The results of a multicentre study have shown that catherisation with the larger profile coil delivery microcatheter and aneurysm occlusion with large volume coils is feasible and safe for aneurysms <10mm. Zsolt Kulcsàr and others report in the Journal of NeuroInterventional Surgery that with the Penumbra Coil 400, they achieved a high packing density of 45%, with a low average number of coils. Further, they write that aneurysm occlusion grades improved during the seven-month follow-up period, achieving 91% sufficient occlusion.
A retrospective analysis of prospective data collected at three different centres was performed on consecutive aneurysms ˂10mm treated with the Penumbra Coil 400 system. A total of 92 aneurysms were included in the study. Feasibility, procedure safety, angiographic and clinical results, and follow-up results were evaluated.
The Penumbra Coil 400 system consists of 0.02 inch primary diameter coils constructed of 92% platinum/8% tungsten round wire filament with a diameter of 0.00125 inch or 0.0015 inch. The nominal outer primary diameter is 0.02 inch and the inner core comprises a second open-pitch coil made with nitinol and an additional thin nitinol wire which is heat-shaped to confer either a complex or helical coil shape. The coil is delivered through a microcatheter with a minimum inner lumen of 0.025 inch. Since January 2013 the original coil delivery microcatheter was replaced by a redesigned version (PX Slim). The PX Slim has a reduced and smoother profile of 2.6F outer diameter at the tip and 2.95F outer diameter (in comparison with the original PX 400 with a distal outer diameter of 2.8F and a proximal outer diameter of 3.4F).
The study authors report the results of 92 patients (mean age 60±12 years). Twenty-three aneurysms (25%) were acutely ruptured. The mean value of maximal aneurysm diameter was 5.8±2mm and the mean neck size was 3.2±1.3mm. Forty-one aneurysms (45%) were ≤5mm and an adjunctive device (balloon, stent or flow diverter) was used in 21% of cases.
“Sufficient occlusion rates (grades 1 and 2) were achieved in 66% of cases (grade 1: 38%, grade 2: 28%). The average number of coils used per aneurysm was 2.5±1.3. The mean length of coils introduced per aneurysm was 18±16cm and the mean packing density of the aneurysms was 45.6±14.4%. Treatment-related thromboembolic events were observed in three cases (3.3%), all in patients with acute subarachnoid haemorrhage (only one of these patients suffered a procedure-related infarct). No procedural aneurysmal rupture was observed,” Kulcsàr et al write.
In terms of follow-up, 79 patients (86%) have had follow-up imaging with a mean time of 7.4±4.6 months. The authors report that aneurysm occlusion grades at the last imaging follow-up have shown a major improvement (sufficient occlusions of 91% vs. 66%). The follow-up results of 44 aneurysms (65%) did not change over time, and 33 aneurysms (42%) have shown progressive occlusion. Only two aneurysms (3%) demonstrated a worsening compared with the initial result. Out of 27 aneurysms with a primary grade 3 occlusion, 67% showed progressive occlusion and 30% remained unchanged. Only one aneurysm from this group worsened in occlusion grade. Of the aneurysms with complete primary occlusion, none demonstrated recanalisation during the follow-up, and none of the aneurysms were retreated during the follow-up period.
As relates to the outcome of aneurysms treated with stent or flow diverter assistance (12/92 aneurysms, 13%), and those treated without parent artery reconstruction (80 aneurysms), the authors write that there was no difference in the immediate occlusion grades (66.7% vs. 66.2% grade 1 and grade 2 occlusions). “At the last follow-up, however, there was a tendency for higher occlusion grades of aneurysms with adjunctive stent or flow diverter implants (83.3% vs. 75.5% grade 1 and 2 occlusions),” they say.
Commenting on the Penumbra Coil 400 system, Kulcsàr et al state that the device “has increased softness and flexibility due to the construction of the 0.02 inch primary coil diameter from a thin primary core wire. These features translate into increased compaction and quicker filling of the aneurysm volume. Compared with conventional coil delivery microcatheters which have a smaller inner diameter, the PX Slim microcatheter has improved stability inside the aneurysm during coil delivery. These coil and microcatheter qualities allow high densities to be achieved with a lower number of coils.”
Finally, they report that the safety of the Penumbra Coil 400 system was demonstrated “by the low thromboembolic event rate of 3.3% and by the fact that no aneurysm perforations were observed during catheterisation of coil delivery.”
On what lessons were learned about the Penumbra Coil 400 system during this study, Kulcsàr et al state:
- There is the need to accurately estimate the packing density that will be achieved with the coil selected prior to insertion. Small aneurysms may be quickly overfilled by selecting a coil that is too long. The entire coil may require removal due to the inability to introduce the last few millimetres of the coil into the aneurysm.
- It is important to try and prevent expulsion of the microcatheter tip from the aneurysm during coil insertion. In general, it was found to be more difficult to re-access the aneurysm (this is probably related to the larger microcatheter outer diameter not fitting into the smaller interstices between the large diameter coils). Furthermore, distally located small aneurysms may not be ideal for treatment with the Penumbra Coil 400 system, mostly due to the limitations of accessing these aneurysms with the higher profile microcatheter.