after treatment as measured by the modified Rankin scale (mRS) at 90 days. NIHSS indicates National Institutes of Health Scale; TIMI, Thrombolysis in Myocardial Infarction; PROACT II, Prolyse in Acute Cerebral Thromboembolism trial; IMS, Interventional Management of Stroke; and MERCI, Mechanical Embolus Removal in Cerebral Ischemia.

Figure 2

A 44-year-old woman with atrial fibrillation admitted for complaint of dizziness progressing to coma and basilar artery occlusion not responsive to intravenous fibrinolysis with full-dose intravenous recombinant tissue-type plasminogen activator (rtPA; National Institutes of Health Stroke Scale score [NIHSS], 25). A, Nonenhanced computed tomography (CT) brain scan shows no infarction or hemorrhage at the time of rtPA administration 2.5 hours after stroke onset. B and C, Left vertebral arteriogram shows midbasilar artery occlusion (arrow). D, Lateral fluororadiography shows the 0.054-in Penumbra suction catheter near the dorsum clivus at the top of the basilar artery. E and F, Left vertebral arteriography shows recanalization of the basilar artery (straight arrows) with residual thromboembolic occlusion of the distal right posterior cerebral artery (curved arrow) within 6 hours of stroke onset. G and H, selected images from a nonenhanced CT brain scan 24 hours after acute stroke treatment shows only a small area of infarction in the distribution of the right posterior cerebral artery (arrows). After treatment, NIHSS measured 7. At 90 days, the patient experienced residual hemiparesis and diplopia (sixth cranial nerve palsy).

Figure 3

A 67-year-old Hispanic man with acute right hemiplegia and global aphasia of 2-hour duration (National Institutes of Health Stroke Scale score, 23). A, Computed tomography brain scan showed early edema in basal ganglia structures and less than one third of the left middle cerebral artery distribution (arrows). The patient received full-dose intravenous recombinant tissue-type plasminogen activator (rtPA; 0.9 mg/kg). B, With no clinical improvement, he was triaged for emergency catheter arteriography. Left internal carotid arteriography in the frontal projection showed left middle cerebral artery occlusion (arrow). C, Mechanical thrombectomy was unsuccessful. Balloon angioplasty restored a thin channel of blood flow in the left middle cerebral artery (arrow). D, Repeat arteriography shows reocclusion despite systemic anticoagulation with rtPA (arrow). E, Stent angioplasty was performed with a 4.5×14-mm self-expanding nitinol stent (arrow). Successive angiographic images show reperfusion of the left middle cerebral artery with luxury perfusion (curved arrow) in the basal ganglia indicative of tissue injury and loss of autoregulation. F, Magnetic resonance (MR) angiography after the treatment procedure shows the patent vessel despite stent artifact. G, MR imaging with diffusion-weighted images shows restricted diffusion indicative of completed infarction in basal ganglia and scattered throughout the middle cerebral distribution. H, Computed tomography brain scan with perfusion-weighted imaging measuring relative cerebral blood flow shows increased perfusion throughout the left hemisphere after stent revascularization. At the time of discharge to rehabilitation, the patient had moderate hemiparesis (strength 4+/5) and resolving expressive aphasia.

Figure 4

A 13-year-old boy with complex cyanotic heart disease develops acute aphasia and right hemiplegia (National Institutes of Health Stroke Scale score, 26) 4 days after a fenestrated Fontan procedure. The patient was ineligible for intravenous fibrinolysis, and was taken immediately for endovascular treatment within an hour of stroke onset. A and B, Left internal carotid arteriography shows proximal occlusion of the left middle cerebral artery (arrow in image A; ellipsoid in image B). C, Computed tomography brain scan after rapid revascularization shows no evidence of stroke or hemorrhage (arrows in D and E). However, the patient did not improve clinically. F, Repeat computed tomography at 24 hours shows extensive infarction with hemorrhagic conversion. The family withdrew care, and the patient died.

Figure 5

Mortality occurs in approximately one third of stroke patients and symptomatic intracranial hemorrhage (ICH) in ≈10% treated with endovascular procedures despite a trend toward higher rates of recanalization and a reduction in the use of fibrinolytic agents. NINDS rt-PA indicates National Institute of Neurological Disorders Tissue Plasminogen Activator for Acute Ischemic Stroke Trial; rtPA, recombinant tissue-type plasminogen activator; PROACT II, Prolyse in Acute Cerebral Thromboembolism trial; and MERCI, Mechanical Embolus Removal in Cerebral Ischemia trials.