Application of finite-element analysis with optimisation to assess thein vivo non-linear myocardial material properties using echocardiographic imaging

An application of finite-element analysis with an optimisation technique to assess the myocardial material properties in diastasisin vivo is described. Using the data collected from an animal model, the three-dimensional geometry of the left ventricular chamber, at several times in diastole, was reconstructed. From the measurement of the ventricular chamber pressure during image acquisition, finite-element analysis was performed to predict the expansion during diastasis. Initially, by restricting the motion of the epicardial nodes and computing the reaction forces, an ‘equivalent pericardial pressure’ was determined and applied in subsequent analysis. The duration of diastasis was divided into three or four intervals and the analysis was performed at each interval to assess the material properties of the myocardium. Using such a step-wise linear approach, the non-linear material properties of the myocardium during passive expansion was determined. Our results demonstrated that the computed ‘equivalent pericardial pressure’ increased with and was smaller than the corresponding left ventricularchamber pressure. The passive myocardium exhibited a linear tangent modulus against chamber pressure relationship which is equivalent to an exponential stress/strain relationship, similar to those suggested byin vitro studies.     

Acute abdominal events and their impact on morbidity and mortality in a CAPD program

A retrospective analysis was done to explore the impact of acute abdominal events other than peritonitis, on morbidity and mortality in a CAPD program over a span of 6 years. Subtlety of clinical manifestations and low yield from investigational attempts (except microbiologic) made decision-making as to whether or not to continue CAPD, hard. An increased prevalence of septicemic shock with its inevitable high risk of morbidity and mortality was striking. Timely termination of CAPD and change over to hemodialysis may help to prevent dissemination of infection in these patients. Among the vascular causes of death in CAPD patients, bowel infarction seemed to be the most common.