Figure 1.

Illustration showing the 2.5 mm thick needle force probe inserted between the myocardial fibres. Also shown is the main direction of the development of contractile force along the axial alignment of the myocardial fibres, along with the perpendicular force vector that acts on the flexible bar within the lateral window, measured by strain gauges mounted on the flexible bar. The fibres are spread during implantation of the probe. Some fibres slip into the lateral window, loading there on the flexible bar. Only those (bright) fibres that are curved around the flexible bar contribute to the signal measured, the innermost curved fibres more than the outer, less curved fibres. In the background are shown the myocardial fibres wrapping around the trunk of the needle probe. Spreading of the tissue is more important in this area than in the indentation of the window.