Risk of recurrent subarachnoid haemorrhage, death, or dependence and standardised mortality ratios after clipping or coiling of an intracranial aneurysm in the International Subarachnoid Aneurysm Trial (ISAT): long-term follow-up

Abstract

Background: Our aim was to assess the long-term risks of death, disability, and rebleeding in patients randomly assigned to clipping or endovascular coiling after rupture of an intracranial aneurysm in the follow-up of the International Subarachnoid Aneurysm Trial (ISAT).

Methods: 2143 patients with ruptured intracranial aneurysms were enrolled between 1994 and 2002 at 43 neurosurgical centres and randomly assigned to clipping or coiling. Clinical outcomes at 1 year have been previously reported. All UK and some non-UK centres continued long-term follow-up of 2004 patients enrolled in the original cohort. Annual follow-up has been done for a minimum of 6 years and a maximum of 14 years (mean follow-up 9 years). All deaths and rebleeding events were recorded. Analysis of rebleeding was by allocation and by treatment received. ISAT is registered, number ISRCTN49866681.

Findings: 24 rebleeds had occurred more than 1 year after treatment. Of these, 13 were from the treated aneurysm (ten in the coiling group and three in the clipping group; log rank p=0.06 by intention-to-treat analysis). There were 8447 person-years of follow-up in the coiling group and 8177 person-years of follow-up in the clipping group. Four rebleeds occurred from a pre-existing aneurysm and six from new aneurysms. At 5 years, 11% (112 of 1046) of the patients in the endovascular group and 14% (144 of 1041) of the patients in the neurosurgical group had died (log-rank p=0.03). The risk of death at 5 years was significantly lower in the coiling group than in the clipping group (relative risk 0.77, 95% CI 0.61-0.98; p=0.03), but the proportion of survivors at 5 years who were independent did not differ between the two groups: endovascular 83% (626 of 755) and neurosurgical 82% (584 of 713). The standardised mortality rate, conditional on survival at 1 year, was increased for patients treated for ruptured aneurysms compared with the general population (1.57, 95% CI 1.32-1.82; p<0.0001).

Interpretation: There was an increased risk of recurrent bleeding from a coiled aneurysm compared with a clipped aneurysm, but the risks were small. The risk of death at 5 years was significantly lower in the coiled group than it was in the clipped group. The standardised mortality rate for patients treated for ruptured aneurysms was increased compared with the general population.

Funding: UK Medical Research Council.

Figure 1

Study profile *Some non-UK centres no longer follow-up patients. †Lost patients had moved abroad (from country of randomisation) or had had no contact with study centre or primary-care physician since the first or second year of study. ‡Patient has withdrawn or they no longer wish to participate.

Figure 2

Kaplan–Meier graph of cumulative risk of rebleed from the treated aneurysm after more than 1 year by treatment allocation Patients followed up for a minimum of 6 years and a maximum of 14 years. SAH=subarachnoid haemorrhage.

Figure 3

Kaplan–Meier graph of cumulative mortality rate Patients followed up for a minimum of 6 years and a maximum of 14 years. SAH=subarachnoid haemorrhage.