Numerical investigation of antegrade flow effects on flow pulsations in Fontan operation

Abstract

This study considers blood flow in Total Cavopulmonary Connection (TCPC) morphology, created in Fontan surgical procedure in patients with single ventricle heart disease. Ordinary process of TCPC operation reduces pulmonary blood flow pulsatility; because of right ventricle being bypassed. This reduction may limit the long term outcome of Fontan circulation. There is an idea stating that keeping Main Pulmonary Artery (MPA) partially open, would increase pulmonary flow pulsations. MPA gets closed in ordinary TCPC operation. The purpose of current study is to verify effects of Antegrade Flow (AF) coming through stenosed MPA on pulmonary flow pulsations, by means of Computational Fluid Dynamics (CFD). The 3-D geometry is reconstructed from CT Angiography (CTA) scan of a patient who has undergone an ordinary TCPC procedure. The stenosed MPA or Pulmonary Stenosis (PS) is virtually added to the original geometry. Inlet velocity profiles are obtained from Echocardiography data of the same patient. AF profile in a cardiac cycle is obtained from a general pressure cycle of left ventricle, assuming a linear relationship between pressure gradient and flow rate in PS. Flow field is studied in six different models in which average AF increasingly changes from 0 to 14% of total cardiac flow, using FLUENT. The results show that adding AF increases Pulsatility Index (PI) in both left and right pulmonary artery (LPA and RPA respectively), with a maximum amount of 140% in LPA. Moreover, adding AF leads to an increase in energy loss of the TCPC region, with a maximum amount of 67%. The addition of AF also increases pulmonaryto- systemic flow ratio which leads to an increase in total cardiac flow rate and hence heart power.