Single-center experience with the new generation Derivo Embolization Device in ruptured dissecting and blister aneurysms

Abstract

Background

Treatment of ruptured dissecting and blister aneurysms is technically challenging with potentially high morbidity and mortality. The Derivo Embolisation Device (Derivo) is a flow diverter stent designed for the treatment of intracranial aneurysms.

Purpose

To assess the safety and feasibility of the Derivo in the treatment of ruptured dissecting and blister aneurysms.

Material and Methods

We retrospectively analyzed all patients with ruptured dissecting and blister aneurysms treated with the Derivo between February 2016 and July 2018. Procedural details, complications, morbidity within 30 days, and angiographic aneurysm occlusion rates, initially and after six months, were assessed.

Results

In 10 patients 11 ruptured dissecting and blister aneurysms were treated with 12 Derivos as monotherapy. No aneurysm rebleeding was observed at follow-up. One treatment-related complication occurred including a coil perforation of an additionally treated aneurysm. One patient died due to brain edema. Initial digital subtraction angiography revealed complete (O’Kelly–Marotta [OKM] classification D) and favorable (OKM D+C) occlusion rate in three aneurysms. Six-month follow-up for digital subtraction angiography and clinical evaluation was available in 6/9 patients with complete (OKM D) occlusion in all aneurysms (6/6). Favorable (modified Rankin Scale [mRS] ≤ 2) and moderate (mRS 3) clinical outcome after a mean follow-up of 10 months was observed in six and two patients, respectively.

Conclusion

Endovascular treatment with the Derivo in ruptured dissecting and blister aneurysms revealed a sufficient initial division of aneurysms from the circulation without rebleeding. The Derivo is associated with high procedural and clinical short-term safety.

Keywords

Ruptured blister aneurysms ruptured dissecting aneurysms Derivo Embolization Device flow diverter

Introduction

The use of flow diverter (FD) implants for reconstructive treatment and vascular remodeling of complex unruptured intracranial aneurysms (UIA) for which conventional reconstructive surgical or endovascular treatment methods are either not feasible or are prone to a high recurrence rate, has been widely accepted in recent years (1). Especially the treatment of ruptured blister aneurysms of the supraclinoid artery and dissecting aneurysms of the posterior circulation is technically challenging. Due to their broad, shallow anatomy and excessive fragility, clipping is technically impossible in most cases. However, the use of FDs for intracranial ruptured dissecting aneurysms (RDAs) and ruptured blister aneurysms (RBAs) has not been widely studied. Only small non-randomized studies are available, reporting encouraging experience with flow diversion in acute ruptured complex aneurysms (2 –4). The need for antiplatelet therapy and risk of rebleeding due to delayed aneurysm occlusion are potential drawbacks to flow diversion that must be considered in the treatment of ruptured aneurysms, especially in the case of highly vulnerable RBAs and RDAs. The Derivo Embolization Device (Derivo) is a novel flow diverter stent that has demonstrated high procedural safety and sufficient occlusion rates in the treatment of UIAs (5). In this case series, we report our single-center experience in treating acutely RDAs and RBAs with the Derivo to evaluate safety, effectiveness, and short-term follow-up.

Material and Methods

This study was a retrospective analysis of the database of the neurointerventional department from the University Duesseldorf with RDAs and RBAs treated acutely by FD implantation. All consecutive cases of subarachnoidal hemorrhage (SAH) secondary to anterior and posterior circulation aneurysms from 2016 to 2018 were included in the analysis. Patient data collection and retrospective analysis was approved by the local Ethics Committee. All procedures performed in the studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Endovascular treatment

