International Subarachnoid Aneurysm Trial

The International Subarachnoid Aneurysm Trial (ISAT) was a large multicentre, prospective randomised clinical medical trial, comparing the safety and efficacy of endovascular coil treatment and surgical clipping for the treatment of brain aneurysms. The study began in 1994. The first results were published in The Lancet in 2002, and the 10 year data were published again in The Lancet in early September 2005. 2,143 study participants were mostly drawn from U.K. hospitals with the rest drawn from North American and European hospitals.

The study found better results with endovascular coil treatment compared to surgical clipping, however subsequent studies have questioned this conclusion. The study was criticised by many clinicians and not well accepted by surgeons. Primary criticisms were related to the study's patient population's generalisability to the wider population, and the long term prognosis of coil embolisation.