Mechanical Thrombectomy in Acute Stroke: Prospective Pilot Trial of the Solitaire FR Device while Under Conscious Sedation

Materials and Methods

The goal of this pilot study was to prospectively evaluate the feasibility, safety, and efficacy of mechanical thrombectomy using the Solitaire FR device in patients with acute ischemic stroke treated under conscious sedation. We compared our results with the other Solitaire series of patients under general anesthesia.

The protocol for this study received institutional review board approval. Informed consent was obtained from the patients or their relatives.

This was a prospective single-center, single-arm, intention-to-treat study. All patients with acute stroke with relevant neurologic symptoms, as defined by an NIHSS score ≥8, presenting within 6 hours of symptom onset for the anterior circulation and within 24 hours for the posterior circulation, with occlusion of a large intracranial vessel (ICA and/or MCA; basilar artery) depicted on MR imaging (or CT angiography when contraindication) and confirmed by angiography (TICI grade 0 or 1), and without initial spontaneous intracranial hemorrhage were consecutively included. The exclusion criteria were spontaneous NIHSS improvement, recanalization before endovascular treatment viewed on the first angiographic run, and contraindication to endovascular treatment (vascular blush, fistula) determined on the first-run angiogram.

Upon admission, each patient with suspected acute ischemic stroke was examined by an experienced stroke unit neurologist. An acute MR imaging was then performed. Blood pressure, pulse, and respiration rate were monitored continuously and watched by the stroke unit neurologists. The NIHSS score was calculated to determine a clinical severity score. The stroke unit neurologist administered IV tPA (alteplase [Actilyse]; Boehringer, Ingelheim, France) at an effective dose (0.9 mg/kg) within a 4.5-hour window, if no contraindication. The interventional radiologist on call was notified, and when the diagnosis was confirmed, the patient was transferred to the angiography suite (immediately for patients who did not receive intravenous thrombolysis, or after 30–60 minutes with no clinical improvement for those who received it). Because we did not have an anesthesia team dedicated to this procedure, the stroke neurologist provided conscious sedation. All patients received 1 mg of IV midazolam before the arterial puncture. Then, in case of agitation or pain, an IV bolus of 1 mg of midazolam was administered and repeated, if necessary. Standby intubation was not available during the procedures, as anesthesiologists were involved only in severe cases. Blood pressure was lowered with nicardipine in case of uncompensated hypertension, defined as systolic blood pressure exceeding 180 mm Hg or diastolic blood pressure exceeding 110 mm Hg. After the endovascular treatment, the patient was transferred to the stroke intensive care unit.

An acute 3T MR imaging (Achieva 2.1; Philips Healthcare, Best, the Netherlands) was performed to confirm the diagnosis of stroke, locate the occluded vessel, and search for exclusion criteria. DWI was used to assess the extent of the ischemic lesion. A time-of-flight sequence focused on the circle of Willis was used to locate the site of vessel occlusion. T2 gradient-echo imaging was performed to screen for intracranial hemorrhage. Flair-weighted imaging completed the protocol. No perfusion-weighted imaging was acquired. We calculated the ASPECT score on DWI to assess the ischemic severity score for the anterior circulation and pc-ASPECT for posterior circulation.^17,18 In case of MR imaging contraindication, a head CT and CT angiography were performed to confirm the vessel occlusion. The occlusion location was divided into 4 categories: MCA including M1, M1-M2, and M2; ICA; basilar artery; and ICA-MCA tandem occlusion (occlusion of the proximal ICA and MCA).