All endovascular procedures were performed under general anesthesia and via a right femoral artery approach, using an 8-F femoral artery short sheath. An intravenous bolus of heparin (5000 IU) was given after groin puncture and, if necessary, continued until a targeted activated clotting time of 250–300 s was achieved. An 8-F guiding catheter was placed into the internal carotid artery. In the anterior circulation, a triaxial approach was attempted using an intermediate catheter (Navien 058, Medtronic, Irvine, CA, USA, or Neurobridge 65, Acandis, Pforzheim, Germany). For the posterior circulation, a 7-F or 8-F guiding catheter was placed on the orifice of the vertebral artery and the vessel was accessed either by a Navien 058-072 or Neurobridge 52-65 catheter. The Derivo was delivered through a 0.027-inch microcatheter in all cases. All patients underwent three-dimensional (3D) rotational angiograms to confirm aneurysm size and location and plan FD placement. The appropriate size of the Derivo was chosen according to the proximal parent artery diameter. Delivery of the Derivo was performed under fluoroscopic guidance and confirmed with angiography and non-subtracted images. Device visibility on digital subtraction angiography (DSA) images was rated by each interventionalist by an unvalidated ordinal rating scale as: (i) poor = contour (c) or radiopaque marker (rp) invisible; (ii) moderate = c and rp partially visible; and (iii) good = c and rp complete visible. The decision to use multiple Derivos or adjunctive coiling was left to the discretion of the operator. Patients were monitored postoperatively in the surgical neurological intensive care unit; blood pressure was maintained in the range of 120–140 mmHg systolic unless they developed signs of vasospasm or delayed cerebral ischemia. Timing of the Derivo placement (post-SAH treatment day), number of Derivos used, dose of antiplatelet agents, perioperative management, and clinical and angiographic follow-up were analyzed.

Clinical and imaging follow-up

Patients were monitored for clinical signs of delayed cerebral ischemia and received daily transcranial Doppler monitoring. They also underwent a 6-h post-intervention cranial computed tomography (CT) and CT perfusion (CTP) follow-up for radiographic vasospasm monitoring. CT angiography (CTA) in dual-energy technique for metal artifact reduction was conducted 14–30 days after FD implantation to detect changes in aneurysm configuration that might indicate insufficient aneurysm protection and would require an immediate angiographic control and re-treatment, respectively. A DSA follow-up control study was obtained within six months after treatment. Patency of the parent artery, presence and degree of in-stent stenosis, and residual filling of the aneurysm were evaluated. The O’Kelly–Marotta (OKM) grading scale for flow diversion was used to assess aneurysm occlusion after the procedure and during follow-up as follows: A = total filling (>95%); B = subtotal filling (5–95%); C = entry remnant (<5%); and D = no filling (0%) (6). Favorable aneurysm occlusion was defined as OKM C+D. Furthermore, the extent of intra-aneurysmal contrast stasis was categorized as follows: 1 = no stasis; 2 = moderate stasis; and 3 = significant stasis. A clinical evaluation was conducted whenever patients returned for follow-up imaging. The patients’ clinical conditions at follow-up evaluations were scored using the modified Rankin Scale (mRS). Patients were discharged from the neurointensive care unit and subsequently from the hospital when clinical criteria were met, typically 10–14 days after treatment.

Antiplatelet therapy

Tirofiban (Aggrastat, Correvio, Bielefeld, Germany) was administered immediately after deployment of the Derivo by a bolus dose of 1.25 mg followed by infusion of 0.1 µg/kg/min. The double antiplatelet therapy (acetylsalicyclic acid [ASA] and clopidogrel) was initiated the next day during continuous tirofiban infusion. Tirofiban infusion was stopped 12 h after the loading dose of ASA (500 mg) and clopidogrel (600 mg). ASA 100 mg/day and clopidogrel 75 mg/day were administered for at least six months after treatment, followed by permanent single antiplatelet treatment with ASA 100 mg/day. Platelet inhibition testing was performed using vasodilator-stimulated phosphoprotein-phosphorylation (VASP) assays (7). Levels in the range of 30–60% for clopidogrel were defined as sufficient platelet inhibition. An insufficient response to either drug was treated by dose escalation (e.g. clopidogrel 150 mg/day) or substitution with ticagrelor (90 mg/day).

Results

Demographic, clinical, and aneurysm characteristics

From February 2016 to July 2018 27 patients with 33 intradural aneurysms were treated by flow diversion with the Derivo, of whom 10 patients with 11 RDAs and RBAs were enrolled in this retrospective review. The group included five women and five men (age range = 31–67 years; average age = 48.3 years). All patients presented with SAH detected at unenhanced CT due to a ruptured intracranial aneurysm. Fisher score was in the range of 3–4. World Federation of Neurological Societies (WFNS) scores were in the range of 1–5 (average = 3.0). Treatment decision was made by interdisciplinary consensus, i.e. interventional neuroradiology and neurosurgery. The mean delay between SAH and the endovascular procedure was 1.2 days (range = 0–6 days). Six aneurysms had a dissecting-fusiform morphology and were located at the V4 segment of the vertebral artery (VA; n = 4), the basilar artery (BA; n = 1), and the internal carotid artery (ICA; n = 1). One aneurysm had a dissecting-dysplastic morphology and were located at the posterior cerebral artery (PCA; P1 segment). Three blister aneurysms were located at the ICA. The mean size of the largest diameter of all aneurysms was 8.2 mm (range = 2–15 mm). In seven patients, indication for pre-interventional external ventricular drain (EVD) placement was a reduced level of consciousness and high risk for developing hydrocephalus. One patient required post-interventional EVD placement due to hydrocephalus (Table 1).

