Single-Center Experience With the Bare p48MW Low-Profile Flow Diverter and Its Hydrophilically Covered Version for Treatment of Bifurcation Aneurysms in Distal Segments of the Anterior and Posterior Circulation

Abstract

Background and Purpose: Flow diversion has profoundly changed the way aneurysms are treated. However, it conventionally requires dual antiplatelet medication and has yet been considered off-label use in the posterior circulation or within peripheral vessels of the anterior circulation. Here, we report our experience with the p48MW/p48MW hydrophilic coating (HPC) in the anterior and posterior circulation. This novel low-profile flow diverter is specifically designed for treatment of small peripheral vessels, and the p48MW HPC has an anti-thrombotic polymer coating, which allows application of a single antiplatelet function medication in conditions that expectably require further surgery. Materials and Methods: Thirty-two patients were prospectively included. Twenty-six treatments were performed with one flow diverter, four required two overlapping flow diverters, one case demanded three overlapping flow diverters, and in one case, extensive dissecting aneurysm telescoping with eight flow diverters was necessary. Twenty-two complex bifurcation aneurysms were treated. Three months' follow-up was available for 14 patients. Results: Deployment was uneventful in all cases. In four cases, undersizing was unavoidable and resulted in significant shortening of the flow diverter, which demanded implantation of further flow diverters to sufficiently treat the target aneurysm. Three flow diverters required balloon angioplasty for optimal wall approximation. All parent vessels remained patent. Available 3-month follow-up studies showed decreased influx or delayed washout in all aneurysms; none was occluded completely. There were no device-related clinical complications. Conclusions: Implantation of the p48MW/p48MW HPC is safe and effective for treatment of distally located cerebral aneurysms. Considering the reported rates of ischemic complications associated with flow diversion of complex bifurcation aneurysms, the p48MW/p48MW HPC potentially provides increased safety for complex bifurcation aneurysms in the anterior and posterior circulation.

Keywords: cerebral aneurysm; flow diversion; p48MW; reduced platelet function inhibition; small cerebral vessels.

Figure 1

An example of p48MW hydrophilic coating (HPC) implantation for treatment of an un-ruptured, broad-based aneurysm of the AcomA complex via the left internal carotid artery (ICA). (A) Digital subtraction angiography (DSA) run in working projection revealing the broad based (neck: 5.3 mm), saccular aneurysm (fundus: 5.2 × 4.3 mm) predominantly filled by the left anterior cerebral artery (ACA). (B) Catheterization of the elongated, demanding ACA using the Excelsior SL 10 and confirmation of the correct endoluminal position distal to the aneurysm as a pre-requisite for safe microcatheter exchange/introduction of the Prowler Select Plus required for device delivery. (C) Plain radiography in working projection demonstrating flow diverter stent (FDS) implantation—note the radiopaque olive tip at the distal end of the p48 wire at the level of the distal A2 segment, which helped to stabilize the equipment during deployment. Implantation of the device has caused significant straightening of the A1–A2 transition, additionally contributing to the redirection of blood flow away from the aneurysmal orifice. (D) Control injection after implantation shows the patency of the vessel in combination with the location of the implanted device (radiogram upper right corner).

Figure 2

An example of p48MW hydrophilic coating (HPC) implantation in the right M1–M2 junction for treatment of an un-ruptured saccular aneurysm arising from the right middle cerebral artery (MCA) bifurcation. (A) Digital subtraction angiography (DSA) run in standard AP projection showing the large, laterally developed saccular MCA aneurysm. (B) Volume rendered reconstruction of the rotational 3D angiography revealing the relationship of the aneurysm to the associated MCA branches as well as the lesion dimensions. (C) Pre-intervention DSA run in working projection. (D) Control injection in working projection after definition of the distal landing zone. (E) Corresponding non-subtracted device radiogram. Note the position of the MW in the M2 segment, additionally stabilizing the device-microcatheter unit during deployment. (F) Final DSA run after p48MW HPC implantation demonstrates significantly reduced arterial filling compared with the initial diagnostic DSA (O'Kelly Marotta A3).

Figure 3

An example of p48MW hydrophilic coating (HPC) implantation in the right posterior cerebral–basilar artery (BA) junction for treatment of a broad-based, partially thrombosed, un-ruptured aneurysm arising from the basilar tip, causing progressive hydrocephalus. (A) Conventional angiogram in working projection shows the perfused part of the saccular, broad-based aneurysm of the BA–posterior cerebral artery (PCA) complex (neck, 7 mm; fundus, 7 × 8 mm). (B) Positioning of the first p48MW HPC. The distal landing zone, aiming to cover the smallest perforator-rich area as possible, was defined as comparatively short. Note the distal end of the movable wire (radiopaque olive) within the distal P1 segment, which was used to further stabilize the system during implantation. In retrospect, a more distal positioning of the MW in the middle part of the P2 segment may have prevented dislocation of the first device, as demonstrated in the following images. (C) Simultaneous to the deployment of the device, significant distal shortening and subsequential proximal dislocation of the entire device occurred, requiring the implantation of a second p48MW HPC in order to sufficiently cover the broad aneurysmal orifice. (D) Device radiogram showing the second p48 implanted in telescoping technique. Now the aneurysm is covered sufficiently. Initially, wall apposition/flow diverter opening appeared to be only moderate, which resolved a few minutes after implantation without the necessity for further manipulation. (E) Maximum intensity projection of the flat-panel CT shows the flow diverter stent (FDS) construct and its relation to the BA–PCA junction and the broad-based aneurysm. (F) Venous phase of a digital subtraction angiography (DSA) run in working projection after successful implantation shows protracted opacification of the aneurysm sac (O'Kelly Marotta: A3) indicating the extent of the flow diversion effect. (G) Follow-up DSA in working projection 3 months later shows the remodeled posterior circulation with a minimally perfused remnant of the aneurysm. (H) Device radiography in corresponding projection.