Cardiac Active Contraction Parameters Estimated from Magnetic Resonance Imaging

Impaired systolic ventricular function is common in patients diagnosed with heart failure (HF) or ischaemic heart disease. The diminished contractile performance with impaired contractility (systolic HF) can be induced by impaired filling function (diastolic HF) and the wall stress (both passive and active) may indicate the progression from diastolic HF to systolic HF. In order to better understand the distribution of active stress during ventricular contraction, a left ventricular (LV) finite element (FE) model incorporating LV fibre geometry and function was developed to parameterise a time-varying model of myocardial contraction by simulating LV mechanics. During systole, the isometric active stress monotonically increased to 95 kPa, and rapidly recovered during isovolumic relaxation. We also observed regional variations of the fibre length dependent contractile stress throughout the LV. The time-varying active stress curve thereby obtained enabled quantification of heart muscle performance. This type of integrative modelling enables the investigation of LV mechanics on an individualised basis.