Table 1.

Clinical presentation and aneurysm characteristics.

No.	Age (years)	Sex	Clinical history	EVDPre-/post-intervention	Aneurysm characteristics				Parent artery diameter (proximal/distal) (mm)
No.	Age (years)	Sex	Clinical history	EVDPre-/post-intervention	No.	Type	Size (mm): H/L × W × D; (neck)	Location	Parent artery diameter (proximal/distal) (mm)
1	31	F	SAH Fisher 4, WFNS 3	Post	1	Blister	1 × 2 × 2; (2)	Right ICA paraophthalmic	3.7/4.3
2	52	M	SAH Fisher 4, WFNS 5	Pre	1	Dissecting-fusiform	14 × 5.3 × 5.3	Right V4	3.9/2.9
3	35	M	SAH Fisher 3, WFNS 2	–	1	Dissecting-fusiform	4.8 × 10 × 4.8	Right ICA paraophthalmic	4/3.2
4	31	M	SAH Fisher 4, WFNS 1	–	1	Dissecting-fusiform	6 × 3.8 × 4	Basilar artery	2.3/3.6
5	57	F	SAH Fisher 4, WFNS 5	Pre	1	Blister	3.2 × 1.4 × 2.2; (3.2)	Right ICA terminus	3.2/3.5
6	63	F	SAH Fisher 4, WFNS 4	Pre	1	Blister	1.4 × 3.2 × 2.2; (3)	Right ICA paraophthalmic	3.8/3.6
7	41	F	SAH Fisher 4, WFNS 5	Pre	11	Dissecting-fusiformDissecting-dysplastic	15 × 4.5 × 4.5 10 × 4 × 4	Right V4 Left P1	4.4/3.42.3/1.8
8^*	67	F	SAH Fisher 4, WFNS 2	Pre	11	Saccular-dysplasticSaccular	4.6 × 7.2 × 4.5; (7.2)4 × 4 × 4; (2)	Right ICA paraophthalmicRight ICA (PCOM)	3.6/3
9	61	M	SAH Fisher 3, WFNS 1	Pre	1	Dissecting-fusiform	12 × 5 × 5	Right V4	4/3
10	45	M	SAH Fisher 4, WFNS 2	Pre	1	Dissecting-fusiform	10 × 4 × 4	Right V4	3.8/3

*Case 8: right ICA (PCOM) aneurysm was treated by coiling alone.

H: height; W: width; D: depth; L: length (in dissecting-fusiform aneurysms); SAH: subarachnoidal hemorrhage; ICA: internal carotid artery; EVD: external ventricular drain.

