Istvan Szikora, National Institute of Neurosciences, Neurointerventions, Hungary, spoke on behalf of the ESMINT Flow Diverter Bleeding Project contributors to tell delegates that a small, real world, unselected series analysis has shown that the characteristics determining delayed rupture of intracranial aneurysms when treated by flow diverters are aneurysm size and symptomatic clinical presentation.
Szikora said that the results of this survey merely provided a superficial overview and should be considered with great caution, as the imaging results were self-assessed, data were not audited and follow-up protocol was unknown meaning that several incidents may not have been recognised.
Referring to haemorrhagic incidents in the literature, he said “From published studies, we see that the SILK experience had 13 delayed haemorrhages out of an estimated 1500 aneurysms treated with SILK stent (Kulcsar et al, AJNR 2011), which accounts for approximately 1% of cases. There was no bleeding seen in the PITA trial with the Pipeline Embolization Device, from 31 aneurysms treated. The Buenos Aires experience had zero incidence of complications from 63 cases, the Budapest study saw one case of haemorrhage from 19 aneurysms treated and the PUFS trial had two haemorrhagic complications from 28 treated.
“In the Pipeline experience, there was a company (ev3/Covidien) initiated data collection on close to 1000 patients with six months follow-up. This demonstrated an incidence of delayed aneurysm rupture slightly over 1% and a similar rate of remote parenchymal hemorrhage,” Szikora said.
He explained that the aim of the study was to analyse the incidence of bleeding in an unselected series of flow diverter treated aneurysms (so that a “real world” experience could be assessed). The study also sought to identify the type of aneurysms prone to delayed rupture and attempted to identify techniques that might be capable of reducing bleeding risk.
Data collection was initiated by a task force established by the ESMINT executive committee (The ESMINT Flow Diverter Bleeding Project). An invitation was sent electronically to all ESMINT members as well as all SILK and Pipeline Embolization Device users identified by the device providers. It was an electronic questionnaire distributed by the ESMINT office, participation was entirely voluntary and no industrial support or control other than an address list was provided. “The results are self-assessed and the data are not audited, and they are processed by the authors,” he said.
There were 53 responders from the European Union, Argentina, Australia, Canada, Brazil, Israel, Lebanon, Russia, Singapore, South Africa, Turkey and the USA. The total number of patients reported was 1,040. There was detailed information on aneurysm characteristics in 699 patients.
With regard to device usage, nearly 600 patients were treated with the Pipeline Embolization Device, over 400 were treated with the SILK stent, fewer than 50 with the Surpasse and nearly 20 with the Cardiatis stent.
“The primary determining factor with regard to complications, seems to be large and giant aneurysms. Such aneurysms may have a much higher likelihood of delayed haemorrhage than previously expected. They are likely to be symptomatic, have a partial intrasaccular thrombosis, diseased or no wall and prone to rupture. Incidence of subarachnoid haemorrhage in large/giant aneurysms was 2.5% per aneurysm.”
Szikora noted that expertise could reduce procedural complication, periprocedural incidents and remote parenchymal haemorrhage. “But this should not affect delayed aneurysm rupture. A lower incidence of this complication in the high-volume centres was seen and is probably related to different case selection, treating more small-medium aneurysms than in the low volume centres,” he said.
Szikora stated that a prospective study focusing on a high-risk aneurysm population was highly recommended. “Aneurysm flow pattern before and after treatment, final mesh density/flow reduction of the applied device should be measured and a rigorous follow-up protocol, progression of aneurysm thrombosis, with sequential MRI studies prior to and following treatment should be done.”