George Sutherland

Post-Systolic Thickening in Ischaemic Myocardium: A Simple Mathematical Model for Simulating Regional Deformation

We present a one-dimensional mathematical model to explain changes in regional radial myocardial deformation during ischaemia. The model makes use of cellular contraction properties of normal and ischaemic myocytes extracted from an animal model of induced chronic, regional ischaemia of the posterior wall. Simulations of the model are compared to the deformation patterns observed in the experimental animal models of regional ischaemia.

Quantitative Assessment of Intrinsic Regional Myocardial Deformation by Doppler Strain Rate Echocardiography in Humans

To the Editor:nnWe have read with interest the recent report of Edvardsen et al1 in which left ventricular regional peak systolic strain values measured by ultrasound were correlated with the corresponding strain data extracted by 3-dimensional tagged MRI. The study showed an overall acceptable agreement between the 2 techniques for several myocardial segments in both normal and pathological myocardium and for both radial and longitudinal deformation.nnAlthough the longitudinal deformation parameters measured were in agreement with prior results, the radial values were not. Indeed, in this study, Lagrangian radial strain in the posterior wall of healthy volunteers was measured to be 18±9% and 17±6% by ultrasound and MRI, respectively. However, previously reported studies using standard M-mode echocardiography had found radial maximal systolic Lagrangian strain values of 69±23%.2 The discrepancy between these values and the ones published in the study of Edvarsen et al1 could, in theory, be attributed …

Estimating systolic contractile forces using tissue Doppler myocardial imaging and mechanical modeling

Quantitative assessment of myocardial function remains an important goal in clinical cardiology. Measuring contractile force is a good way of assessing this. However, currently there is no direct method to do this. Force development within the myocardial wall maybe described by a stress sensor that is the sum of passive/elastic and active/contractile stresses. In this study a simplified cardiac mathematical model was combined with ultrasound velocity imaging and haemodynamic data to determine whether the contractile force development could be estimated during systole. This methodology was validated in ten pigs. The mean peak value of active stress was 46/spl plusmn/9kPa which was in good agreement with experimental data measuring active stress in isolated muscle strips. Five pigs were given an incremental dobutamine infusion and an increase in peak active stress paralleled the increase in dobutamine. The estimation of contractile force development as described above could easily be transferred to a clinical setting.