Treatment and adverse events

Procedural data are summarized in Table 2. Ten patients were treated with Derivo as monotherapy. The diameter of used devices was in the range of 3.5 × 15 mm to 5.0 × 20 mm. In all 10 patients; Derivo deployment was technically successful with complete wall apposition of the device. All Derivos were clearly visible during the procedure and visibility was rated good in all cases. One patient had two overlapped Derivos placed because of increased aneurysm inflow (Case 3); in another patient, two Derivos were used because of bilateral aneurysms (Case 7). Ten arterial side branches were covered (including ophthalmic artery [OA], posterior communicating artery [PCOM], anterior choroideal artery [AChA], anterior inferior cerebellar artery [AICA]) and all of them were patent at the end of the procedure. Immediate angiographic outcomes are presented in Table 3. Complete immediate angiographic occlusion (OKM D) was achieved in two aneurysms and functional occlusion in one further aneurysm (OKM C). None of the aneurysms re-bled after the implantation of the Derivo. No intraprocedural Derivo device related events (aneurysm perforation by intraluminal device prolapse, dissection, vasospasm, incomplete device opening, thrombosis, contrast extravasation) occurred. One patient (Case 7) died one day after endovascular treatment because of a generalized brain edema. This patient initially presented with SAH Fisher 4 and suddenly deteriorated in the emergency room (WFNS 5). Emergent CTP revealed a severe cerebral perfusion restriction. The patient underwent intubation and EVD placement. Subsequent endovascular treatment was uneventful. Since the causal aneurysm for severe SAH could not be identified free of any doubt, and both aneurysms (right V4 segment and left PCA) could have been responsible, we decided to treat both aneurysms (Fig. 1). Follow-up CTs demonstrated a massive generalized brain edema with transtentorial herniation and cerebellar infarction. One patient (Case 8) had a dissecting aneurysm and a saccular PCOM aneurysm of the right ICA. The additional saccular aneurysm was treated by coil embolization. Similar to case 7, it could not be ruled out that the saccular aneurysm was responsible for the SAH and thus both the dissecting and the saccular aneurysm were treated. A small amount of contrast extravasation occurred due to coil prolapse in the saccular PCOM aneurysm. The subsequent implantation of the Derivo at the dissecting-dysplastic paraophthalmic target aneurysm was uneventful. Increase of SAH was excluded by follow-up CT. Vasospasm at days 8 and 17 was successfully treated by nimodipine infusion into both ICA (2 × 0.8 mg nimodipine/ICA). In one patient (Case 2) a symptomatic intraparenchymal bleeding occurred a few days after intervention. Tirofiban infusion was stopped for 12 h after an intraparenchymal bleeding around an EVD was depicted on CTA. Following evacuation of the hematoma, and when no new bleeding had been found in a follow-up non-enhanced cranial CT, Tirofiban was continued with 0.1 µg/kg/min without further complications.

Table 2.

Procedural data.

Case no.	Type/Location	No device	Device size (mm)	Endovascular strategy		Days to treatment	Anticoagulation/platelet inhibition at procedure	Intraprocedural complications/comments
Case no.	Type/Location	No device	Device size (mm)	FD	Coiling	Days to treatment	Anticoagulation/platelet inhibition at procedure	Intraprocedural complications/comments
1	BlisterRight ICA paraopthalmic	1	4.5 × 25	Single FD	No	1	Heparin/Tirofiban	No
2	DissectingRight V4	1	4.5 × 25	Single FD	No	0	Heparin/Tirofiban	No
3	DissectingRight ICA paraopthalmic	2	4.5 × 204.5 × 20	Double FD (Stent in Stent)	No	1	Heparin/Tirofiban	No
4	DissectingBasilar artery	1	4.5 × 20	Single FD	No	1	Heparin/Tirofiban	No
5	Blister Right ICA terminus	1	4.5 × 30	Single FD	No	2	Heparin/Tirofiban	No
6	BlisterRight ICA paraopthalmic	1	4.5 × 25	Single FD	No	1	Heparin/Tirofiban	No
7*	DissectingRight V4DissectingLeft P1	2	4.5 × 303.5 × 15	Single FDSingle FD	NoNo	00	Heparin/Tirofiban	NoNo
8*	1. SaccularRight ICA2. SaccularRight ICA PCOM	1	4.5 × 25	Single FD	1. No2. Coiling alone	0	Heparin/Tirofiban	Rupture due to coil prolapse of right sided ICA aneurysm (PCOM)
9	DissectingRight V4	1	5 × 20	Single FD	No	6	Heparin/Tirofiban	No
10	DissectingRight V4	1	4 × 40	Single FD	No	0	Heparin/Tirofiban	No

*Cases 7 and 8 are described in detail in the “Results” section.

FD: flow diverter; ICA: internal carotid artery.

Table 3.

Angiographic and clinical follow-up.

