Stagnating blood flow related to thrombus formation in pulmonary vein stump after left upper lobectomy

Abstract

Objectives A thrombus can occur in the stump of the pulmonary vein after left upper lobectomy, potentially causing postoperative cerebral infarction. This study aimed to verify the hypothesis that stagnation of blood flow inside the pulmonary vein stump causes thrombus formation. Methods The three-dimensional geometry of the pulmonary vein stump after left upper lobectomy was recreated using contrast-enhanced computed tomography. Blood flow velocity and wall shear stress (WSS) inside the pulmonary vein stump were analysed using the computational fluid dynamics (CFD) method and compared between the two groups (those with or without thrombus). Results The volumes of average flow velocity per heartbeat < 10 mm/s, 3 mm/s, 1 mm/s (p-values 0.0096, 0.0016, 0.0014, respectively) and the volumes where flow velocity was always below the three cut-off values (p-values 0.019, 0.015, 0.017, respectively) were significantly larger in patients with a thrombus than in those without thrombus. The areas of average WSS per heartbeat < 0.1 Pa, 0.03 Pa, 0.01 Pa (p-values 0.0002, < 0.0001, 0.0002, respectively), and the areas where WSS was always below the three cut-off values (p-values 0.0088, 0.0041, 0.0014, respectively) were significantly larger in patients with thrombus than in those without thrombus. Conclusions The area of blood flow stagnation in the stump calculated by CFD method was significantly larger in patients with than in those without thrombus. This result elucidates that stagnation of blood flow promotes thrombus formation in the pulmonary vein stump in patients who undergo left upper lobectomy.