Robert W. Regenhardt, MD, PhD
@rwregen

International Stroke Conference 2021
March 17–19, 2021
Session: New Frontiers in Endovascular Therapy (122, On Demand)

The session “New Frontiers in Endovascular Therapy” had a great line-up of panelists discussing hot topics in neuroendovascular therapies.  

Dr. Jenny Tsai spoke on a “Combined open vascular and endovascular approach for complex cerebrovascular cases.” She emphasized that open microsurgery has many advantages. In fact, open surgery and endovascular approaches can complement each other. A combined approach may be preferable in several scenarios: 1. Challenging anatomy and disease processes. 2. Limited access by individual approaches. 3. Complimentary treatment effects. Tsai emphasized that combined approaches can sometimes be simpler. In the past, combined approaches have been utilized especially for AVM and vascular tumor treatments, where embolization can be offered in stages before open surgery. However, joint approaches do not always require staging. More centers are developing hybrid combined open and endovascular rooms.

Tsai then described several cases where a combined approach offered distinct advantages to either in isolation. She discussed a case of an indirect CCF. Previously, it had been embolized with Onyx through a transarterial approach; there was significant residual shunting, for which radiosurgery did not provide a benefit. A transvenous approach was considered, but the SOV was not visualized and access into the angular vein by way of the facial vein was not possible. Ultimately, a pterional craniotomy allowed intracranial venous access through the Sylvian vein for Onyx embolization to cure. She subsequently described a case of ICA occlusion causing recurrent symptoms despite medical management. A decision was made to perform CEA for proximal plaque removal and subsequently place a stent distally in the superior cervical ICA that was inaccessible by an open approach. Tsai concluded that standard approaches are preferred for many cases, but there are unique situations where thinking outside the box is necessary, and collaborative surgical and endovascular expertise can be key. 

“Robotics in neuroendovascular treatments” was discussed by Dr. Stavropoula Tjoumakaris. She described that the Corpath GRX (Corindus) is the primary robot in use today. It obtained CE Mark approval in January 2018 and FDA approval in March 2018 for PCI/PVI. The Corpath GRX was used for the first robotic PCI in Dubai in 2018. In the United States, we are currently limited to using it only for extracranial procedures, but intracranial approval is pending. Several centers have utilized the Corpath GRX for carotid stenting. Tjoumakaris stated that the robot requires a two-person team at minimum, one at the bedside and another at the console. Through videos, she demonstrated the preparation and use of the robot. While it requires manual loading of catheters and wires, a separate console can drive the microcatheter and microwire remotely. In the case of stenting, two joysticks are utilized, one for advancing the stent and another for the microcatheter.

Primary benefits of the robot include increased precision, reduced radiation exposure, and the possibility of remote intervention. However, there are some noteworthy limitations in its current state. Implementation requires significant training in robotics and patient simulators. Furthermore, current robots lack haptic feedback, and resistance cannot be felt when advancing devices. There is also additional time required for interventions, approximately 30-45 minutes for carotid stenting. Their group recently published 10 cases of angiography and stenting (Sajja et al. JNIS). Another comparison of robotic vs manual stenting (Weinberg et al. JNS) showed robotic stenting was associated with longer procedure times (85 vs 61 min), but no difference in fluoroscopy times, radiation exposure, technical success, or morbidity. In Canada, the first robotic stent-assisted coil embolization was performed for a left SCA aneurysm. Approval in the United States for intracranial procedures will likely be forthcoming.

Dr. Justin Fraser summarized his group’s translational research approach in “Turning cath lab into a real lab…what’s coming from the bench to the bedside.” His group has started the first thrombectomy sample tissue bank, BACTRAC (Blood and clot thrombectomy registry and collaboration). During clinically indicated thrombectomy, they save three specimens: proximal blood from carotid or vertebral arteries, distal blood from the microcatheter beyond the occlusion, and the thrombus itself. Given the acute nature of thrombectomy, their IRB has allowed 72 hours for consent since these specimens are otherwise disposed of during treatment. They have shown their protocol for sample collection and storage yields good quality RNA and protein. Fraser’s group has shown several cytokines and chemokines (CXCL9, IL1a, IL3) were elevated distally compared to proximally in the blood. Other proteins were also found to be more highly expressed distally, including AXIN1 and SOD1. Interestingly, distal SOD1 protein expression was correlated with smoking. Fraser and colleagues have also utilized flow cytometry to assess cells in blood distal to thrombus; CD4 and CD8 cells were increased, while myeloid and macrophage populations were decreased.

Dr. Ronit Agid discussed “Flat panel cross sectional imaging in neurointervention: Can we skip the CT scanner?” Performing parenchymal imaging and vessel imaging with venous access from within the angiography suite offers several advantages. The most obvious is that there is no need to transfer the patient to a CT scanner. Time saving can be key, especially in acute ischemic stroke diagnosis and treatment. Furthermore, there are less artifacts from metal using cone beam CT in the suite. One downside is that it can be more susceptible to motion artifact, however. Cone beam CT can be performed with or with contrast, which can be administered by arterial or venous injection.

Agid then presented several cases where 3D roadmap and dilute contrast cone beam CTA proved especially useful. She highlighted that cone beam CTA can be used to better assess stent wall apposition and WEB placement. It can also be utilized to better delineate precise perforator anatomy as well as AVM and DAVF feeders. In the case of acute stroke, significant time can be saved. Cone beam CT can rule out hemorrhage. Then, cone beam CTA using IV contrast injection can produce early phase CTA, late phase CTA, and perfusion maps.

“Venous sinus thrombectomy: Should it be the new standard of care?” was asked by Dr. Paul Singh. He feels that while there has been substantial progress in arterial thrombectomy in the setting of stroke, progress has been slower for cerebral venous thrombosis thrombectomy. Singh began by reminding us there are several etiologies to cerebral venous thrombosis: OCPs, pregnancy, malignancy, infections, trauma, hypercoagulable states, and severe dehydration. In terms of anatomy, cerebral venous thrombosis can occur in the superior sagittal sinus (62%), transverse sinus (45%), straight sinus (18%), cortical veins (17%), and internal jugular vein (12%). Both the AHA 2014 and ESO 2017 guidelines recommend that anticoagulation is the mainstay of therapy, while cautiously recommending thrombectomy be considered only in those with high-risk features or a declining neurologic status. The more recent SNIS 2018 guidelines recommended anticoagulation as standard of care but gave more specific indications for thrombectomy consideration: clinical deterioration despite anticoagulation, contraindication to anticoagulation, intracerebral hemorrhage, deep cerebral venous thrombosis, and coma. The TO-ACT Trial compared medical management vs medical management with EVT among high-risk patients. Recanalization was more likely with EVT (79% vs 52%). The trial was stopped early as there was no difference in mRS at 1 year; however, Singh highlights that the EVT group had sicker patients. He highlighted a study by Ilyas et al. (JNIS 2017) that included 235 patients and showed 76% had complete recovery or only mild deficits after treatment with thrombectomy. Singh reminded us that the arterial thrombectomy revolution was only seen after devices improved. Larger inner diameter catheters generate higher suction forces on aspiration. We have recently seen dramatic increases in the size of aspiration catheters over the last decade: 0.054 (in 2012) to 0.060 (in 2013) to 0.070 (in 2015) to 0.074 (in 2019) to 0.088-0.101 (in 2020). Guidelines have not changed pace with the pace of technology advances. Singh concluded that we now have the tools to remove clots safely that couldn’t be removed before.