Case no.	Location	Initial DSAocclusion rates	CTA 30-day follow-up Change of aneurysm configuration	DSA 6-month occlusion rates	Covered side branches6-month DSA	Postprocedural complications/morbidity/mortality	Clinical follow-up, mRS at last follow-up (days)
1	Right ICA paraophthalmic	D	No	D	OA, AChA, PCOM patent	None	mRS 0 (750)
2	Right V4	A3	No	D	PICA patent	Symptomatic EVD-tract hemorrhage day 8, EVD revision, hydrocephalus	mRS 2 (630)
3	Right ICA paraophthalmic	A2	No	D	OA patent	None	mRS 0 (360)
4	Basilar artery	C1	No	D	AICA (bilateral) patent	None	mRS 0 (450)
5	Right ICA terminus	B2	No	n.a.	OA patent	None	mRS 3 (487)
6	Right ICA paraophthalmic	A1	No	D	OA patent	Pneumonia, poor clopidogrel response required escalation to 2 × 75 mg clopidogrel/day	mRS 0 (240)
7	Right V4Left P1	A3A3	n.a.	n.a.n.a.	n.a.n.a.	Death due to generalized brain edema day 1	mRS 6 (1)
8	Right ICA paraophthalmic	A2	n.a.	n.a.B3^*	OA patent	Vasospasm day 8, day 17	mRS 3 (101)
9	Right V4	D	No	n.a.	n.c.	Pulmonal infection, increased ICP	mRS 4 (91)
10	Right V4	B3	No	D	n.c.	Asymptomatic EVD tract hemorrhage after removal, poor response required double clopidogrel dose (2 × 75 mg/day)	mRS 1 (180)

*Angiography at second spasmolysis 17 days after treatment revealed OKM B3.

OA: ophthalmic artery; AChA: anterior choroideal artery; PCOM: posterior communicating artery; PICA: posterior inferior cerebellar artery; AICA: anterior inferior cerebellar artery; n.a.: not available; n.c.: no covered side branches; ICP: intracranial pressure; ICA: internal carotid artery.

Fig. 1.

(a, f) Non-enhanced CT shows SAH in the supratentorial basal cisterns and the premedullary cistern (arrowhead). (b, c) DSA and 3D rotational angiogram of the left P1 segment and (g, h, j, k) right V4 segment demonstrated dissecting aneurysms, of which both had to be considered as the potential cause for SAH. (d, i) The unsubstracted angiogram shows the completely opened FD in the left P1 segment and the partially opened FD in the right V4 segment during deployment, which cover the dissecting aneurysms. (e) The final DSA series shows nearly complete occlusion of the dysplastic part of the P1 aneurysm. (i, l) Wall-associated stasis in the V4 aneurysm can already be observed in the early venous phase.SAH: subarachnoidal hemorrhage; DSA: digital subtraction angiography; FD: flow diverter.

The patients mRS was 3 at follow-up after 21 months. One patient had an asymptomatic intraparenchymal tract hemorrhage after EVD removal and had a mRS 1 when discharged to rehabilitation (Case 10).

Follow-up evaluations

A clinical evaluation was conducted 1 day–25 months (mean = 10.9 months) after the endovascular treatment: mRS 0 = 4, mRS 1 = 1, mRS 2 = 1, mRS 3 = 2, mRS 4 = 1, and mRS 6 = 1 (Table 3). Six-month DSA follow-up was available in 6/9 surviving patients and demonstrated complete aneurysms occlusion (OKM D) without hemodynamic relevant in-stent stenosis or fish-mouthing in all 6/6 aneurysms. A low-grade stenosis due to a hyperplasia at the proximal end of the FD was observed in one patient with a paraopthalmic blister aneurysm (Case 6). Among the other three patients from the entire case series without six-month angiographic follow-up, DSA already showed complete aneurysm occlusion at initial angiogram in Case 9. In all 8/10 patients available for 30-day CTA follow-up, no changes of aneurysm configuration that might indicate aneurysm growth were detected. No clinical and angiographic side branch occlusion or perforator infarction was observed during the follow-up period.

