Cardiac muscle contraction from coordinated force-length changes results in ventricular pressure volume loops. When subjecting isolated muscles to work-loop contractions that mimic the pressure volume loop, the length-change phases (shortening and re-stretching) are conventionally simplified to result in ‘flat-topped’ work-loops. Such simplification overlooks the dynamic nature of the cardiovascular load as the tissues may experience in vivo. In this talk, I present novel methods for mechanically loading isolated cardiac muscles with real-time models of the preload and afterload experienced by the heart. Using these loading methods, I address the following: Do isolated muscle samples produce more work under these model-based contraction methods? Do they contract more efficiently? These new methods reveal the limitations imposed by conventional, simplified, loading protocols. This project thus enables potential avenues for exploring the cardiac force length space, physiologically and pathophysiologically.

Dr Amy Garrett

Amy is a postdoctoral researcher at the Auckland Bioengineering Institute (ABI) where she is developing novel experimentation technique for the study of uterine smooth muscle electrophysiology. Her PhD work, completed at the ABI, investigated mechano-energetics of isolated cardiac muscle, subjected to newly developed real-time model-based impedance loading methods.

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