Coiling of <5mm aneurysms safe and efficacious in Target registry sub-analysis

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Based on a sub-analysis of the data from the prospective Target aneurysm multicentre registry, the coiling of aneurysms <5mm in size with Target coils is as safe and effective at than that of larger aneurysms.

According to Sam Zaidat (Mercy Hospital, Toledo, USA), the shape, the size and the site of the aneurysm are common predictors of rupture, and technology, therefore, is advancing to cater to these predictors.

“The packing density is the most important predictor of aneurysm recurrence and growth—the higher you pack the aneurysm the less likely that the aneurysm will compact, we know that from several studies. The technique that is used to increase the packing density will ultimately, in theory, reduce the likelihood of aneurysm recurrence and growth. Techniques such as improving the coil design to increase the packing density. With that in mind, we designed the prospective Target registry to look at real-life data on the Target 360 coil and the subsequent Nano coil in improving the packing density and reducing the risk of aneurysm retreatment and recurrence,” he said during a presentation at the Society of NeuroInterventional Surgery 14th Annual Meeting (SNIS; 24–27 July, Colorado Springs, USA).

Phase 1 of the Target registry took place at 10 sites across the USA and enrolled 150 patients. The primary endpoint was the aneurysm packing density and the sub-group analysis, which Zaidat shared in his SNIS presentation, was the outcome for aneurysms ˂5mm.

The secondary endpoints were the occlusion rate, retreatment rate, the long-term modified Rankin Scale (mRS) score, the length of hospital stay, procedure time, reaccess rate, outcome of the adjunctive device and outcome of ˂3mm aneurysms. The safety endpoint was intraprocedural perforation, intraprocedural thrombus formation and rebleeding rate, morbidity and mortality and procedure-related adverse events.

Zaidat presented follow-up angiogram data for 148 patients. He reported that 94 patients were treated only with the Target 360 coils and 55 were treated with both Target 360 and Target Nano coils. The baseline mRS score for the majority of patients (95%) was 0, 1 or 2 (65%, 22% and 8%, respectively), 60% of the aneurysms were on the right side and the ICA was the most common location (37%). The rupture rate in the registry was 40%. The maximum aneurysm diameter was 5.5mm and the maximum aneurysm neck diameter was 3mm.

The overall packing density, regardless of aneurysm sizes, was 26%. Near complete occlusion Raymond scale 1 or 2 was 91.3%, and from those, class 1 was 66%, class 2 was 25.3% and class 3 was 8.7%. Modified Rankin Scale (mRS) score 0–2 after the procedure was 89% and mRS 0–2 at follow-up was 95.5%. Long-term occlusion rate was 87.5%. The retreatment rate, regardless of aneurysm size, was 15% (10/150 patients). Mortality was 0.06%.

Zaidat explained that when the investigators looked at the predictor of the packing density, the aneurysm size was found to be the independent predictor. Also, he added, stent-assisted coiling more than balloon-assisted coiling looked like an independent predictor of better packing density.

In terms of the treatment of small aneurysms (˂5mm) in the registry, Zaidat reported that there were 60 patients (38.7%). The ˂5mm aneurysm group presented with worse subarachnoid haemorrhage—50% of the subarachnoid haemorrhages within the ˂5mm group had Hunt & Hess 3.

“You would expect that the outcome would be bad, but the packing density in the ˂5mm group was 25.3% versus 26.7% in the >5mm group and there was no difference in the safety or efficacy profile between the groups: mRS 0–2=93.5% vs. 96.4%; occlusion rate 1–2=88% vs. 85% in the ˂5mm and >5mm groups, respectively; retreatment rate=2% in both groups; thrombus formation was asymptomatic in both groups and intraoperative perforation only occurred in one aneurysm in the >5mm aneurysm group. It seems to me that the treatment of ˂5mm aneurysms is safe and efficacious and not more dangerous or different to the treatment of >5mm aneurysms according to the sub-analysis,” Zaidat maintained.

As it relates to phase II of the Target registry, Zaidat said that so far 57 patients have been enrolled and it will examine purely small aneurysms treated with 25% Target Nano coils.

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