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 may be described by a stress tensor 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+/-9 kPa which was in good agreement with experimental data measuring active stress in isolated muscle strips. Five pigs were then 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 transfered to a clinical setting.