Discussion

In this small single-center case series we report our experience in the treatment of RDAs and RBAs with the Derivo Embolization Device. The treatment of these aneurysms by flow diversion was feasible without procedure-associated intra- or post-interventional complications. Two patients suffered from bleeding in the EVD tract, one of which was symptomatic. Clinical outcome in this small patient collective was overall favorable compared to other smaller case series and reports (2,3,8). RDAs and RBAs are associated with a very high risk of rebleeding when left untreated (9,10). Open surgical techniques carry a high risk of morbidity and mortality, predominantly due to intraoperative rupture due to the fragility of the parent vessel wall (11,12). In particular, the fusiform morphology and lack of a defined neck makes conventional endovascular techniques and surgical clipping impossible or inadequate in many cases (13,14). The placement of coils into the saccular component of acutely ruptured intracranial aneurysms (IAs) and especially blister aneurysms is a potentially dangerous maneuver and may lead to perforation and re-hemorrhage (15,16). In this context, the advantage of sole FD treatment might be that direct manipulation of the lesion is not required. Endovascular treatment by flow diversion represents a promising alternative also in ruptured intracranial aneurysms, with lower mortality and morbidity compared to open surgical techniques (3,4,8,15,17,18). The use of FDs in acutely ruptured wide-neck, fusiform-dissecting, or blister aneurysms has been reported in several case series, but the experience in the treatment of acute aneurysmal SAH is limited (2 –4,17,18). After FD implantation, a remodeling process over the course of weeks leads to occlusion of the aneurysm, whereas a protective effect seems to come into effect immediately after FD implantation, supposedly by reducing the hemodynamic stress on the aneurysm and parent vessel wall by diversion of the flow and mechanical stabilization (19,20). However, the process of gradual aneurysm thrombosis may be prolonged and the need for dual antiplatelet therapy after FD implantation may be an increased risk of rebleeding. Contrarily, a meta-analysis of endovascular treatment of ruptured blister-like aneurysms in that FDs were used in a subgroup, as well as results from smaller studies and reports, which used FDs as the primary treatment, indicating that these risks are not substantial, and RBAs and RDAs may benefit as reported from FD treatment without an increased risk of rebleeding compared to deconstructive techniques (2,3,8,15,17,18,21 –24). In line with the literature, no events of rebleeding after short- and mid-term clinical follow-up were observed in our case series after FD treatment. DSA follow-up of the present case series was available in 6/9 surviving patients at six months follow-up and revealed complete aneurysm occlusion in all patients. These results correspond to reported occlusion rates in several smaller case series, in the range of 63–86%, in that blister and dissecting aneurysms were treated by flow diversion with various FD devices (2,3,8,23,24). In a recent meta-analysis, the rate of hemorrhagic or ischemic complications in the acute phase of SAH in various types of ruptured intracranial aneurysms treated by FD were 16% (25). Peri-procedural complications for treatment of RBAs with FD were reported with a rate of 17% including stroke and morbidity, and a periprocedural mortality rate of 8.7% (15). A high correlation between perforator infarction and the posterior circulation after FD implantation is reported, although those from the BA usually remain patent after FD implantation (16). Whenever possible, we avoided coverage of perforators or side branches (Fig. 2). In cases where such a coverage was unavoidable, no ischemic stroke or perforator infarction occurred (Fig. 3). In-stent thrombosis or stenosis leading to stroke are rare complications, which have been described in association with FD treatment (18). FDs are thought to be more thrombogenic than other intracranial stents, so that dual antiplatelet therapy is mandatory but the optimal antiplatelet regimen for FD in the acute phase of SAH has still to be determined (26,27). The use of dual antiplatelet therapy may increase the risk of a major bleeding in neurosurgical procedures, such as EVD placement or decompressive craniectomy. The authors approach the problem of the antiplatelet therapy in acute procedures by administrating glycoprotein (GP) IIb/IIIa inhibitors immediately after the deployment of the FD and by introduction of dual antiplatelet therapy in the following hours, after a new intracranial hemorrhage was excluded by follow-up CT. Administration of GP IIb/IIIa inhibitors in the treatment of RIAs in the acute phase of SAH has been reported from other authors (2,3). A recent in vitro study by Habijan et al. demonstrated a significant decrease in platelet adhesion on the stent surface when prepared with hydrophilic polymer coating compared to uncoated surfaces. Recently, the Pipeline Shield (Medtronic) has entered the market. This device, the first FD with a thrombo-resistant coating, has a 3-nm thick covalently bound phosphorylcholine surface modification (28). However, there are currently limited clinical data available on the use of this technology. Various FD devices are currently approved for the treatment of intracranial aneurysms including the Pipeline Embolization Device (PED; Medtronic), Flow-Redirection Endoluminal Device (FRED, MicroVention), Silk (Balt Extrusion), Surpass/Streamline (Stryker), Derivo (Acandis), p64 Flow Modulation Device and p48 Flow Modulation Device (both phenox). Common features of the current FDs are the high flexibility that allows device adaption to tortuous vessel anatomy and resheatability when not fully deployed in the range of 70–90% depending to the respective device. Special features of the various FDs are pointed out below (1,29,30). The PED is one of the first FD and received approval for clinical use in Europe in 2008 and in the USA in 2011. It is a braided mesh tube of 48 interwoven microfilaments, with 30–35% metal coverage of the inner surface of the target vessel. The second-generation PED, named Pipeline Flex includes numerous delivery system changes to enhance device opening and provide additional safety with a re-sheathing feature. A special feature of the p64 flow modulation device that consists of 64 interwoven microfilaments with 8 proximal radiopaque markers is resheatability of 100% of its length after complete deployment due to its controlled mechanical detachment. The SILK FD consists of 48 braided nitinol and four platinum micro-filaments, with a pore size of 110–250 mm and 35–55% metal coverage. For vessels with a discrepancy between their proximal and distal diameters, a tapered SILK + variant is available. The FRED system is a self-expanding nickel titanium paired stent, designed with integrated dual-layer coverage. The inner layer has low porosity (48 braided nitinol wires), while the outer layer has high porosity (16 nitinol wires). The Surpass Streamline FD has a metal surface area coverage of 30% with a variable number of braiding wires according to the device size (48, 72, and 96 strands) that provides a more uniform pore density over different sizes. The special delivery system allows the maintenance of a continuous endoluminal guidewire access that is uncoupled from the device deployment. The Derivo (Acandis, Pforzheim, Germany) is a self-expandable highly flexible FD composed of 48 nitinol composite wires with a radiopaque platinum core and three additional platinum–iridium markers at both ends to enhance its visibility on X-ray imaging. The thin surface layer of titanium oxides and oxynitrides is supposed to reduce friction during delivery and may lower thrombogenicity of the device. The delivery system enables subtotal resheathing until 80% of its length and repositioning. In the present case series, the Derivo was applied because the operators had a lot of experience with the device that provided a good visibility and trackability with good wall apposition also in tortuous vessel anatomy in previous treatment procedures already.

