Hemodynamic factors of thrombus formation in coronary aneurysms associated with Kawasaki disease

BACKGROUND: We studied the mechanism of thrombus formation in coronary aneurysms based on rheological findings. METHODS: We studied 43 coronary aneurysms in 33 patients with Kawasaki disease (mean (+/- SD) age 6.1 +/- 4.3 years). These lesions were divided into three groups on the basis of maximum diameter: (i) small (group S); (ii) medium sized (group M); and (iii) large (group L) aneurysms. Using a Doppler flow guidewire and a pressure-monitoring guidewire, we measured coronary flow velocity and perfusion pressure inside aneurysms and in adjacent normal-looking vessels. We calculated the average peak velocity (APV) index, the mean coronary perfusion pressure (P) index and shear index. RESULTS: The APV index and shear index decreased significantly (p < 0.005) as the aneurysm size increased (APV index in groups S, M and L was 0.893 +/- 0.149, 0.573 +/- 0.242 and 0.128 +/- 0.131, respectively; shear index in groups S, M and L was 0.750 +/- 0.149, 0.328 +/- 0.153 and 0.020 +/- 0.028, respectively). However, coronary perfusion pressure showed no relationship to aneurysm size and was not significantly different from that in adjacent normal-looking vessels. CONCLUSIONS: The results of the present study suggest that the stagnation of flow and the reduction of shear stress in coronary aneurysms could initiate thrombus formation.