The long term follow up of patients entered in the ISAT trial continues to give insight into a number of important research questions.
What is the natural history of early rebleeding?
There was a marked variation in time taken from ictus to both randomisation and to treatment seen between ISAT centres with a range of 0-28 days. During this period they were 50 rebleeds seen in the 2143 patients. This allowed a conditional risk can be calculated for the first 15 days post ictus; day 1-9 fluctuates around 1% per day but on day 10 the rate of rebleed- ing suddenly increases to 4.14% and then from day 11-15 fluctuates around 2-3%. However it should be noted that only a few bleeds were recorded on any day.
Does early treatment of the aneurysm by clipping or coiling increase the chance of poor outcome?
This is the converse question. It has long been argued by neurosurgeons that delayed treatment is of benefit in older sicker patients so does early treatment result in poorer outcome (table 1).
Table 1.
The risk of poor outcome from neurosurgery and endovascular treatment performed early 0-2 days, 3-6 days or late 7+ days post ictus.
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There is no significant difference in the number of poor outcomes in those treated late and those treated early. So it does not appear that early treatment by either modality increases the risk of poor outcome. It should be noted, however, that there was an increased number of elderly and sicker patients in the 7+ group treated by neurosurgery. Treatment in those whom it is clinically feasible should therefore not be delayed in patients who can be treated.
What are the risks of recurrent subarachnoid haemorrhage both in treated aneurysms and de novo aneurysms?
The risk of rebleeding from a cerebral aneu- rysm per year is higher in endovascular treated patients at 0.21% per year as opposed to 0.08% per year for neurosurgery treated patients. The overall risk of bleeding is 0.15% per year for all patients. increase in rebleeding rate in en- dovascular patients does not affect the overall ISAT result. The cumulative mortality (Kaplan Meier) curves show that the early benefit from endovascular treatment is maintained at 7 years. This may be related to the fact that patients who rebled from an endovascular treated aneurysm (9 patients) had half the mortality rate of those who rebled following surgery all whom died (3 patients) (table 2).
Table 2.
Rebleeding of treated and other aneurysms after 1 year.
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Conclusions
The rebleeding risk after 1 year from a coiled aneurysm is about 0.12% per year.
The risk of death or disability from rerupture is approximately half this rate at 0.07% per year. (> 1:1000).
The risk of bleeding from another or new an- eurysm is similar at 0.07%.
The risk of treatment small aneurismal remnants must be carefully weighed against these very small risks.