Fig. 2.

(a, b) 3D rotational angiogram and unsubstracted angiogram obtained pre-treatment of a right ICA dissecting aneurysm (arrowhead). (c, d) Initial angiogram after deployment of two overlapping Derivos; note the very good visibility of the Device contour and especially the X-ray markers allowed a precisely accurate deployment of the device just before the origin of the AChA (arrow). (e–g) 3D rotational angiogram, substracted and unsubstracted angiograms at six-month follow-up demonstrating complete occlusion of the aneurysm without in-stent stenosis. (h) Fish-mouthing or foreshortening of the device is excluded by native fluoroscopic imaging.ICA: internal carotid artery; AChA: anterior choroideal artery.

Fig. 3.

Treatment of a dissecting-fusiform aneurysm of the right vertebral artery (VA) with the Derivo Embolisation Device. (a) 3D rotational angiogram, (b) angiogram in working position, unsubstracted angiogram after complete deployment of a Derivo in the VA; (c) the device is passed by the microcatheter (arrows indicate proximal and distal markers) after deployment again to ensure wall apposition. (d) Angiographic follow-up after six months demonstrates complete thrombosis of the aneurysm with patent PICA in the working position. (e, g) Initial angiogram after deployment shows residual inflow into the aneurysm in the oblique view with complete excluded aneurysm at six-month follow-up. Initial unsubstracted angiogram after deployment and at six-month follow-up demonstrated complete wall apposition of the Derivo in the oblique view without fish-mouthing or foreshortening. (f, h) A mild hyperplasia at the proximal end of the device is noticeable.

Limitations of our preliminary retrospective case series include the small sample size, that may explain the lower-than-average rate of complications. The short-term follow-up periods and the low rate of patients with angiographic follow-up examinations are the main limitations of this study. Thirty-day dual-energy CTA was performed to detect changes of aneurysm configuration that would require an angiographic control, but this image modality was not eligible to assess grade of aneurysm occlusion. Still, the present study showed promising results regarding procedural and short-term safety, indicated by clinical absence of perforator infarctions or rebleeding. Nevertheless, further studies with larger cohorts and long-term follow-up periods will provide a definitive conclusion about the safety and efficacy of the Derivo and other FD devices in RBAs and RDAs.

In conclusion, the Derivo Embolisation Device appears to be safe in the current case series for parent artery reconstruction in RBAs and RDAs, which are not treatable by conventional endovascular and surgical techniques.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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