A Dynamometer for the Heart - Nature's Engine

Abstract

The heart is an amazing organic engine that converts chemical energy into work. Each heartbeat begins with an electrically-released 'spark' of calcium, which triggers force development and cell shortening, at the cost of energy and oxygen, and the release of heat. We have developed new measurement systems to measure all of these processes simultaneously while subjecting isolated samples of heart tissue to realistic contraction patterns that mimic the loads experienced by the heart with each beat. These devices are effective 'dynamometers' for the heart, that allow us to measure the performance of the heart and its tissues, much in the same way that you might test the performance of your motor vehicle on a 'dyno.'

In this talk, I will overview how we have developed our own actuators, force transducers, heat sensors, and optical measurement systems to study nature's engine: heart muscle. Heart muscle force and length are measured and controlled, beat by beat, to microNewton, and nanometer precision by a laser interferometer. At the same time,  the muscle is scanned in the view of an optical microscope equipped with a fluorescent calcium imaging system. The changing muscle geometry is monitored in 4D by a custom-built optical coherence tomograph, and the spacing of muscle-proteins is imaged in real-time by transmission-microscopy. Muscle heat production is measured to nanoWatt precision using thermopile sensors. We combine all of these technologies with a hardware-based real-time acquisition and control environment and interpret results with the aid of a computational model.

Our dynamometer allows us to diagnose the 'performance' heart tissue, even as it is affected by disease, exercise, drugs, and diet. By applying this 'bioengineering approach' to the study of heart tissues, we have gathered new insight into the function of the heart - information that we hope will lead to better treatment and management of the engine upon which we all rely!