Reduced shear stress and disturbed flow may lead to coronary aneurysm and thrombus formations

BACKGROUND: With Kawasaki disease it is important to clarify the mechanisms of coronary artery aneurysm and thrombus to avoid acute myocardial infarction. The authors tested the hypothesis that shear stress is reduced at coronary branching sites and in coronary artery aneurysms, and that this reduction of shear stress can promote formation of coronary artery aneurysms and thrombus. METHODS: The subjects were 111 children with Kawasaki disease with left coronary artery aneurysms, classified into three groups: giant coronary artery aneurysm (n= 28, diameter of coronary artery >8 mm), aneurysm (n= 44, diameter of coronary artery =8 mm), and normal-appearing coronary (n= 39). Averaged peak flow velocity (APV), flow patterns and shear stress were measured and calculated at normal-appearing coronary vessels, left coronary artery branching sites and intra-coronary aneurysm using flow wire, and coronary angiography. Also, presence and appearance of thrombus were detected by intravascular ultrasonography. RESULTS: The authors found that 90.3% of the coronary artery aneurysms occurred at major left coronary branching sites. APV and shear stress were significantly decreased in giant coronary artery aneurysms (APV, 7.1 +/- 2.1 cm/s; shear stress, 3.8 +/- 2.1 dyne/cm(2)) and at the left coronary artery branching site (APV, 9.1 +/- 1.2; shear stress, 1+/-+/-.2 3.0). In total, 20 of 24 thrombi were detected only in giant aneurysm, and all patients exhibited disturbed flow pattern in their giant coronary artery aneurysms. CONCLUSIONS: Reduced shear stress and disturbed flow pattern may lead to coronary artery aneurysm and thrombus formation.