Estimating Regional Myocardial Contraction Using Miniature Transducers on the Epicardium

This paper describes an ultrasound system to monitor cardiac motion using miniature transducers attached directly to the epicardial surface. Our aim was to develop both a research tool for detailed studies of cardiac mechanics and a continuous, real time system for peri-operative evaluation of heart function.

We have developed an experimental ultrasound system using small transducers directly sutured on the epicardium to measure the heart contraction pattern at high spatial and temporal resolution. We have demonstrated how this can be used to track myocardial deformation and study regional myocardial strain. The velocity-based layer tracking was combined with an automatic boundary detection algorithm to find and track the endocardial border. The high temporal resolution allowed for detection of changes in phases during the myocardial motion. The high spatial resolution together with up-sampling and time delay estimation increased the accuracy of the velocity estimates, showing very little drift through the cardiac cycle. The presented study demonstrated the feasibility of the measurement system and the layer tracking method, with emphasis on the technological solution. The main purpose of this study was to develop and investigate the technology, algorithms and method, and no conclusions about the clinical usefulness are drawn from this study.