Three neurointerventionalists performed the mechanical thrombectomy on a biplanar system (Axiom Artis dBA; Siemens, Erlangen, Germany). All patients were treated via a femoral arterial approach while under conscious sedation. In either the anterior or posterior circulation, we used a 6F guide catheter (Chaperon 6F; MicroVention, Aliso Viejo, California) or a 6F long sheath (Flexor Tuohy-Borst; Cook, Bloomington, Indiana) to reach the target artery. No intravenous heparin was administered if an intravenous thrombolysis was performed before the mechanical thrombectomy. If not, 2500 IU of heparin was delivered at this time. Occlusion of the target vessel was verified angiographically and rated on the TICI scale. Using a coaxial system, we advanced a 0.21-inch internal diameter microcatheter (Prowler Select Plus; Cordis, Miami Lakes, Florida, or Rebar −027; ev3) over a guidewire (Tracker Excel 14; Boston Scientific, Natick, Massachusetts) placed through the thrombus. After removal of the guidewire, a microcatheter angiographic run was performed to confirm the correct positioning and visualize the vasculature distal to the thrombus. All patients were treated using the Solitaire FR device (ev3). Under fluoroscopic control, the Solitaire was advanced through the microcatheter across the vessel occlusion and deployed completely by pulling back the microcatheter. An angiographic run was performed to evaluate the correct placement and expansion of the device and control for flow restoration. The stent was kept deployed for 3–5 minutes before retrieval. We did not use a balloon guide catheter to achieve flow arrest, nor did we work with a special aspiration catheter. The unsheathed Solitaire stent and microcatheter were then removed (as a single unit) into the guide catheter, while applying suction through the guide catheter using a 20-mL syringe (VacLok Syringe; Merit Medical, South Jordan, Utah). An angiographic run was performed to evaluate flow restoration. If necessary, the entire process was repeated until the end of the therapeutic window. Groin punctures were routinely closed with an Angio-Seal (St. Jude Medical, Minnetonka, Minnesota). In cases of tandem occlusion, the choice of whether to treat the ICA or MCA occlusion first was decided by the neurointerventionalist, considering technical conditions (tortuous vessel), remaining time to treat, and extent of the lesions. The interruption of the procedure before complete recanalization was decided on a case-by-case basis by the interventional neuroradiologist and the neurologist, according to remaining time to treat, the clinical status of the patient (growing agitation), and vascular anatomy (very atheromatous vessels), avoiding any technical complications or clinical worsening.

Clinical data were recorded for every patient upon admission, at the end of the endovascular procedure, at day 1, at discharge by the neurologists in the stroke unit, and at the 3-month consultation conducted by an independent neurologist. When a face-to-face visit was impossible, the independent neurologist performed the Rankin assessment by phone.

The following time points were collected for every patient: time from symptom onset to the beginning of the endovascular procedure (defined as the first angiographic run); duration of the procedure (from the first to the last angiographic run); and time from symptom onset to recanalization (last angiographic run). Revascularization was assessed on a final angiographic run performed immediately after the end of the procedure. Flow restoration was evaluated by the neurointerventionalist using the TICI flow classification. Symptomatic hemorrhagic events were evaluated using a 24-hour CT. A symptomatic hemorrhagic event was defined as any intracerebral bleeding causing neurologic deterioration (NIHSS increase ≥4).

Schematically, we had 3 categories of results: “recanalized” if TICI score ≥2a, “treatment failure” if we were unable to attempt a recanalization (the stent was not opened), and “no recanalization before exceeded deadline.” The efficacy and safety criteria were evaluated in the whole series and defined according to the trial design and reporting standards for intra-arterial cerebral thrombolysis for acute ischemic stroke suggested by Higashida et al.¹⁹ The main efficacy judgment criterion was functional outcome at 3 months, defined by an mRS ≤2. Recanalization, defined by the final TICI scale on the last angiographic run, and neurologic score, according to NIHSS criteria at 3 months, were secondary outcomes. The main safety outcome was mortality at 3 months. Symptomatic hemorrhage and procedural-linked or procedural-unlinked complication rates were also reported.

The patient characteristics and results were represented by extreme values, mean and standard deviation, median and interquartile range for continuous variables, and by frequencies and proportions for categoric variables. Statistical analysis was performed using Openstat 17.08.10 software (Softonic, Barcelona, Spain).