Determinants of Cardiac Function in a Biventricular Finite Element Model: Geometry versus Myofiber Orientation

The Faculty of Informatics is pleased to announce a seminar given by Tammo Delhaas

DATE: Monday, April 20th, 2015
PLACE: USI Lugano Campus, room SI-006, Informatics building (Via G. Buffi 13)
TIME: 09:30

ABSTRACT:
Previous studies showed that left ventricular (LV) mechanics is sensitive for myofiber orientation. Because patient-specific myofiber orientation is difficult to determine, a generic myofiber orientation is routinely used in patient-specific biventricular (BiV) geometries. For maximum agreement between model-predicted and clinically measured cardiac function, myocardial tissue properties are tuned. However, it is questionable whether the effort to address patient-specific geometry while using a generic myofiber orientation is imbalanced for modeling patient-specific cardiac function. Therefore, the sensitivity of cardiac function for geometry and myofiber orientation was tested in a biventricular (BiV) finite element (FE) model of cardiac mechanics. Three different geometries with initially identical transmural myofiber orientation patterns were created: reference geometry REF, a more elongated geometry LONG, and geometry RVATT in which the attachment of the RV was located more towards the equator. In each geometry, myofiber orientation was adapted in response to fiber cross-fiber shear. Differences in both local myofiber and global pump function were below 10% between the geometries with unadapted myofiber orientation (see Figure). Due to reorientation of myofibers, local myofiber function increased by ~40% and global pump function increased by ~60% in all three geometries with adapted myofiber orientation. Differences in both local and global function were again small (<8%) between geometries with adapted myofiber orientation. In all three geometries, the change in orientation was only ~7° between the initial and adapted state, and predominantly occurred in transmural direction. The findings indicate that cardiac function is more sensitive for myofiber orientation than for geometry. We therefore suggest that more effort should be put in determining the patient-specific myofiber orientation because a patient-specific geometry alone is not enough for realistically simulating patient-specific cardiac function. As current techniques for measuring myofiber orientation lack sufficient accuracy, the model for adaptive myofiber reorientation can be used to first refine myofiber orientation in BiV FE models, before optimizing for myocardial parameters.

BIO:
Tammo Delhaas obtained his MD at the University of Groningen in 1988. He received his PhD degree from Maastricht University in 1993 on the basis of a thesis on cardiac mechanics under normoxic and ischemic circumstances. He was trained in Pediatrics at the University Hospital Maastricht and at the Wilhelmina Children's Hospital in Utrecht and qualified as a Pediatrician in 1997. He received a Fulbright grant and an ICIN Fellowship to spend one year in 1996/1997 at the Departments of Bioengineering and Medicine from the University of California at San Diego. Thereafter he was trained in Pediatric Cardiology at the University Hospital Aachen, Germany, and the Royal Children's Hospital in Melbourne, Australia. In 2000 he qualified as a Pediatric Cardiologist, was appointed as Clinical Fellow of the Netherlands Heart Foundation, and was appointed at the Departments of Pediatrics and Physiology of Maastricht University. In 2009 he was appointed professor and chair of Biomedical Engineering at Maastricht University. He is involved in projects related to cellular and cardiac mechanics, cardiac pacing, and mathematical modelling of the heart and circulation.

HOST: Prof. Rolf Krause