Objective: To determine the effect of adequate scientific research on the treatment of extracranial stenosis of the internal carotid artery.
Design: Retrospective and comparative.
Setting: Twenty Medical Spectrum, Enschede, the Netherlands.
Method: A comparison was made of the relevant data from 2 years of carotid artery surgery before (1989-1990; period I) and after the publication of two randomized multicentre studies (1994-1995; period II).
Results: The number of patients treated surgically and the number of carotid artery desobstructions had increased during period II by 339% and 319%, respectively. In period I, 25% of the patients had an asymptomatic ipsilateral stenosis of the internal carotid artery; in period II, this had decreased to 11%. In period I, 65% of the patients had a stenosis in excess of 70% of the diameter of the vessel; in period II this was 85%. The combined mortality and permanent disabling morbidity after 30 days was 6% in period I and 3% in period II.
Conclusion: After the publication of two high-quality studies in 1991, the number of carotid artery operations increased by over 300%. The indications for the surgical treatment of stenosis were stricter rather than less strict in period II. The increase of the number of carotid desobstructions can be explained by the fact that GPs' and neurologists' referral to the vascular surgeon has changed. This change in the referring pattern may be the consequences of use of 'evidence-based' medicine.