On-X Heart Valve Prosthesis: Numerical Simulation of Hemodynamic Performance in Accelerating Systole.

Numerical simulation of the bileaflet mechanical heart valves (BMHVs) has been of interest for many researchers due to its capability of predicting hemodynamic performance. A lot of studies have tried to simulate this three-dimensional complex flow in order to analyze the effect of different valve designs on the blood flow pattern. However, simplified models and prescribed motion for the leaflets were utilized. In this paper, transient complex blood flow in the location of ascending aorta has been investigated in a realistic model by fully coupled simulation. Geometry model for the aorta and the replaced valve is constructed based on the medical images and extracted point clouds. A 23-mm On-X Medical BMHV as the new generation design has been selected for the flow field analysis. The two-way coupling simulation is conducted throughout the accelerating phase in order to obtain valve dynamics in the opening process. The complex flow field in the hinge recess is captured precisely for all leaflet positions and recirculating zones and elevated shear stress areas have been observed. Results indicate that On-X valve yields relatively less transvalvular pressure gradient which would lower cardiac external work. Furthermore, converging inlet leads to a more uniform flow and consequently less turbulent eddies. However, the leaflets cannot open fully due to middle diffuser-shaped orifice. In addition, asymmetric butterfly-shaped hinge design and converging orifice leads to better hemodynamic performance. With the help of two-way fluid solid interaction simulation, leaflet angle follows the experimental trends more precisely rather than the prescribed motion in previous 3D simulations.

Prognostic value of left ventricular myocardial performance index in patients undergoing coronary artery bypass graft surgery.

BACKGROUND: Left ventricular myocardial performance index is a Doppler-derived parameter of nongeometrical ventricular function that measures both systolic and diastolic function of the left ventricle. The objective of this study was to compare prognostic value of left ventricular myocardial performance index with global left ventricle function in patients undergoing coronary artery bypass graft surgery. METHODS: One hundred consecutive patients who underwent coronary artery bypass graft surgery for coronary artery disease were studied from March 2004 through September 2006. Recovery of global left ventricle function and left ventricular myocardial performance index were measured serially by Doppler echocardiography after coronary artery bypass graft surgery. The patients were under supervision for four months after discharging from hospital. We studied the incidence of atrial fibrillation, postoperative myocardial infarction, pericardial and pleural effusion, infection, and also ventilation time and intensive care unit stay. For analysis of the events, we divided the patients into two groups. Group A was considered with left ventricle ejection fraction of <40% and group B had a left ventricle ejection fraction of >40%. RESULTS: Global left ventricle ejection fraction and left ventricular myocardial performance index were not related to pericardial effusion, pleural effusion, and postoperative infection. In group A, left ventricular myocardial performance index had more prognostic value for prediction of incidence of atrial fibrillation rhythm and postoperative myocardial infarction than the global left ventricle ejection fraction. But global left ventricle ejection fraction had more prognostic value for ventilation time and intensive care unit stay in comparison with left ventricular myocardial performance index. These associations were not seen in group B. CONCLUSION: The prognostic effect of left ventricular myocardial performance index was no more than global left ventricle ejection fraction in early and late complications of coronary artery bypass graft surgery but only affirm global left ventricle ejection fraction in some situations.

Cesarean section in a patient with Wolfe-Parkinson-White syndrome.

A 30 year old woman with abnormal fetal presentation was scheduled for emergency cesarean section. The patient had been a known case of Wolff-Parkinson-White syndrome, and appeared exceedingly anxious. She was given diazepam 5 mg and sufentanil 15 microgram as premedication following which routine and conventional general anesthesia was administered. The perioperative course was uneventful, and both the patient and the child were discharged fully well on the 5th postoperative day.