Pathogenesis of carotid thrombosis.

We histologically examined specimens from 11 patients with recent occluding thrombi at the carotid bifurcation to study local factors in the vessel wall that precipitated the thrombi. The area of stenosis of the vessel lumen was determined morphometrically. Severe atherosclerotic stenosis was frequent but was not a prerequisite for thrombus formation since specimens from almost one half of the patients had only moderate narrowing of the lumen (less than 60% stenosis). Specimens from three patients showed ulcerations, those from one showed intraplaque hemorrhage, and those from one massive plaque rupture, all of which were thought to be important in thrombogenesis. All such types of plaque complications may thus precipitate thrombi but no single complication was particularly predominant, and specimens from one half of the patients showed no complications at all. Screening of the carotid arteries for stenosis can therefore detect only one half of the individuals who ultimately will develop thrombosis, and the risk caused by plaque complications seems to be moderate in unselected materials.