Miniature C-shaped transducers for chordae tendineae force measurements.

C-shaped strain gauge force transducers were designed to enable dynamic measurements of the tension of the individual mitral valve chordae tendineae during the cardiac cycle. The force transducers were constructed from a C-shaped brass ring with a diameter of 6 mm, width of 2 mm, thickness of 0.5 mm, and a mass of <80 mg. Miniature strain gauges elements were cemented onto the inner and outer side of the ring. The strain gauges were connected to thin Teflon wires and coupled in a Wheat-stone half-bridge circuit to a signal conditioner and amplifier. The transducer was coated with a resistive sealing ensuring electrical insulation as well as mechanical protection. Technical testings of sensitivity, linearity, noise level, and frequency response characteristics demonstrated that the transducers were suitable for dynamic chordal force measurements performed under in vitro and in vivo experimental conditions.