Critical appraisal of the International Subarachnoid Aneurysm Trial (ISAT)

The results of the International Subarachnoid Aneurysm Trial (ISAT) drew attention from both scientific and lay press, impacting the management of aneurysm patients significantly. In this review, the ISAT report was analyzed critically and the available literature was scrutinized stratifying the common criticisms as to the weak aspects of this study. The aim of ISAT was to compare the safety and efficacy of endovascular coiling with neurosurgical clipping for aneurysms, which were suitable for both treatments. The results showed a 22.5% relative and 6.9% absolute risk reduction at one year in the disability outcome of patients who were treated with coiling. However, long-term risk of re-bleeding from the treated aneurysms and the risk of repeat procedures was higher in this group also. Lack of angiographic data following the initial treatment and long-term follow-up represents one of the main flaws of this study. The outcome assessment scale, biases regarding patient selection and center participation criteria were further issues of criticism. The results of ISAT are not sufficient to provide a definitive answer as to the superiority of endovascular treatment over microsurgery, although coiling appears to produce less peri-procedural morbidity in a selected group of patients. An optimum outcome assessment should include a universally accepted scale and a detailed long-term angiographic outcome.